Voltage drop over Cat5e

[Basjke]

+1^^ to what @Teken and @Griswalduk posted above.

I really like this Voltage Drop Calculator because I can get results by wire gauge or resistance/foot, etc.

Below is the results for 1 cam (rounded off to 9 W / .75A vs. it's stated 8.6W) and just 1 has too much drop for that distance, wire size, etc.
Its gets worse as you add cams (double the drop for 2 cams, quadruple the drop for 4 cams).

View attachment 132883

I just figured that all those online voltage drop calculators aren't worth their money, even when they are free.

My installation is now completed.

In 2 locations I used 2 core 1.5 sq mm copper multi strand VCT power cable, over a length of 25 - 30 meter.

1.5 sq mm is between 15 and 16 AWG.

According to the online calculators, my voltage drop over 25 meters would be 1.2V, or 10%

My power supply delivers 12.39V, and at the end of the cables I measure 12.35 V and the other one 12.32V

Am I missing something?

 

[tigerwillow1]

Instead of using the online calculators I start with resistance per 1000' from an AWG table and calculate the drop from there. Using a POE splitter at the camera always comes out a lot better than sending 12 volts down the wire. The nominal 48 volt feed needs 1/4 of the current, so the voltage drop is 1/4 compared to a 12 volt feed. Adding to that, the voltage drop is a smaller percentage of 48 volts than with 12 volts. When calculating remember to use the round-trip wire length, and that each side of the DC circuit is sent on 2 parallel conductors.

 

[Basjke]

Instead of using the online calculators I start with resistance per 1000' from an AWG table and calculate the drop from there. Using a POE splitter at the camera always comes out a lot better than sending 12 volts down the wire. The nominal 48 volt feed needs 1/4 of the current, so the voltage drop is 1/4 compared to a 12 volt feed. Adding to that, the voltage drop is a smaller percentage of 48 volts than with 12 volts. When calculating remember to use the round-trip wire length, and that each side of the DC circuit is sent on 2 parallel conductors.

I don't have POE, but a 12V power supply

I'm using below calculator, which states single length has to be used.

Voltage Drop Calculator

Wire / cable voltage drop calculator and how to calculate.

www.rapidtables.com

I now also notice my mistake, by measuring the voltage with no load at the end, which obviously will have no loss.

Sorry but I'm not familiar with the formula calculation, maybe you could tell me what the expected voltage drop would be, using the manual formula?

I use 2 core multi strand copper wire size 1.5 sqmm.

Length is 25 meter, assumed load is 1.6 Amp (2 cameras)

Voltage at power supply is 12.39 V and according to the above calculator wire resistance is 1.72e-8 ohm / meter

 

[tigerwillow1]

Here's an old thread where I compared voltage drop via ~48 volt POE against 14 awg and 12 awg at 12 volts. 23 AWG at ~48 volts won with about half the voltage drop and power loss compared to 12 awg at 12 volts. PoE Switch Suggestion List

 

[Basjke]

I do not have POE, and it isn't an option either

 

[Griswalduk]

The equation you are looking for is Voltage drop = current * resistance.

Resistance is usually given in ohms / meter. Remember electrically you have a distance to the load and a distance back....... so double the distance

Since the resistance of the cable is constant the volt drop will be current dependent.

Check out link below. There's tutorials available to work through which may be of benefit

https://www.allaboutcircuits.com/

 

[Basjke]

The equation you are looking for is Voltage drop = current * resistance.

Resistance is usually given in ohms / meter. Remember electrically you have a distance to the load and a distance back....... so double the distance

Since the resistance of the cable is constant the volt drop will be current dependent.

Check out link below. There's tutorials available to work through which may be of benefit

https://www.allaboutcircuits.com/

Thanks for the suggestions, but I explained already that I can't get my head around those formula calculations.

So I rely on the online calculators.

I only wanted to know if the manual calculation gives a different result from the online calculator.

 

[Flintstone61]

Just plug the motherfuckers in and see if they work. I got a 12 VDC power supply box that powers some of my older cams.
They used telephone wire.
Back in 19-whatever-year it was installed. I have 9 cams running but 3 are 200 foot runs.
And the cams are working. 2MP amcrest turrets.
i have one like this. below.....
it appears they used all 4 wires to carry the juice. 2+ and 2-.
I think you'll be fine.

 

[Griswalduk]

Power

Thanks for the suggestions, but I explained already that I can't get my head around those formula calculations.

So I rely on the online calculators.

I only wanted to know if the manual calculation gives a different result from the online calculator.

View attachment 141377

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www.allaboutcircuits.com

 

[Basjke]

Just plug the motherfuckers in and see if they work. I got a 12 VDC power supply box that powers some of my older cams.
They used telephone wire.
Back in 19-whatever-year it was installed. I have 9 cams running but 3 are 200 foot runs.
And the cams are working. 2MP amcrest turrets.
i have one like this. below.....
it appears they used all 4 wires to carry the juice. 2+ and 2-.
I think you'll be fine.

View attachment 141378

This is mine, with built in UPS, which switches without any interruption.

 

[Flintstone61]

if you have a known length of cat5e that you can cut from the box for one of your runs. you can hook up a cam and try it. or hook up a volt meter. 30 meters is about the average of my other 6 runs. they get plenty of juice. no outages in 5 years due to the power supply being insufficient.

 

[Basjke]

if you have a known length of cat5e that you can cut from the box for one of your runs. you can hook up a cam and try it. or hook up a volt meter. 30 meters is about the average of my other 6 runs. they get plenty of juice. no outages in 5 years due to the power supply being insufficient.

You mean your 30 meter lengths are powered over LAN?

It was the main reason why I started this thread, and I was advised against.

Had I known your real life experience, it would have saved me quite some hassle.

 

[Flintstone61]

no these are the remaining analog cameras. 30 meters of CCTV. where they used Rg-59 coax for image and telephone wire UTP for the 12VDC

 

[Flintstone61]

probably close to the same gauge as cat5e.

 

[Flintstone61]

i installed an IP system to replace/supplement the analog system and I was able to use a Cisco c3560x 24 port LAN switch to power them all. ( should have bought the 48 Port

 

[tech_junkie]

I will use Cat5e to transfer power from my power supply to my cameras, but I don't know exactly how to calculate the voltage drop.

Hopefully someone here will be so kind to calculate it for me

These are the specs. The Cat5e UTP has 24 AWG solid bare copper wires.

I will use a pair for supply and a pair for return

My power supply outputs 12V DC 20A

Cameras are rated 12V ~25% and use maximum 8.6 Watt.

So what will be the voltage drop over 35 meters please?

Thanks in advance

24 Ga is 25.67 ohms per 1000 ft and 84.1967 ohms per Km and max current capacity of 0.577 A
Now you know why POE is 52V and recommend limiting to wire runs to less than 300 Ft.