/diy/ - Do It Yourself

>>2781091
This is what I’d do as one of the simplest ways to get this together.

you can use one of the 555 timer circuits you found. Just use an appropriate capacitor and use a potentiometer to adjust the time. The setting of the pot “stores” the time. Just label it accordingly on the outside. There’s going to be a button to start it.
The optional display will use a LM3914 chip to generate a bargraph of the voltage across the timing capacitor for the 555 timer. You may have to adjust both your potentiometer and the bar graph generator with a resistive voltage divider, and a switch to run it constantly is simple enough.
You can do the same thing with an lm324 if you only want a 3-led bargraph.
The drive circuit can be either a mosfet or a bjt transistor, if you want old school, use a bjt like a 3055 and mount it on the back on a heatsink like a boomer, although you’d use a real motorola.
All this is 80s boomer tech.