Pazzy

Anyone performing their own automobile tune-ups knows how important it is to know your engines speed. With this tachometer, you can measure your engines speed without any connections or annoying timing lights.      Wireless Auto Tachometer Circuit Diagram PC board layout and parts placement  Calibrate the unit as folows: Set up this circuit: Turn on the Tach and allow a few minutes for temperature stabilization. Set S2 to 4 cylinders and adjust R5 for a meter indication of 180 (1800 rpm). Set S2 to 6 cylinders and adjust R6 for a meter indication of 120 (1200 rpm). Set S2 to 8 cylinders and adjust R7 for a meter indication of 90 (900 rpm). To use the Tach, turn it on and let it sit for one minute to allow for temperature stabilization. Extend the antenna, select the right number of cylinders and hold the unit over the engine. If the reading is erratic or the needle jumps around, move the antenna closer to the ignition coil or spark plug wires. The unit draws power fr...

The author is a motorbike racer in the Classics class of a Dutch Motorcyclists Association. He recently replaced the contact points  on the engine of his motorbike (a 500-cc BSA  Goldstar with a single-cylinder four-stroke  motor) by an electronic ignition. The new  ignition system produces a spark for every  rotation of the motor, compared with a  spark for every two rotations with the con-tact points, so there are twice as many spark  pulses. As a result, the tachometer indication was no longer correct. Circuit Diagram : Tachometer Pulse Divider Circuit Diagram A new tachometer suitable for use with an  electronic ignition (such as a Krober unit) is rather pricey at around €  175. Accord- ingly, the author first looked through past Elektor July & August issues for a suitable divider circuit — after all, it should be possible to solve this problem with a bit of electronics. It didn’t take long to find something suitable in the form of a mon-ostable multivibrator. The circuit sh...