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Guide to Closed Circuit TV (CCTV)

So would you like to play "Spot the CCTV Camera?". Eagle eyed visitors may recognise the profusion of street furniture, surrounding a single heritage dome camera keeping watch over part  of Londons' prestigious Oxford Street shopping area.

Making light of a dark place ...
the inside track on Infra Red.

Power Supplies for Infra Red lamps

Most people think that plugging an Infra Red lamp into a power socket is all there is to it.

With a solid state LED array, that may well be true; feed it the correct voltage and it will glow away quite happily until the criminals come home.

Most LED panels contain all the circuitry required to drive the individual LED’s at their optimum supply, which generally is about 20% below their maximum permitted voltage.

Any higher and they can burn out prematurely; any lower and the quantity of light output will suffer considerably, so always make sure that the unit is designed and built for operation on the local power supply. Although LED panels are generally more expensive pro rata than a normal hot filament type, their inherent reliability can pay dividends over a period of years. (Remember if a dozen LED's fail on a large array, there's still plenty more to keep you going).

With a Tungsten filament bulb, the principle is pretty much the same, in that if you ‘under run’ a bulb it will output less light but last considerably longer.

Interestingly if you operate a 12v bulb from a battery, it may not last as long, as if it had been powered from a 12v AC supply.

This somewhat unusual result is due to a little known ‘cleaning effect’. If the filament is powered from an AC supply, the gentle oscillation resulting from the 50 hertz frequency (60Hz in some other countries), helps to disperse any ‘dead material’ from the filament, and so reduce the risk of hot spots which could result in a total ‘burn out’.

The main method for prolonging any bulbs life is to simply incorporate a ‘soft start’ circuit which gently raises the bulb to operating temperature over a short period of time.

Top Ten 'Must Know' things about Infra Red >>

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