According to the 555 cookbook:
"4.7 RESTARTABLE ONE-SHOT
During normal operation, a 555 monostable circuit will ignore input triggers that may occur during the timing cycle and will produce uninterrupted output pulses. On occasion, the need may arise to bypass this mode of operation and to restart the output timing with the application of a trigger pulse during the normal timing period. A circuit that accomplishes this is shown in Fig. 4-7. In this circuit, the reset and trigger pins of the 555 are tied together and used as a single trigger input. When the input is driven to zero, it has reached the threshold level of the reset input. Since the reset function is overriding, the output is held low even though the trigger input is below its l/3V+ threshold. When the input rises, the reset function loses control and the trigger input assumes command. The output then rises, and a timing cycle begins."
This is really encouraging! I have a project I am dreaming up where jarring a motion switch turns on an LED for 60sec. If I jar it again in that time, the counter resets and triggers a restart. If ~60sec expire, the LED turns off.
I have simulated this successfully in an Arduino, but I'm told that a 555 chip is a cheaper alternative to my problem.
I'm trying to breadboard out a working product before I have a circuitboard made. Can anyone confirm that if I tie the 2nd and 4th pins, that this will function like I need it to?
Thanks!
-Dave in TX
"4.7 RESTARTABLE ONE-SHOT
During normal operation, a 555 monostable circuit will ignore input triggers that may occur during the timing cycle and will produce uninterrupted output pulses. On occasion, the need may arise to bypass this mode of operation and to restart the output timing with the application of a trigger pulse during the normal timing period. A circuit that accomplishes this is shown in Fig. 4-7. In this circuit, the reset and trigger pins of the 555 are tied together and used as a single trigger input. When the input is driven to zero, it has reached the threshold level of the reset input. Since the reset function is overriding, the output is held low even though the trigger input is below its l/3V+ threshold. When the input rises, the reset function loses control and the trigger input assumes command. The output then rises, and a timing cycle begins."
This is really encouraging! I have a project I am dreaming up where jarring a motion switch turns on an LED for 60sec. If I jar it again in that time, the counter resets and triggers a restart. If ~60sec expire, the LED turns off.
I have simulated this successfully in an Arduino, but I'm told that a 555 chip is a cheaper alternative to my problem.
I'm trying to breadboard out a working product before I have a circuitboard made. Can anyone confirm that if I tie the 2nd and 4th pins, that this will function like I need it to?
Thanks!
-Dave in TX