Re: [oopic] Reed switch help

At 05:44 PM 8/11/2008, Brian Lloyd wrote:
>If all I am doing is counting pulses I try not to tie inputs to Vcc at
>least not without a series resistor. Drive the input as an output and
>you could smoke the pin. I would use the reed switch to ground and a
>pull-up resistor to Vcc/Vdd. I agree with your value of 10K.
>
>
>
> Vdd
> |
> 10K
> |
>pin<-----+
> |
> reed switch
> |
> Vss (ground)

You could still hurt the micro if the pin is driven high and the reed
switch is closed. I'd add a protection resistor:

. Vdd
. |
. 10K
. |
pin<--330---+
. |
. reed switch
. |
. Vss (ground)

...Andy

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