While the LR8 is about $1. each (TO-92), it can take any DC voltage up to
+450 and with 2 resistors take it to any lesser voltage (-~12v)  again as I
remember.  20 ma out...  a handy circuit without dealing with larger wattag=
e
dropping resistors in optos.

FYI...

Rich

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Carl Denk
Sent: Monday, September 16, 2013 11:14 AM
To: Microcontroller discussion list - Public.
Subject: Re: [PIC} AC inputs to a PIC

Thanks again for the inputs, but I should have mentioned, there will be mor=
e
than a few maybe 8 of these inputs, and any could be any of the voltages.
Looking for something inexpensive and small footprint. the opto isolator
fits that spec. Didn't know the details of implementing.=20
Thanks again.

Incidentally I use a 120VAC in, 5VAC out wall wart as PIC ADC input to
measure the AC voltage. it's a little more complicated than that, but works
nicely.
On 9/16/13 10:43 AM, David Bearrow wrote:
> I think I would just use a small 5VDC power supply. Then you could=20
> detect 5V or 0V depending on if it was on or off. There are lots of=20
> off the shelf supplies or you could build one.
>
> David Bearrow
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On=20
> Behalf Of Carl Denk
> Sent: Monday, September 16, 2013 7:34 AM
> To: PICLIST
> Subject: [PIC} AC inputs to a PIC
>
> I have a home project coming down the road mainly HVAC stuff of=20
> digital inputs to a PIC probably a 18F??. THe inputs would be only to=20
> sense on/off. The voltages would be 24 VAC, 120 VAC, and 240 VAC. I'm=20
> thinking through an Opto isolator with a resistor and capacitor on the AC
side.
> Values ? Configuration? or something else?
>
> This is a low priority at the moment, but thought I would generate=20
> some traffic for Bob. :)
>
> Thanks again.

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