need a circuit that'd be basic to many but magic to me

Thread Starter

dogfuel

Joined Apr 13, 2009
10
Hi -

I have an instantaneous switch that completes a circuit ... for the solution (gps-based) to work, the circuit needs to be closed for 2 seconds or as long as the switch is closed.

My problem is obviously when the operator closes the switch for less than two seconds ... would someone describe how to delay the opening of the circuitfor 2-3 seconds (exact time is not critcal)? It is ok if the same delay comes after the switch is opened, regardless of how long the switch is closed.

Thanks!
 

eblc1388

Joined Nov 28, 2008
1,542
It is ok if the same delay comes after the switch is opened, regardless of how long the switch is closed.
In the following circuit, the relay will activate immediately upon closing of switch and only release about 2 seconds after switch is opened. Relay will be keep energised as long as switch is closed.

 

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eblc1388

Joined Nov 28, 2008
1,542
The circuit timing is determined by the resistor from pin7 to +V (47K shown above) and the 47uF capacitor.

Increase the value of either or both will increase the delay timing. Avoid resistor value higher than 1MΩ and capacitor value larger than 470uF.
 
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