I recently bought a Nissan Micra K11 with the aim to slap a turbo on and use it for some budget track day smiles. The platform was chosen for its availablilty here in the UK, the low price of parts and its handling and performace potential (yes really!). Small fast cars are great fun to throw around on the track.
Anyway, being a crappy old micra it didn't come with a tachometer. I could have sourced some clocks from a better equiped model, or purchased an aftermarket tacho, but being a tight-arse and already having all the parts I need I decided to make one.
No. It should work on most crap cars. You just need a 5v tacho signal.
In my case, a square wave tacho signal from the ECU via a voltage divider is fed into pin 3 of an Ardiuno Nano. Two TPIC6C595 shift registers wired in series are connected on the SPI pins (13 11 & 10 for latch). The shift registers sink 14 leds - 8 green, 3 orange and 3 red. Pin 2 controls blue shift light led.
As the engine revolutions climb, the leds are illuminated in order with each led representing an increment of 500rpm.
When the 6500rpm rev limiter is hit all the leds flash on and off.
When 4000rpm is reached the blue shift light is illuminated.
Everything is easily configured to suit your application.
Not yet, but I'll add once it's fully installed.
To follow. I need to clean it up and correct a mistake or two first.
Thanks to deepsyx whose arduino-tachometer project provided inspiration and a little maths.