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Thread: Poe

  1. #1
    SG Enthusiast blacklab's Avatar
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    Poe

    Hi, Not sure if this is the right place but maybe someone can steer me in the right direction.

    I am looking for a POE with a 24V output and DC volts in.

    Not sure if there is such a device so any help would be appreciated.

    Thanks
    Terry

  2. #2
    Moderator YeOldeStonecat's Avatar
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    Yup there are such devices as many locations are "off the grid"...thus running on solar/battery. Need just a single POE? Or a POE switch?
    We got most of our outdoor and wireless stuff at Streakwave..they have a few ones with shrouded DC jack.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  3. #3
    SG Enthusiast blacklab's Avatar
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    Hi YeOldeStonecat I don't know why I didn't start out at SpeedGuide. It seems there is always someone there that can answer any question.

    What I am trying to do is a better signal for our computers inside my camper and trailer. I think all I need is a single POE that I can connect to a step-up module.

    I have a Bullet M2 and a pole antenna that I want to feed into a router. This should give me Ethernet connections inside the camper. The POE is needed to supply 24V to the Bullet from the 12V I have. I would like to stay DC, but if I have to I will dedicate a small Inverter to the system.

    If you have a better way to accomplish this I would appreciate the input.

  4. #4
    Administrator Philip's Avatar
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    I believe all PoE standards are DC, so you can just use a step-up from 12v to 24v. I would measure the exact outputs of the Ubiquiti PoE injector, as they are not compatible with some other brands (Engenius PoE injectors don't work with them, some PoE switches don't work either).

    Actually, the voltage you need with PoE is greatly dependent on distance and the device itself, so some devices may work at 12V DC straight with shorter distances of up to let's say ~25 feet. At longer distances the resistance of the Ethernet cable plays a big role, that's why most PoE injectors/switches are 24/48V. If you are wiring up your own injector, and the distance is small, you may want to try it without a step-up first.

    There is a lot more info on PoE here: https://en.wikipedia.org/wiki/Power_over_Ethernet

    Tell us what you end up doing, I am curious what works for your setup also.

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    Assistant Admin Ken's Avatar
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    Terry,
    Please check your private messages...

  6. #6
    SG Enthusiast blacklab's Avatar
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    Will do Ken.

    I have been very busy learning about POE from the link Philip gave me.

    Thanks Philip, I now know more than I ever wanted to know about POE, but I am still not sure what to use. I think all I need is an injector because the Bullet gets its power from the Ethernet cable. All this will be mounted inside my camper so cable length should not be a problem.

    I am anxious to try this out, but the snow is still almost three feet deep in my yard and I am not going to try and get through that. Nature brought it here, nature can take it away.
    Last edited by blacklab; 04-11-18 at 02:05 AM.

  7. #7
    Administrator Philip's Avatar
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    Basically, PoE is DC (no need for inverter), and it is usually 48V DC, Ubiquity usually uses 24V DC, however it can work with as low as 12 volts for shorter distances. Most PoE devices use/need 12V or less, the reason injectors supply more is for long runs of Ethernet cables (because they are so thin there is a lot of loss at long distances).

    So, I was trying to suggest to try it with straight 12V DC on the proper Ethernet wires and see if it works, before trying more complicated setups, like stepping it up to 24 or 48v.

    If you decide to try this, you would need to find which two wires from the Ethernet cable the Bullet uses for power input though. Alternatively yes, you can use an injector, but most of them work off of 110v AC.

    There are some "passive injectors" that just pass the voltage supplied to them, you can use one of those and directly supply 12V DC to it, here is one example:
    https://www.amazon.com/Gigabit-Passi.../dp/B00ENNUWO4

    You can even get the same injector with a power supply, and just cut/use the cable from the power supply connected directly to 12v DC (just don't reverse the polarity).
    https://www.amazon.com/Gigabit-Injec...rds=WiFi-Texas



    The wiring pinout on Ubiquity Nano is:
    https://community.ubnt.com/t5/airMAX...C/td-p/1110257
    pins 1,2 and 3,6 for data, 4 and 5 are positive, 7 and 8 are negative. It's actually printed right on the large 24V UBNT power bricks.
    I imagine it is the same pinout on the Bullet, you may want to verify it.


    That Amazon passive injector I linked is the same, i.e. pins 4/5 positive, pins 7/8 negative. All it needs is DC power

  8. #8
    SG Enthusiast blacklab's Avatar
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    Thanks Philip, the Gigabit POE Injector is what I think I need, at least I hope so because I just ordered one. The Bullet uses pin 4 & 5 and 7 & 8 for power up to 24V. The higher the voltage, the longer the range. I will probably be putting a directional antenna on it before I am done if I can mount it to the Bat-wing antena so it will be adjustable.

    I found a 3-35V in - 4-34V out step-up voltage regulator for $14. It has a digital voltage readout that I thought would be useful. If it draws too much current I will look for something better. I want to use this for long periods on solar power.

    If things really work well I will be able to plug the ATA for my VOIP phone directly into the Bullet or a router and have my home number with me.

  9. #9
    Administrator Philip's Avatar
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    Sounds good I doubt it will draw a lot of power.

    You got me interested, found another very informative thread about the bullet used in marine environment directly from 12v batteries, reportedly it worked with anything above ~5.5vdc, power consumption 3.9-4.25 watts, ~0.5v voltage drop over 25' Ethernet cable.

    https://community.ubnt.com/t5/Bullet...0/td-p/1160384

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