I am thinking of making a set of dimmers for Christmas lights. They operate at 120 VAC 0.03A (35 LEDs per string). I have tried to use a normal 300 watt wall dimmer to control the brightness but with out a small incandescent lamp in parallel with the LEDs. The string of Christmas lights will not light until the dimmer is above some unknown voltage (I have not measured). Does anyone have a dimmer circuit that I could make that would not need the small incandescent lamp in parallel with the LEDs?

thanks for the info
Gordon

 

If you use the "Search" link in the blue bar above, and look up "PWM" or "Pulse Width Modulation" you will be well on your way to achieving your goal!

 

The LEDs have a forward voltage that must be overcome, assuming they're in series, something like: 35 x 2V = 70V, plus some amount of drop over the ballast resistor in order to generate enough current for them to appear as lit.

 

The LEDs have a forward voltage that must be overcome, assuming they're in series, something like: 35 x 2V = 70V, plus some amount of drop over the ballast resistor in order to generate enough current for them to appear as lit.

Thank you for understanding my issues. If I am correct a square wave PWM out put would deal with problem. correct?

 

That is correct. The LEDs will be brighter with a longer duty cycle and dimmer with a shorter duty cycle.