I have a single 12V 2A power supply which is powering 4 CCTV cameras which require a 12V 1A power supply each in addition to an illuminator lamp which requires 12V 2A supply. At the moment everything is working fine. Is that arrangement ok into the future?
If not please advise me on what single power supply is needed to meet the needs of the 4 cameras and the illuminator lamp.
You can ask 72 Watts (12V * 6A) from a 24 Watts power supply, and it would probably deliver it to you, but you must understand that the power supply is working at 300%, and it would damage the components sooner or later. So yes, you can connect all the items you want, until it fails.
I would recommend you to buy another 2 power supplys, or even better, a standard 12V 10 Amps device.
You appear to have done the math: a 2A supply can't power a total 6A load, so I'm guessing you're here because it's working & you want to know why? ;)
The only way could work is if the documented current requirements have been substantially exaggerated, or, you're simply going by what's printed on the power-supplies; say, each camera is using typically 500mA, so to be safe their spec is a 12V/1A supply and because there's not much difference in price between the 0.5A and the 1.0A. So there's 2A for 4 cameras.
And maybe the illuminator isn't quite 2A either, and so you're probably just lucky the 12V/2A supply isn't falling over in a blind sweat. I wouldn't depend on this for the long term. And no, you can't just connect two 12V/2A PSUs in parallel and call it a day, either :).
If you have a multimeter, try to measure the current drawn by each device (might need to butcher some cables to get the multimeter's current probe in series). Then you can make an educated assesment of what current capability your 12V supply needs to have to power them all without fear of short term failure.
