Lamp dimmers using traics can be quite simple, nothing more than a potentiometer, resistor, capacitor and triac with a built-in diac. (See Teccor’s application note for examples and other technical data.) This circuit is similar to designs using unijunction transistors to generate the triggering pulse. The unijunction is replaced by a two-transistor “flasher” circuit that drives a pulse transformer. This type of circuit gives a wide range of control while exhibiting little hysteresis or line voltage sensitivity.

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