12VDC versus 24VAC for "Dual Power" Cameras

[vmgtlexi 0]

For cameras which are "dual power" (12VDC or 24VAC), is there any benefit to powering those cameras with 12VDC versus 24VAC?

 

In other words, when would a 12VDC power source be preferred and when would a 24VAC power source be preferred? What are the trade-offs of each when running "dual power" cameras?

[Birdman Adam 0]

There is no benefit of 12VDC over 24VAC, other than the fact that non-dual-voltage devices usually stick with 12VDC (this could be helpful - so you only need one supply). Also, almost everyone has a 12VDc power supply sitting around if you need one in a pinch!

 

24VAC is better for very long and/or high-draw runs. Double the voltage = ~half the current! AC PSU's may be cheaper, as they are more simple. No SMPS to make nice DC, just take down the voltage from mains with a transformer, maybe regulate it with a PTC or fuse...

[mike_va 0]

For cameras which are "dual power" (12VDC or 24VAC), is there any benefit to powering those cameras with 12VDC versus 24VAC?

In addition to what was mentioned, transformers do not wear out. I have transformers that are 80 years old and work fine.

 

Nor do they fail in a manner that takes out a bunch of cameras like a 12V PS made from questionable parts in some cases.

[vmgtlexi 0]

Thanks for the info and for helping me learn.

 

I have a 12VDC, 5-AMP, 9-camera power supply box. I only run 4 dual-voltage cameras off that box. Recently, two of those cameras started having issues. I am 99% certain it has nothing to do with the power supply, but thought I'd better consider the power supply as a possible part of the puzzle anyway.

 

In that vein, I started wondering if it might just be better to power my cameras with a 24VAC power supply box just to eliminate any chance of "under-powering" the cameras. That was the genesis of this thread.

 

But, in the end, I think I'll leave things as is. I took a voltage reading at the power source and at the camera end (approx 150' cable run for my furthest camera). Even at the camera location, my multimeter showed basically 12 volts. So, I am pretty sure my power supply to the cameras is AOK.

 

The cameras in question are 3 1/2 year old Nuvico's with IR. They have become washed out images during the day. I am replacing them with Samsung IR cameras. Will post reviews/feedback once the new Samsung's are installed.

[vmgtlexi 0]

Of course, maybe I should re-check the voltage at the camera at night when the IR is on. Maybe that could be an issue if the IR draws too much?

[Soundy 1]

If the voltage drops too much when the IR comes on, it will usually result in the camera simply dropping out... it wouldn't cause it to wash out during the day (when the IR isn't on anyway).

[vmgtlexi 0]

SOUNDY - I am sure you're correct. I think the issue with my whitewashed day-time images must be a filter that does not adjust in the day time hours. I guess I was thinking that perhaps a power issue could possibly cause the filter to not move as it's supposed to.

[tomcctv 190]

SOUNDY - I am sure you're correct. I think the issue with my whitewashed day-time images must be a filter that does not adjust in the day time hours. I guess I was thinking that perhaps a power issue could possibly cause the filter to not move as it's supposed to.

 

 

 

the other thing to look at ..... if you are using 12 5amp with 4 cameras that are over 1amp running you still could have a power problem if you have long cable runs

[vmgtlexi 0]

I'll check voltage at the cameras tonight with IR on. I checked yesterday during the day without IR and voltage at the power source and at the cameras was about equal (12 volts). That was measured on my longest cable run which is 150' or slightly less.

[SDM Group 0]

Voltage drop calculator link

 

http://www.altronix.com/app_notes/calc.php

[Birdman Adam 0]

I'd bet the iris mechanism is dying. Not much you can do, except buy better cameras!

[vmgtlexi 0]

I'd bet the iris mechanism is dying. Not much you can do, except buy better cameras!

 

Probably correct. The manufacturer (Nuvico) told me the same thing. They said the iris controller has gone bad.

 

Oddly, one of the malfunctioning cameras works perfect some days and is washed out on other days. I wish it would just outright die or work 100%, but life is never that simple.

[tomcctv 190]

I'd bet the iris mechanism is dying. Not much you can do, except buy better cameras!

 

Probably correct. The manufacturer (Nuvico) told me the same thing. They said the iris controller has gone bad.

 

Oddly, one of the malfunctioning cameras works perfect some days and is washed out on other days. I wish it would just outright die or work 100%, but life is never that simple.

 

 

 

 

another test you can do, is disconnect 1 camera and see how you get on with just running 3 (this will tell if you have problems with amps)

[HTElectrical 0]

I'll check voltage at the cameras tonight with IR on. I checked yesterday during the day without IR and voltage at the power source and at the cameras was about equal (12 volts). That was measured on my longest cable run which is 150' or slightly less.

 

That doesn't sound correct. You will have substantial drop on a 150' run with DC, unless you are running very large wire.

[vmgtlexi 0]

HT - I am certainly not an electrician, but the voltage at the camera was still basically 12 volts (I actually took the reading about 2' from the camera where my power feed connects to the camera's power cable. The cable length is probably short of 150' by 10-20'. I was just guesstimating on the high end.

 

The cable is 18/2.

[vmgtlexi 0]

So, I just retested - this time INSIDE the camera.

 

First test with my multimeter: I opened the camera housing and placed the multimeter leads on the incoming power feed on the first circuit board. I got 12.5 volts. Note this is on a shorter cable run, maybe 75 feet max.

 

Then, with IR on, I placed the multimeter leads on the IR circuit board where the red/black power cables are soldered on. I got about 10.5 volts.

 

With IR off, and placing the multimeter leads on the IR circuit board where the red/black power cables are soldered on, I got about 6 volts.

 

Does anyone who knows electricity have any feedback on these numbers? Normal? Abnormal?

 

I wonder if the 6 volts while measuring the actual IR circuit board was indicating "draw" rather than how many volts were being pushed thru the wire from the power source?

 

I know NOTHING about electricity other than it can shock !

[SEANHAWG 1]

Its quite common for your power supplies to have a higher voltage right at the power supply to account for long cable runs so that is perhaps why you are still getting around 12 volts at a 150'