Oscillating dimmer design?

A simple way would be to replace the normal control pot in a standard scr dimmer circuit with an light dependent resistor and led/ optoisolator, say from Silonex, and drive the led from a simple oscillator.

It also will also give you good isolation from the mains supply

martin

In article , wrote: [....]

Ok, here's a bad idea:

Find an old induction motor with a wound rotor, a gear box and a smaller electric motor.

Hook the lightbulb across 2 of the rotor connections.

Apply mains voltage to 2 of the field connections.

Using the smaller motor and gear box to slowly rotate the motor's shaft.

In a nutshell, fire a triac with a variable trigger that itself is trigger by a zero-crossing detector. The closer to (before) zero-crossing you fire, the less time the lamp will be supplied with power and, therefore, the dimmer it will be. Fire soon *after* the zero-crossing and the lamp will be brightest.

Two weeks ago I did something similar (in the DC realm) using some white LEDs and a PIC set up to do pulse-width-modulation (PWM). Continuously sweep up and down, from full brightness to off.

In article , Michael wrote: [....]

You cna isolate the high voltage for the timing circuits with transformers.

The zero crossing on the output of the same transformer as you use to make the supply voltage, will be well enough aligned with that of the mains input.

SCRs and TRIACs can be triggered with small transformers.