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Thank you for reading this…..
I a wondering about protection for the PIC port if I am using a Dallas iButton device. I have seen circuits using a 33R resistor in series and a FR107 Fast recover diode across the probe. And another up to the supply rail.
My question is why the use (specific) of a fast recovery diode… Will a ordinary or even a Schottky diode be the same …..Is there a reason ?
Sorry if posted in wrong place.
Anything is better than nothing - it's to protect from fast transients like lightning striking some distance away or ESD.
There's a continuum here. Some energy source / device sensitivity combinations will do no damage with no diode at all, some combinations will leave a smoking hole where your circuit used to be. Faster protection is better, but the difference in protection from fast recovery vs. Schottky is pretty small. I use Schottky and have never seen a failure (touch wood). If the lead to the device is fairly short - say under a couple meters, you will be safer yet. YMMV.
Thank you
I guessed the any protection is better than nothing.....
Now I guess I just need keep my operators away from man made fibres !
Don't want smoking holes !
BR
Andy
Hi, Andy
may be it's a good idea ...
as iButton devices are generally hand held by everyone ( understand people ignoring what is ESD ! ), the diodes inside the Pic may be somewhat weak ...
so, a couple of fast diodes and a small series resistor are to consider.
don't forget to read Maxim AN244 ... http://www.maximintegrated.com/app-n...dex.mvp/id/244
Alain