3.8 Thyristors, TRIACs and isolation

Outcome 8 of 9 in domain 3 · Semiconductors and analog

The family that switches AC, and how you keep two circuits apart.

My targets

I declare:

Explain the thyristor and the TRIAC (triggering, holding) and where you find them: dimmer, solid-state relay, soft starter.
Build a TRIAC dimmer on a low-voltage load and observe the chopped wave.
Explain the solid-state relay and compare it to the mechanical relay: wear, noise, voltage drop, heat.
Isolate a control from a power circuit by optocoupler or relay, and say why the ground doesn’t cross.
Diagnosis: a dimmer that makes its load jump or buzz, inductive load, spurious triggering or tired TRIAC.