DC power questions

[int0 0]

Hello-

 

I recently purchases 2 security cameras. I need to place them approximately 300' from the nearest power source. I took a 12VDC power supply with 2A output and measured the voltage, and it was 12.25. I then spliced in 300' of 18 gauge twisted cable between the ends. I then measured the voltage again and was suprised to see it barely dropped, it was reading 12.23. So here are my questions:

 

1. Does this seem legitimate to run 300' with barely any voltage drop? If so, I wonder how far I could push it?

 

2. Is there a drop in amps over the distance?

 

3. Can I daisy chain the power to these 2 cameras? The cameras require at least 1A and the power supply is 2A.

 

4. Is there any risk of fire or damage to the camera with this setup? I assumed that as long as my voltage drop wasn't too great, it wouldn't be a big deal, but I don't know alot about these things.

 

Thanks for any help.

[StanLee2066 0]

Hello-

 

I recently purchases 2 security cameras. I need to place them approximately 300' from the nearest power source. I took a 12VDC power supply with 2A output and measured the voltage, and it was 12.25. I then spliced in 300' of 18 gauge twisted cable between the ends. I then measured the voltage again and was suprised to see it barely dropped, it was reading 12.23. So here are my questions:

 

1. Does this seem legitimate to run 300' with barely any voltage drop? If so, I wonder how far I could push it?

 

2. Is there a drop in amps over the distance?

 

3. Can I daisy chain the power to these 2 cameras? The cameras require at least 1A and the power supply is 2A.

 

4. Is there any risk of fire or damage to the camera with this setup? I assumed that as long as my voltage drop wasn't too great, it wouldn't be a big deal, but I don't know alot about these things.

 

Thanks for any help.

 

You're right in expecting a larger voltage drop. I suspect you made the measurements without the load? (cameras powered @ 1A each). Attach both cameras and measure again. You'll probably find you need an 18-24DC power supply to get that 12Vdc at the other end. Also, if both cameras require 2A, best to go with at least 3A. A supply with at least 4A or more is better.

[int0 0]

Hello-

 

I recently purchases 2 security cameras. I need to place them approximately 300' from the nearest power source. I took a 12VDC power supply with 2A output and measured the voltage, and it was 12.25. I then spliced in 300' of 18 gauge twisted cable between the ends. I then measured the voltage again and was suprised to see it barely dropped, it was reading 12.23. So here are my questions:

 

1. Does this seem legitimate to run 300' with barely any voltage drop? If so, I wonder how far I could push it?

 

2. Is there a drop in amps over the distance?

 

3. Can I daisy chain the power to these 2 cameras? The cameras require at least 1A and the power supply is 2A.

 

4. Is there any risk of fire or damage to the camera with this setup? I assumed that as long as my voltage drop wasn't too great, it wouldn't be a big deal, but I don't know alot about these things.

 

Thanks for any help.

 

You're right in expecting a larger voltage drop. I suspect you made the measurements without the load? (cameras powered @ 1A each). Attach both cameras and measure again. You'll probably find you need an 18-24DC power supply to get that 12Vdc at the other end. Also, if both cameras require 2A, best to go with at least 3A. A supply with at least 4A or more is better.

 

 

Ok, I tested with 1 camera on, and voltage was down to 10.25 with the infrared lights on. I believe that's a little too low for recommended use. If I use an 18-24DC power supply, can I hook that up directly or do I need some sort of converter on the other end?

[StanLee2066 0]

Ok, I tested with 1 camera on, and voltage was down to 10.25 with the infrared lights on. I believe that's a little too low for recommended use. If I use an 18-24DC power supply, can I hook that up directly or do I need some sort of converter on the other end?

 

2Vdc voltage drop for a single camera tells me it actually only uses about 0.5amps - hence the 1A camera requirement (you can measure that too). You could probably get away with 2A supply after all and even a 16Vdc supply since it looks like you'll be dropping about 4v total. Ideally, you would select a DC power supply at the source that would provide the ~12Vdc at the required 2-camera load so no special conversions needed.

[int0 0]

Ok, I tested with 1 camera on, and voltage was down to 10.25 with the infrared lights on. I believe that's a little too low for recommended use. If I use an 18-24DC power supply, can I hook that up directly or do I need some sort of converter on the other end?

 

2Vdc voltage drop for a single camera tells me it actually only uses about 0.5amps - hence the 1A camera requirement (you can measure that too). You could probably get away with 2A supply after all and even a 16Vdc supply since it looks like you'll be dropping about 4v total. Ideally, you would select a DC power supply at the source that would provide the ~12Vdc at the required 2-camera load so no special conversions needed.

 

I have a extra laptop power supply lying around, rated for 20VDC and 11A. I think I will try using that, although I am guessing I will need to step down the voltage anyway.

 

Thanks for the help!

[StanLee2066 0]

Just a warning though. The longer the DC run, the more dependent the DC output at the other end will be with regards to total current draw. You'll be fine as long as both cameras are both powered together. If you connect/disconnect one at a time or one craps out on you, just know the remaining camera will see a 2Vdc voltage change. Most devices are designed to handle such fluctuations... but you never know.

 

PoE applications don't worry about this because there is one cable run per camera.

 

Play with this calculator. Enter your data, then see what happens to the voltage when it drops from 1A (both cameras) to 0.5A (one camera). You'll also notice that as the run becomes shorter, the voltage change become less significant.

 

http://www.calculator.net/voltage-drop-calculator.html

[int0 0]

Just a warning though. The longer the DC run, the more dependent the DC output at the other end will be with regards to total current draw. You'll be fine as long as both cameras are both powered together. If you connect/disconnect one at a time or one craps out on you, just know the remaining camera will see a 2Vdc voltage change. Most devices are designed to handle such fluctuations... but you never know.

 

PoE applications don't worry about this because there is one cable run per camera.

 

Play with this calculator. Enter your data, then see what happens to the voltage when it drops from 1A (both cameras) to 0.5A (one camera). You'll also notice that as the run becomes shorter, the voltage change become less significant.

 

http://www.calculator.net/voltage-drop-calculator.html

 

Thanks. I think my safest bet is to wire each camera separately, I have enough wire and old power supplies to handle that, and I think I can just get a voltage regulator for each one to make sure I only have 12 volts at the camera.

[swin22 0]

Hi guys

Sorry for jumping in I this post but I don't know where else to look. I have installed a dahua Dvr 1604hfue hybrid Dvr sometime ago and I was asked to wire in alarm outputs for the customer to use with the idmss plus app for home automation. I connected a 500mA 12v power to the 12+ port on the alarm and the outputs through relays. Everything worked perfect for a few weeks until I was told the Dvr all the lights on the panel are flashing and so are all the outputs. When I disconnect the power to the alarm outputs it stops and I have to restart the Dvr. Also when the Dvr front panel is flashing no recording happens. Any ideas and thanking yup in advance for any advice