Position Sensors

Mice are often overlooked as motion or position encoders.

Position related sensors:

Motion: Change of position

Fluid Flow: Change in position in a fluid

Strain: Force of change of position

Acceleration: Change in the rate of change of position.

Proximity: Difference in position

Altitude: Vertical position with respect to ground

Direction: of change in position

Radar: for $25.00 each and $18.00 in small qty. Siemens offers a 2.4 GHz Doppler radar sensor, with antenna built in. (Part number KMY 24) A complete sensor that will determine distance and direction by monitoring 2 sensor outputs with your A/D microcontroller. Up to 15 feet possible,and very small in size. (1.125"x1.5"x.375" approx.)

A 'spiffy' position sensing system is air. It's sometimes used for precision gages, usually in the form of a gage to measure the difference between desired size and actual size.
A simple application would be measuring the diameter of a hole, like a gas engine cylinder. A test plug is inserted in the hole. Around the periphery of the plug are several small holes that lead to a central air supply. A T from the supply also leads to a fine needle valve. A sensitive pressure sensor between the arms of the T is nulled out by adjusting the needle valve, with the plug inserted in a standard cylinder. When the plug is inserted in a larger cylinder, the air pressure in this leg will be reduced. The pressure sensor can be calibrated for size.

This technique has been superseded for many applications by the linear differential variable transformer. It might make more sense to move this comment to 'proximity'.+

Create a gradiant in photoshop from black to white. Print it onto overhead transparency film. Arrange to run in the slot of a transmissive optoswitch. something like a Vactec 13D7-20 would work good

I also just made a cool discovery. You know the rubbery ferrite fleximble magnet material? It's available in sheets to make 'fridge magnet' type things, with an adhesive backing. Any crafts store. I just noticed that the polarization is in narrow strips, horizontally like this

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The spatial wavelength is about 1/8", so you could make a handy position sensor or linear stepper out of it.