Now it so happens that I stol^H^H uh, came across this large illuminated pushbutton recently. It has a large 25mm button illuminated by an incandescent lamp. The switch is a highly reliable microswitch. It was just begging to be used in this project. So I’m designing the thing around it.

To the left is my first conceptual design (scanned off the back of an envelope!). It has the big button at the left, an LED readout for the speed (in BPM) and a knob to set the speed. Underneath the knob is a slide switch to turn the power on and off.