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Tachometer Wiring Ideas

13132 Views 6 Replies 4 Participants Last post by  Mr. Sharkey
Continued from the EV Calculations Thread

KiwiEV, the 1.5 volts that you're supplying to the tach isn't really what the gauge needs. It is just a coincidence that 1.5 volts moved the tach to 4,000 rpm. A conventional 4 stroke piston engine will send a signal (a 12 volt signal IIRC) to the tach one time for every 2 rotations of the crank. I have heard of people placing inductive pick-ups on the front shaft of a Warp8 or similar double shaft motor, but that would send a signal to the tach twice as often as needed. I guess it depends on the car as to whether or not the tach would like that signal. How is it possible to divide the number of pulses by two?
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I understand what you mean. This would be why the light-sensor tachometer 'generators' that you can get for EV's use pulses.
What I've done is a little different, and destructive (my favourite method!).
As you can guess, I was one of those kids who took apart his toys.

After doing some playing around with different voltages, I bypassed the circuit completely (see the photo below) and soldered a new power source straight to the needle 'motor' spring thingy.

This way varying the voltage changes the reading. It's very crude I admit but it is fascinating and I reckon I could figure out a cheap way to make it work, even if it's only accurate just before red-line for safety.
What do you reckon? I hope you're going to tell me it could work, or at the very least lie to me.
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