Modified Monostable Multivibrator Circuit
Ripped from @faceblast, basically that is how I role (e.g. looking for gems that solve problems).
A few years ago I worked on a project that had a liquid meter calibration device (a.k.a. prover) that had a few switches. Each time the positive displacement device (pipe pig) passed a switch it closed a number of times but for calibration I needed the first close to be used. Things could move fairly slow e.g. worst case needed was about 10 seconds for the pig to go past. Everything ran at 24V.
Anyway I'm going to make a small board and test it so the next time this problem crops up I will have a better way to solve the problem (last time was a cluster <bleep>).
NOTE: this seems to work at 5V or 24V without circuit change.
Link to board:
http://epccs.org/indexes/Board/OneShot/
Update:
Add Zener at the switch NPN because that's about what the reverse Vb-e breakdown is (its not going in the real circuit and is just a ball park). Also a diode to get things working again. Next I added a resistor through the switch to limit the current to prevent damaging arcs on the contacts (and then found it fixed a glitch).
