[sdiy] Digital Input Circuit

[Tim Ressel]

TVS diodes have a higher 
voltage. Schottky diodes have a 0.3 volt drop when conducting. This 
means the inputs to the processor do not exceed specifications.

Tim Ressel
Circuit Abbey
503-750-9331
timr at circuitabbey.com




>________________________________
> From: cheater00 . <cheater00 at gmail.com>
>To: Tim Ressel <timr at circuitabbey.com> 
>Cc: stew <stewpye at optusnet.com.au>; synth-diy <synth-diy at dropmix.xs4all.nl> 
>Sent: Thursday, August 8, 2013 5:27 AM
>Subject: Re: [sdiy] Digital Input Circuit
> 
>
>
>
>On 8 Aug 2013 03:01, "Tim Ressel" <timr at circuitabbey.com> wrote:
>>
>> I use a current limiting resistor (2K) followed by a BAS40-04 dual schottky diode which acts as a clamp, then into a 74HC14 schmitt trigger for cleaning up the edges. This arrangement can handle +/- 15 volts on the inputs without damage. Also good for analog inputs, except the HC14 turns into an opamp buffer.
>In a parallel thread on TekScopes, TVS diodes were recommended.
>Cheers,
>D.
>
>