Is This the Ideal Solution for Switching 120V 3A AC Lines?

  • Thread starter Thread starter jordanstreet
  • Start date Start date
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
1 reply · 2K views
jordanstreet
Messages
7
Reaction score
0
Hey guys I'd like to run a few things by you guys. I will be switching 120V 3A AC lines and am considering the following solution. I do not need synchronous switching by the way.

This TRIAC
http://www.digikey.com/product-detail/en/BT134-600E,127/568-5015-5-ND/1155119
The datasheet says its rated up to 4A and has a max gate current of 2A.

This Optoisolator
http://www.digikey.com/product-detail/en/MOC3021/160-1374-5-ND/385844
The datasheet lists the trigger current at about 15mA so I'll go with 20mA to be safe, and has a peak surge current of 1A.

I will be triggering the optoisolator with 3.3V signals.

So with these parameters I've gone with
(3.3V - 1.3V) / .02A = 100 Ohms for the diode current limiting resistor on the optoisolator input.
170Vpk / .95A ~= 180 Ohms for the gate current limiting resistor on the triac

I will be using this schematic
http://www.simpleio.com/design/triacout/images/TriacOut4Sch_L.gif

Does this all sound good?
 
Last edited by a moderator:
Engineering news on Phys.org
To me the design looks good. The only thing I can think of is that if the load is at all inductive, you should have snubbers on the main triacs.