Hi,
Unfortunately the voltage produced by the speedometer output was not sufficient to trigger the transistor. I did some probing and found out that the output was at ground between pulses. I then found a web page that detailed how to use a transistor as a ground triggered switch (
Using Transistors As Switches). Using this circuit I have been able to get the MPGuino to read pulses from my speedometer output.
I have done some preliminary calibration and it seems about 2500 pulses/kilometre works well.
Now to get some fuel usage information!
Cheers,
David