In Reply to: Help me build an cartridge tester posted by Peter Lingman on 03/23/00 at 5:33 AM:
It seems like you have a set of DC threshold conditions to detect. The way I'd approach this is to use LM339 quad comparitors, a device which is offered by several vendors and which was originated by National Semiconductor,
When doing this, I prefer to run the comparitor sections in the inverting mode and introduce hysteresis at the non-inverting input. This keeps the hysteresis feedback voltage from affecting the input I'm trying to monitor.
The published application notes are very good, but if you need more specific circuit details, I can send them as an attachment to an e-mail.
John Dunn - President