Making motorcycle clutch housings and keyways.

[@KravchenkoAudioPerth]

Nice slotter Tony! Could the variable timing not be easier with a variable resister and capacitor in from of your relay? Just like on a variable wind screen wiper timer.

[@MotoChassisByTonyFoale]

Thanks for the suggestion. There are several ways to get a time delay. I did consider using a 555 chip which is a common timer but it would have needed more components than the Arduino. An RC system as you suggest could work but the relay might not switch at the same threshold each time, it would depend on its internal coil heating for one. The dV/dT at the thresold would be slow and so the contacts may not close or open quickly. It is better to generate a fast pulse to feed the solenoid to ensure rapid switching. The Arduino solution is very easy and not expensive. The nanos cost around 3 euros.