Can someone provide me a (simple) schematic for a dimmer that would control 12 VAC about 80 watts. This would be used to control a lamp with halogen bulbs.
Anonymous asked on a comment few years back – Circuits FAQ
Here is a listing study them and choose, try out, learn and then build the one right for you.
- Light dimmer circuits
- 1200 Watt Lamp Dimmer Circuit
- discovercircuits.com – Light Dimmer
- Application Notes for Thyristors
- PWM Motor Speed Controller / DC Light Dimmer
- Lantern Dimmer/Flasher
- Halogen light dimmer provides infinite control
This is a phase angle control of a Triac which is a evolution from an SCR. The 50 Hz or 60 Hz Sine wave of mains can be turned on at any point after the Zero Crossing
The Voltage ramps up in the sine wave which gives a near “Linear” slope which can be used to trigger the ON at a time delay after zero crossing when the voltage is zero. This is like a PWM but works on low frequency only. Some of the early SMPS(HV for TV and Mains Inverter) by Siemens were built around SCRs. Turning off a SCR is a difficult job for a designer, MOSFETS and IGBT are now used for PWM drive stages.
You can use it with a bulb to vary brightness of bulb, this is a live circuit it can give a shock, enclose in plastic box, the pot should have a plastic knob, use a fuse, you can also use it for temperature control of soldering irons.
The Source file in CadSoft EAGLE format is here del00004.zip