New To Forum-voltage drop question

S

sho_presni

n3wb
Oct 16, 2024
6
2
USA
I have cctv system with a max of 57m distance using cat6 with 12v 2000mA power supply for each cam.

I am having what appears as a voltage drop on the most distant cam (57m). I am looking for the best / the correct solution. Can I simply use a different power supply at higher voltage, or use an in-line injector?

The symptom is when motion is detected and secure light comes on, the picture glitches and a bunch of stats are shown for a few seconds. Seems like a reboot for power loss.
Oh, this is in a Central American country, and I am not in that location at this time. Looking to see what I may bring for next trip there.
Thanks in advance.
Steve (newbie) ;-)
 
You're better off with using cameras that can be powered over ethernet PoE. PoE uses a higher voltage ~48VDC and is less susceptible to voltage drop.

You could also use PoE over ethernet and a PoE splitter at the camera that converts the voltage down to a regulated 12V. You'd need a PoE switch or PoE injector.
 
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Yes you can. Or you might buffer with a battery at the cam end. Another
way would be a higher voltage and current supply with a DC/DC down converter
at the cam. But, check the input specs of the camera 1st.
 
In keeping with Gary's second suggestion abobve, I'd use a 24VDC power supply at the source and a regulator with 12VDC output at the camera end. The source power supply linked is UL- listed, something I highly recommend but is for indoor use, the regulator is outdoor rated.

SOURCE END:
F1TP 24V 2.5A Power Supply Adapter, AC 100V-240V Output DC 24 Volt 0-60W Transformer Charger UL Listed with 5.5 x 2.1 and 5.5 x 2.5 Male Plug Jack Connector, Compatible with 24Volt 0-2.5Amp

CAMERA END:
DC Voltage Reducer Converter DC 8V-40V to 12V 3A 36W Automatic Step Down Up Voltage Regulator Power Converter Waterproof Module
 
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tangent said:
You're better off with using cameras that can be powered over ethernet PoE. PoE uses a higher voltage ~48VDC and is less susceptible to voltage drop.

You could also use PoE over ethernet and a PoE splitter at the camera that converts the voltage down to a regulated 12V. You'd need a PoE switch or PoE injector.
Click to expand...
Yes, I agree with switching things out. Eventually I will swap the whole system but for now I have to use what I have. $$$. Thank you!
 
Running the numbers shows why it's so much better to use ~48 volt POE to run the power. You didn't say that the load is pulling the full 12 amps, but I'm going to use that for the example anyway.

The listed resistance for 23 AWG copper wire is 66.78 ohms/1000 meters
For a circuit, the 57m distance is actually a 114m wire run, making the resistance 7.6 ohms.
Since the power is carried on two wires with POE, the final resistance is 3.8 ohms.

What's the voltage drop of 2 amps through 3.8 ohms? 7.6 volts.
So with a 12 volt source your're losing 63% of the voltage. Power in is 24 watts, power at the far end is 8.8 watts, for a 63% loss of power in the wiring.

Running the numbers with a 48 volt source. Current for 24 watts is 0.5 amps. Voltage drop of 0.5 amps through 3.8 ohms is 1.9 volts.
In this case you're losing 4% of the voltage. Power in is 24 watts, power at the far end is 23.05 watts, for a 4% loss of power in the wiring.
Huge difference!

Yes, a POE splitter at the far end will add to that 4% power loss. I found one claim that the typical efficiency is 80%. I would have guessed higher. But even if you lose 20% in the splitter the total power loss is 24% compared with 63% with the 12 volt wiring, plus the power at the camera will be at an honest 12 volts. Another issue is the maximum current for power transmission of 23 AWG copper is .725 amps, or 1.45 amps for 2 paralleled conductors, so sending 2 amps through that is busting the pubished limit.
 
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Nominal 48 volts is the IEEE standard for POE. That's what standard POE switches and injectors supply, as well as NVRs with POE ports for the cameras. Part of the splitter is the voltage reducer. The other part of the splitter passes the data connection through to the camera.
 
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