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How to make a regular light switch gradually fade up ?

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Junior Member level 3
Jan 28, 2006
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I would like to make a regular light switch, that when turned on, it gradually fades up the light bulb to full power. If the light bulb took about 4-5 seconds to reach full power it would be very nice. That way it would give people's eyes time to adjust to the changing light level rather that have the light flash them. I think it's not normal and almost rude to have lights flash at you, especially in the morning.

The light switches I use are your standard 110 volts switches.

A company called Lutron makes a switch with this function.
Their switches cost $30.0 each and I need about 30 for all the light switches in my house. Regular switches cost $1.00. Then, I don't like that their switches are pushbutton. The toggle up/down switches are better.

There must be a way to combine resistors and capacitors and something else to make this work.

Any ideas?

Yeah, it seems to be good idea to turn on the bulb slowly.
One way to do it can be be having digitally controlled potentiometer.
The resistance of the potentiometer is slowly decreased such that changes made is small for humans eyes to notice the change.

The digitally controlled pot and the microcontroller connected to it can ofcourse be
powered by the same power supply powering the the lamp.

Since microcontrollers have flash the present status can always be maintained in the flash memory of the device.

Hi Privas,

It will certainly give a very sophisticated feel if one can fade up the light in a room.
I propose a solution that could be constructed for about 3$.

Below is the circuit diagram. The only limitation is you need to use a transformer. The triac is trigerred based on zero voltage crossing.

A PWM waveform could be easily obtained from a SG3525 IC whose reference is driven by a high RC time constant capacitor. Once powered on, the capacitor voltage rises, the PWM increases. One could use a period of 600ms to 1s. (I have not put up this part - if needed I'll post later)

So, the number of cycles passing through the lamp keeps increasing as PWM increases. Finally it's always on - so full brightness.

Comments welcome on this solution.
I can post a better solution without the transformer if I get time later.


H Giri,

Adding a transformer would not be an option since there is a limited amount of space to work with, plus it adds too much the cost. The product made by Lutron doesn't have a transformer so there must be a way to do this without a transformer.


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