Simple Tachometer

Project updated 12.05.2005



My friend Bo likes to play with small machines. Last summer I promised to build test tachometer for him. Almost a year later I did prototype from recently build Mitsubishi thermometer board. Hardware provided too few and too small numbers. New hardware was designed for this project. Also small LED stroboscope was added to the circuit. Signal is taken from ignition cord with simple capacitive sensor. Keep this secret from your mother. With push button selector you can select either four stroke or two stroke mode.



Pictures Bottom | top | side / strobo LED


PCB artwork

Component placement

Software v0.2

Proto board software

Sample signal1 | signal2

You may have to experiment with C3 value

Test drive1 | test drive2


Tests with different engines and ignition configurations have not all been successful. Few improvements have done and new "frequency counter type" tested. I found also cheap magnetic pickup. This should be more noise tolerant than capacitive pickup.

Improved spark interval measurement type software v2.1

New frequency counter type software v3.1

Magnetic pickup test1 | test2 | opened1 | opened2