Arduino controlled motorcycle tachometer

I found a smashed Kawasaki dash in the dump. The speedometer was destroyed, but the tachometer was OK. The first thing I did was connect the tacho to 12v. It had three contact points marked IGN, GND and an unmarked one. I figured that IGN was +12V and the unmarked one was the signal input. So I powered up the tacho and flicked a 12V wire on the unmarked contact. Surprisingly it started indicating about 3000 revs.

I then Google’d a way to output a +12V square wave with the Arduino and I found this:

The next thing I did was hook everything up on a breadboard to test it out:

Using a potentiometer I varied the delay in microseconds for the off time of the signal used to drive the tacho.

I had to fiddle a lot with the Arduino program. I figured out that because I had inserted a Serial.println(val); to print out the value of the delay I was using to modify the signal was adding a bit of a delay. The next thing to be done is to receive some data over the serial port and display it on the tachometer.

Arduino controlled motorcycle tachometer

Finally, I own an oscilloscope!

After a long wait (my whole life), I was able to buy my very own oscilloscope. It’s the DSO 203 (quad). Momentarily, I’m very pleased with it, even though I haven’t used it a lot ( i got it this week), only for basic testing with its own wave generator and some PWM signals from a motor controller. Later this week I hope I’ll have some time to hook it up to my car ignition system because it’s an electronic ignition system to figure out a way to interpret the engine speed for data-logging. Sadly, I only received a single probe but i found MCX connectors on so I’ll be able to DIY my own logic probes at least, or if I get my hands on a BNC probe, changing the connector shouldn’t be too difficult.

DSO quad oscilloscope
The DSO 203

Before the DSO I used the sound card oscilloscope and made my probes with the help of ladyadas’ tutorial and managed not to damage my sound card. The software I used was written by Christian Zeitnitz and it was free. Still, I wanted more mobility and precision because with the sound card scope you need to drop the voltage down to a maximum of 1.5-2V and voltage spikes can damage the sound card.

I bought the Quad from for 200$ including express delivery being the cheapest one I could find. Shipping from Hong Kong took only three days (over the weekend). I was very pleased with that to say the least. Definitely worth the shipping cost.

The DSO looks quite well built, I chose the one with the black aluminium casing and it seems sturdy and worth the money. I recommend it to anyone in need of a cheap, portable and versatile oscilloscope.

Finally, I own an oscilloscope!