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Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
Geez, this could fall under Computer Science, HV and General...
I just bought a 1993 Ford Ranger with a 4 speed. What bothers me is that it didnt come with a tachometer and since it has something like 80HP or less I need to keep the RPMs really high during acceleration.
I cant afford any of the commercial product so my idea was to wrap a coil around one of the spark plug wires and transform that to a TTL signal and input that into a PIC. The pic would multiply by 4 and average the last X readings and then it would display low red, green, orange, red and blinking red.
Anybody have any ideas on how to get the TTL signal? Sounds like its time to crack out the o-scope.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
I once made a tachometer based on a similar principle but using an optical sensor
apart from the pulse treatment, this is the same principle
all you have to do is make a frequency to voltage converter and put a buffer amplifier at the output which will also be an integrator for the frequency range you are measuring
this way you can drive comparators and set different leds on
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
You could just find the fly wheel or a similar rotating object that is connected directly to the drive or cam shaft and mount 1 or 2 magnets on it and use a hall effect sensor then just divide by 2 or not at all and still use a pic.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
in that manner, you can also put a line of white text corrector (tipp-ex or something) and place an IR led and a phototransistor facing the disk, with a bit of heatshrink tubing around the phototransistor to keep parasitic light out
the advantage is you can also find IR emitters/detectors bundled in a vertical package specially made for this kind of usage
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Tachometer
