RB750UP - Issue

wispvt · Wed Dec 28, 2011 7:52 pm

After getting a RB750UP in, we began testing it. It works great except for if you try to power a Motorola Canopy unit from it using POE. If the Motorola is connected and the RB750UP is rebooted, the switch will not turn on the poe for that port even though it says it is on when looking at the ethernet interface, all other POE ports power up just fine. If you disconnect the radio after 5 seconds the switch works normal and turns on the poe for that port and the Motorola works just fine when you reconnect it. The switch powers Ubuiqiti and Trango units up just fine upon reboot. I think it is an issue with the current limiting circuit upon power up. It is easily reproducible. We have tried everything we can think of, we know the Motorola's draw less than 500ma which the port is rated for.

danielchisholm · Wed Dec 28, 2011 8:36 pm

Don't the Canopy radios use "reverse polarity" on their PoE wires?

jandafields · Wed Dec 28, 2011 11:38 pm

Are the ports POE on/off controllable through Mikrotik command terminal? If so, try a Mikrotik startup script that powers off, waits, and then powers on the POE on that port (as a workaround until you find something better to fix it)

wispvt · Thu Dec 29, 2011 1:37 am

Yes the canopy and trango are reversed. We made up cables accordingly and they work great as long as you connect the Canopy once the poe output on the mikrotik has fully switched on. We measured the Canopy and they seem to draw about 200mA vs the Trango's which draw 130mA at startup which is still a far cry from the 500mA advertised. A startup script wouldn't work due to as long as the canopy is plugged in, you can't get the poe to come up on that port. Though once it is enabled and working you can plug in the canopy and it works great.

jandafields · Thu Dec 29, 2011 2:11 am

Yes the canopy and trango are reversed. We made up cables accordingly and they work great as long as you connect the Canopy once the poe output on the mikrotik has fully switched on. We measured the Canopy and they seem to draw about 200mA vs the Trango's which draw 130mA at startup which is still a far cry from the 500mA advertised. A startup script wouldn't work due to as long as the canopy is plugged in, you can't get the poe to come up on that port. Though once it is enabled and working you can plug in the canopy and it works great.

Sounds like a hardware problem with the Mikrotik, as you were thinking.

Something you might try: Parallel a couple of ports together (the poe pins). This would spread the load over multiple ports, perhaps enough so that they would work properly. If that works well, you could do that on the internal of the unit instead of the outside, as not to use up any usable ports.

I've not seen the board layout, but if there is something that actually limits current per port, it may be possible to bypass it internally on the board as well.

Have you reproduced this on multiple Mikrotik units?

janisk · Thu Dec 29, 2011 10:09 am

It could be problem with other devices if it does not adhere to standart and does not have correct resistance - as a result it is detected that PoE cannot be turned to to not to burn out the port it is connected to. Load values you are calling should not cause any problems what ever you are doing on port or all of them.

some clarification from wikipedia:

A PD (Powered device) indicates that it is standards-compliant by placing a 25 kΩ resistor between the powered pairs. If the PSE (power supplying equipment) detects a resistance that is too high or too low (including a short circuit), no power is applied.

and

PSE detects if the PD has the correct signature resistance of 19–26.5 kΩ

this is the case of "P"ower feature used on these boards to make sure that no other equipment is burned needlessly (or only their Ethernet ports)

marekm · Thu Dec 29, 2011 1:22 pm

It could be problem with other devices if it does not adhere to standart and does not have correct resistance - as a result it is detected that PoE cannot be turned to to not to burn out the port it is connected to. Load values you are calling should not cause any problems what ever you are doing on port or all of them.

some clarification from wikipedia:
A PD (Powered device) indicates that it is standards-compliant by placing a 25 kΩ resistor between the powered pairs. If the PSE (power supplying equipment) detects a resistance that is too high or too low (including a short circuit), no power is applied.

and
Code: Select all
PSE detects if the PD has the correct signature resistance of 19–26.5 kΩ
this is the case of "P"ower feature used on these boards to make sure that no other equipment is burned needlessly (or only their Ethernet ports)

The standard you're referring to is 802.3af, and that's not what the RB750UP implements. Simple "passive PoE" doesn't define any signature detection, so I'd expect any device that doesn't draw too much power to work. As I can see, I'm not the only one with such troubles (the mysterious Bullet2 that won't power up, even though two Bullet5s and one NanoBridgeM5 work fine).

I hope Mikrotik has made the MCU that controls PoE upgradeable in the field (the ATTINY461 chip itself does support self-programming, if supported by a properly written bootloader), so we will see some improvements later. I'd like to see support for poe-out=force option - "enable power, I know what I'm doing" (as in most of the simple, passive PoE adapters).

Thu Dec 29, 2011 1:25 pm

The standard you're referring to is 802.3af, and that's not what the RB750UP implements. Simple "passive PoE" doesn't define any signature detection

Yes! Just because we don't fully comply with the 802.3af standard doesn't mean we can't use the same detection method for the RB750UP "auto" detection. JanisK is correct on this one.

janisk · Thu Dec 29, 2011 1:52 pm

The standard you're referring to is 802.3af, and that's not what the RB750UP implements. Simple "passive PoE" doesn't define any signature detection, so I'd expect any device that doesn't draw too much power to work. As I can see, I'm not the only one with such troubles (the mysterious Bullet2 that won't power up, even though two Bullet5s and one NanoBridgeM5 work fine).

I hope Mikrotik has made the MCU that controls PoE upgradeable in the field (the ATTINY461 chip itself does support self-programming, if supported by a properly written bootloader), so we will see some improvements later. I'd like to see support for poe-out=force option - "enable power, I know what I'm doing" (as in most of the simple, passive PoE adapters).

your magic devices just do not have the resistance required, so it will not be powered up. And where did you read that it is passive poe

Also, it has overload protection and short protection. It is not a simple hack.

Also, i have checked a lot of 100Mbps interface routers and everything worked fine. As well as attempted to burn ports on RB1000 just to be sure that our customers does not damage their equipment.

Edit: so you think that "burn" or "kill" option would be useful?

oh and this is how it works:
http://wiki.mikrotik.com/wiki/Manual:In ... et#PoE_out

marekm · Thu Dec 29, 2011 2:21 pm

your magic devices just do not have the resistance required, so it will not be powered up. And where did you read that it is passive poe Also, it has overload protection and short protection. It is not a simple hack.

Also, i have checked a lot of 100Mbps interface routers and everything worked fine. As well as attempted to burn ports on RB1000 just to be sure that our customers does not damage their equipment.

Edit: so you think that "burn" or "kill" option would be useful?

Well, it's "burn" or "kill" only if the wrong device is connected to that port. I had such an accident - wrong side of UBNT PoE connected to my good old IBM T41 laptop, it was gigabit and now it's only 100Mbps... (Still auto-negotiates gigabit but then doesn't work, have to force lower speed on at least one end.) So I'm more careful now, use patch cords of different color (orange) where PoE is used, etc.
I just want UBNT radios to work powered from the RB750UP, that's all. It doesn't have to work with "auto", just with "on". The strange thing is, some of the radios work fine with "auto", and some don't even with "on".
If your PoE implementation has specific requirements, please document them clearly. Mikrotik has been using passive PoE for a long time (just like UBNT), so I was hoping to be either that or proper 802.3af standard, it turns out to be something in between.

Edit:

on - similar to auto setting just upper bound of detection range is removed.

would it be possible to change the lower bound from 19k to something like 1k ohm? Many devices that don't support PoE have 150 ohms (two resistors 75 ohms each in series) between the unused pairs, so called "Bob Smith termination", so it should still be reliably detected.

janisk · Thu Dec 29, 2011 3:53 pm

please measure resistance between the spare parts on devices that does not work.

jandafields · Thu Dec 29, 2011 3:59 pm

If the Mikrotik is shutting the PoE off to protect itself due to incorrect resistance... then why does it work fine when you plug that device in AFTER the Mikrotik is booted? If it is the "wrong resistance", then it should never work... and should shut off the PoE as soon as you plug it in.

How is the Mikrotik protecting itself from damage if it still powers this device if you plug it in after booting?

Because of that, the resistance theory doesn't make much sense.

wispvt · Thu Dec 29, 2011 6:20 pm

I measured the resistance across the POE wires of the Motorola that doesn't work, its 2.5K - 3K Ohms, the units that are working fine are 2-3M Ohms. These aren't even close to the resistance someone was talking about earlier.

janisk · Mon Jan 02, 2012 9:18 am

resistance measured when device is off may be different from what it is when it is turned on. Devices with less resistance will generally have lower values displayed when measuring.

And board is not protecting itself, it protects device that is connected. Also if you pay attention to what is written in manual then resistance measurement is only done while port is not turned on. When PoE is turned on the port - short and overload is measured, this is why when you set ON and then plug in the device port is not turned off.

So, only self protection is turn on when port is on. (that is short and overload)

wispvt · Tue Jan 03, 2012 4:23 pm

But we still need a way to make this work for all devices, other people are having the same issue, the port won't turn on when equipment is connected, but once it is on it will power the equipment just fine. So maybe there needs to be an option to turn the checks off on a port by port basis for problem equipment so that way most ports can still maintain the built in protection but give us an option to still hookup all out equipment to and use the poe ports which is the reason any of us are buying this equipment to begin with.

complete2006 · Tue Jan 03, 2012 8:18 pm

I agree. The board should reduce the cabeling in our setup and it should give us the ability to do a power reset. I dont want to have some resistance checks to decide if port should be powered. I want a protection against overload and nothing else. This is no consumer product where the customer have to be protected from himselfs.

By the way: is the 500mA a hardware limit? If not please raise the limit to 750mA. With that we are able to use our existing 12V installations (<5m cable length and one 12V block backup)

janisk · Wed Jan 04, 2012 9:35 am

we are working on possible solutions to turn on as much as possible devices. Most probably it will be additional setting added to enable unsafe mode. As soon as we receive the device that does not work properly (AFAIK it is or soon will be on route)

Beone · Wed Jan 04, 2012 11:11 am

Are the ports POE on/off controllable through Mikrotik command terminal?

I'd like to know that too!
Is it possible to enable/disable PoE on each individual port?

thx

janisk · Wed Jan 04, 2012 12:36 pm

yes, it is described in manual (ethernet section)

but some highlights:
each port is controlled separately, so each can have its settings set.
can be configured through CLI, winbox and webfig (so everywhere)

there is one exception - if short is detected, then power is cut on all ports. It is done so to ensure that on short (that can damage the board) power down is done in fastest possible time.

wispvt · Wed Jan 04, 2012 3:05 pm

we are working on possible solutions to turn on as much as possible devices. Most probably it will be additional setting added to enable unsafe mode. As soon as we receive the device that does not work properly (AFAIK it is or soon will be on route)

What did you mean by as soon as you receive the device that does not work properly. At least for me in my post it was a Motorola Canopy unit. Are you ordering one of those up to test with or are you waiting on one of us to send you something.

janisk · Wed Jan 04, 2012 3:14 pm

AFAIK it is already arranged.

Beone · Wed Jan 04, 2012 4:13 pm

yes, it is described in manual (ethernet section)

but some highlights:
each port is controlled separately, so each can have its settings set.
can be configured through CLI, winbox and webfig (so everywhere)

there is one exception - if short is detected, then power is cut on all ports. It is done so to ensure that on short (that can damage the board) power down is done in fastest possible time.

thx m8, didn't see it.

jabbatron · Fri Jan 06, 2012 3:56 am

I have just installed 4 rb750up's, 3 on mains power and one on solar. I want to use the built in voltage monitoring for the solar site but i've noticed that what the rb is measuring the voltage incorrectly. When the input is at 13.3v the mikrotik is actually reporting 12.4v. Is there a way that this can be corrected? The 3 other 750's are all reporting 22v for the 24v power supply...

Thanks
Damien

janisk · Fri Jan 06, 2012 8:55 am

over PoE or Jack. If PoE, then that is ok, voltage drop is how much drops on protection.

jabbatron · Fri Jan 06, 2012 12:32 pm

I'm using the DC Jack...

janisk · Mon Jan 09, 2012 11:59 am

as far as i have tested RB750UP has very precise voltage monitor. Have you some devices powered by it?

jabbatron · Tue Jan 10, 2012 2:52 am

I'm using it on a solar site. Its powered from a 12v 12ah sealed lead acid battery connected to a 38w solar panel. When i put the multimeter across the battery on a sunny day it reads 13.3v while the mikrotik only reports 12.2...

I have 1x ubiquiti pico station connected to a POE port.

remit · Tue Jan 10, 2012 4:48 am

as far as i have tested RB750UP has very precise voltage monitor. Have you some devices powered by it?

I am seeing exactly the same results. Roughly .9 volts below the actual voltage on the DC jack. I have the same problem with RB450Gs (as do many others, as listed in a few threads).

janisk · Wed Jan 25, 2012 4:03 pm

try with 5.12 there has been some adjustments to compensate for drop on protection chain. As i said previously, measurement is precise and can be relied on.

jabbatron · Tue Jan 31, 2012 8:53 am

Its gone from reporting 11.5v to 12.1 with the latest update (5.12). Next time I'm at that site ill put a multimeter across the battery and see how accurate it is

.

Thanks!

Damien

jabbatron · Sun Feb 05, 2012 12:35 am

I checked the solar site with a multimeter and when the multimeter reported 12.6v the rb reports 12.3v. Good enough for me!

.

Thanks

Damien

jabbatron · Mon Feb 27, 2012 11:26 pm

I upgraded from 5.12 to 5.14 and the rb750 is reporting the wrong voltages again, i've downgraded to 5.12 again. Is there a way i can add the correction myself?

Hello, The problem you had posted in this thread is really interesting but i am here wondering for information about solar panel. Please can anyone suggest me which is best brand of solar panel and what is the installation cost.

I bought a AU$100 40w ebay solar panel, a ebay mppt charge controller and a 12ah 12v battery. It runs a rb750up, a ubiquity pico station and air cam and a data probe ipio-8 relay board no problems.

jabbatron · Tue Feb 28, 2012 12:50 pm

not a problem, feel free to pm me if you have any more questions

. We are using the solar site to control the stock water for cattle wirelessly

.

TIKTAK · Wed Mar 21, 2012 12:50 am

Has anyone had issues with powering UBNT rockets via the 750UP.?
is there a write up somewhere on how to do the cabling?
We upgraded the firmware on the 750UP to 4.17 Level 4 and we can interact fine with the 750UP but the Rocket resets continuously.

Sounds like a cabling issue but can't find a cabling diagram for Mikrotik RB750UP on one end and UBNT Rocket M on the other.

appreciate all input.

regards,

TIKTAK

wispvt · Thu Mar 22, 2012 2:23 am

We have them working. The RB750UP has issues with the POE. I have found it works better if you set the POE to on and not use the auto setting as it is more flaky. Cabling is just a straight through cable. Hopefully they will make some changes to the firmware to allow more user adjustment. But they are a great unit and also allow you to remote reboot your site if there is an issue without any extra equipment.

RK · Thu Mar 22, 2012 7:50 am

Has anyone had issues with powering UBNT rockets via the 750UP.?
is there a write up somewhere on how to do the cabling?
We upgraded the firmware on the 750UP to 4.17 Level 4 and we can interact fine with the 750UP but the Rocket resets continuously.

Sounds like a cabling issue but can't find a cabling diagram for Mikrotik RB750UP on one end and UBNT Rocket M on the other.

Yes, we have one test installation with a RB750UP and a UBNT RM5. The the rocket reboots every few hours in both "auto" and "on" mode. We verified a stable supply of 18V to the RB750UP.

Raf · Thu Mar 22, 2012 9:34 am

Has anyone had issues with powering UBNT rockets via the 750UP.?

We've got same issue. Rockets reboot if only some traffic comes on radio interface. Specification says that Rocket takes no more than 6-8W which should be doable by 750UP.

Edit: Hasn't Rocket got special circuit for managing remote device reset from DC power supply? Maybe this collides with RB750UP/Omnitik UPA chip?

wispvt · Thu Mar 22, 2012 3:11 pm

We use 24V to supply the RB750UP which could be the difference. Remember as voltage drops, your current draw will increase which could be triggering the protection circuit on the RB750UP. Try a 24V power supply, and make sure it can handle the load easily from all the equipment it is supplying.

Raf · Thu Mar 22, 2012 3:23 pm

Myth busted.
We've tried stock 24V DC power supply which should be good. MikroTik declares 500mA per port which gives 12W per port (0,5*24). We're using short patchcords (2-3 meters) to power three Rockets. The cable is AWG 24. Don't tell me that voltage drop on 3 meters is so high. Not possbile

Such configuration doesn't working properly on RB 750UP/Omnitik UPA. Rockets reboot on any load given to them or randomly by few hours.

What could be the issue? Could they have peak power draw when load is given to radio module?

Thu Mar 22, 2012 3:36 pm

Raf, if possible, measure the resistance of the port, and the expected polarity. Read more here:
http://wiki.mikrotik.com/wiki/Manual:PoE-Out

So try the "forced" mode. You might need the latest RouterOS v5.15rc1 also

wispvt · Thu Mar 22, 2012 4:09 pm

When I said voltage drop I didn't mean across your cable I meant the supply voltage. If your supply voltage is 18V vs 24 volts, the equipment will normally draw more current at 18volts vs 24 volts. Which is why I said to try the higher voltage as these units are a little finicky with their current sense protection.

Raf · Thu Mar 22, 2012 4:26 pm

@normis: Wiki was first place where I've looked at

Could You give me a link to ROS 5.15rc1 (e-mail or PM).

Edit: OK. Got 5.15rc1. I'll try to test it in the same location where problem showed up.

clannet · Fri Mar 23, 2012 12:37 pm

Hi,

Is it possible to obtain a copy of 5.15rc1? We are having the same issue with Rockets and the RB750UP and would like to test out the new release.

Kind regards,

Dean Welbourn
CLANNET

Łukasz · Fri Mar 23, 2012 1:27 pm

http://www.mikrotik.com/download/share/ ... .15rc1.npk

alexjhart · Sat Mar 24, 2012 7:14 am

We are having issues with devices connecting to a 750UP as well. We have a site that has two Nanobridges attached to it. The logs show that the interfaces go down. We end up cycling the POE power on-off-on (or forced on in the newer firmware). We have tried to 750UP devices thinking we may have just had a faulty unit. I have tried the 5.6 that shipped on it, 5.12 and 5.13. All seem to have the same problem. I also have a 750UP running 5.6 with only 1 nanobridge powered off of it and it seems to be running better. I am going to try the 5.15rc1 firmware as mentioned to see if we have any improvements. Has anyone else had better luck with it? What is it supposed to fix?

RK · Sun Mar 25, 2012 7:46 am

@normis: Wiki was first place where I've looked at Could You give me a link to ROS 5.15rc1 (e-mail or PM).

Edit: OK. Got 5.15rc1. I'll try to test it in the same location where problem showed up.

Any updates?

alexjhart · Sun Mar 25, 2012 8:40 am

The update did not work for me on my problem unit.

RK · Mon Mar 26, 2012 10:07 am

We are having issues with devices connecting to a 750UP as well. We have a site that has two Nanobridges attached to it. The logs show that the interfaces go down. We end up cycling the POE power on-off-on (or forced on in the newer firmware). We have tried to 750UP devices thinking we may have just had a faulty unit. I have tried the 5.6 that shipped on it, 5.12 and 5.13. All seem to have the same problem. I also have a 750UP running 5.6 with only 1 nanobridge powered off of it and it seems to be running better. I am going to try the 5.15rc1 firmware as mentioned to see if we have any improvements. Has anyone else had better luck with it? What is it supposed to fix?

Same problem here. Upgrade to 5.15rc1 did not fix it.

mar/25 12:33:57 interface,info ether3-sector link down
mar/25 12:34:05 interface,info ether3-sector link up (speed 100M, full duplex)
mar/25 12:34:22 interface,info ether3-sector link down
mar/25 12:34:23 interface,info ether3-sector link up (speed 100M, full duplex)
mar/25 12:34:29 dhcp,info dhcp2 deassigned 10.62.85.254 from 00:27:22:16:D4:E9
mar/25 12:34:29 dhcp,info dhcp2 assigned 10.62.85.254 to 00:27:22:16:D4:E9
mar/25 21:34:10 interface,info ether3-sector link down
mar/25 21:34:17 interface,info ether3-sector link up (speed 100M, full duplex)
mar/25 21:34:35 interface,info ether3-sector link down
mar/25 21:34:37 interface,info ether3-sector link up (speed 100M, full duplex)
mar/25 21:34:42 dhcp,info dhcp2 deassigned 10.62.85.254 from 00:27:22:16:D4:E9
mar/25 21:34:42 dhcp,info dhcp2 assigned 10.62.85.254 to 00:27:22:16:D4:E9
01:24:10 interface,info ether3-sector link down
01:24:18 interface,info ether3-sector link up (speed 100M, full duplex)
01:24:35 interface,info ether3-sector link down
01:24:36 interface,info ether3-sector link up (speed 100M, full duplex)
01:24:43 dhcp,info dhcp2 deassigned 10.62.85.254 from 00:27:22:16:D4:E9
01:24:43 dhcp,info dhcp2 assigned 10.62.85.254 to 00:27:22:16:D4:E9

janisk · Mon Mar 26, 2012 10:46 am

Does any of you have this setup available (test-bed maybe?) Then do the following:
lock your AP capable device to 6MBps rate (for 802.11a/g) and send traffic so that device has to transmit. See if RB750UP still can power the device. Also, if by any change, you have programmable power supply, you could measure the load on the supply (power RB750UP board with it)

In my tests with provided 2.5A @24V at full load (all channals at max) voltage was around 21V at PoE-out port. Still 8W device should be handled easily.

weird thing is that power goes out twice in the row for the board. as you can see from the logs - it goes down, then up and then down again.

also, those who had problems to power the board that did not turn on on auto or on modes - changed forced-on will be the solution.

RK · Tue Mar 27, 2012 7:25 am

weird thing is that power goes out twice in the row for the board. as you can see from the logs - it goes down, then up and then down again.

I can't assist with the remainder of your test request, hopefully somebody else will, as I have these deployed in the field.
But I can provide this useful bit of info:power only goes out once, not twice.

mar/25 21:34:10 interface,info ether3-sector link down <---- device reboots
mar/25 21:34:17 interface,info ether3-sector link up (speed 100M, full duplex) <--- device starts booting and eth0 on device goes up
mar/25 21:34:35 interface,info ether3-sector link down <--- normal behavior of device when it finishes booting
mar/25 21:34:37 interface,info ether3-sector link up (speed 100M, full duplex) <--- normal behavior of device when it finishes booting
mar/25 21:34:42 dhcp,info dhcp2 deassigned 10.62.85.254 from 00:27:22:16:D4:E9 <--- device starts DHCP client

I have been able to reproduce this on two RB750UP devices with exactly the same model of components but different actual components.

jabbatron · Tue Mar 27, 2012 4:11 pm

I upgraded from 5.12 to 5.14 and the rb750 is reporting the wrong voltages again, i've downgraded to 5.12 again. Is there a way i can add the correction myself?

wispvt · Wed Mar 28, 2012 6:33 pm

We tested the new firmware as well and it does not resolve the issue of not being able to power Motorola Canopy from these units. Tried both settings, "forced-on" and "auto" to no avail. If the new firmware was supposed to fix these problems with the POE than it is still broken.

janisk · Thu Mar 29, 2012 8:09 am

you should really head here:
http://wiki.mikrotik.com/wiki/Manual:PoE-Out#Wiring

and read at least section about wiring. So you know how to wire your ethernet cable so it is able to power the Motorolla Canopy devices as these are using reverse wiring.

wispvt · Thu Mar 29, 2012 3:26 pm

They were wired right. Update though, the new firmware seems to be much better and is powering the Motorola Canopy just fine. My techs issue was a an issue the the Canopy and not the Mikrotik. So far we have half a dozen deployed over the last couple of months and they work great. No issues, love the ping watchdog and voltage monitoring. It has made our site installations cheaper with less equipment to buy, and much cleaner as there is lots lets cabling. Keep up the good work Mikrotik.

RK · Fri Apr 06, 2012 10:29 pm

janisk, any updates for us with the reboot issue?

Inssomniak · Wed Apr 11, 2012 1:16 am

Anyone using one at the top of a tower site? We tried one with 150 feet of cable and it didn't work well for powering devices (kept resetting)

But at the bottom of towers with no cat5 POE it seems to work good

We saw the voltage monitor had 21 volts. 4 devices. Rocket m2, 2 nano bridges, and a rb433. The 433 seemed fine but the ubiquiti stuff would reset or simply shut off and toggling the Poe setting would bring it back for a while.

Should I not try this again?

The Poe setting were forced on. Is there a way to disable the current limiter?

CoxWireless · Wed Apr 11, 2012 4:12 am

I've ran into the same problem and have it duplicated in the lab.
If the RB750 is powered via a long PoE cable (24v 2A), it can not power ubnt equipment without tripping the over current sensor. I've checked the voltage output at each port (21V using a 24v supply) and ran a current draw check (.14 A) per port. After a few cycles of the port, the MT disables the port until the RB750UP is rebooted.

i'm trying to power a NB5M on port 5 and a NS2M on port 4.

Another site is doing the same thing, there i'm trying to power a LOCO900 and NS2M

I'm contemplating an attempt to solder in a inline capacitor or removing the overload protection circuit, unless I can find an answer quick....

taduikis · Wed Apr 11, 2012 4:22 am

I have also noticed that rb750 and rb250 doesn't like long ethernet cable runs (no poe). I'm talking here around 80-90 meters. As every other device in my possesion worked without problems in few particular cases rb's dropped lots of packets..

Inssomniak · Wed Apr 11, 2012 5:36 am

I've ran into the same problem and have it duplicated in the lab.
If the RB750 is powered via a long PoE cable (24v 2A), it can not power ubnt equipment without tripping the over current sensor. I've checked the voltage output at each port (21V using a 24v supply) and ran a current draw check (.14 A) per port. After a few cycles of the port, the MT disables the port until the RB750UP is rebooted.

i'm trying to power a NB5M on port 5 and a NS2M on port 4.

Another site is doing the same thing, there i'm trying to power a LOCO900 and NS2M

I'm contemplating an attempt to solder in a inline capacitor or removing the overload protection circuit, unless I can find an answer quick....

Yup identical symptoms.

It sucks I had real high hopes for using them at the top of towers to simplify wiring.
Do you know how to disable the sensor?

CoxWireless · Wed Apr 11, 2012 6:27 am

I've been browsing the forum. From what I can collect by MT support, the overload protection is "monitored" in software, and if it senses an overload condition, it shuts off the port...

If this is correct, a simple firmware change could fix our woes....

janisk · Wed Apr 11, 2012 11:00 am

we are working on new FW that would add useful features that are currently missing. One of them is reworked power management.

janisk · Wed Apr 11, 2012 11:41 am

if these are wireless routers connected you can check weather they are using lower data rates, if they are, try to upgrade the link with better antennas, so link would stay in higher data-rates while using less power. Or remove lower data-rates altogether, but that could cause link instability.

It looks like device is reaching power limit.

CoxWireless · Wed Apr 11, 2012 4:16 pm

I'm currently running 5.15RC1
Are you referring to something else? If so, i'd love to test it as I have duplicated my problem in the lab and currently seeking work-arounds.

janisk · Thu Apr 12, 2012 10:24 am

yes, i am referring to control chip soldered on the board. And that is what brings some complexity on board due to some restrictions it has.

luhiwu · Thu Apr 12, 2012 10:50 pm

Same issue here, 5.12 monitoring is OK but 5.14 reports about 1 to 1.5V less.

scampbell · Thu Apr 12, 2012 11:11 pm

Its gone from reporting 11.5v to 12.1 with the latest update (5.12). Next time I'm at that site ill put a multimeter across the battery and see how accurate it is .

Thanks!

Damien

I notice you are comparing the voltage at the battery terminals against the Mikrotik's internal measurement.

Notwithstanding the noted change between RoS v5.12 and v5.14 I would recommend testing at the DC Jack of the Routerboard as anything between the battery and the Routerboard can also cause voltage drop.

A silicon diode for example will always give a drop of 0.6v, cables and connectors can also add to voltage drop etc.

jabbatron · Fri Apr 13, 2012 12:32 am

The DC cable is only about 4" long, i can't see the drop over such a small distance making any difference. They did fix it in the other firmware, measured voltage at battery and MT were about .4 or .5 apart. Much more like it... I could take a measurement of the voltage at the poe ports and see what they put out i guess...

scampbell · Fri Apr 13, 2012 1:29 am

I guess in this case 4" is better than 10"

You are right that should not make any significant difference - as long as the wire gauge is reasonable and connectors are making clean contact.

I suspect the RB probably has a diode on the input circuit hence the voltage difference and in RoS 5.12 they allowed for that but forgot to do it in RoS 5.14.

It seems they take 3 steps forward then 2 back when they release a new version.......

Any idea what the current draw on your setup is ?

stmx38 · Fri Apr 13, 2012 6:05 pm

We have trouble to power 4 RB751 using 40-60m of cat5 on our RB750UP.
With short patchcord it work fine but with long cable and patch panel we can't do this.
Any cable length limitation ?

[admin@WAPSw1] > system health print 
          voltage: 22.2V
  cpu-temperature: 43C

                       Patch Panel --> 60m cat5 --> RB750UP -- PoE Port
                     /
DC --> PoE Injector 
                     \  
                       Switch

RB750 can start, but on eth2/3/4/5 RB751 can't start

Thanks.

janisbvp · Fri Apr 13, 2012 7:16 pm

You can probably raise the voltage on input to some 25-27 volts if you can.
That should overcome voltage drop in cable. Known fact is that routerboards have a little current spike on connecting power and the they consume next to nothing.
Bad thing is that 25-27 volt supplies are not a common thing in all shops...

taduikis · Fri Apr 13, 2012 11:58 pm

Check out meanwell psu's. They are what you need. Options with battery backup also exist

CoxWireless · Sat Apr 14, 2012 4:37 am

This is already being discussed in another thread, try searching.
Another PSU wont help, even 30v will do the same thing.....

CoxWireless · Sat Apr 14, 2012 4:43 am

Can you identify the silk screen location for this chip so that I can manually disable it?

stmx38 · Sat Apr 14, 2012 8:38 pm

Thank you, guys.
RB750up at top of tower?

fcucci · Sun Apr 15, 2012 12:11 am

We have the same problem, when a solution?

jabbatron · Mon Apr 16, 2012 8:07 am

i have a ip relay board, MT and bunt pico on the site and it all draws less than .8a

janisk · Mon Apr 16, 2012 1:28 pm

Can you identify the silk screen location for this chip so that I can manually disable it?

what you mean by - manually disable it?

take note that board health is taken from the same chip. It is near ethernet port at power chain marked with 4U.

maurymw1 · Mon Apr 16, 2012 3:59 pm

I have using one RRF cable and working good and feature:
Amplitude and phase stable with flexure
• Reliable and repeatable measurements
• Durable, ruggedized and crush-resistant
• Longer flex life

scampbell · Tue Apr 17, 2012 2:25 am

At that current the voltage drop over the wires should be negligable, perhaps 0.1v at most.

I have an RB750UP running RoS 5.14 FW 2.38. The /system health command gives a voltage of 22.7v.

If I take a voltage reading directly off the DC Jack it reads 24.12v

If I take a voltage reading off the PoE Output on the Ether3 port it reads 23.28v (This port powers an Omnitik).

So we have :-

1. 1.4V differential from the DC Jack to the CPU

2. 0.84V differential from the DC Jack to the PoE Jack

3. 0.6V differential from the CPU to the PoE Jack

We are not alone in this voltage discussion - check out http://forum.mikrotik.com/viewtopic.php ... &start=100

I've also noticed I need to set POE to "On" rather than Auto for my Omnitik as it keeps power cycling without this setting.....

janisbvp · Thu Apr 19, 2012 4:11 pm

From what I have found out, most of these problems come from being economical on psu circuits of routerboards.
My current setup:

                                                    ====>RB711-5hn-m (uplink)
                                                 /
PSU 24v/3A >===92m cat5e outdoor cable===>RB750UP - =====>RB711-5ufl (sector)

Just could not get it to work with 24v psu.
With 36v psu, RB750UP did not start - protection.
I took the measurement of cable resistance (2+2 wires) 10.2 Ohm - not too bad, but not too happy either. Since the load is about 1A, we should get up to 10.2 volts loss, which is no that bad, if not for saved capacitors in routerboards and horrible current ripple because of that. Plus, rated consumption for routerboard is 0.2A at 24v, which is 0.5A at 12v.
So, I just made a small circuit (a diode and a pair of 35v/4700uF capacitors) and attached it before RB750UP - problem solved - ripple gone and things work fine.

      +  ----|>|----------------->  +
                   |  +       | +
from psu           ==         ==       to router
                   |          |
      -  ------------------------->  +

Afer this circuit we get:
[admin@MikroTik] > system health print
voltage: 18.7V
cpu-temperature: 44C
(at the time of measurement it was around 8C outside, so cpu temp is rather alarming, if it is correct...)

janisk · Fri Apr 20, 2012 9:14 am

if you are powering other devices - that is the temperature.

stmx38 · Fri Apr 20, 2012 10:44 am

janisbvp
Do you mean that this issue can be resolved by using another PSU for 750UP ?

janisk · Fri Apr 20, 2012 12:16 pm

no, that that is the working temperature if you are powering other devices. Since there is certain voltage drop and that drop generated the heat. That is why there is that limitation on how much power can be delivered over PoE-Out ports.

janisbvp · Sat Apr 21, 2012 11:26 am

Not exactly.
The heating and power supply is not the exact problems - power supply of rb750up looks solind and rather heavy, so there should be no problems. Tested it with a resistor @ 2amps and it works perfect with almost no ripple.
The problem on tower is that you have long cable runs with a rather high resistance plus some inductance as well. When these routerboards start up, they induce some current spikes. Also, since they feature stabilising power supply rail (they can power from 10 to 30 volts) that power supply rail generates high frequency noise in power cable (frequency depends on routerboard) and that noise disrupts normal work of other routerboards, connected to the same power cable.
What I did was simply put capacitors at the top of tower, right before rb750up, to filter that noise. Also, it made power consumption more linear. Just like soma maniacs, that put a couple 1000W amps in car and kill electronics of car, because the voltage starts to jump in the rhytm of their music. What they do is put a large capacitor before amps. We do the same, but with higher frequencies, we need smaller caps.
What I also suggest - a simple LC filtering circuit in RB750UP, or, if there is one, an upgrade. rb750up would be a great thing with that.
Also, why rb750up and no rb250gs-up?
I just hope noone will say TMLDR...

janisbvp · Sat Apr 21, 2012 11:29 am

if you are powering other devices - that is the temperature.

Would this mean, that RB750UP is not meant for what it is meant - powering 2,3 or 4 routerboards in tower? What is the reason to pay the difference for 'UP'?

Mon Apr 23, 2012 10:10 am

if you are powering other devices - that is the temperature.
Would this mean, that RB750UP is not meant for what it is meant - powering 2,3 or 4 routerboards in tower? What is the reason to pay the difference for 'UP'?

RB750UP doesn't really have an outdoor enclosure - you should be using it inside a tough enclosure, together with some other devices. Also consider the OmniTIK UPA, which is an outdoor wireless device.

janisbvp · Mon Apr 23, 2012 12:03 pm

RB750UP doesn't really have an outdoor enclosure - you should be using it inside a tough enclosure, together with some other devices. Also consider the OmniTIK UPA, which is an outdoor wireless device.

Well, no one has put it outdoors - we do have a good and spacy outdoor enclosure with good heat dissipation - aluminium of course and in shade.
The thing is - I am more than sure, it is a problem of temperature sensor - should take quite a power to heat it up to 40C at 8C ambient temps...
But well, I am not about whining - just trying to make a good idea work. And I got it to work.

Mon Apr 23, 2012 12:10 pm

I am glad you have a working setup now! Let us know if you need more help.

mmc1800 · Tue Apr 24, 2012 12:00 am

I am having the same issues as reported here (UBNT devices rebooting and hanging occasionally needing to be turned to POE off and then ON before they will come back online). I was under the impression that the same issues would occur on a omnitikUP that are happening with the 750UP. I would be happy to replace the 750UP which is inside a roomy die cast enclosure (and this issue happens regardless of the ambient temperature) with a OmnitikUP if that would solve this problem. Is that likely to actually solve the problem of the UBNT devices getting turned off and rebooting? We are still running 5.15rc1 as I saw absolutely nothing in the 5.15 release notes about these power issues with the 750UP. Are the power fixes included in the actual 5.15 release? The RC1 did actually make it better, though it is still far from working as expected.

I just ordered some 4:1 DC power splitter cables and was planning on just putting some POE inserters and bypass the 750UP for the purposes of the power which gives up the ability to remote power cycle etc. (and basically turns it back into a non POE router, which was working for us before this fiasco with the 750UP). Running the OmnitikUP as a POE router would be fine for us if there is actually some difference between the way that handles the power issues compared to the 750UP. Please advise, as I have enough angry customers off of this AP as it is without going through another round of failures. Can anyone verify the OmnitikUP working in a situation where the 750UP was fail?

janisbvp · Tue Apr 24, 2012 8:57 am

-------stripped--------
I just ordered some 4:1 DC power splitter cables and was planning on just putting some POE inserters and bypass the 750UP for the purposes of the power which gives up the ability to remote power cycle etc. (and basically turns it back into a non POE router, which was working for us before this fiasco with the 750UP). Running the OmnitikUP as a POE router would be fine for us if there is actually some difference between the way that handles the power issues compared to the 750UP. Please advise, as I have enough angry customers off of this AP as it is without going through another round of failures. Can anyone verify the OmnitikUP working in a situation where the 750UP was fail?

Well, you did not give a cable length to the rb750up...
Even simple splitter cables will not protect you from this tiny and annouying problem.
Othervise I would suggest trying capacitor+diode idea - it will cost you a couple $, but will probably do the magic, if the cable is long (30, 50, more meters...)
Since my first posts, I have tested with oscilloscope and confirmed this little problem - psu rail noise from one routerboard, disrupts normal work of other rb psu rail... filter the noise and get rid of problem.
I doubt, that Omnitik has some magical advantages in power line circuit, as I did not need omni solution just yet and haven't tested it...

JoeSemler · Tue Apr 24, 2012 1:47 pm

Hi, Im playing around with your great RB750UP using OpenWRT.
I´ve identified GPIOs 12-17 to control the LEDs, but was not successful with the control of PoE-Power. Some Infos avaliable here in the forum?
Tnx Joe

mmc1800 · Tue Apr 24, 2012 4:01 pm

We are not really interested in making modifications to the equipment. If it doesn't work we just wont use it.

This particular location has DC cable (not POE) making a 500 foot run before it hits the 750UP. The power at the 750UP is fine. We bypassed the 750UP during one stage of trying to figure out what was going on with this and the radios did not power cycle as they do when they are plugged into it. I really wanted remote power cycle capacity at this site and I dont really know of any other workable options for us (it is not quite a tower climb to get to it, but it is a pain). We are not using any other Mikrotik equipment, the rest of the stuff is all UBNT at that site. What you are saying makes sense but if I understand correctly it would just cause trouble with other Mikrotik stuff which is not the problem we are seeing.

04:37:23 interface,info ether3-m5 link down 
04:37:26 interface,info ether3-m5 link up (speed 100M, full duplex) 
04:37:43 interface,info ether3-m5 link down 
04:37:45 interface,info ether3-m5 link up (speed 100M, full duplex) 
04:37:48 interface,info ether3-m5 link down 
04:37:50 interface,info ether3-m5 link up (speed 100M, full duplex)

I am trying to get rid of these outages which happen every few hours, and about once a day the interface stays down and needs to be turned to POE out off then on to bring the radio back. Occasionally it is a different radio that does the same thing (it has happened on all 3 UBNT radios plugged into this 750up). The OP on this was reporting UBNT equipment resetting and others confirmed. I have the same issues with this 750up install.

mmc1800 · Tue Apr 24, 2012 4:06 pm

Still interested in what the basis of using an OmnitikUP rather than a 750UP might have to do with any of this?

janisbvp · Tue Apr 24, 2012 8:56 pm

Still interested in what the basis of using an OmnitikUP rather than a 750UP might have to do with any of this?

I think none, but MT staff will correct me if I am wrong.
Think about this thing though - power consumption of routerboard "example1" is 0.2A at 24Volts, so at 12Volts it could reach 0.5A or a bit more. So, if you have steep voltage drop up in the tower, you are looking at higher currents and probably, tripped safety in rb750up.
Your goal then is - raise and stabilise the voltage up there and be happy. Also - do check the consumption of ubnt's, although, probably no different from mt products.
At the moment, my tower has worked for 3 days with no glitches or reboots. RB750UP is a very good start for such devices at a bargain price.

mmc1800 · Tue Apr 24, 2012 9:03 pm

I have no voltage drop. The voltage is constant at over 20V. I took a battery in an enclosure running 24V directly to the device over a 3 foot jumper cable and it was still doing the same thing. This has nothing to do with the power supply, the device is not working correctly to power these devices (as reported by many in this thread and elsewhere).

RB750UP is not really an outdoor device, you should be using it inside a tough enclosure, together with some other devices, where temperature is somewhat stable. Normally you would use in some attic and then run cables to the roof. For true outdoor power, you need the OmniTIK UPA, which is an outdoor device.

I was referring to the comment of Mikrotik staff that somehow the OmnitikUP would make some difference.

Wed Apr 25, 2012 8:21 am

There is a misunderstanding! I did not imply that using OmniTIK would somehow make a difference in power output. I was just saying it would be physically easier to install/mount. They have the same power output functionality.

mmc1800 · Wed Apr 25, 2012 8:17 pm

I have had some contact with Mikrotik support and followed a few threads here, and I think it should be stated very clearly that the 750UP will not reliably work to power NSM5s and Rockets in many situations that the specifications indicate it should. The specifications say it will provide 500ma at whatever voltage you are feeding the 750UP on each port, but that has not been our experience with these in several situations.

To say they are picky is being conservative, there are many situations where they will not work even when the situations are well within the specifications. I do have a couple of sites where rockets are being powered and they seem to be solid, but these are very short cable runs (under 20 feet) with large 24V power supplies and a large gap between what is actually being used and the specs. The 8W the UBNT radios are pulling and the 12W the specifications say we should be able to supply on each port.

As you get anywhere near where the actual specification power is being pulled these radios become very unstable, especially it seems where you have any kind of long cable runs. You can find various topics here detailing all the different scenarios where these routers fail to meet specifications, but just a heads up to anyone considering using these to power UBNT equipment, I would say if you don't have absolutely the best scenarios for power don't bother with a 750UP, it will be very disappointing.

I would take a good 50% off of the power specifications Mikrotik gives before you can trust them (which by the way makes the product almost completely useless to run UBNT). We have sites where we are feeding over 20V to the 750UP and it will not run UBNT radios reliably (over current protection seems to be kicking in and turning off the ports).

We are abandoning the product for these locations, and just thought it should be said clearly somewhere that though these things are supposed to work in these situations on paper, we have found that in the real world they do not. Hope this saves you some of the headaches we have had with this underwhelming product.

syadnom · Wed Apr 25, 2012 10:36 pm

Have you considered voltage drop over your cable length? With limited amps, a voltage drop of maybe 2v ( to 22v ) might not be enough AMPs to power the radios anymore. I would point out that it is 500ma MAX per port, not that it supplies 500ma, only that the port can only handle 500ma passing through.

You likely just need a better power supply.

If you could test with a 26v or 28v supply and see if that solves your issue?

Also, I suspect that the 750UP has all the ports tied together so maybe try to power 1 less device and see if it stabilizes.

mmc1800 · Thu Apr 26, 2012 12:08 am

Of course I have considered the voltage drop on the cable.

Your assumptions about the specification are not correct. It is 500ma per port not total, and the specifications allow for 500ma on each of the 4 ports (we are running 3).

Power options PoE:  8-30V DC on Ether1 (Non 802.3af). Jack: 8-30V DC
Power output Supports PoE output on ports 2-5. Max current 500mA per port

That would be a theoretical maximum of 30V at 500ma on each port (15W), so 60W. Adding the power draw of the 750UP itself, 3W, the maximum power you should ever need to send to this device would be 63W. We are of course only drawing a maximum load of 27W with 3 UBNT radios rated for 8W each and the 750 at 3W. The power supply we have is a 6amp 24V, obviously well beyond the power needs of everything there. This is verified by the fact that when we split off the DC jack that is going into the 750 and run power directly to all the exact same equipment we do not have any power issues (and we can run them all at full power usage without the voltage dropping below 19V at the farthest end). Our power supply system is working just fine, the 750UP turns the interfaces off, when it should not, period.

mmc1800 · Thu Apr 26, 2012 12:27 am

So we just finished with the bypass of the 750UP, we split off the same DC jack that was plugged into the 750UP and ran 3 POE injectors to the 3 UBNT radios and plugged the data port of the injectors into the 750UP. So everything is identical other than the 750UP is no longer providing power to the devices. We can run full speed tests across all 3 radios simultaneously without dropping the voltage below 19.9V at the 750UP, and none of the radios power cycle or show any issues. Running a speed test from the same clients the same way on any one of these radios would cause at least one radio on the 750UP to power down and occasionally need to be completely powered off and back on (through the winbox interface) to bring the port back online.

The 750UP is not working according to its specifications, do not try to run UBNT radios on these things across longer cable runs, even when the specifications say it should work, it might not. I am not saying it wont, and there are some great threads on these forums about ways to solder modifications on the board or put filters and capacitors in line that have solved various theories and incarnations of why these things don't work, but if your like me and you expect products to work according to the specifications, be warned, the 750UP does not.

FYI the cable run from the 750up to the radios in this scenario was less than 10 feet. The cable run coming into the radio is not even POE it is a DC power cable that is more than sufficient for the task, and as mentioned did not create a voltage drop below 20V even at full load.

janisk · Thu Apr 26, 2012 8:40 am

mmc1800 your math is somehow weird.

you are correct that at 30V with 500mA per port +board usage at that voltage is 63W
you are powering board with 24V psu, so if there is no voltage drop you end up with 51W maximum.

But there are additional voltage drops involved. Lets start with obvious ones - you have long lead to the board, 30 - 50 meters, as result with higher consumption on the other end you can end up with 1 V drop form your 24V budget. Next up is PoE protection that is additional drop, then there is powering chain to control the port resulting in another drop. Resulting 20V results in around 43W maximum output. And now, if you use 3 ports, you end up with 33W.

janisk · Thu Apr 26, 2012 8:47 am

Othervise I would suggest trying capacitor+diode idea - it will cost you a couple $,

Capacitor should be enough as diode is already in RB750UP input. It is all down to PSU - how much capacitance it has. If the value is low, there will be noise. If measurement is done at the moment of low peak - power is turned off for the port.

janisbvp · Thu Apr 26, 2012 9:25 am

Yep, probably right - the diode was just for reverse-polarity protection anyway.

janisbvp · Thu Apr 26, 2012 9:35 am

At the moment I am thinking of CAT6 and higher voltage (48-60v dc) anyway. As the insulation between colours in cat6 is much better, for near-100m runs it would make a great poe carrier. And the voltage converter for 48>24v would be rather easy.
Of course, nothing beats dedicated cable and full voltage up the tower, but let's not forget security issues. Even >48v is rather extreme on that matter.

janisbvp · Thu Apr 26, 2012 3:52 pm

As I said before - you should find out the 'unreliable' link and point it out.
If you would check the power consumption of the devices you can safely assume, they are not the case of problems.
As I said before - try to get rid of power fluctuations under load and you will get stable system. At least I did.

Thu Apr 26, 2012 3:56 pm

merged some topics

mmc1800 · Thu Apr 26, 2012 10:11 pm

Well if you want to mix this all into one topic I guess that is one way to make sure people are not really easily made aware these 750up do not work as they should and confuse the issues from very clear to very muddled (apologies to anyone trying to make sense out of the out of order and out of context posts now in this thread). There are some issues about not having a stable power load or supply and that can cause problems. I was pointing out a situation where none of those things are the case and the same kinds of problems are happening anyway.

At the site I discussed here the voltage does not fluctuate hardly at all. I bypassed the 750UP with a DC splitter and everything runs fine, voltage never drops below 19.9V even at full load (20.2 at no load) and there has been no issues at all since. These 750UPs just do not work like they are supposed to. If you get plenty of voltage so you have nearly twice as much power as the specifications say you need you are fine, my experience is getting anywhere near the actual rating and they fall apart. The UBNT Rockets and NSM I was powering are on a stable and non fluctuating DC line with plenty of amperage overhead and no significant voltage drop running at well within the specifications listed for the 750up and they constantly reset and rebooted until I stopped using the 750up for power.

As far as my math:

19.9V*500ma = 9.95W

9.95W > 8W

8W per port required to run UBNT Rockets and NSM should work when you provide 19.9V stable DC to the 750UP, but it does not. When you hire an electrical engineer and get a specific voltage requirement at a particular location, and purchase a product to fit in at that spot, having it turn out to not be enough voltage is a problem.

The power kick out should not be kicking in on these ports unless the voltage hits 16V. We never even get close to that.

Continuing to blame mysterious voltage drops and power problems that are not any problem for any other device other than the 750UP is one option I guess, the other is to realize the device just doesn't do what it says it will do.

So far in situations where the specifications say the 750UP would provide 12W per port it supports 8W stable, when you get anywhere near the actual load it randomly kicks in and turns off the ports. After my actual experience with these things, I adjusted my internal rating on these ports to 350ma instead of 500ma and that seems to keep me from having problems. That means if I want to run UBNT rockets and NS I need to be at 24V solid and nothing less, any voltage drop for cable length at all makes the whole thing unstable. That means in order to use these things to power 8W rated radios I need to make sure my voltage sits between 30V and 24V all the time, as over 30V is past the input range, and under 24V is a problem. When you are trying to run long DC cable runs that have fluctuations in voltage based on load, it is not always easy to keep inside this range, which requires more equipment and work which defeats the whole purpose of this product.

Short cable runs and plenty of power, no problem. Somewhere power is actually an issue at all, problems. Since this device is obviously something people will try to use to help extend power in places it is not so easy (like at the top of towers), that is a problem. Wonder how many people are going to waste time having to figure this out for themselves after reading the specifications and assuming they can use this device in situations and then finding out the hard way it doesn't work.

alexjhart · Fri Apr 27, 2012 4:58 am

I have spent hours upon hours trying to figure out the problems with these. Turns out, they do just fine if you power them directly or have them powered by a very short cable run. With a 100ft cable run (for example), a Nanobridge M5 runs just fine, but if you put a 750UP at the end of that run and plug the Nanobridge into it, the Nanobridge constantly reboots. All of that is well within spec. If you put the 750UP in front of that 100ft run, power it directly and have the Nanobridge plugged in to the other end, it is rock solid as well. Im guessing if you had a device (like the 750UP) that took 48v in and output 24v, there would be less loss over the long cable run and it would be able to power other devices (like the Nanobridge) reliably. If we are talking about another device, it would be nice to have a heavier duty model anyway (faster cpu, gigabit ports, etc). It could be powered with 802.3at (POE+). I will test this with a 48v to 24v converter between the 100ft cable run and the 750UP to see if it works and report back.

janisk · Fri Apr 27, 2012 3:31 pm

we are working on new controller firmware that should remedy these problems.

alexjhart · Fri Apr 27, 2012 4:35 pm

we are working on new controller firmware that should remedy these problems.

Do you have an ETA on that firmware? Which problems exactly will it remedy?

mesquito · Sat Apr 28, 2012 2:56 am

@janisbvp - would you post a picture of your capacitor and or cap + diode solution?
Would be nice to see how you wired it in terms of the power lead and or ethernet cable.

RK · Sat Apr 28, 2012 3:27 am

we are working on new controller firmware that should remedy these problems.

That's nice to hear, as, in their current state, all our RB750UP devices can't fulfill they main purpose and we had to go back to using DC splitters and individual POE injectors.

CoxWireless · Sun Apr 29, 2012 5:54 am

I've been able to resolve my powering issue.

I soldered a 35V 2200uf capacitor onboard (the board still fits in the case) and all is well.
I put this back on the tower 200ft up in the air and now can power 3 UBNT devices!
Finally it works as expected!!!

alexjhart · Sun Apr 29, 2012 6:13 am

I've been able to resolve my powering issue.

I soldered a 35V 2200uf capacitor onboard (the board still fits in the case) and all is well.
I put this back on the tower 200ft up in the air and now can power 3 UBNT devices!
Finally it works as expected!!!

$2 and its fixed? Where do we solder? Have some close up shots?

jandafields · Sun Apr 29, 2012 6:14 am

I've been able to resolve my powering issue.

I soldered a 35V 2200uf capacitor onboard (the board still fits in the case) and all is well.
I put this back on the tower 200ft up in the air and now can power 3 UBNT devices!
Finally it works as expected!!!

That is a great fix!!!!! I wonder if you could have used a smaller cap, that is massive!

CoxWireless · Sun Apr 29, 2012 6:18 am

probably can, but I had to start somewhere...
It still fits in the case, and the axial wires were long enough to reach the locations, so it worked just fine.

I think a smaller radial cap would be better and consume less power.

I could experiment in the future I guess. But I needed this to work today, and couldn't afford to lose any more time on a product that didn't perform as stated and expected, just like all of you reading this have found out (did I mention this is my first Mikrotik product I've ever purchased and/or used)

I tried everything even 30v power supplies, nothing seemed to work to keep the PoE ports from triggering the overlimit protection. However, this works just perfectly fine and if you're having PoE powering issues, put this cap in and your problems are behind you...

CoxWireless · Sun Apr 29, 2012 6:47 pm

specs of working modified 750UP seen above:
OS v5.5
24v PoE injector
200ft of CAT5 cable

details of capacitor modification:
Radio Shack 272-1020 which is a 35v 2200uF Axial Capacitor
positive end of capacitor soldered to positive end of onboard capacitor C14
negative end of capacitor soldered to negative ends of onboard capacitors C34 and C59
don't forget to isolate the exposed leads to prevent accidental shorting.

details of wiring:
RB750UPether1<-->200ftCAT5<-->24vPoE<-->120VAC
RB750UPether2<-->empty
RB750UPether3<-->UBNT900Mloco
RB750UPether4<-->UBNTM2Rocket
RB750UPether5<-->UBNTM5Rocket

no devices plugged in:
[admin@MikroTik] > system health print
voltage: 22.5V
cpu-temperature: 44C

ether3 plugged in:
[admin@MikroTik] > system health print
voltage: 21.5V
cpu-temperature: 44C

ether3,4 plugged in:
[admin@MikroTik] > system health print
voltage: 20.5V
cpu-temperature: 44C

ether3,4,5 plugged in:
[admin@MikroTik] > system health print
voltage: 19.5V
cpu-temperature: 44C

System is stable. No reboots or shutdowns.

alexjhart · Sun Apr 29, 2012 7:02 pm

specs of working modified 750UP seen above
OS v5.5
24v PoE injector
200ft of CAT5 cable

RB750UPether1<-->200ftCAT5<-->24vPoE<-->120VAC
RB750UPether2<-->empty
RB750UPether3<-->UBNT900Mloco
RB750UPether4<-->UBNTM2Rocket
RB750UPether5<-->UBNTM5Rocket

no devices plugged in:
[admin@MikroTik] > system health print
voltage: 22.5V
cpu-temperature: 44C

ether3 plugged in:
[admin@MikroTik] > system health print
voltage: 21.5V
cpu-temperature: 44C

ether3,4 plugged in:
[admin@MikroTik] > system health print
voltage: 20.5V
cpu-temperature: 44C

ether3,4,5 plugged in:
[admin@MikroTik] > system health print
voltage: 19.5V
cpu-temperature: 44C

System is stable. No reboots or shutdowns.

This is with the included power supply?
Have you saturated all 3 APs to their clients and from upstream to the 750UP for say 30 minutes?
How long has your setup been working?
How quick was it failing before?
Any idea how many AC watts the power adapter is using with everyone running behind the 750UP?
Can you provide information and close up pictures on where to solder?

CoxWireless · Sun Apr 29, 2012 8:30 pm

This is a little off topic, but does the 750UP support VLAN tagging and trunking?
I'm trying to set this up, but keep getting: "failure: not supported for this switch"

jandafields · Sun Apr 29, 2012 10:15 pm

This is a little off topic, but does the 750UP support VLAN tagging and trunking?
I'm trying to set this up, but keep getting: "failure: not supported for this switch"

No, rule table is not supported on 750up. See the wiki below.

"Rule table is very powerful tool allowing wire speed packet filtering, forwarding and vlan tagging based on L2,L3,L4 protocol header field condition. "

http://wiki.mikrotik.com/wiki/Manual:Sw ... p_Features

odie · Sun Apr 29, 2012 10:45 pm

i have a new problem since 2 days now
we have 4x 750UP each powering 2 or 3 devices (ubnt rockets) on a tower
that configuration has been running now for about 2 month without a problem - since 2 days now the rb750UP hang up - all of them a t the same moment !! we are still testing and only 3 customers are connected - so there is only traffic going over 2 of the 750 UP boards.
power comes from parallel running 3x battery backuped 24V powersupllies - a rb 1100AH and some other devices connected to the same supply run without problems.
the rb1100 does all the routing and the 750up just have 2 Vlans passing from ether1 to the ubnt devices, upstream comes from 500MBit 26 Ghz wireless link.
2 of the ubnt devices are connected directly to the 1100 board and only power comes from the 750 up boards (wires 4,5 and 7,8)
those 2 boards runn fine - so at least the power stays up .... and all the ubnt devices seem to run, only the rb750UPs hang up
the only thig that changed is that we have a bit warmer weather sinc a few days - but the tmeoerature n the rb1100 is just 38C and on the CPU it is 47C - this is no so much...
either it is a famous data packet that stops tho box from working or we have a temp problem or somthing else...
any ideas ?

mmc1800 · Sun Apr 29, 2012 10:55 pm

If what CoxWireless says is true and adding a capacitor to the board is required to fix everything so it works according to the specifications seems it is probably time for Mikrotik to fix the product and recall/replace the defective units that have been shipped. At least it would seem reasonable to update the specifications to what they actually are so as to save the rest of their customers time and frustration of trying to use these where they will not work and apologize for releasing a product with incorrect specifications.

CoxWireless · Sun Apr 29, 2012 11:29 pm

This is a little off topic, but does the 750UP support VLAN tagging and trunking?
I'm trying to set this up, but keep getting: "failure: not supported for this switch"
No, rule table is not supported on 750up. See the wiki below.

"Rule table is very powerful tool allowing wire speed packet filtering, forwarding and vlan tagging based on L2,L3,L4 protocol header field condition. "

http://wiki.mikrotik.com/wiki/Manual:Sw ... p_Features

Thanks, I was afraid of that. As this is what I was beginning to conclude myself (I was hoping to find some work-around). I guess without tagging and trunking, these 750UP devices are no more than paperweights to me. I guess I should have looked into the specs more carefully as I assumed they could do something as simple as this.
I hope MT comes out with a "P" type device that supports the "rules table"

Thanks,
Duane

janisk · Mon Apr 30, 2012 1:00 pm

question about cap was my first question to designers - reply was simple - you do not what to shorth anything anywhere near that board. larger the cap, larger the discharge voltage that can cause serious damage do the board and connected equipment. Better option is to add it near the PSU to make power over wire more stable, so that mdern impulse PSUs do not have noise issues when load is high over ethernet cables. If cap is places on the board - wire is still full of noise and induction uses power and warms up the wire, while cap at psu remedies these issues.

this is why we cannot suggest adding cap at the either of ends, since that is hazardous.

Anyway, we are expecting new controller firmware with some nice options to manage loads on ports.

Mon Apr 30, 2012 1:04 pm

If what CoxWireless says is true and adding a capacitor to the board is required to fix everything so it works according to the specifications seems it is probably time for Mikrotik to fix the product and recall/replace the defective units that have been shipped. At least it would seem reasonable to update the specifications to what they actually are so as to save the rest of their customers time and frustration of trying to use these where they will not work and apologize for releasing a product with incorrect specifications.

Specifications are correct, any issues you might be seeing, are depending on specific conditions and ripple noise from the PSU. We will make software upgrade that does some output adjustments to compensate for this noise.

janisk · Mon Apr 30, 2012 3:16 pm

just an material for thought.

to get 24V over the 100m Cat5e cable to the RB750UP loaded with 2A, i had to have 45V in the cable
to get 24V over the 54m Cat5e cable to the RB750UP loaded with 2A, i had to have 37V in the cable

first one had 21V drop other had 13V drop. And that drop only depends on how much current you have and length of cable.

CoxWireless · Mon Apr 30, 2012 4:54 pm

This is with the included power supply?
Have you saturated all 3 APs to their clients and from upstream to the 750UP for say 30 minutes?
How long has your setup been working?
How quick was it failing before?
Any idea how many AC watts the power adapter is using with everyone running behind the 750UP?
Can you provide information and close up pictures on where to solder?

Yes, the stock power supply. I'm also using the UBNT 24v 1A supply for another site with only 2 radios.
Yes, I ran this thing through a battery of tests with 3 APs in full modulation streaming video to subscriber endpoints in the lab for 24 hours before I put this into live production in the field. I had been working on this since April 11th, see my first post.
Without the cap, I would see my APs reboot within 60 seconds.
I took amperage measurements and calculated wattage while trying to figure out this problem, and the wattage changes as the volts change, and the volts change as more devices are plugged in or the current devices start to transmit.
I added details in my post above for soldering capacitor. Attempt at your own risk!

I will say, that with all of my measurements, everything was in spec, but I couldn't get anything to work prior to adding the capacitor.

I'm working now, and if MT release updated controller firmware, I'll remove the cap and see if they've got it working without.

alexjhart · Mon Apr 30, 2012 6:23 pm

We will make software upgrade that does some output adjustments to compensate for this noise.

When??? Days, weeks, months?

mmc1800 · Wed May 02, 2012 5:18 pm

Specifications are correct, any issues you might be seeing, are depending on specific conditions and ripple noise from the PSU. We will make software upgrade that does some output adjustments to compensate for this noise.

I have already stated I was not using POE to bring the DC power to the site, and I had stable voltage with an electrical engineer setting up and then verifying the power at the location. We have solid DC power at the location. There is a simple calculation for voltage drop which includes load, cable size, and length, and we have solid 20V DC power at the site. We had stable power without any meaningful voltage drop under the required load, and nothing else fails to function, just your equipment. If you have some mysterious undocumented, immeasurable requirement for special voodoo power for your device to work, and is not in your specification, then your product is not working to specs.

You can say the specifications are correct all you want, these boards do not work like they are supposed to, period. Other manufacturers equipment all works as it is supposed to at this site, only the 750UP is failing to meet its specifications. Instead of bringing 24 volt across the line, bring 20V across the line, and then run near rated capacity at 20V-500ma (10W) and see what happens. We could bring the radios online, but they were unstable and rebooted/hung all the time, a problem that has been alleviated by using equipment that can actually deliver the load we need under the conditions that are well within what is to be expected. I am not going to rework a perfectly functioning electrical system that has been in place for years in order to give my radios 24V when 20V is plenty.

I will say, that with all of my measurements, everything was in spec, but I couldn't get anything to work prior to adding the capacitor.

This is everyones experience with these products, your specifications are wrong. Here is a guy that has gone out of his way to work out some work around for your faulty device and you still wont even give him the respect to admit your product is failing to do what it is specified to do.

I guess if it helps you sleep you can keep telling yourself it is bad power at every site in the world, but it just isn't.

alexjhart · Thu May 03, 2012 8:06 am

This is a little off topic, but does the 750UP support VLAN tagging and trunking?
I'm trying to set this up, but keep getting: "failure: not supported for this switch"
No, rule table is not supported on 750up. See the wiki below.

"Rule table is very powerful tool allowing wire speed packet filtering, forwarding and vlan tagging based on L2,L3,L4 protocol header field condition. "

http://wiki.mikrotik.com/wiki/Manual:Sw ... p_Features
Thanks, I was afraid of that. As this is what I was beginning to conclude myself (I was hoping to find some work-around). I guess without tagging and trunking, these 750UP devices are no more than paperweights to me. I guess I should have looked into the specs more carefully as I assumed they could do something as simple as this.
I hope MT comes out with a "P" type device that supports the "rules table"

Thanks,
Duane

With ports 1-5 removed from the master port and put into a bridge, I added the vlan under the switch to ports 2-5. I also added the vlan interface to the bridge. This allowed me to attach an IP address to the vlan. Let me know if you need more information.

janisk · Thu May 03, 2012 12:09 pm

mmc1800

you say you have solid PSU, you have 20V etc.

what are the rest of the values, how long is the wire, what wire it is, what was the voltage drop at what load you have tested. What was the reading son out ports.

About cap fix, yes that is one way how to do it until he gets first short on the channel - results will be simple - burned out channel at best, at worst - burned equipment at the other end, read that this way - there is a 100% certainty that with capacity that big will damage the port where short occurs.

CoxWireless · Thu May 03, 2012 4:32 pm

With ports 1-5 removed from the master port and put into a bridge, I added the vlan under the switch to ports 2-5. I also added the vlan interface to the bridge. This allowed me to attach an IP address to the vlan. Let me know if you need more information.

Yes, but from what you are describing, this hass nothing to do with tagging and trunking.
I believe this unit isn't capable of it. I'm using the attached ubnt rocket to do this, it actually can...

alexjhart · Thu May 03, 2012 6:01 pm

With ports 1-5 removed from the master port and put into a bridge, I added the vlan under the switch to ports 2-5. I also added the vlan interface to the bridge. This allowed me to attach an IP address to the vlan. Let me know if you need more information.
Yes, but from what you are describing, this hass nothing to do with tagging and trunking.
I believe this unit isn't capable of it. I'm using the attached ubnt rocket to do this, it actually can...

This has everything to do with tagging and trunking. In my tests, I was plugging the 750UP ports into a switch (I used port 1 and 2-5, one at a time). I had a different IP on each VLAN on the 750UP. Those VLANs were sent over a trunk with tagging (1 ethernet cable between 750UP and the switch). On other ports of the switch, I confirmed that only the VLAN that was untagged could be communicated with (pinging the IP assigned to that VLAN on the 750UP, connecting to the 750UP and running a bandwidth test) or that I could also setup another device to use a trunk port on the switch and communicate with the 750UP on whichever VLANs were tagged on that trunk port of the switch. All you do is add the VLAN interfaces under the bridge interface on the 750UP. You can assign IP addresses to those VLANs. I think the draw back and limitation isn't that the device can't do this, but that the CPU is handling all of the processing instead of the switch chipset.

Edit:
I found out with further testing you don't even have to put all the ports in a bridge. You can add VLAN interfaces to a bridge with just the port you want to do trunking with. If you want another port on the 750UP to have an untagged VLAN, just create a bridge with that port and the VLAN interface on the bridge with the trunk port. Bottomline, this is very possible. I think the Wiki needs an update. This seems to be a common misunderstanding.

CoxWireless · Thu May 03, 2012 9:09 pm

This has everything to do with tagging and trunking. In my tests, I was plugging the 750UP ports into a switch (I used port 1 and 2-5, one at a time). I had a different IP on each VLAN on the 750UP. Those VLANs were sent over a trunk with tagging (1 ethernet cable between 750UP and the switch). On other ports of the switch, I confirmed that only the VLAN that was untagged could be communicated with (pinging the IP assigned to that VLAN on the 750UP, connecting to the 750UP and running a bandwidth test) or that I could also setup another device to use a trunk port on the switch and communicate with the 750UP on whichever VLANs were tagged on that trunk port of the switch. All you do is add the VLAN interfaces under the bridge interface on the 750UP. You can assign IP addresses to those VLANs. I think the draw back and limitation isn't that the device can't do this, but that the CPU is handling all of the processing instead of the switch chipset.

Edit:
I found out with further testing you don't even have to put all the ports in a bridge. You can add VLAN interfaces to a bridge with just the port you want to do trunking with. If you want another port on the 750UP to have an untagged VLAN, just create a bridge with that port and the VLAN interface on the bridge with the trunk port. Bottomline, this is very possible. I think the Wiki needs an update. This seems to be a common misunderstanding.

OK, I think I didn't describe what I'm wanting to do appropriately.

Yes the above works when using the 750UP as the router and having a trunk port to a switch upstream (and the upstream switch is removing the tag for egress traffic to the end device, and adding the tag to ingress traffic from the device).

But what I am trying to do is use the 750UP as the upsteram switch (I am using other vendors for the core routing and vlan trunk) trunking one port to my router, and pealing off the vlans at the 750UP. Now if you can tell me that is possible, tested, and proven true - you'd make my day.

alexjhart · Fri May 04, 2012 4:49 am

This has everything to do with tagging and trunking. In my tests, I was plugging the 750UP ports into a switch (I used port 1 and 2-5, one at a time). I had a different IP on each VLAN on the 750UP. Those VLANs were sent over a trunk with tagging (1 ethernet cable between 750UP and the switch). On other ports of the switch, I confirmed that only the VLAN that was untagged could be communicated with (pinging the IP assigned to that VLAN on the 750UP, connecting to the 750UP and running a bandwidth test) or that I could also setup another device to use a trunk port on the switch and communicate with the 750UP on whichever VLANs were tagged on that trunk port of the switch. All you do is add the VLAN interfaces under the bridge interface on the 750UP. You can assign IP addresses to those VLANs. I think the draw back and limitation isn't that the device can't do this, but that the CPU is handling all of the processing instead of the switch chipset.

Edit:
I found out with further testing you don't even have to put all the ports in a bridge. You can add VLAN interfaces to a bridge with just the port you want to do trunking with. If you want another port on the 750UP to have an untagged VLAN, just create a bridge with that port and the VLAN interface on the bridge with the trunk port. Bottomline, this is very possible. I think the Wiki needs an update. This seems to be a common misunderstanding.
OK, I think I didn't describe what I'm wanting to do appropriately.

Yes the above works when using the 750UP as the router and having a trunk port to a switch upstream (and the upstream switch is removing the tag for egress traffic to the end device, and adding the tag to ingress traffic from the device).

But what I am trying to do is use the 750UP as the upsteram switch (I am using other vendors for the core routing and vlan trunk) trunking one port to my router, and pealing off the vlans at the 750UP. Now if you can tell me that is possible, tested, and proven true - you'd make my day.

I am having no problem doing what you are describing. I would be happy to help you figure this out. Maybe we should work with specifics.

odie · Fri May 04, 2012 8:51 am

you cant mix tagged and untagged vlans on one physical lan port - on all mikrotiks !!
i have thrown out all my 750 UP boards 2 days ago because they are unstable and not the remote powerd UBNT devices
i am looking forward to a solution with the power problem

RK · Sat May 05, 2012 6:08 am

This is a little off topic, but does the 750UP support VLAN tagging and trunking?
I'm trying to set this up, but keep getting: "failure: not supported for this switch"

Yes, it does. All routerboards released in the last few years can do this.
Read the manual or ask in the software forum. Let's try to focus on the electrical/load issue in this thread.

RK · Sat May 05, 2012 6:09 am

positive end of capacitor soldered to positive end of onboard capacitor C14
negative end of capacitor soldered to negative ends of onboard capacitors C34 and C59

Thanks for this info.
How did you figure out the optimal connection points for the capacitor?

InoX · Sat May 05, 2012 6:20 pm

bigger is better

wifiqos · Sat May 05, 2012 7:48 pm

here is an online calculator to determine the line loss as a function of distance from the power injector to the load device. It will predict the delivered voltage after you enter the line length and the power needed by the device, and it will calculate the power loss in the CAT-5.

http://beyond-wifi.com/poe/poe-calc.html

This is an iterative calculation - note that some combinations of high power, long length and low voltage are actually mathematically in-stable - it will oscillate and your voltmeter will show you the average when in fact it is actually dropping out.

The online calculator warns of this and you can figure out the max distance.

I suspect that the addition of the remote capacitor is an attempt to resolve this oscillation. The problem with the huge capacitor is that when power is applied - it is a short circuit while it charges up - you can actually see sparks when you connect the injector if DC is live. If you install this capacitor - be sure to apply 110/220 power to the mains power supply AFTER all low voltage connections are made - otherwise you can damage the cat-5 connectors with the inrush current.

Better is to feed the POE with the max voltage that the device allows. For example, with 20v, 33 watts at the remote end, 100 ft - the total power needed including line loss is 55 watts - and you have 2.7 amps in the cat-5 If you increase to 28volts - the current is cut in half, and the power loss is only 5 watts.

With a 20v feed, your max distance before instability is 100 ft
With a 28v feed, your max distance is 200ft

You can do in excel - but the online calculator saves time.

RK · Fri May 25, 2012 8:07 am

Specifications are correct, any issues you might be seeing, are depending on specific conditions and ripple noise from the PSU. We will make software upgrade that does some output adjustments to compensate for this noise.

How is this coming along?

ottoshr · Tue May 29, 2012 11:04 pm

question about cap was my first question to designers - reply was simple - you do not what to shorth anything anywhere near that board. larger the cap, larger the discharge voltage that can cause serious damage do the board and connected equipment. Better option is to add it near the PSU to make power over wire more stable, so that mdern impulse PSUs do not have noise issues when load is high over ethernet cables. If cap is places on the board - wire is still full of noise and induction uses power and warms up the wire, while cap at psu remedies these issues.

this is why we cannot suggest adding cap at the either of ends, since that is hazardous.

Anyway, we are expecting new controller firmware with some nice options to manage loads on ports.
Posted: Mon Apr 30, 2012

When will be information about firmware update? Or info that this failure can be solved with firmware upgrade! And it will be nice to warn resselers of this BUG, either you can loose faith in MT as a googd devices !!! We lost week to find out where problems hiding! Does these problems can fix with better PSU for example 27VDC 3,8A or 7,5A cable to 750up is around 50m, and is turned into PowerJack (in poe port is almost not working at all), now we try 2 default 24VDC 2,5A parallel connected psu and PROBLEM NOT SOLVED !

Wed May 30, 2012 9:04 am

Sorry for not replying sooner - we are still working on it, and developers promise a solution hopefully next week.

MyThoughts · Wed May 30, 2012 5:41 pm

I just ran into the over-current protection issue.

We have started to use these RB750UP units quite a bit, and were just lucky in that all the initial deployments were ~65 ft of cat 5 cable between our 24V x 2A PoE injectors and the RB750UP. In this config we have had no problems powering 2 x RB411AH, and a NanoBridge M5 from the RB750UP.

HOWEVER while building another unit I put a 100 ft Cat5 cable and the over-current protection on ports 2-5 kept tripping and preventing any external devices from powering up.

We removed all the external units and started testing them one at a time. The Ubiquiti equipment wass always fine at 100ft, the RB411 however would never power on. We tested numerous PoE injectors and they didn't make any difference. The only thing that would allow the RB411 to turn on was shorter Cat5 cables to the RB750UP. We tried different lengths and found that anything above 70ft from PoE to RB750UP would cause the RB411 to trip the over-current protection.

To get the RB411s to work on longer cables we basicly made a patch cable where we had pins 1,2,3,4,6,7 on one RJ45 end, and pings 5,8 on the 2nd end. This halves the current and thus allowed the RB411 to boot with a 100ft cable no problem.

While in this working config with a single RB411AH with XR5, and a NanoBridge M2 running off the RB750UP we are measuing 22.2V on the ports 2-5 output, and the /sys health is reporting 21.1V.

I do not think I should have to use this workaround, but it was a easy solution, and one that does appear to work fine (you do need to make sure you set the RB750UP to "PoE Out = on" and not auto). Our 2nd solution that we are awaiting parts to try is a 48V to 24V PoE Converter, silimar to Mikrotik's but the one we ordered has 30W output instead of 24W, I would've preferred a >40W unit, but we couldn't find one that was readily available and at a resonable price. This would allow us to use a high power 48V PoE injector at ground level and convert it to a good 24V at height for the RB750UP. This should give us the extra few volts we need to keep the current required lower.

If anyone has tried the 48V to 24V converter and it works what brand/model did you use?

And to Mikrotik Support, is the new firmware designed to help this issue or it this just a IMHO a design flaw we'll have to work around?
Time for a RB750UHP, something that can do say 0.8-1A per port, I don't need more power overall, just more power available at each port.

Cheers

ottoshr · Thu May 31, 2012 1:52 pm

question about cap was my first question to designers - reply was simple - you do not what to shorth anything anywhere near that board. larger the cap, larger the discharge voltage that can cause serious damage do the board and connected equipment. Better option is to add it near the PSU to make power over wire more stable, so that mdern impulse PSUs do not have noise issues when load is high over ethernet cables. If cap is places on the board - wire is still full of noise and induction uses power and warms up the wire, while cap at psu remedies these issues.

this is why we cannot suggest adding cap at the either of ends, since that is hazardous.

Anyway, we are expecting new controller firmware with some nice options to manage loads on ports.
Posted: Mon Apr 30, 2012

When will be information about firmware update? Or info that this failure can be solved with firmware upgrade! And it will be nice to warn resselers of this BUG, either you can loose faith in MT as a googd devices !!! We lost week to find out where problems hiding! Does these problems can fix with better PSU for example 27VDC 3,8A or 7,5A cable to 750up is around 50m, and is turned into PowerJack (in poe port is almost not working at all), now we try 2 default 24VDC 2,5A parallel connected psu and PROBLEM NOT SOLVED !

Problem "solved" with connecting 4 pairs 5cat to main current 220V and other 4 pars to other current. When PSU is connected beside 750UP with short power cord with jack, then Voltage is 22,4V and almost 23 hours is working without restarts.

janisk · Fri Jun 01, 2012 9:55 am

ottoshr ethernet cable only have 4 pairs with 2 wires each (a pair) or i am missing someting from your post?

MyThoughts you effectively reduced by half the power loss over the cable, of course that works perfectly well.

MyThoughts · Sat Jun 02, 2012 6:13 pm

MyThoughts you effectively reduced by half the power loss over the cable, of course that works perfectly well.[/quote]

Your right it has been working perfectly well. Plus I feel a bit more at ease knowing the amount of current per port isn't approaching the limit during cold starts.

I would love to see a higher powered version, and/or a RB11xx class unit with PoE output support.

Cheers

alexjhart · Sat Jun 02, 2012 8:39 pm

Our 2nd solution that we are awaiting parts to try is a 48V to 24V PoE Converter, silimar to Mikrotik's but the one we ordered has 30W output instead of 24W, I would've preferred a >40W unit, but we couldn't find one that was readily available and at a resonable price. This would allow us to use a high power 48V PoE injector at ground level and convert it to a good 24V at height for the RB750UP. This should give us the extra few volts we need to keep the current required lower.

I considered this solution myself. I wasn't able to get an answer from MikroTik as to if this would actually fix the problem. Sounds like it does. Where did you find the 30W? The MikroTik was the highest one I found. What all are you running on it? What cable lengths?

janisk · Mon Jun 04, 2012 9:50 am

anything that reduces power-loss over the cable will help.

ottoshr · Wed Jun 06, 2012 4:42 pm

ottoshr ethernet cable only have 4 pairs with 2 wires each (a pair) or i am missing someting from your post?

MyThoughts you effectively reduced by half the power loss over the cable, of course that works perfectly well.

we have 2 cables in that tower i describe.

ottoshr · Wed Jun 06, 2012 4:48 pm

Sorry for not replying sooner - we are still working on it, and developers promise a solution hopefully next week.

Normis (Mikrotik) we are still waiting and hoping that someday these problems/issue/bug will be solved somehow with firmware update !

MyThoughts · Wed Jun 06, 2012 5:50 pm

I considered this solution myself. I wasn't able to get an answer from MikroTik as to if this would actually fix the problem. Sounds like it does. Where did you find the 30W? The MikroTik was the highest one I found. What all are you running on it? What cable lengths?

Tycon Power TP-DCDC-4824-HP
http://tyconpower.com/products/files/TP ... _Sheet.pdf

We haven't recieved them yet, so we haven't actually tried this. Mikrotik's unit is much more rugged looking and is quite elegant, too bad its only 24W.

When we ran into these problem this was the config we were aiming for.
Injector -> ~100ft -> RB750UP -> ~6-10ft -> (2 x Nanobridge M2/M5, 1 x RB411AH)

It was the RB411AH that kept tripping the over current so that is the one we split the current on, the Ubiquiti equip seemed fine.

Just prior we had this setup and it worked fine without any modifications.
Injector -> ~65 ft -> RB750UP -> ~6-10ft -> (1 x Nanobridge M5, 1 x RB411, 1 x RB411AH)

We did some bench testing with different cable lengths and it appeared that as soon as we had >70ft going to the RB750UP the over current would trip during startup with any RB4xx based product attempting to power on.

Cheers

ottoshr · Thu Jun 14, 2012 9:53 am

Sorry for not replying sooner - we are still working on it, and developers promise a solution hopefully next week.
Normis (Mikrotik) we are still waiting and hoping that someday these problems/issue/bug will be solved somehow with firmware update !

Normis, Mikrotik any news concerning RB750UP poe issues ?!

Thu Jun 14, 2012 9:54 am

Please be assured, that we will post any news as soon as we have them.

ottoshr · Thu Jun 14, 2012 10:00 am

Please be assured, that we will post any news as soon as we have them.

5.17 is without updates in this POE issues?

janisk · Thu Jun 14, 2012 10:14 am

no, 5.17 does not introduce anything new, in the mean time, you can
9if possible) run longer power cable to the RB750UP to power connected devices successfully.

ottoshr · Thu Jun 14, 2012 10:23 am

no, 5.17 does not introduce anything new, in the mean time, you can
9if possible) run longer power cable to the RB750UP to power connected devices successfully.

Yes, we do that. But better will be if there is going low voltage not 220V for fire safety and etc.

janisk · Thu Jun 14, 2012 11:45 am

you can do that with low voltage (from same supplied power supply as electrical cable has less resistance as result less voltage drop over the cable and less fluctuations on power spikes.

ottoshr · Thu Jun 14, 2012 12:22 pm

you can do that with low voltage (from same supplied power supply as electrical cable has less resistance as result less voltage drop over the cable and less fluctuations on power spikes.

we tried but there is also loss of voltage and with 21,9V it almost not working , restarts poe devices from time to time.

janisk · Fri Jun 15, 2012 8:47 am

losses on electrical cable should be lower than though ethernet as last is only gauge 24.

ottoshr · Mon Jun 18, 2012 7:49 pm

looks like problem with powering up ubnt devices with poe soon can be solved with
http://www.ubnt.com/airmax#toughswitch
http://dl.ubnt.com/guides/toughswitch/T ... rt_QSG.pdf
http://dl.ubnt.com/guides/toughswitch/T ... rt_QSG.pdf

janisk · Tue Jun 19, 2012 12:10 pm

if you are powering RB750UP with power-cord you do not have any problems powering other devices within allowed powering range. So how exactly these will solve the problem?

ottoshr · Tue Jun 19, 2012 12:46 pm

if you are powering RB750UP with power-cord you do not have any problems powering other devices within allowed powering range. So how exactly these will solve the problem?

problem was when we powered up 750up with standart psu 2,5A 24VDC with power cord , poe devices restarts from time to time, cable length aprox 50-70m, we try 2 psu units put together for 5A 24VDC and problem still exists, system>health show 21,2V and poe devices resets... as i describe earlier solved only when place on tower psu.
of course our hope will be that 750up can be powered up trough poe in 1-port, and distribute poe to 2-5 ports, but i understud that every port can get no more 15w and 1-port too? but in this scenario devices restarts.
in scenario psu then 50m power cord and power jack in 750up also faills, it restarts from time to time by itself.
in scenario psu beneath rb750up all is working system health>voltage>22,2V
delta between 21,2 and 22,2 is 1V ? you think that gap is outside power range for devices that can work from 12V? where i am wrong? maybe you can guide us to better scenario or workaround? i think most of rb750up installations on towers is the same...

janisk · Tue Jun 19, 2012 1:09 pm

2.5A@24V PSU is over what rb750UP can consume (it is close to that value, so there should not be any issues regarding lack of power).

next problem - 50m - 70m with minimum set resistance for cat5e cable of 0.18Ohm per meter (and this is taken straight out of physics book) so we are talking 9Ohm (50m) and 12.6Ohm(70m) (usually higher quality cables have less resistance) so now calculate the voltage loss over the length of the cable. And then calculate how much power will use connected device when it uses 8W@24V

jcem · Tue Jun 19, 2012 1:24 pm

Yesterday I tried to power UBNT Airvision with 750UP ROS 5.17 and the Camera reset to factory defaults. I tried 2 different
cameras with the same result.

Had to go back and use the factory POE adapters

I wonder if the camera have some kind of undocumented poweshoot reset function that
gets triggered from by some kind of resistance in 750UP?

RGDS
Jörgen

janisk · Tue Jun 19, 2012 2:09 pm

And these devices are within 500mA required (for current FW) at voltage they are receiving?

jcem · Tue Jun 19, 2012 8:29 pm

And these devices are within 500mA required (for current FW) at voltage they are receiving?

According to Ubiquity 12-24V 2.5W

2.5W at 24V ≈100mA

Their own powersupply is on 24V/0.5A

janisk · Wed Jun 20, 2012 9:42 am

100mA devices should not have any problems, have to re-check this

bridgh20 · Thu Jun 21, 2012 6:20 pm

not a problem, feel free to pm me if you have any more questions . We are using the solar site to control the stock water for cattle wirelessly .

Very interested in your design!.

Can you please provide a bit more detail on your solar solution? What size of mppt charge controller? Do you have installation picture? Can contact me at admin@cobasystems.net

alexjhart · Fri Jun 22, 2012 6:52 pm

we are working on new controller firmware that should remedy these problems.

Got this today:

What's new in 5.18 (2012-Jun-21 17:20):

.....
*) fix health and poe access reliability on OmniTIK UPA and RB750UP boards;

......

Is that what we are all waiting for or a tease?

mesquito · Sat Jun 23, 2012 5:52 pm

The POE-out problems are still there in 5.18.
My System Health shows a constant 20.4V on the Mikrotik, but the 2 slave devices with poe-out=forced-on continue to lose power.

Mikrotik: you really need to publish some specs about the supported uses of poe-out on the RB750up and the limitations.
You have a lot of unsatisfied customers here.

janisk · Wed Jun 27, 2012 11:57 am

what is the configuration, how you are powering the RB750UP and what length cable you are using to power end device and what is the device (potential power consumption)

mesquito · Wed Jun 27, 2012 6:18 pm

My desired setup (and how I'm testing) is with the Mikrotik-provided power supply (24V @2.5amp) feeding through a passive poe injector (y-cord) through 120' of cat5e cable. The 750UP is fed on the DC plug from that 120' cable. Then I have a 1 or 2 Nanostations on a 30' cat5e cable connected to one of the LAN ports with poe-out=forced-on.
The Nanostation reboots regularly. When I change a setting on 1 Nanostation and apply changes (in AirOS), then the other Nanostation will reboot.
Otherwise, reboots happen sporadically. Maximum uptime of the Nanostations in the past 72 hours is about 10 hours.

[Edited] Assume each NSM5 is 8W and the RB is 6W. That's a total of 22W and even with the long POE run, I would expect that's sufficient.
The 750UP is showing constant voltage of 20.4V in system health.

alexjhart · Wed Jun 27, 2012 6:23 pm

My desired setup (and how I'm testing) is with the Mikrotik-provided power supply (24V @2.5amp) feeding through a passive poe injector (y-cord) through 120' of cat5e cable. The 750UP is fed on the DC plug from that 120' cable. Then I have a 1 or 2 Nanostations on a 30' cat5e cable connected to one of the LAN ports with poe-out=forced-on.
The Nanostation reboots regularly. When I change a setting on 1 Nanostation and apply changes (in AirOS), then the other Nanostation will reboot.
Otherwise, reboots happen sporadically. Maximum uptime of the Nanostations in the past 72 hours is about 10 hours.

[Edited] Assume each NSM5 is 8W and the RB is 6W. That's a total of 22W and even with the long POE run, I would expect that's sufficient.
The 750UP is showing constant voltage of 20.4V in system health.

Unless Mikrotik comes out with a magical software fix (they said they would) or you run higher voltage up 120' (AC or maybe 48V DC with 48-24V converter at the top), this setup just isn't going to work for you and you will continue to see reboots.

mesquito · Wed Jun 27, 2012 8:26 pm

Yes. I was responding to their 5.18 update which supposedly had a magical poe fix.
No magic here...

janisk · Thu Jun 28, 2012 10:32 am

5.18 does not include new firmware for poe-out controller however addresses some issues that where not resolved before.

New firmware will be able to mask some of the spikes, so increasing stability of connected devices. But in your case i would suggest to get higher voltage PSU, so that over the wire you get ~24V - 26V at the router. Because when there is power spike voltage drops and as result amps increase, so losses over the wire increases.

Also note that router has some capacity, that in turn will show higher voltage that there is actually on the wire where voltage is fluctuating.

RK · Fri Jun 29, 2012 10:14 am

New firmware will be able to mask some of the spikes

When will it be made available?

In our setup, we see random reboots wit ha 24V feed and cables which are less than 5 feet long.

janisk · Fri Jun 29, 2012 1:11 pm

it does not matter much how long cables are from RB750UP to device you are powering since there you can have up to 500mA. Issue is, that cable that is powering RB750UP itself, as there you will have sum of all powered device and losses and fluctuations will be bigger there.

helectro · Sat Jun 30, 2012 6:49 pm

recently installed my first 750UP with 5.18, and evidence on the table that works great with a 433ah +2 r52n and a rocket M5 old, but when attaching a new rocket with mac address 00:27: the new rocket restarts constantly someone can verify if the new rocket are the some the problem, that I have one with mac address 00:15 works fine
I've tried putting interface in auto and on, and No makes difference continuous restarting

my configuration is as follows =

Meanwell ADD155B -------- to 27V plug to RB750UP ---
Ether 2 = no more than 6 meters of cable shield UTP5 rocket M5 mac Ether 00.15
Ether3 = no more than 6 meter cable shield UTP5 433Ah+2 r52n
Ether 4 = no more than 6 meters of cable shield UTP5 new rocket M5 mac Ether 00.27

and I have the following question
someone tried this
if you want to put to work a rb800 with the rb 750UP

I can put 48 to 24V PoE Converter, in reverse so that IN=24v Out 48V?
http://routerboard.com/pdf/386/RB-POE-CON-HP.pdf
RB750UP---------24 v Poe Converter in reverse out 48V--------RB 800?

excuse my little English

janisk · Mon Jul 02, 2012 10:55 am

someone tried this
if you want to put to work a rb800 with the rb 750UP

no, it is not possible, RB800 works with 802.3af/at and RB750UP does not support that

I can put 48 to 24V PoE Converter, in reverse so that IN=24v Out 48V?
http://routerboard.com/pdf/386/RB-POE-CON-HP.pdf
RB750UP---------24 v Poe Converter in reverse out 48V--------RB 800?

excuse my little English

no, power conversion happens only in one dirrection. Also, RB800 uses a lot of power and it is not possible even theoretically to power it using RB750UP.

RK · Fri Jul 06, 2012 7:03 am

it does not matter much how long cables are from RB750UP to device you are powering since there you can have up to 500mA. Issue is, that cable that is powering RB750UP itself, as there you will have sum of all powered device and losses and fluctuations will be bigger there.

Yes, I understand all that. That's very basic.

Now, let's have that firmware fix already

janisk · Fri Jul 06, 2012 8:33 am

kategrin611 - check the polarity of the cabling. Also, what device exactly you have? We have tested Motorolla Canopy and they should work with auto-on mode, of course, you have to have latest RouterOS as with version they are shipped it will not work.

RK - release is coming along nicely.

marekm · Wed Jul 18, 2012 12:51 pm

I've been waiting for the RB750UP PoE out fixes, but don't see any in the just released 5.19 changelog. Is the changelog complete?

I've tried 5.19rc1 once, and it seems to have bricked the MCU that controls PoE out and voltage monitor (now ports 2-5 are powered and red LEDs blink all the time, voltage monitor shows no result, the router itself is still working though). Any way to reflash it without RMA? Downgrade to 5.18 with netinstall didn't help.

CoxWireless · Thu Jul 19, 2012 8:45 pm

Meanwhile....

I would like to report my "hardware fix" has been running perfectly fine in the field now, for what, three months almost. I've got 10 units deployed, all running stable with no device reboots.

RK · Tue Jul 24, 2012 6:50 am

RK - release is coming along nicely.

How much longer will we suffer?

mesquito · Fri Jul 27, 2012 3:38 am

CoxWireless you say you could have used a smaller capacitor. What size? That level of electrical is over my head, but I was hoping to solder a cap on my 750UP. Is 24V 1200uf reasonable or what would you recommend?

mesquito · Wed Aug 01, 2012 12:31 am

CoxWireless you say you could have used a smaller capacitor. What size? That level of electrical is over my head, but I was hoping to solder a cap on my 750UP. Is 24V 1200uf reasonable or what would you recommend?

Bump.

janisk · Wed Aug 01, 2012 4:10 pm

solution with capacitor is dangerous if short is happening, it can damage the router and connected hardware when on short that large capacitor is discharging, on the other hand, if you know that no shorts are going to happen - it is not that bad to stabilize the fluctuations.

alexjhart · Wed Aug 01, 2012 7:05 pm

solution with capacitor is dangerous if short is happening, it can damage the router and connected hardware when on short that large capacitor is discharging, on the other hand, if you know that no shorts are going to happen - it is not that bad to stabilize the fluctuations.

People are just looking for a solution to the problem. The problem being the hardware doesn't work quite as advertised. The solution could be this promised software fix. Right now, the only thing that we know works is this capacitor.

Are you guys making any progress on the software fix?

marekm · Fri Aug 03, 2012 10:42 pm

Bump. I have to work around the PoE out issues, by using an external 4-port PoE injector and a few patch cords. Looks messy and can't reboot radios remotely, but no more random reboots and very little voltage drop on PTC resettable fuses. Still keeping the RB750UP for its voltage monitor (to know AC/battery state), otherwise an ordinary RB750 (or even just a simple unmanaged switch) would do.

janisk · Mon Aug 06, 2012 9:52 am

yes, there is good progress regarding software fix, however - you cannot cheat the physics.

marekm · Mon Aug 06, 2012 12:45 pm

OK, waiting for another "rc" to test. I understand the software can't do anything about voltage drop (but please consider hardware redesign - there exist protected 4-channel high-side switch chips built just for that purpose, such as Infineon BTS711L1), but I hope it can fix the over-sensitive protection (triggered by supply voltage changes, like when battery voltage rises from 12V to 14V after AC power is back).

janisk · Mon Aug 06, 2012 3:12 pm

all the changes will be described in the wiki. So, read the manual before jumping to test version.

gnuttisch · Tue Aug 07, 2012 1:41 pm

I also have a strange problem.

Running 750up over powerjacket and 5.19.

I have connected 2 450 and 2 450G. The interfaces are set to auto-poe and when I boot the 750UP the two 450G doesn't power up. I have to set interface poe to on to get it work. All of the 4 routers have a 2m patchcable.

Also the Ethernet interfaces not showing and current, 0 mA.

Will this be fixed in the new firmware?

edit: I had a look at the wiki for PoE-Out. Are the sxts, grooves, 751 and 951 not reliable whit 750UP?

janisk · Tue Aug 07, 2012 3:12 pm

if you did not use 5.19rc1 then you have older FW where current monitoring is not implemented.

will check on my test router what is happening with rb540G and auto-on mode.

luhiwu · Tue Aug 07, 2012 3:50 pm

I´ve upgraded a few rb750up to 5.19 and current monitoring always shows 0mA, is it correct?

gnuttisch · Tue Aug 07, 2012 3:51 pm

yes I´m only using firmware 5.19.

How about my other question? "edit: I had a look at the wiki for PoE-Out. Are the sxts, grooves, 751 and 951 not reliable whit 750UP?"

luhiwu · Tue Aug 07, 2012 4:41 pm

Is it possible to download 5.19rc1 so the current monitoring works?

janisk · Wed Aug 08, 2012 9:01 am

sxts, grooves, 751 and 951 not reliable whit 750UP?

they are working ok. List is not updated.

better avoid using 5.19rc1 when stable is released. As there was a reason why poe-out changes where pulled out of final release.

RK · Sun Aug 12, 2012 3:30 am

Not sure if 5.19 was supposed to fix the power problem, but it hasn't.