I'm using a 74LS192 DECADE counter which has a RESET pin on it. I've come up with a simple circuit that seems to work just fine for now. Should I be concerned that my switch effectively shorts out the capacitor? We're only talking 5 volts at most here, with pretty low capacitance, but still....

 

Should I be concerned that my switch effectively shorts out the capacitor? We're only talking 5 volts at most here, which pretty low capacitance, but still....

You have a valid concern. The shorting of the capacitor will create a spark and cause premature failure of the reset switch contacts.

The solution is simple. Just place in series a resistor with the reset switch of any value between 10Ω and 100Ω as this will then reduce the short-circuit current to a safe level for the switch contacts.

 

Thank you...now I just need to throw in a de-bouncer of some kind and call it done.

 

Thank you...now I just need to throw in a de-bouncer of some kind and call it done.

If you follow the the tip from eblc1388 the circuit will act as de-bouncer. Due to the charge and discharge of the capacitor

 

True, but wouldn't the concern then be that as the capacitor charges/discharges, it will have to pass through TTL's undefined input voltage zone of .8 to 2.0? Theoretically there could be problems...but probably not.

 

True, but wouldn't the concern then be that as the capacitor charges/discharges, it will have to pass through TTL's undefined input voltage zone of .8 to 2.0? Theoretically there could be problems...but probably not.

Take a look here. Debounching is due to the mechanical properties of a switch.
http://www.ikalogic.com/debouncing.php

 

Theoretically there could be problems...but probably not.

If the pin is a gate input, then undefined input voltage zone will cause problem as the gate output might change state unpredictably.

For undefined voltage on a reset pin, it could also cause multiple resets but since what reset operation does is to force the chip into a well defined state so multiple resets will effectively changes nothing after the first reset.