POE Splitter to power Mic from a PTZ camera?

[DanielR44]

Hi

I have a PTZ ip camera which is power by a POE injector. I assume the power its getting is 22w as this is what is specified by the camer maker. The Camera has a RCA plug for a mic so I ordered a simple mic which needs to be powered.

Now I dont want to run another seperate power cable just to power the mic so Im looking at the option to use a POE splitter with power through so my question is if the current POE is providing 22w and I use a POE splitter to power the mic, then from the mic power out into the power in of the camera, will the PTZ camera receive enough power as I assume the POE splitter will bring the voltage down for the mic, and output this same low voltage which in turn would be too low for the camera, is this how it works?

Thanks, Daniel.

 

[tigerwillow1]

When you use the camera's power input connector, it's expecting 12 volts, which is hopefully what your POE splitter provides, and what the camera wants. Do verify this with the specs for your camera in case it's an oddball. All the ones I know about expect 12 volts.

 

[DanielR44]

When you use the camera's power input connector, it's expecting 12 volts, which is hopefully what your POE splitter provides, and what the camera wants. Do verify this with the specs for your camera in case it's an oddball. All the ones I know about expect 12 volts.

Thanks for the reply. Im not totally wised up on the differences between the poe and a direct plug in for power. In the camera specs it says DC 12V & 48V PoE (IEEE 802.3at) Can you explain why PoE is 48v, where as the other is DC 12v in either case it says Power consumption is <20w. Im not a electrician so dont know what relation volts have to watts? I assume what Im wanting to do is quite common, but I cant find much on this subject regarding PTZ cameras which I assume would use significantly more power than normal IP cameras.

Dan

 

[tigerwillow1]

When working with DC power, the relationship is simply watts=volts*amps, also amps=watts/volts. From this you can see that 20 watts of power requires 1.67 amps at 12 volts, or 0.42 amps at 48 volts. The resistance of the wire results in power being lost in the wiring, and the amount of this loss is directly related to the amps (i.e. current). So transmitting 20 watts at 48 volts results in less wiring-related power loss than transmitting it at 12 volts. For the relatively thin cat5/6 wires running up to 100 meters, this loss can be significant. I believe that 48 volts was chosen as the highest voltage that doesn't present an electrocution hazard. The camera runs on 12 volts, and converts the 48 volts down to 12 to power itself. Using the higher voltage over the long thin wires reduces the power loss in the wiring.

This same principle is why power transmission lines carry extremely high voltages, although the math gets a bit more complicated with AC power.

 

[DanielR44]

When working with DC power, the relationship is simply watts=volts*amps, also amps=watts/volts. From this you can see that 20 watts of power requires 1.67 amps at 12 volts, or 0.42 amps at 48 volts. The resistance of the wire results in power being lost in the wiring, and the amount of this loss is directly related to the amps (i.e. current). So transmitting 20 watts at 48 volts results in less wiring-related power loss than transmitting it at 12 volts. For the relatively thin cat5/6 wires running up to 100 meters, this loss can be significant. I believe that 48 volts was chosen as the highest voltage that doesn't present an electrocution hazard. The camera runs on 12 volts, and converts the 48 volts down to 12 to power itself. Using the higher voltage over the long thin wires reduces the power loss in the wiring.

This same principle is why power transmission lines carry extremely high voltages, although the math gets a bit more complicated with AC power.

Thank you for that explanation, very helpful. So my only question is when a splitter divides the 48v from the POE cable then converts it to 12v I assume it also reduces the 22w to something much lower to power up the mic? Being as the poe splitter works on the basis of power through would this then mean what ever the mic ends up needing it passes this to the camera, or does the poe splitter determine that combined both the mic and camera requires more watts, in simple terms will the camera still get its 22w after being passed through the poe splitter to first power the mic?

Thanks, Daniel.

 

[tigerwillow1]

I'm assuming your camera has a connector for power input from the splitter, then another connector for power input to the camera. That power output connector is a just a convenience feature to help keep the wiring simpler. There are multiple ways to explain. In your case, the power flows from the poe splitter to the microphone, the microphone takes what it needs (hardly any), then passes the rest along to the camera. Power is supplied by the splitter, but it's up to each device to consume what it needs. There's a pretty good water analogy here: A hose with a few daisy-chained sprinklers. The first sprinkler emits a certain amount of water, then the rest flows down the hose to the next sprinkler. If the faucet supplies enough water to service all of the sprinklers, the pressure is maintained and they all function correctly. If there's not enough water supply, the pressure drops and the sprinklers do not work correctly. The pressure is analogous to the voltage, and the amount of water flowing is analogous to the power.

 

[DanielR44]

Perfect, thanks so much for your clear help. Yes my camera is a Reolink 423 PTZ it has both POE and power input. The splitter will work then as you explain it which is great. My logic was that maybe the splitter gave what it needed for the mic, then that same output was fed to the camera by the mics thru loop but thats not the case.

Thanks, Dan

 

[Joseph Marmo]

Perfect, thanks so much for your clear help. Yes my camera is a Reolink 423 PTZ it has both POE and power input. The splitter will work then as you explain it which is great. My logic was that maybe the splitter gave what it needed for the mic, then that same output was fed to the camera by the mics thru loop but thats not the case.

Thanks, Dan

Hi Daniel,
I am ordering the RLC-423, and am in the same situation
Can you tell me what I need to be able to record audio on the RLC-423?
I have an 802.3af/at POE switch. I'm a bit new to this, and not sure which microphone and poe splitter I need. I'm also unsure how to connect them to the RLC-423.
Any advice would be helpful.