Saturday, 11 November 2017

power electronics - How to switch 220 VAC? (Magnetic relay, SSR relay or triac)?




I want to switch 220V AC with a microcontroller. Before I used magnetic relays or SSR relays, but now I want to use a triac for this function (like in this circuit) and my load can be any 220 V AC object. The reason is, triacs are cheaper, smaller and have more ability for high currents than magnetic or SSR relays.


1) Please guide me at the choice between magnetic relay, SSR and triac.
2) Someone told me that triacs for switching AC current creates noise. Is this correct? And what is the solution?



enter image description here



Answer



You need to provide more information about your load : is it inductive or resistive? How much current does it draw? Also unless special case (inductive motor, for which this circuit is not suitable anyway), you may want to use a zero-crossing opto-isolated diac (MOC308x) rather than the random phase MOC3021 shown here. Last point, triacs are great but heats-up, so unless your load is very small this heat has to be accounted for and dissipated properly.


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