DIAC-TRIAC

Diacs are bidirectional trigger diodes whose work is to trigger Triacs or SCRs. SCRs are Silicon controlled rectifiers. They are similar to four layered diodes and are non conducting till we reach there breakdown voltage. When we connect a diac across a voltage supply with resistor it acts like a high impedance until 35 volts then as zener diode at 30 v. Triac on the other hand are used for Alternating Current. It is an electronic device equivalent to two silicon controlled rectifiers joined in inverse parallel with their gates connected together