Built my own for the Moose Truck many many MANY years ago, as a tach was not availble until 85'.
Designed it to use a popular digital gas engine tach that Radio Shack sold at the time. I built this interface to work with reflective muffler tape stuck to the flywheel. Still set up that way, and almost 29 years later, it still works great. I've since simplified the circuit two years ago, using a 40106B CMOS Hex Schmidt trigger IC in place of the transistors. Works even better now. The tach is set to work with a 4 cylinder, so I only needed 2 reflectors 180 degrees apart on the flywheel.
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Designed it to use a popular digital gas engine tach that Radio Shack sold at the time. I built this interface to work with reflective muffler tape stuck to the flywheel. Still set up that way, and almost 29 years later, it still works great. I've since simplified the circuit two years ago, using a 40106B CMOS Hex Schmidt trigger IC in place of the transistors. Works even better now. The tach is set to work with a 4 cylinder, so I only needed 2 reflectors 180 degrees apart on the flywheel.
