Hullo. My very first post. I am an amateur, so any simple advice would be appreciated.
I have built an analog tachometer using an Arduino Nano and an automotive stepper motor. It all works nicely when bench testing. However, put the signal generator (Hall effect or photoreflector etc) near an old motorcycle magneto, and the connecting leads pick up interference from the spark plug lead. Magnetos are of a completely difference construction to a normal coil ignition system. Designed over a 100 years ago, the primary, secondary coils, capacitor and points all rotate, while the magnet is stationary - completely the wrong way around! There is no access or tapping into any of the system. So next idea is picking up the signal from the spark plug lead itself. Above is my initial idea for feeding a Voltage into the Arduino. I don't have an osilloscope, but can use one at work. I have to bring in a battery, a magneto and electric motor to drive the magneto (needs a hefty 12V motor to spin a magneto), so would like thoughts on if the above is worth a trial. Thank you. Rob Steward