Simple way to make a position measuring hinge

I wanted to make some swell shoes but balked at the price. It seems easy enough to make a hinged pedal, but how do you transmit the motion to a potentiometer in a way that does not put undue pressure on the pot's bearing (which is really only designed for fingers).

I came up with a series of linkages of varying complexity, but they all required significant framing work and precision, neither of which is practical with a few cordless tools in an apartment. So I was thinking about how to get the potentiometer to align precisely with the hinge axis. What I really wanted was a carefully placed 1/4" hole exactly aligned to the hinge axis. I thought about some carefully drilled blocks of wood. Then it struck me: the solution is simple:

Take a suitable door hinge, with a 1/4" pin. Remove the pin (I used a hammer, a piece of steel rod and a patient wife) and cut it just short enough that the potentiometer shaft can reach the second finger. I then had to drill out the outer finger because it was slightly smaller than the 6.8m shaft. Drill a hole in the second finger and tap in a small screw. I used a HDD mounting screw (the sort with the big cylindrical stub head) so that I could use it as an end stop too. Then glue the pot to the outer finger. Total cost: $3 hinge and $1 pot. Total time: 1 hour for the prototype.




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