sebastiantombs
Known around here
Don't pay attention to current, think about the power available which is a function of current and voltage. 12 volts at 2 amps equals 24 watts. 48 volts at .6 amps equals 28.8 watts. More power Scotty!
Strange icon on Dahua IP camera server page
- Thread starter hdtvjeff
- Start date
When you put power down a cable, a certain amount of voltage is lost. It varies based on what the wire is made of, the wire gauge, amount of amps being drawn, temperature of the wires, etc. The interactions between all these factors is complicated, but suffice it to say the PoE standards such as 802.3af take all this into account to deliver a usable amount of power. When you use passive PoE adapters and your own 12 volt power supply, nothing is guaranteed.
When you use standard PoE, you don't need any adapters. Just plug one end of your network cable into the PoE switch and the other end into the camera.
If you need to power microphones, then you can probably use your passive PoE adapters simultaneously with the standard PoE switch. Wires 1,2,3,6 will be used by the camera for data and power from the PoE switch, while your passive injectors separate out wires 4,5,7,8 to use for 12v DC power.
If you need to power something more demanding like a large IR illuminator that uses more than about 6 watts, then it would be best to use real low voltage landscaping wire or something like that, instead of cat5e.
To the OP the problem is you are experiencing voltage drop on your 12V PASSIVE POE injector setup. Sure you have 12V@2A, but 100 feet from where you need it and with some of the thinnest conductors (CAT5) used in wiring. I'm sure you are dropping volts, and the higher the current requirement the worse the effect.
Your power sourcing equipment (PSE) is a 12VDC transformer that is applying power to the network cable and I guarantee the powered device (PD) is receiving less voltage than it needs to operate properly.
True POE/POE+/POE++ equipment overcomes this problem by sourcing much higher voltages and handshaking with the PD device to make sure the drop in voltage is factored in and the device receives the required amount of voltage and current (up to POE spec limits). You could confirm this problem to an extent by measuring the voltage on the DC plug at the far end, whatever voltage you measure without the camera connected is actually the best the camera will ever see, and camera power draw will only further impact this voltage driving it lower. I wouldn't be surprised if the voltage is below 10V at the far end of such a small pair of copper conductors. If you have sharp Multimeter probes you could even connect the camera and pierce the rubber wire coating on the DC plug to potentially take an in-circuit measurement under load, but it will get worse for sure.
If you conduct the same experiment with a true POE setup and a POE tap/adapter you shouldn't see this problem as voltage drop from the poe adapter to the camera (usually over a couple inches) will be negligible, but if the camera supports POE built-in you can even eliminate that entirely by direct connection from camera to POE switch.
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SpacemanSpiff
Known around here
Does cat 6/ 7 have better numbers for AWG?
It can, but it will be a marginal increase in wire size.