AVR-Chat

On Jul 28, 2009, at 9:51 PM, Jim Wagner wrote:

> One way is to add a series resistor to each input (say 4.7K to 10K),
> then add a diode (preferably Schottkey,j but silicon junction will
> work) from each input to the processor Vcc, cathode to Vcc. That will
> limit each input at the micro to the current Vcc )(plus one diode  
> drop).


There is an Atmel apnote describing how one might monitor AC zero  
crossings which states there is already a protection diode on all  
inputs which is good for up to 1 mA. The apnote used a large value  
1000V rated resistor in series to connect direct to 120V AC. And then  
goes on to say something to the effect, "Use at own risk."

--
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.