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Switching AC w/ Logic Level

I've found a few threads but nothing with exactly looking for what I'm
looking for.

I need to switch 24VAC (HVAC control) and 120VAC (2A and 10A) with a
PIC. What is the best way to do this? Opto-Isolated TRIAC, SSR?

Your suggestions on your favorite parts for the job would be greatly
appreciated.

Thanks,

John
 
J

Jamie

Jan 1, 1970
0
I've found a few threads but nothing with exactly looking for what I'm
looking for.

I need to switch 24VAC (HVAC control) and 120VAC (2A and 10A) with a
PIC. What is the best way to do this? Opto-Isolated TRIAC, SSR?

Your suggestions on your favorite parts for the job would be greatly
appreciated.

Thanks,

John
just drive a low voltage coil relay via a NPN transistor in open
collector state through the coil. Emitter to common and base to
an output via a resistor to force the tranny into saturation.
P.S.
put a FlyBack diode on the coil other wise, you'll take out
your tranny and maybe the pic in a short time.
also., make sure you mount the relays away from the pic. We had
cases where the EMF of the coil actually caused problems with the
program in the PIC which forced a reload of the code.
 
J

John Popelish

Jan 1, 1970
0
I've found a few threads but nothing with exactly looking for what I'm
looking for.

I need to switch 24VAC (HVAC control) and 120VAC (2A and 10A) with a
PIC. What is the best way to do this? Opto-Isolated TRIAC, SSR?

I like opto isolated solid state relays for my home
projects, for their ruggedness and simplicity of a direct
logic drive. But for production designs, they are high cost.
 
R

Robert Wilson

Jan 1, 1970
0
John said:
I like opto isolated solid state relays for my home projects, for their
ruggedness and simplicity of a direct logic drive. But for production
designs, they are high cost.
I agree. When your are coming to do your own circuit, then you cannot
beat an isolating transformer and a SCR/Triac for cost saving. You
would have to cide into your pic to drive them with a few kilhertz
square wave though.


Rob.
 
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