Community discussions

 
marktomlinson
newbie
Topic Author
Posts: 35
Joined: Wed Aug 03, 2016 12:22 pm

PoE Voltage Drops

Fri Feb 16, 2018 4:24 pm

Hi Guys

I am looking for a little advise as its out of my comfort zone this one.

I have a radio that is circa 130m from the core router and taking into account max cable runs, I decided that the best way would be breakup the run with 2 PowerBox Pro's but I am having some issues with voltage drops and need a little advise on how best to resolve.

Router <-- 30M 24V --> PB01 <-- 80M --> PB02 <-- 20M --> 922UAGS-5HPacD

From the router I am using the 24V provided PoE injector to the PB01, voltage at PB01 is 20V...the voltage then at PB02 is 16.2V and then onto the 922UAGS-5HPacD - the voltage is just 14V

The issue that I have is the 922UAGS-5HPacD will reboot continually and I can only put this down to the voltage, plugged directly into a POE injector it works flawlessly.
 
jarda
Forum Guru
Forum Guru
Posts: 7604
Joined: Mon Oct 22, 2012 4:46 pm

Re: PoE Voltage Drops

Fri Feb 16, 2018 6:06 pm

Kackele, I am warning you.
Stop offending others and excuse yourself.
 
mistry7
Forum Guru
Forum Guru
Posts: 1326
Joined: Tue Oct 13, 2009 11:57 am
Location: Germany

Re: PoE Voltage Drops

Sat Feb 17, 2018 11:09 am

First step try a power supply with about 36-40v Dc if this don’t work you have to exchange your cable to a better on
 
savage
Forum Guru
Forum Guru
Posts: 1213
Joined: Mon Oct 18, 2004 12:07 am
Location: Cape Town, South Africa
Contact:

Re: PoE Voltage Drops

Sat Feb 17, 2018 12:09 pm

14V at the end of a 130M 24AWG (presumably) cable run is actually quite good. The voltage drop is quite normal over that distance, but it SHOULD be sufficient as the RB's SHOULD operate on 12V.

As others suggested, I would also recommend trying a 30V PSU. Just to be safe. My guess however, is that you have a 24V/1A PSU, and the 1A isn't providing enough juice to power all 4 devices. Try a 30V, 3A or 5A PSU. It may, or may not work.

The problem with daisy chaining things like this, is that the PoE out on all these devices, limit the amount of current on the ports (and for very good reasons). Personally, I would run power and Ethernet separately here, and not use POE but rather just tap a steady 24V off the power cable at each device. You running a very high risk here that the RBs closer to the PSU (thus pulling more current), could actually burn out.
Regards,
Chris
 
jarda
Forum Guru
Forum Guru
Posts: 7604
Joined: Mon Oct 22, 2012 4:46 pm

Re: PoE Voltage Drops

Sat Feb 17, 2018 1:19 pm

For long cables or high consuming devices at the end I use dc converters. First creates 70v, injects into long cable by passive poe injector, extracted at the end and another dc step down converter to desired voltage is used between the extractor and the device. A bit work with cheap chinese toys, but surprisingly reliable.
 
jarda
Forum Guru
Forum Guru
Posts: 7604
Joined: Mon Oct 22, 2012 4:46 pm

Re: PoE Voltage Drops

Sat Feb 17, 2018 1:33 pm

Few pictures:

PHOTO_20160228_105201_res.jpg
PHOTO_20160228_110928_res.jpg
PHOTO_20160228_151427_res.jpg
PHOTO_20160409_162507_cr_res.jpg
You do not have the required permissions to view the files attached to this post.
 
User avatar
Madumi
newbie
Posts: 27
Joined: Mon Apr 23, 2018 6:07 pm

Re: PoE Voltage Drops

Tue May 29, 2018 12:39 am

For long cables or high consuming devices at the end I use dc converters. First creates 70v, injects into long cable by passive poe injector, extracted at the end and another dc step down converter to desired voltage is used between the extractor and the device. A bit work with cheap chinese toys, but surprisingly reliable.

Wow @jarda, that sounds like a pretty nice solution. You have my curiosity, you're going DC-to-DC right?, are you then relying on the step down converter to maintain your desired voltage (regardless of the length of the cable run)?

I'm also curious: what style of cable are you using for the long 70v cable run... POE right?...

thanks!
 
jarda
Forum Guru
Forum Guru
Posts: 7604
Joined: Mon Oct 22, 2012 4:46 pm

Re: PoE Voltage Drops

Tue May 29, 2018 2:30 pm

I use normal ordinary cheap utp cable. Does not matter what is the voltage at the end because the step down converter makes its job well to produce the stable output regardless its input (in normal ranges). It works without any intervention for more than two years now. And yes, all voltages are DC. As you saw the powering system is more complex: main power supply, solar regulator, battery, different step up converters and inverter for powering the server by 220v AC.
 
User avatar
Madumi
newbie
Posts: 27
Joined: Mon Apr 23, 2018 6:07 pm

Re: PoE Voltage Drops

Tue May 29, 2018 4:56 pm

@jarda

You've definitely piqued my interest on the 70v system... That must be quite a long cable run. I'm curious how long (approximately)?
 
jarda
Forum Guru
Forum Guru
Posts: 7604
Joined: Mon Oct 22, 2012 4:46 pm

Re: PoE Voltage Drops

Tue May 29, 2018 11:18 pm

Not so much. The cameras can draw around 40w at 12v. This means it is impossible to reliably power them directly by 12v over poe, especially when cable is between 20-50 meters. Therefore step up / down conversion took the place. For sure it is not the best thing from the efficiency point of view, but not so bad. Its cheap and easily repairable in case of any problem.

Who is online

Users browsing this forum: No registered users and 34 guests