DC input as output when utilizing POE?

[1.21 jiggawatts!]

i have noticed that when utilizing POE, if you test probe the DC input (be it barrel jack or wires depending on camera) you can measure voltage on it with a voltmeter.

is it possible to use the DC input as a power source when utilizing POE instead of a power adapter? what kind of current capabilities would it have, if so? could you use this as a source of power for an external microphone? or IR illuminator?

i didn't try hooking anything up just in case it's not a good idea. couldn't find any info on this.

 

[tigerwillow1]

You didn't say which camera(s) you measured, and the behavior could vary with different cameras. Having said that, I suspect you are measuring leakage voltage with a high impedance meter and the voltage will quickly drop to zero if you apply a load. Here's a thread specific to dahua cameras that will answer the question: Dahua camera mod to power external IR light

 

[pozzello]

you could almost certainly use it for a microphone (very low current draw).
It may or may not work for an IR illuminator, depending on your camera,
and drawing too much might burn out your cam's PoE circuitry, so you're basically rolling the dice there. Try it if you dare...

 

[Cameraguy]

i have noticed that when utilizing POE, if you test probe the DC input (be it barrel jack or wires depending on camera) you can measure voltage on it with a voltmeter.

is it possible to use the DC input as a power source when utilizing POE instead of a power adapter? what kind of current capabilities would it have, if so? could you use this as a source of power for an external microphone? or IR illuminator?

i didn't try hooking anything up just in case it's not a good idea. couldn't find any info on this.

If you try this let us know it it was able to power a mic

 

[1.21 jiggawatts!]

tried it out with a 20ma load on a HDW4231EM-AS. the load brings the voltage down to 0v. no usable current available.

 

[pozzello]

interesting. i guess Dahua tends to put a diode on that part of the circuitry,
per discussion in thread linked from comment #2 above:
Dahua camera mod to power external IR light

I have used the same output on a Hikvision min-bullet (2032) to power an IR illuminator, tho only temporarily (just to see if it might work.)
I ended up not using it that way for fear of blowing up the PoE circuitry, but I'm sure it would be fine for a low-current draw (like a microphone).

 

[tigerwillow1]

I checked this on the one Hikvision camera I have, and it won't drive any load. With no load, the expensive DMM reads nominal 12 volts. The 25k ohm per volt meter drags the output down under 3 volts, and the IR illuminator with the LEDs off drags it under a volt.

 

[pozzello]

i must have tested on a different cam then (not Hik or Dahua). Maybe one of my Huisun PTZ's. nevermind.
in any case, you could always bypass that diode if you dare. would prolly be OK for a mIc...