AVR-Chat

On Sun, 09 Jul 2006 17:34:39 -0000 you wrote:

>Sealed metal box - check.  :-)
>
>It's going into an automotive environment, which is inherently noisy.  
>
>Now just so I can make sure I'm not confusing myself, take a look at
>this diagram I whipped up:
>
>http://i6.tinypic.com/1zf3b6b.jpg
>
>The 1k resistor keeps any current through the diodes to a minimum if
>the user accidentally connects the pin to power.
>
>The diodes protect the mcu from any static by shorting anything below
>0.6V to ground, or above 5.6V to 5V.  
>
>The 0.01uF cap filters out any AC noise.
>
>Whaddaya think?  It's a relatively low frequency 0-5V DC signal (the
>input).  I doubt it could switch from 0 to 5V in less than 50mS.
>
>btw, thanks for pointing out the polyswitches.  I knew they existed, I
>just didn't know what they were called.  I'll have to look into those
>for current limiting the outputs.  I'll have to see if they make them
>in 5 amp'ers.  

With that low a frequency I think you'd be ok raising the resistor value
quite a bit. The cap. won't filter much below 10KHz using 0.01uF
How about 39k and 0.1uF giving around 40Hz cut off.
--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
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