DC supply on AC CCTV camera

In the US most CCTV cameras with Analog video outputs run off AC to derive sync for video switchers and recorders. A dead giveaway is a "Phase" adjust ment pot on the back of the camera.

The main reason for this is to avoid having to run sync wiring to every ca mera. A few of the very best Analog CCTV cameras have a external video BNC for sy nc to a master "black burst" video source.

I just ran into a curious situation at a church where the new system would not sync the eight channel "Picture in Picture" monitor. Two thirds of the cameras were "rolling" periodically. The donated cameras came from a buildi ng that ran on three phase. Adjusting the phase pot on two thirds of the ca mera's was required. This was done on a antique Hitachi oscilloscope that has a dedicated sync f unction. Once that was done, there was no roll on the eight channel DVR nor the eight picture LCD display.

So the 24VAC serves a purpose. Unless you have one of the new dual mode AC/ DC cameras.

A few "free running" cameras were manufactured. These are a PITA to use, al though some of them do sync the CCD with tungsten or fluorescent lighting. A surprising amount of camcorders will also self sync to the local lightin g, mainly Sony units.

Analog Lab grade cameras have either "start field/start frame" or Vsync and Hsync inputs.

I spent eight years using normal, thermal, digital, and high speed video in my lab. Including field sequential stereo using shutter glasses. For the s equential Three D I used ordinary 24VAC security cameras at first, then the ones with external video sync, and finally ones with V-clock and H-clock i nputs.

Steve R.

On a sunny day (Tue, 7 Oct 2014 11:32:39 -0700 (PDT)) it happened " snipped-for-privacy@nyucknyck.net" wrote in :

Yes, new to me, the CCTV cameras I used certainly had no such feature, the ones I am using now has picture in picture in the sense that my PC has a good video grabber card, and I can position the picture wherever I want, and is actually next to 2 ethernet cameras on the same virtual desktop. These have no AC input either and run on 12V DC. Any decent analog camera should have a sync input for genlock.

That is only the shutter I think, not really the V, but I could be wrong. My Sony starlight (0.01 lux) has a menu option for different sort of lights, it has a digital signal processor on board tough, stil analog out, 12V DC, used a lot in low light security systems.

Right.

Yes I have done the shutter thing too, simple:

And also with digital webcams:

That is the only way, and now you also need color lock if it is real PAL or NTSC. Thats is the way it was done in the studios, although those cameras were a bit bigger. We has CCTV type cameras in the film editing tables, free running of course. I designed my own vidicon camera, way back then, in the sixties, way before everybody had or even thought about cameras.

I've repaired CCTV cameras with a power transformer. They wouldn't ask for AC, if they didn't need it. Why would they simply put a bridge rectifier on the input? As others have said, 32V is too high. You haven't given a brand or model number, so you can't get any real answers without opening one of them. My first CCTV camera repairs were made in the '70s.

Why is it too high? (Its less than peak 24v ac.)

NT

Transformers, and AC motors, don't survive DC, they pop a fusible link inside the winding. That means, they die.

As for point #2, you have never seen a transformer in a halogen or high-intensity desk lamp?

I spoke with a "professional" who does this sort of thing for a living. In fact, this was EXACTLY the feature for which the cameras rely upon the AC input.

If I elect to use those cameras, I'll have to find a suitably sized 24V transformer to power them (everything here are DC bricks).

But, I've also collected a couple dozen other cameras with different power and signal requirements. I'll just have to find the sweet spot for a suitable subset of them. :-/

Thanx!

a wrong answer

We're talking dc from a wallwart here, not an unfused high current source like a lead acid.

In mains ones yes, in 12v powered lamps as the first component no. It makes no sense.

NT

Oh, I'm sure I can "find them"... just not in my "goodie box"! (I can't recall the last time I used a bare transformer for power). As I mentioned, I bumped into a guy who does this for a living who has agreed to donate whatever "odds and ends" they need. I just have to sort out which cameras to use, get them mounted, aimed, configured, etc.

Has to be "pretty" and "safe" as they will be in a commercial setting. Everything is exposed so it's not like they can be hidden away in a closet or "back room".

As they won't be located adjacent to each other, I'll just assume a "supply" (whether that turns out to be AC or DC, as dictated by the camera) per camera.

Likewise, arrange power for Ir illuminators.

Biggest problem is sorting through "what's available" to determine "what's appropriate". It's always easier when you can write up your own "shopping list"; considerably harder when given boxes of kit and asked to "make something happen". :<

You did mention this part...

...but you didn't mention this part.

So the power supplies will be in different locations in the building? Any concern that the people in the building will figure out that "unplugging that box in the janitor closet will shut off the camera for the side door" or equal? You can't protect against everything, though.

"We've got to make *this* fit into the hole for *this* using nothing but *that*." :)

Matt Roberds

Well, there are limits as to what he'll be willing to supply. But, the only power things that I can't provide from my own personal stash would be "transformers".

Some of the cameras have AC line cords. Others are DC. So, I'll have to figure out which subset to exploit... Ideally, pick some that are reasonably identical in their capabilities and requirements.

Yes. A very large space (tens of thousands of sq ft)

I plan on covering each "component" with a camera. So, you might be able to blind one or more cameras -- but, you'd then have to explain why you *did* that (on the recordings)!

Yes. "And don't spend any money (unless, of course, you want to DONATE those funds out of your own pocket!)" :-/

On a sunny day (Sun, 12 Oct 2014 04:11:04 +0000 (UTC)) it happened snipped-for-privacy@att.net wrote in :

And in case of a power failure..... looting starts...

Really 24 V AC cameras... even if they have some diesel come online, that takes time.

On a sunny day (Sat, 11 Oct 2014 21:31:54 -0700) it happened Don Y wrote in :

Recordings? Why not get some cheap IP cameras, and be done with it. Those have pan tilt too.