I am looking for an inexpensive* circuit to control filament lamps running on 240V 50Hz AC supply, such that a single-pole switch closing causes the lamp to go from off to full brightness over a period of one to two seconds. Opening the single-pole switch would cause the lamp to turn off over a similar time period. The circuit should be in-line in the live supply, and the neutral may not be accessible (should be assumed not to be).
Ideally, the circuitry would fit behind the switch in a standard 75mm x
75mm patress. The switch can be a single-pole changeover if it makes life easier.
The idea behind it is to extend the life of the filament bulbs by turning them on and off gradually. Many of our light fittings have multiple bulbs - as many as 5 - and the cost of them is getting beyond a joke. But I think it would be an aesthetically pleasing operating mode too.
I have scoured the internet for such a circuit without success. I did a degree in electronic engineering back in 1980, but having worked in I.T. ever since, I am not really up to speed on electronic circuit design, especially for AC, which did not figure prominently in our course.
- Should not cost more than a triac dimmer - the alternative solution.