I would like to know what kind of strategies might exist for making the 555 timer retriggerable. I want to be able to restart the timer with a second pulse to the trigger input, extending the duration of the HIGH on the output. Is it possible without giving a high to the reset input, or is there a neat way to feed the reset input a high each time I hit the trigger?

 

Here is a re-triggerable 555 timer circuit from my 555 cookbook.

The circuit works by discharging the timing capacitor each time a trigger pulse is applied to pin 2 of the 555 timer.

 

Awesome, thank you!

 

Hello,

The circuit that @Hymie showed is also called a missing pulse detector.
In the attached PDF you will find the circuit on page 12.
(page 8 of the PDF).

Bertus