No power to the camera over POE

[Hazmot]

Hi folks. I'm new here.. I bought a 360deg pano ip camera off E-bay knowing the poe was dead. I got the camera running off 12vdc just fine and the picture is very good. I enjoy tinkering around with board level repair on electronics as that is what I did most of my working life(now retired).
The poe circuit uses one of these lan filter/transformers. One of the toroid coils appears to be open. That coil is on the dc+ line. (pins 5&4 from the cat5 plug). I did order a new transformer from aliexpress so I have a month or two wait.. I was wondering if any one may have a general schematic of the cat5 cable circuit that uses this type of interface. I am interested in learning how it works. The part # is 30FB-22NL
Thanks

 

[alastairstevenson]

I was wondering if any one may have a general schematic of the cat5 cable circuit that uses this type of interface. I am interested in learning how it works.

Typically for a PoE PD (Powered Device) implementation, a couple of bridge rectifiers will feed a PD controller, which handles the initial PoE classification handshake, which when activated turns on its power switch that then supplies the resulting 43v to a PWM switch-mode downconvertor, usually providing a regulated 12v to downstream power supplies.

There are many integrated PD controller devices available.
If you take a look on the circuit board of your camera, you should be able to find the part number and therefore the data sheet of the one in your device.

Attached is the data sheet of one of the common PD controllers I've come across.
As most of these do - it provides some sample operating schematics.

One of the toroid coils appears to be open.

There will be a cause of the open circuit that should probably be investigated.
It might just be that replacing the ethernet transformer is just one stage of the repair.
Check out for damage or discolouration the PCB traces that connect the transformer to the ethernet connector on the PCB.
Check out the bridge rectifiers that feed the raw 48v to the PD controller, and check there are no shorted transient suppression devices on the output side.

 

[alastairstevenson]

just a thought, and a question :

One of the toroid coils appears to be open.

Do you know this because you've done resistance checks on the actual pins of the ethernet transformer?
Presumably you've not removed it as the device is still working off 12v.

That coil is on the dc+ line. (pins 5&4 from the cat5 plug).

As the device is presumably 10/100 ethernet, as opposed to gigabit, pins 4/5 and 7/8 will only connect to the bridge rectifier that supports one of the PoE modes, as opposed to being connected to the ethernet transformer.
So I'm puzzling over the origin of your statement above.

 

[Hazmot]

Yes I did resistance checks on all the transformer leads. The one is open for sure. Pin 7&8 on the cat cable goes to one of the toroids. 4&5 goes to a seperate toroid (the one that is open). When I measure the voltage between 7/8 and 4/5 of the cat cable I see 3.58vdc switching on and off slowly. The other side of the transformer looks to be very low power stuff. There is however a mechanical relay that I can hear click when the camera boots. On the left side of the board their appears to be the power regulator circuit.
On the left side there are 2 Schottky diodes feeding a small switching transformer (step down) and one of the Schottky diodes was shorted. I did replace that diode. The conformal coating on the board is driving me crazy. Its virtually invisible and runs me around in circles with the ohm meter. I see Amazon has these poe splitter adapters. Maybe that is the simplest fix for right now..
Oh and BTW I did look for a chip like you showed and really could not find anything. The SMT's are so tiny they just have code marking on them...

 

[tigerwillow1]

If you're using a POE switch it's likely mode A POE where pins 4, 5, 7, and 8 aren't used. The power will be on the data pins 1/2 and 3/6. If using a POE injector, it's likely mode B is in use, with the power on 4/5 and 7/8.

 

[Hazmot]

Ok thanks. I will check out those lines also.

 

[alastairstevenson]

Pin 7&8 on the cat cable goes to one of the toroids. 4&5 goes to a seperate toroid (the one that is open).

Interesting.
I'd missed that detail on the datasheet that you attached, the ethernet transformer has 4 pairs of inputs instead of the usual 2 pairs.
That arrangement is usually for a gigabit connection where all 4 wire pairs carry signals, not something I've seen on an IP camera.
When / if you replace it, it will be interesting to see what the link detect on the switch shows for link speed.

There is however a mechanical relay that I can hear click when the camera boots.

That will be the IR cut filter in the lens assembly clicking over.
To show that - cover up the light sensor (or the lens if there isn't a light sensor) for a few seconds, you should hear it clicking back as it goes into night mode.