Electronics > Beginners
Learning the Art of Electronics - keypad
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David1:
@bd139. Do you know what's different about the old and new keypads?
David1:
@rstofer If you Google "student manual for the art of electronics" someone has pirated the whole thing...
bd139:
Look on libgen.io :)

The 2nd edition keypad (sorry wasn't 1st) is used to load SRAM up for a 68k CPU so had some stuff in it to support that.
rstofer:
I'm pretty sure the keypads are identical.  Signals not used in the latest edition simply won't be used.  I suppose the logic could be eliminated for unused signals but that might be unwise.

I have never heard of the MC14490 Hex Debounce Circuit - surprisingly, they are in stock at DigiKey.  Very handy chip!
David1:
Update on 20 June 2018:

The author, Thomas Hayes, has been away on vacation but has got in touch to say he will put up-to-date details of the keypad on the Learning the Art of Electronics website. It is different from the one in the old Student Manual as he has re-designed it with a microcontroller in place of the many IC's of the older version, to do keypad scanning, switch de-bouncing and display.
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