Custom PoE and Voltage Drop

[zaphbeeble]

Hi all. I've been frequenting these forums as a lurker for some time now, while I was researching how to implement a DYI home security system using ZoneMinder.

While I got the software all setup properly, I ran into an unexpected snag, and I was wondering if one of you good people has come across it before.

I recently purchased a Foscam FI8904W camera. It's an IP camera that also has 25 IR LEDs for night-time operation. Everything worked great with ZoneMinder and all my tests were successful.

But here's the catch: I need to install this camera in a place (outdoor) where I have no power supply available. Therefore, I built a custom Power over Ethernet injector/splitter - that is, I use 4 wires from the 8 in my CAT6 cable for the network signal (pins 1,2,3 and 6) and four wires for power (4,5,7 and 8. 4 and 5 for positive, 7 and 8 for negative).

The problem is that due to the distance from where the power supply is located (~30 meters), I experience a drop in voltage. When measuring the voltage at the power supply, I measure about 5.3V DC (nominal voltage is 5V according to the power supply's casing).

When I measured it at the point where the camera is installed, and with the camera in operation (with IR LEDs turned off), the voltage was 4.4V DC -- not enough. I compensated for this by using a 6V power supply instead of the 5V power supply included, which did the trick! The camera worked fine, and when measuring voltage at the point of installation, it was about 5.5V DC.

However, as soon as it goes dark and the camera's LEDs light up, the voltage again drops, this time down to 4.4V (with the 6V power supply!) and again that is not enough for the camera to work.

In order to compensate for this, I can raise the power supply's voltage to 7.5V, which would give the camera the proper voltage to operate when its LEDs are turned on. I am concerned, however, that when the LEDs are off (during the day for example), the excess voltage may damage the camera.

Has any of you got any experience with this? Is this a real concern, or do these cameras employ an internal voltage regulator, and I can therefore use 7.5V DC without problems?

If not, what do you guys recommend?

Thanks in advance for your time and assistance.

[kingofkya]

Hers what i would do. go to radio shack(if they still have them) buy a 5volt regulator. Then run a 12v power supply on the line.

Also it is very likely there is a voltage regulator inside the device but we don't know what it limits are.

Ether way less that $5 trip to radio shack.


http://www.radioshack.com/product/index ... =107597886

IF you need help let me know. It fairly trivial though.

[zaphbeeble]

Thanks for the reply, kingofkya. I sort of figured I'd need to do something like that, but I wasn't sure if the 7.5V I had in mind would be enough to trigger the voltage regulator. Running 12V is a good idea though, and should be OK.

I'll try it now and let you know how it worked out.

[zaphbeeble]

Complete success! Running 12V on the line and regulating it at the camera end with a 7805 worked perfectly.

Yesterday I built the injectors/splitters for all 4 of my cameras. Given that they draw around one Amp each, I got a variable transformer that provides 5 amps at various voltages, selected the 12V setting and I can now power all 4 cameras easily.

On to setting up the various alarm modes now.

[rmorrison100]

Thanks for the tips.