I was looking to make a tachometer for my car using an arduino. I don't think that an IR emitter/receiver will be the best way, so I was wondering if I could do it using the signal that my car's crank position sensor produces. It produces a +5 volt pulsed output every revolution. Is this possible to input this pulsed signal into an arduino Uno and count RPMs?
Hi.
You could look at Pulsein.
It can also be done with timers catching the rise.
There is a lot of information on the forum about reading fast pulses.
And there even more on Google:)
And welcome to the forum .
Regards Antony.
Edit.. Have a look here
http://tushev.org/articles/electronics/43-measuring-frequency-with-arduino
And here.
http://interface.khm.de/index.php/lab/experiments/arduino-frequency-counter-library/
Do you know where that signal comes from? If it's directly from an MVR pickup or similar, the voltage produced will be proprtional to engine speed and you will need some gain control - you will also need to watch out for interference with the ECU's use of that sensor since the sensor produces almost no current and really should only have one circuit driving it. On the other hand if this is a nice conditioned digital output then you're laughing. (It seems a bit odd that a car with a digital tacho output doesn't already have a tach gauge fitted, though.)
There are two kinds of sensors used for crank and cam position. One is inductive 2-wire and the other is hall effect 3 wire. Inductive has the change in voltage in relation to rpm, hall effect's voltage is usually 5 volts but, I would measure the voltage to be positive.
Use fuses and maintain the integrity of the factory wires or you may end up on the side of the road broken down.
Yes, the sensor on my car is a hall-effect. I measured with a multi-meter and the sensor produces a +5v signal for a revolution.