DIY POE Power

V

vahidasadi

n3wb
Mar 8, 2015
2
0
Hi i'm vahid new here and new here
last week i was installing cams in a local school with hikvision 2132 3MPixel cameras.i used cat6 copper wires but i think cat5 wires could be the best choice to save bucks. because cams use 10/100 NIC and i think there is enough bandwidth with Cat5E .but i didn't take risk and wired them tonon POE Gbit switch.
to power the cameras i used 12V -30A power supply and i cut the brown and blue wires in the both end of cable and then i connected the Blue as positive and Brown as negative at power source side and connected the pair to camera with it's power jack/socket and patched orange/green with RJ45. every thing went well until night i noticed voltage drop when cameras turning their IR light ON.some of them are alright but 3 of them don't have enough illumination so i changed the voltage of power supply to 15 V but i scared to increase it more
here is my question :camera has 802.3af POE standard which means i can increase the power voltage up to 48V but i haven't used RJ45 jack only and i'm powering them with the other power socket.is this the same or the other power port is only for 12 V powering???
 
If I've understood your description correctly you are connecting the cameras to a PoE switch.
If that's so, you don't need to power the cameras via a separate power supply as the switch is already providing power.
You MUST NOT use a fixed power supply through a long run of Ethernet cable as the end result will be supplying an out-of-spec voltage to the cameras due to the unknown and variable resistance of the various cable runs, and the fact that the cameras will draw different currents depending on their activity level. As you have already discovered.
The least that will happen is that the cameras will malfunction as the voltage of the power supply is sometimes too low. The worst that will happen is that you damage the camera with an over-voltage power source.

Just stick with the PoE switch as the power source. The camera internal PoE module provides a closely regulated 12v to the camera, and accommodates the variable feed from different lengths and types of Ethernet cable.

The only way to use an external 12v power supply for the camera is to have a 12v power source right next to each camera connected via a short (say under 1m to have a low voltage drop) extension lead, connected to the 12v power jack of the camera.
 
Thanx for the reply
No i am not using POE switch and as i mentioned above i have used seprate power supply with 30A output
 
I was commenting based on this information:
but i didn't take risk and wired them tonon POE Gbit switch.
Click to expand...

But my comment about not being able to use Cat5E Ethernet cable to reliably provide 12v power over long and variable lengths still stands. I presume your 3 troublesome cameras are on the longest runs.
How many cameras are you deploying?
It may be easy and cheap to use a 10/100 PoE switch to power the cameras of you have wired them back to a central location.
You are correct that Gigabit speeds for individual cameras is not needed - the cameras will generate generally under 10Mbps of traffic. But the switch uplink will likely need to be Gigabit, depending on how many cameras.
 
just use a poe switch but you will have to rewire both ends with new jacks since you went un orthadox on the other jacks
 
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