Measuring across the ignition cable

Projects General Guidance
1

Hi

I need some help to chose or make a module that can measure every impulse of an ignition by measuring across the ignition cable.
I have made a dyno already measuring speed km/h. but would now like to add revolutions from the engine a Zenoah R230G with magneto ignition with 0 to 25,000 rev / min.
I have seen some ignition guns that can be put over the ignition cable for measuring and i'm looking for the same type just to send the signal to my Arduino board.

2

Your magneto has a "kill" connection to stop the high voltage ignition pulses. Check the kill connection with an oscilloscope. Perhaps that will provide a low voltage pulse that you can use.

Paul

3

I've done this with racing motorbike engines.

Wind 3 or 4 turns of insulated wire round the ignition lead. The current pulse as the plug fires induces volts in the pickup coil.

Use a LM2907 with voltage catch diodes (1N4148's) to rail and ground to prevent overvoltage damage.

You get a dc output proportional to revs.

Worked fine.

Allan

4

olesj:
I need some help to chose or make a module that can measure every impulse of an ignition by measuring across the ignition cable.

Surely that can't be hard. It's just a single wire held against the ignition cable with a clothes peg - capacitive pickup.

5

Grab one of those ignition guns. They can probably be found very cheaply at your local discount tools shop.

Strip it open and have a look. You will probably find the sensor cable comes in to one side of the board and there's large gaps between that side and the rest of the board. Whatever penetrates the gap is probably a good low-voltage signal you can use. Break off the rest of the board and throw it away.

6

Thank you :slight_smile:

I have ordered the parts , i will return when i have tried it out ....

Thanks :slight_smile: