Voltage Loss Over Cat5 - 12V DC and 24VAC

If using (2) Twisted pairs in the Cat5 cable what would be the max you would run power using 12V DC and 24 VAC. How long could you run before you start to experience detrimental voltage loss?

I have researched the forum and found many different answers peppered throughout several different threads so I thought I would start a dedicated thread to this topic. I would really like to see if anyone has any scientific data backing up their answer but would also like to get some general opinions as well.

If using (2) Twisted pairs in the Cat5 cable what would be the max you would run power using 12V DC and 24 VAC. How long could you run before you start to experience detrimental voltage loss?

This is as vague a question as "how big a hard drive do I need for X number of days of storage" - there are too many factors missing.

I have researched the forum and found many different answers peppered throughout several different threads so I thought I would start a dedicated thread to this topic. I would really like to see if anyone has any scientific data backing up their answer but would also like to get some general opinions as well.

There are four main things you need to add into your calculation:

First and foremost, power requirements of the camera: most voltage-drop calculators ask for this in amps; many cameras, especially dual-voltage types, list only the camera's power draw in watts (mainly because current draw is inversely proportional to supply voltage). It's easy enough to calculate one from the other (I=P/V).

Second, the number of conductors used: normally you'll be using two or three pairs for power, and the losses could depend substantially on that difference.

Third, the *actual* voltage produced by the power supply: this is especially true of 12VDC source, as unregulated ones may actually be outputting upwards of 16-19V, which means not only will you have less drop at the camera, you'll be able to ALLOW more drop before the camera cuts out.

Fourth, along that same line, some cameras can actually handle much lower voltages than they're "rated" for - they may spec 12V but still function properly at 9-10V. Others may crap out if you feed them voltages more than a few percentage points outside their design.

A good voltage-loss calculator is your friend - I find this one particularly useful: http://www.netkrom.com/voltage_loss_over_cat5_calculator.html

Using a CNB VCM-24VF as an example: it's rated for 2.2W power consumption. At 12V, that's about 180mA; at 24V, current draw is approximately half that. However, this camera will operate, if memory serves, on anything from 10V to 30V, DC or AC.

So at one end of the scale, with a 12V supply and using only two pairs, you would see barely .3V loss at the end of a 300' run, according to the above calculator (which, oddly, complains if you enter anything over 300' for the cable length). At that rate, you could theoretically power THREE 24VFs off a two pair of 24 AWG Cat5e, with a regulated 12VDC supply (.54A gives 1.9V loss at 300'). Use an unregulated supply running at about 16V, and you could conceivably power six cameras over those two pair (1.2A, 16V input, gives 4.6V loss, meaning you still see over 11V at the cameras... higher, in fact, because at 16V, the current draw drops to under 140mA ).

Bump up to a 24VAC supply and two pairs would be enough for a dozen cameras (remember that the current draw is cut in half, so in the calculator, we plug in 24V source, but back down to .6A, and see a loss of only 2.3V). The calculator doesn't accept the number, but we can extrapolate that at 600', you'd still see less than 5V loss running a dozen of these cameras on a 24VAC source... which would bring us down to 19V at the cameras, still well within their operating spec.

And on it goes from there. Obviously it isn't really recommended to hang that many cameras off a single Cat5e, for logistical reasons if nothing else... but it is possible, and it illustrates that concerns about voltage loss over long Cat5e runs often tend to be overstated. Naturally things get a lot worse when you add built-in IR to the mix, where cameras start drawing upwards of a full amp... added to the fact that most of those kinds of cameras only support 12V input, so you're stuck with the inherent higher losses there.

according to the above calculator (which, oddly, complains if you enter anything over 300' for the cable length).

I think they are just mentioning the distance limit for networking?

If using (2) Twisted pairs in the Cat5 cable what would be the max you would run power using 12V DC and 24 VAC. How long could you run before you start to experience detrimental voltage loss?

 

I have researched the forum and found many different answers peppered throughout several different threads so I thought I would start a dedicated thread to this topic. I would really like to see if anyone has any scientific data backing up their answer but would also like to get some general opinions as well.

When in doubt just run 18awg or 14awg.

There are four main things you need to add into your calculation:

 

First and foremost, power requirements of the camera: most voltage-drop calculators ask for this in amps; many cameras, especially dual-voltage types, list only the camera's power draw in watts (mainly because current draw is inversely proportional to supply voltage). It's easy enough to calculate one from the other (I=P/V).

 

Second, the number of conductors used: normally you'll be using two or three pairs for power, and the losses could depend substantially on that difference.

 

Third, the *actual* voltage produced by the power supply: this is especially true of 12VDC source, as unregulated ones may actually be outputting upwards of 16-19V, which means not only will you have less drop at the camera, you'll be able to ALLOW more drop before the camera cuts out.

 

Fourth, along that same line, some cameras can actually handle much lower voltages than they're "rated" for - they may spec 12V but still function properly at 9-10V. Others may crap out if you feed them voltages more than a few percentage points outside their design.

 

A good voltage-loss calculator is your friend - I find this one particularly useful: http://www.netkrom.com/voltage_loss_ove ... lator.html

 

Using a CNB VCM-24VF as an example: it's rated for 2.2W power consumption. At 12V, that's about 180mA; at 24V, current draw is approximately half that. However, this camera will operate, if memory serves, on anything from 10V to 30V, DC or AC.

 

So at one end of the scale, with a 12V supply and using only two pairs, you would see barely .3V loss at the end of a 300' run, according to the above calculator (which, oddly, complains if you enter anything over 300' for the cable length). At that rate, you could theoretically power THREE 24VFs off a two pair of 24 AWG Cat5e, with a regulated 12VDC supply (.54A gives 1.9V loss at 300'). Use an unregulated supply running at about 16V, and you could conceivably power six cameras over those two pair (1.2A, 16V input, gives 4.6V loss, meaning you still see over 11V at the cameras... higher, in fact, because at 16V, the current draw drops to under 140mA ).

 

Bump up to a 24VAC supply and two pairs would be enough for a dozen cameras (remember that the current draw is cut in half, so in the calculator, we plug in 24V source, but back down to .6A, and see a loss of only 2.3V). The calculator doesn't accept the number, but we can extrapolate that at 600', you'd still see less than 5V loss running a dozen of these cameras on a 24VAC source... which would bring us down to 19V at the cameras, still well within their operating spec.

 

And on it goes from there. Obviously it isn't really recommended to hang that many cameras off a single Cat5e, for logistical reasons if nothing else... but it is possible, and it illustrates that concerns about voltage loss over long Cat5e runs often tend to be overstated. Naturally things get a lot worse when you add built-in IR to the mix, where cameras start drawing upwards of a full amp... added to the fact that most of those kinds of cameras only support 12V input, so you're stuck with the inherent higher losses there.

 

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Great answer. Thanks!!! Good voltage calculator too - Bookmarked.

When in doubt just run 18awg or 14awg.

LOL, I know, but too many customers asking why I dont carry Cat5 so I gotta give them what they want.

LOL, I know, but too many customers asking why I dont carry Cat5 so I gotta give them what they want.

Tell them stop being cheap and lazy and run the 18awg

When they get the EX30 they will be thankful they ran 18awg

, if they were to buy something such as an EX30, that would not be a cheap customer.

this subject couldn't of come along at a better time, i just purchased all the items needed to run Cat5e, and i was worried about the possible voltage drop to each camera...

the cameras i am using are the CNB VCM-24VFs...

the power panel i have is 12v 1.5 amp each channel, in fact i used a meter to measure the output, and found each of the 16 channels was between 11.85 to 11.86 volts...none below and none higher...

the length of the longest run of Cat5e will be approx 75 feet...

the Cat5e will replace those cheap eBay Siamese cables that came with a package i bought...

i will be using these Mini-baluns...the price is just incredible...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260756824400&ssPageName=STRK:MEWNX:IT

and i will be using this Cat5e cable...

http://www.amazon.com/gp/product/B000067RWR

i do plan on adding a PTZ, and when i do that, the PTZ will have a separate power supply and be fed by 18-2 wire, along with the Cat5e for video and data...

again this post has really put my mind at ease...

Let us know if you run into any problems

, if they were to buy something such as an EX30, that would not be a cheap customer.

you'd be surprised, people would spend an arm and a leg on the latest and greatest toy but still want to be cheap on the labour ...

Let us know if you run into any problems

i definitely will, as i said before, i know what voltage is originating at the box (11.85v), so when i run the cable, to the camera, before connecting the camera, i will measure voltage at the camera end, and post my findings...

Let us know if you run into any problems

 

 

i definitely will, as i said before, i know what voltage is originating at the box (11.85v), so when i run the cable, to the camera, before connecting the camera, i will measure voltage at the camera end, and post my findings...

Wrong

u wanna measure voltage at the camera end with camera connected

Let us know if you run into any problems

 

 

i definitely will, as i said before, i know what voltage is originating at the box (11.85v), so when i run the cable, to the camera, before connecting the camera, i will measure voltage at the camera end, and post my findings...

 

Wrong

u wanna measure voltage at the camera with camera connected

well i will do it both ways....

Well i will do it both ways....

I would strongly recommend this link

http://lmgtfy.com/?q=basic+electricity+101

Well i will do it both ways....

 

I would strongly recommend this link

 

http://lmgtfy.com/?q=basic+electricity+101

i don't need that, maybe you should check it out,,,humoring someone goes a long way..LOL