Anyone design a toner wheel..., ...for an electronic speedometer? Options

[neo914-6]

For neo914's Audi instrument panel, I need an inductive sensor mounted to the wheel that will have have app.10-12 holes evenly spaced. Every time a hole goes by the sensor, it will deliver a signal to the speedometer.

[lapuwali]

Felix, the "inductive" sensor is also known as a VR sensor (variable reluctor), and you can get one off a junkyard Ford Escort from the early 90s: the crank sensor for the EDIS ignition. The wheel you use must be made of steel, since these sensors will only "see" a ferrous tooth. You'll need to know the number of teeth exactly, unless the gauge is somehow adjustable.

There are a variety of mounting options. Since you're going to have to have the wheel custom made, anyway, you could have it made as a toothed ring that fits snugly on a CV and is held in place with set screws. The diameter of the wheel won't be important to the sensor, only the number of teeth. The bracket that gets made to hold the sensor will need to be able to hold the air gap between the sensor and the wheel fairly constant, or you'll miss teeth and get an inconsistent signal.