Cheap and easy digital tachometer?
I convert engines from weedeaters, leaf blowers, etc. for use on large model airplanes. I use an aftermarket electronic ignition on the engines. The ignition uses a Hall effect sensor and a magnet to trigger the CDI ignition. I would like to build a digital tachometer that would use that same trigger. They sell them for $25.00, but I thought it would be fun, and cheaper, to make one (or several) myself.
Can anyone help with a circuit and parts list?