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Light dimmer

     This dimmer is used to adjust the brightness of incandescent bulbs (dimming) from zero to maximum. Regulation from zero is achieved using double delay circuit. The circuit is two-terminal connected and so it can be installed into switch box without modifying the installation. To regulate the phase angle the dimmer uses ordinary thyristor (SCR) such as KT505 (or KT504, KT508, etc.). The maximum current is 1A, so you can connect up to 200W load. Brightness can be dimmed to zero, so there is no need use the switch. Capacitors are just at the low voltage, so you can use electrolytic ones.

     Warning - the circuit is electrically connected to the mains - deadly voltage. The light bulb must not be replaced under voltage, even when the dimmer is set to minimum. Before replacing the bulb or handling the circuit you must disconnec it from mains. The potentiometer must have a plastic shaft.

Schematic of simple light bulb dimmer circuit.