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SCR - TRIAC - SSR

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mammanoti

New Member
Okay, got my PICs and havin' fun. Now I want to be able to turn on and off 120vac power outlets. I have found several things on the web. I want to stick with small and have found sites that say to use either SCR, Triac, SSR - all showing the same type circuit.

So I pose my question to you:
Which should I use, and can you give me a clue as to part#s?
 

Sebi

Active Member
The key of choice the load. If it`s an inductive load, use antiparallel thyristor pair (SCR-s) e.g. TIC126N up to 2A without heatsink, up to 6A with heatsink. If You want switch on-off ohmic load (heating apparat,bulbs...) use triac TIC226N. The solid state relays (SSR-s) available with SCR and triac output, depending from application, but expensive. You can build it own with triac or SCR-s and MOC3041 optocoupler..This have a LED input and optotriac output, can direct triggered SCR-s and triac.
 

pebe

Member
The trouble with using any of those devices is that there is no electrical isolation between the mains supply and your PIC circuitry. Play it safe - use a relay, especially if you want to cater for any type of load.
 

mammanoti

New Member
Isn't the purpose of the optocoupler to isolate the the controller circuit? I thought that was why most applications that connect to a PC use optocouplers? That way the load voltage is isolated from the controller.
 

kinjalgp

Active Member
Opto-couplers are better than relay for triggering triacs. You can use one of the most common opto-coupler for triac i.e. MOC3011 from Fairchild Semi.
 

pebe

Member
kinjalgp said:
Opto-couplers are better than relay for triggering triacs. You can use one of the most common opto-coupler for triac i.e. MOC3011 from Fairchild Semi.
I was referring to using a relay on its own - ie. without an SCR.
But you are quite right, my fault, I misread the post :oops:
 
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