just gonna ask how to post lol.
coz I cant post my question about TRIAC ,
could an electrolytic capacitor be used in such circuit? sorry ^^

 

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Electrolytic capacitors are usually not used with triacs because triacs are usually used with rather high voltages and they don't need a lot of capacitance in their snubber circuit. Cheaper and safer to use film caps or ceramics.

ps, triacs are used with AC current. A non-polar electrolytic is rather expensive.