Tachometer Works!

After finding that the tach wasn't displaying anything after installing the tach sensor unit from RechargeCar, I did some additional research.

The sensor is putting out a 12V signal, but the tach is expecting 100V+ signal from the coils of the gasoline ignition system.  Folks on 914 forums suggested either designing a booster circuit with parts from Radio Shack, or just buying a tach adapter unit by MSD.

This is how it looks out of the package.  The wiring is very simple, with 12V power, ground, tach sensor in and tach output out. 

 I wired it up and it worked first time.

Tach sensor

The Electro Automotive kit comes with no provision for a device to collect motor RPM data.  They do have the tach wire terminate on a block in the rear contactor area.  While I was at EVCCON, I saw the WarP Speed Sensor from ReChargeCar.  The picture I took of my unit is horribly out of focus, so I've copied the one from the ReChargeCar web site.

The speed sensor is a simple but effective and flexible tach sender.  You see the 4 setscrews in the ring?  Those are removable in case your tach requires 1, 2, or 4 pulses per rotation.  I left all 4 setscrews in place until I get the motor running, and I'll be able to adjust it if the tach reading isn't correct.  Here you see the ring with the sensor bolted to the front end of the motor.  The sensor can be adjusted closer and farther away from the shaft, but I left it at the factory setting.  I'm very disappointed that my motor shaft is rusting!

And here is the ring, tightened up to the shaft.  The setscrews fire the sensor as the ring spins.

 Finally, I wired the sensor's cable to +12V, Ground and the tach wire.  Can't see if it works until the motor turns for the first time.