On 9/16/2013 8:33 AM, Carl Denk wrote:
> I have a home project coming down the road mainly HVAC stuff of digital
> inputs to a PIC probably a 18F??. THe inputs would be only to sense
> on/off. The voltages would be 24 VAC, 120 VAC, and 240 VAC. I'm thinking
> through an Opto isolator with a resistor and capacitor on the AC side.
>

I always think non contact whenever working with sensing AC. Have you=20
thought about using a circuit like those in the non contact voltage=20
detector pens ? You would only have to place the coil near the HVAC wire=20
that becomes live when powered.

The circuits are as simple a couple transistors and would be very safe=20
since you don't have to alter the HVAC at all.
Mark

--=20
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