POWER SUPPLIES

[ian.cant]

I think maybe the psu maybe a bit of red herring, some basic fault finding needed here first maybe, dodgy bnc seems likely. Is the same fault on all camera's?

Take a camera and connect it direct to the monitor locally, on about a 1mtr cable.

No fault then the problem isnt your psu, if you still have the fault then it could be the psu but not definitly.

Now try a different psu, fault still there then its unlikley to be a psu, same fult on 2 psu's is unlikely.

Best way to trace the cause is trial and error, save's a lot of timewasting and some cash usually.

[ian.cant]

And to answer your initial question, in my opinion the best power supplies to use are a single 500mA psu per camera or a boxed psu with a seperate fused output for each camera, this way if a psu or fuse pops you only lose 1 camera instead of all or some of them.

Unless of course the mains goes down, in which case you wont be able to switch the monitor on anyway!

[Guest Andyp]

Ian

Very good points well made. Just shows I have been a salesman too long, I have lost basic fault finding ability!! Now where was that toolbox?

Andy

[ian.cant]

Thank you Andy, it could be an expensive psu if the coax to the monitor has a dodgy BNC on it

[Paul Giles]

we had a similar thing in a large night club.

We spent ages doing the normal checks to see if they were on the correct phase etc but to no avail.

The picture looked like what can only be described as water runing across the screen, just a constant haze across the picture.

We could only prove the cable was leaking 0v down the signal cables between the two cameras, i know it should be ov screen anyway but i think it was leaking to earth too (1st and 2nd fix job so probably a nailed cable)

we used an elmdene plug in psu for the two external cameras and it cleared the rest all ok.

The problem we had was that one camera can throw the rest out, you should unplug one camera at a time and see what the picture does.

A bloody nightmare that job was, especially when we had a full RIO decide it didnt want its tamper switch to work anymore!!!

If only the galaxy could show RIO tamper status!!

[Guest CCTVINSTALLER]

Thanks for all comments they've really helped, the elmdene PSUs are fantastic but they're a little to expensive for domestic installation. Someone mentioned there's nothing wrong with using 500ma PSUs. I think i lack electrical knowledge, could someone explain what is meant by connecting all the 'equipment to one phase' and how this can contribute to the problem we're having with Camera pictures.

Also is there anything else electrical related i should be aware of to prevent getting bad pictures, because it seems we only get them with certain installations. Our biggest problem is getting pictures that Jump up and down. This has been a big problem, i don't know if any of you use Geovision but with the new version you get a object counter. When we set it up, because of the picture jumping up and down, we get exagerrated figures, and our customers seem to get very annoyed with this problem. Can anyone provide solutions to this problem?

Many thanks

Mathew

[ian.cant]

If a camera draws 250mA then using a 500mA psu is advisable (2x capacity of the psu) as opposed to using a 250mA psu which would be insufficient based on the fact that everything has a tolerance (it could be +/- 10%).

You can find out what amperage a camera uses in the literature that comes with the camera.

Connecting all the cameras to the same phase isnt exactly what its all about. All the maims fed components of a system should be connected to the same electrical phase, IF the electrical supply of a building is 3 phase. Usually you will only find this in a factory or large building, generally most small buildings only have a single phase supply so its not an issue.

If the equipment is on different phase's then you will have camera's and equipment out of sync with each other. If you dont know the theorehtical difference between AC and DC electricity then sorry but, its to much to explain here. Basically it causes picture roll when you switch between cameras and or it can give you other strange picture problems, such as framing!

If you have humbars travelling up or down the screen, then you have an earth potential difference, this can be cured with with a humbug (sometimes)!

When you describe pictures jumping up and down, its never that simple!

I would suspect it is an earth problem or a sync problem, however referring to your original post i still think it maybe simpler than that.

I worry about your BNC connections as these are the most likely causes of intermitent picture faults such as jumping and tearing.

As i have posted previously, your best bet is to go through some logical fault

finding, starting with the basics.

[Guest dale]

Make sure you use a BNC crimp tool, the screw on type just dont last and don't give a good connection.

[CompostCORNER]

I recall installing the CCTV at Pozition nightclub here in Hull a couple of years ago. Every single camera had picture interference. We had about 20 'Q cameras' on 2x4amp psu's. The cure was a simple one. The cameras connected to the coax and power cables (12vdc) on a single terminal strip inside the camera housing. A simple link on each camera between the 0v of the power to the screen shield of the coax remedied the picture roll. Maybe worth a shout.

Tony.

[secure4]

Hi There,

We use the 12vdc 1amp regulated powersupplies from fineplan.

They work out about a tenner each i think, never had a problem with one.

As for day / night with a good range. Tell me what you think of these.

They are an integral unit available in 4.3, 6, 8 and 12mm lens.