TRIAC CIRCUIT

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So I need a last word of wisdom.
Following advices given in my other thread I've bought opto-triacs to trigger the power-triacs.

Are my resistors reasonable sized?
What to use to see if power-triac is properly triggered by opto-triac?
Would a LED work if i place diodes at both ends of it to prevent voltage going reverse direction?

To look at the AC-signal in a scope, can I connect a diode to one of the lines to make it work as GND for the scope? I just want to see it coming on and off? IIRC I used this method when I wanted to see if the zero-crossing detection code I wrote was working? (There is no need for ZCD in this application). Just want to see that AC is flowing through triac.

Other considerations before I finally hook the 24VAC motor up?
I have a varistor connected between AC-lines to suppress current-rush.
Attached is datasheets for triacs and the circuit I intend to use.

Attachment(s): 

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OK, so I hooked up a DVM to AC-lines where motor should be connected.
Seem to turn on properly. No magic smoke.

But when triac is off DVM still measures appx 1.9 VAC.
Same for all four triacs connected.

Is this normal or is resistor value from opto-triac to power-triac too high/low?
Should I see 0VAC when AVR pin is low and not turning LED in opto-triac on?

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Triacs are leaky, DVMs are high impedance. I'm surprised you only see 1.9V and not almost the full 24! Try it with a load across the meter probes, like a 1k resistor, and the voltage should be zero.

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Yeah, that worked.
Thanks a lot Peret!

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Do not add your questions to ancient threads. Moderator.

 

hi

i want to drive a triac

first with moc3021 i drived the triac but in inductive load doesnt work properly :(

i find some circuit in internet but when i want to off the triac it doesnt off and alwase is on...

somebody say me use optomos,i dont know what to do

can u help me plz

tnx

Last Edited: Sat. Feb 7, 2015 - 10:01 PM
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Snubber design...

 

http://www.st.com/web/en/resourc...

 

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Snubber is one, when you trigger the triac is another. You might want to time from current zero crossing rather than voltage zero cross.

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tnx all

excuse me did u have some circuit with triac and zerro crossing and snubber?

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This link might help:

http://www.rsp-italy.it/Electron...

 

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tnx