I am facing a problem of firing multiple interrupts on nodemcu 1.0 on single rising edge pulse.what is problem and what are the solutions?

Question

I am working on a project which involves counting the drops falling in a drip chamber of a IV fluid gravity based therapy bottle(saline bottle).I am using IR trans-receiver at the drip chamber to detect a drop falling. I am using a comparator to generate a pulse when ir voltage drops below a certain threshold. The output of comparator is connected to D1 of nodemcu. The ISR is called at rising pulse of comparator .But the nodemcu calls the ISR 3 to 5 times on a single drop.what should I do?plz help.

Answer 1

The signal is probably "bouncing" between HIGH and LOW instead of performing a clean edge, just like it happens with buttons.

Two simple solutions:

1. Hardware solution: use a schmidt-trigger instead of a comparator
2. Software solution: define a dead-time for the signal aquisition (disable the interrupt when the desired edge has been detected and enable it again after "dead-time")