Sights at the IDT tech seminar

A better way to track motor shaft position: Inductive sensing

Cars made in 1965 typically carried two electric motors, one for the starter, the other for the windshield wipers. Vehicles today, even those that aren’t EVs, have more than a 100 electric motors. And most of them are applied in situations where it’s important to know the position of the motor shaft.
That’s why several technical sessions and one of the table demos covered a relatively inexpensive inductive sensor that uses the physical principles of induction a wire loop and eddy currents to detect the position of an electrically conducting target. The target slides or rotates above one transmitter coil and two receiver coils. The three coils typically take the form of copper traces on a PCB. The transmitter coil induces a secondary voltage in the receiver coils that depends on the position of the metallic target overhead. Circuitry demodulates the voltages from the receiver coils to get a signal indicating the target’s position. The target can be any kind of metal or a PCB with a printed copper layer.
The chip that makes the sensing possible is the ZMID5201/02/03. There’s a development kit that helps devise the metallic sensor patterns which pretty much have to be created from scratch for each application. (In the top image, the circular reference design is shown along with a board used as a driver.) IDT engineers we talked to said there’s software that helps create the right pattern for specific uses. Shown here are examples of both a linear and rotary sensor using the technique.
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