Inductively sense workpieces of any material

-May 16, 2014


Presenting one of the runners-up in the TI LDC1000 inductive sensor design contest.

The problem originally undertaken was to sense the presence and position of nonmetallic objects in a gritty environment – such as a paper mill or woodworking operation – that requires accurate workpiece sensing for certain cutting and routing operations. Microswitches are fragile and clog easily.

The use of the LDC1000 inductance–to–digital converter for woodcraft applications is problematic since wood has no inductance effect. The solution is a sealed, compliant metallic interposer placed between workpiece and the converter coil. A demo workpiece feeder prototype comprising a gear-motor, a motor driver with logic control, the LDC1000, a laptop with the GUI/setup software installed, and a 16V power supply was designed and built. The demo prototype worked as expected. The interposer is displaced slightly when the workpiece is placed into the demo prototype, causing the motor to propel the workpiece. On exiting, the motor automatically shuts off.

A range of applications can be realized by the innovative employment of a compliant metal interposer that the workpiece displaces a small amount; the inductance change is independent of the material. This device would find great acceptance in the woodworking industry, where sawdust, shavings, and wood chips have plagued sensors. This efficacious innovation is actually specified for a currently active development. Moreover, the Interposer Inductance Sensor can be marketed as a stand-alone, rugged, general-purpose position transducer that can replace microswitches in harsh environments, be used for liquid and gas pressure, for weighing, etc.

Sensing Design Challenge 2013 winners:

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