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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

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  • \$\begingroup\$ This is a SSR relay. \$\endgroup\$ – Marko Buršič Aug 8 '19 at 8:17
  • \$\begingroup\$ No matter what you use, make sure to always use an optocoupler (or use a SSR relay / triac with builtin optocoupler) to isolate your microcontroller from the 220 VAC for safety. \$\endgroup\$ – 比尔盖子 Aug 8 '19 at 23:53
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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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    \$\begingroup\$ @比尔盖子 the MOC3021 in his schematic is a random phase diac + optocoupler... \$\endgroup\$ – Owayl Aug 9 '19 at 0:53
  • \$\begingroup\$ thanks my friend \$\endgroup\$ – ali Aug 10 '19 at 5:10
  • \$\begingroup\$ thanks my friend, my loads are Lighting lamps whit max current 2 A and I want to use BT151 triac How hot is it with my circuit specifications? \$\endgroup\$ – ali Aug 10 '19 at 5:16
  • \$\begingroup\$ for 2A lamps BT151 should be fine, do not forget to use a zero cross optoisolated triac driver such as MOC3083. \$\endgroup\$ – Owayl Aug 10 '19 at 9:21

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