You are here

Home » Forums » General discussion

Actual Power Requirements...

10 posts / 0 new
Log in or register to post comments
Last post
Tue, 01/19/2016 - 19:26
#1
K6OQK
K6OQK's picture
Actual Power Requirements...

I know that the POE supplies 24 volts at the bottom end of the cable, and I assume that there is an internal voltage regulator inside the radio itself.  My question is: What is the minimum voltage that the Rocket or Bullet needs at its input for reliable operation? Will it run reliably on 12 VDC?

Thanks,

Burt, K6OQK

Top
Tue, 01/19/2016 - 20:10
KG6JEI
http://dl.ubnt.com/wiki/UBNT
http://dl.ubnt.com/wiki/UBNT-AOS_prod-specs-gen_5.pdf lists some devices (they haven't published newer statistics)  but 10.5 was the general absolute minimum voltage AT the CONNECTOR.

So for 12v you should be fine as long as its not a really long run of CAT5 (25foot is my recommendation but the math seems to say up to 50ft I'd you really want to push it it IIRC)


 
Top
Tue, 01/19/2016 - 20:25
VE2DTL
VE2DTL's picture
Don't work with 100 feet of

Don't work with 100 feet of cat5e 24 gauge wire with 12 volts battery power.

need one of these:

http://www.cafr.ebay.ca/itm/XL6009-Replace-LM2577-DC-DC-Adjustable-Module-Step-up-boost-Power-Converter-BG-/252229313399?hash=item3aba09e377:g:7bIAAOSw1S9WgXCv

André VE2DTL 

Top
Tue, 01/19/2016 - 23:29
K6OQK
K6OQK's picture
You guys answered my question...
You guys answered my question perfectly and that's why I asked about the minimum power at its input.  I understand about the voltage drop over a long run of CAT-5 cable. As I recall, the load is somewhere around 1/2 Amp.  In some cases I would only be using about 10-feet or less and running it from my car.  For some initial testing in my car I used an inverter to generate 120 VAC and then going through the supplied POE adaptor.  From my "shack" to my tower it could be as much as 100-feet dressed.  I remember reading somewhere that you can power the Ubiquiti stuff from 24 VDC.  Is that correct?  I have plenty of clean  24 volts DC from a UPS.  Can the negative side of the 24 VDC be earth ground referenced?

Thanks,

Burt, K6OQK
Top
Wed, 01/20/2016 - 03:54
(Reply to #4)
KG6JEI
Make sure voltage does not go

Make sure voltage does not go above 24v. There is  Zener on these units that clamps at 25v shorting the input to ground to protect the unit.

Yes negative can be ground referenced and in fact this is somewhat required by warranty and design. CAT5 sheild must be grounded to discharge static and internally on these units the SHEILD and negative ground are tied together meaning ultimately your
reference should be "ground".  Though don't rely on the negative ground for the SHEILD bonding, make sure to tie that directly so EMI / lighting induced currents can have a chance to stay on the sheild.

Top
Wed, 01/20/2016 - 11:37
(Reply to #5)
K6AH
K6AH's picture
Running Mobile on 12v

Hey Burt,

I've been running an M2 Bullet mobile for the past year and a half.  No problems running nodes on 12v up to about 50'.  These PoE injectors work great for that purpose: http://www.ebay.com/itm/1PC-Passive-PoE-Injector-Spliter-Module-Wall-Mount-for-Mikrotik-Tranzeo-OpenMesh

Andre, K6AH
 

Top
Fri, 01/22/2016 - 18:42
kc1bhd
Power
M2 bullet, rocket & loco all run with 6 volts at the load side. Internal board runs at 3.3 I think
Top
Fri, 01/22/2016 - 20:35
(Reply to #7)
KG6JEI
You may have pushed them this
You may have pushed them this low but doesn't mean it's supported or recommended or even within design tolerances.
Also have you ran it at that voltage for 2 years in the desert?

Lower voltage will mean much more heat in the SMPS circuit, and while it may work for a short while at that low a voltage your pushing past way to many variables to treat it as reliable. It also means there is less safety margins for a sudden need for current (sudden heavy math, sudden sustained RF data stream, etc)

This all becomes especially important when one is building an EMCOMM network.
Top
Sat, 01/23/2016 - 14:05
K6OQK
K6OQK's picture
Actual Power Requirements...

Ok guys...  It seems like 12 volts is probably doable for testing purposes when I have a need to run a unit in my car with probably no more than 10' of CAT-5.  My permanent installation, yet to be built, will be from home and used as a fixed point to point link with maybe a 100' run from my Hazetorium to the dish on my tower.  As I mentioned earlier, at home I have plenty of clean 24 VDC from a UPS and that will probably be the supply for that link.  I've been reading a lot of the posts on the AREDN group and have learned a lot from all of your experiences.

Thanks to everyone,

Burt, K6OQK

Top
Sat, 01/23/2016 - 14:31
(Reply to #9)
K5DLQ
K5DLQ's picture
FYI, I have a 425' run of
FYI, I have a 425' run of CAT5 powered with 24V no issues.  At 12V, it would drop out at that distance around 10V.
(yes, even the ethernet works at this distance/beyond spec, but, it's in armored-heavy cat5)
Top

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer