The case for regulated power supplies

[jets 0]

Greetings.

I'm new to the world of CCTV, having been in the commercial audiovisual systems realm serving, at various times, as troubleshooting technician, installer, consultant, project mgr, engineer.

 

Now I'm troubleshooting CCTV installations. I've found cameras with poor images and discovering they are being powered by unregulated supplies.

 

So, in an unregulated supply, if the mains voltage is high, and/ or if the power supply engineering/ construction is lacking integrity, then the output will be high.

 

In some cases I found 16VDC powering cams that were rated for 10-15VDC. ANd 29VAC powering cams that were rated up to 28VAC.

 

In both cases the supplies were exceeding the ratings of the cams. The mfr says when this occurs, the cameras' electronics will likely fail over a relatively short period of time.

 

Which apparently was occurring in these systems that are 3 yrs old.

 

Why, then, are unregulated supplies spec'd?

 

Is it because they are cheaper? And the contractor will reap a greater profit?

 

Is it because designers/ installers don't care? (Can't see it from my house?)

 

Is it because the cams are purposefully being killed to ensure a repeat customer?

 

When I questioned the local cam/ supply dealer (who is conveniently owned by the cam 'mfr'), they said they rarely stock/ sell regulated supplies cause everyone installs the unregulated ones and 'they work fine- never had a problem'.

 

Yet engineers at that same cam mfr, whose co. owns the dealership, insist that best practices are to spec regulated supplies.

 

And common sense says to use regulated supplies.

 

Why would you risk the integrity of a system being affected by the mains voltage by skimping on a comparatively basic and low cost power supply?

 

Please forgive the long query but I'm baffled by the apparent acceptance of poor images/ installations I've seen in my limited CCTV experience thus far.

 

Am I missing something here?

 

Happy and prosperous New Year to all!

[kensplace 0]

Personally I use regulated DC supplies, with battery backup, the AC supplies are basically just a transformer in a box with fuse though, not easy to get a regulated AC supply unless your powering from a UPS (which I do, so thats the AC side taken care of).

 

A lot of cams I use in the house have their own regulation build in, usually in the form of 7812 type regulators (or similar) so they can take a fairly wide swing in voltage as they do their own regulation, so a unregulated supply would not bother those type.

 

Not all cams do have their own regulation inside them though as you say, and those could suffer from over voltages etc.

 

3 Years is a very long time, I would have expected a camera to fail a lot sooner than that if it was getting to much voltage for it to handle, usually either straight away or as soon as it was a hot day, and that pushed its temperature over the edge (heat from the day + heat from the overvoltage).

PS - Where are you measuring the voltages, if its at the PSU end then it could be higher than the cams rating to cover voltage loss in the cable so by the time it gets to the cam its at the right voltage.

[survtech 0]

In the case of 24VAC supplies, 29 volts usually doesn't affect the cameras negatively, probably because most, if not all, 24VAC cameras have internal rectifiers, filters and regulators.

 

I would agree with you for DC cameras, though. In fact, some manufacturers (Dallmeier for one) specify 12VDC +/- 5%. Personally, I think that is stupid on their part. I burned one of their cameras out because the supply I used was actually 13.8VDC.

 

How do camera manufacturers expect the installer to maintain regulation that tight? If you have relatively long power cable runs, you would need to adjust the voltage under load and keep anything that varies the load (IR LED's, heater/blowers, etc.) on a separate power circuit. STUPID!

 

In that regard, I would put as much blame on the camera manufacturers as I would on the installers. There are a number of ways to regulate or limit the voltage within the camera and the cost to add these is piddling. In quantity, voltage regulator circuits should not add more than $1.00 to production cost of a camera and a simple "crowbar" zener and fuse would be even cheaper.

 

The same applies to DC polarity protection. A full-wave rectifier bridge costs maybe 10¢, yet many manufacturers don't bother to incorporate them into their cameras.

 

All of this makes an installer's job more difficult than necessary. If you really want to be consciencious with DC cameras, in many installations you would have to use either separate power supplies for each camera or supplies with separately adjustable regulators for each camera. Then you would have to carefully connect each camera to the supply and jump through hoops trying to adjust each supply so that each camera receives the proper voltage. Not an easy task!

 

That is a prime reason why we almost never use DC cameras.

[Soundy 1]

Gotta agree with Survtech - cameras are generally pretty robust with regard to their power, especially those that use AC power. Remember the electronics themselves don't run on AC, they still require DC, so the cameras have to at the very least step down and rectify the power internally. If the camera also says it can run on DC power, as many do now, then one would have to expect it already has some form of internal regulation as well.

 

In fact, a bridge rectifier and simple voltage regulator are so cheap, there's no excuse not to just use them in any camera design (except maybe those with really tight size restrictions). A bridge rectifier across the power inputs not only makes for universal AC/DC support, but negates polarity concerns when using DC. Design the camera electronics to work at 12VDC, slap in a 7812 regulator for about 50c (probably a quarter that if a mfr. is buying them wholesale), and you can feed it anything up to 35-40V with no issues.

 

Yep, this one's on the camera manufacturers. A cynic might suggest they wouldn't want to spend the extra buck or two to make their cameras more robust, because they wouldn't be able to sell as many replacements for the blown cameras.

 

But yeah, I have run across a few CHEAP board cameras that want regulated 12VDC and are very fussy about over-voltages. But again, those are CHEAP.

[survtech 0]

But yeah, I have run across a few CHEAP board cameras that want regulated 12VDC and are very fussy about over-voltages. But again, those are CHEAP.

Unfortunately, the Dallmeiers are not cheap. In fact they are relatively expensive compared to many.

[Soundy 1]

Just because they're expensive, doesn't mean they're not CHEAP

[survtech 0]

True, but in other respects, they do make excellent cameras. Just another case of engineers being uncoupled from the real world!

[Soundy 1]

True, but in other respects, they do make excellent cameras. Just another case of engineers being uncoupled from the real world!

 

Bingo! Happens all the time!

[jets 0]

Thanks all for responding.

 

I was measuring power at the cams.

 

The DC xformer converters were producing 16+/- a few millivolts VDC at the cam and at the supply (relatively short runs not providing much v-drop on the conductors). I've since insisted that only regulated DC supplies be used whose outputs measure their rated outputs.

 

I also found 4 pr. of cam power conductors wire-nutted to the output of 1 AC-AC xformer. I'm a proponent of using channelized pwr for some measure of isolation from ground loops and to contain probs to individual circuits

 

Question- one respondent stated 3 yrs is a long time (for a camera to operate). Coming from the commercial AV world where switchers, audio devices, monitors etc are warranteed for usually 3 yrs, remaining in service often far longer- what is the expected service life of typical small dome non-PTZ cams w/ 1/3"CCDs,

 

Granted there's widely varying qualities from different mfr's. I'd expect SOny, Bosch, American Dynamics and the like to provide a better image and last longer than say, Honeywell and speco.

 

And I believe their prices reflect that.

 

Or am I wrong?

 

Can anyone categorize mfr's cam general quality re: crappy, good and best?

 

For those mfr's offering DVR's, does the same typical quality level follow suit?

[survtech 0]

We've had many cameras, both indoor and outdoor, operating for over 7 years. We use mostly Pelco, Ganz and Ikegami.

 

By the way, Ikegami warranties many of their cameras for 10 years.