So I found this Geiger counter at https://mightyohm.com/blog/products/geiger-counter/. You can also find the detailed electronic schematics there. I tried to figure out how this apparatus works, but I'm stuck with the boost converter and the timer to create the PWM signal. Can someone explain?
Because it's not the typical 555 timer setup for an astable multivibrator. I don't get how the frequency and duty cycle of the PWM signal is setup. It boost up 3 V input to 400 V output.