How to generate a high delayed pulse triggered by a falling edge?

Thread Starter


Joined Jun 22, 2020
I have an IR sensor that has an output pin that goes low when you put your hand over the sensor. I have a motor that I would like to turn on when you put your hand over the sensor. Currently I am using a mosfet to do that but the motor keeps running while my hand is over the sensor. This is not what I want. I want the motor to turn only for few seconds after the sensor is triggered, meaning I want the falling edge of the output signal to be a trigger. I do not want to do it with microcontroller. How do I do it. Thanks!!


Joined Jul 11, 2016
it may turn out to be not a reliable method to trigger anything as the iR backround may vary -- such as the reflections from moving doors , men animal bugs (fly sitting next to sensor and blinking eyes ... actually they can't do such ... well cleaning it's head . . . they always crawl up where they shouldn't ...) . . . room/outside light change