Slow-on Slow-off filament lamp control circuit

[stairforce]

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.

 

[Frithiof Andreas Jensen]

* Should not cost more than a triac dimmer - the alternative solution.

Why not *hack* a triac dimmer?

 

[Nico Coesel]

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.

Get fluorescent bulbs, saves money on your electricity bill as well.

 

[Roger Hamlett]

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.

The traditional solution is a thermistor. The switch 'off', is not a
problem, it is the rate of heating, when you turn on a cold filament, with
low resistance, that is the 'killer', which is why such systems are
standard on projector lamps etc..
There are semiconductor equivalents. Motorola has an application note
about inrush current control on SMPS units, which is directly applicable
to lamps as well.

Best Wishes

 

[Rene Tschaggelar]

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.

Those unwilling to spend a fortune on filament changes use LEDs.
You could use a FET in a bridgerecifier to gradually change the
brightness, but not at the cost of just a triac.

Rene

 

[Al]

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.

What worked for DC filaments was this. A resistor was placed across the
contacts of the switch. The value of the resistor was chosen so that the
filament would be warm but not glowing. When the switch was closed, the
resistor was shorted out and the bulb lit as intended. Of course, this
wastes power, but what is more important, bulb life, or power usage, in
your application?

Al