Measuring pendulum deflection.

Projects General Guidance
1

Hi,

I'd like to be able to measure the deflection of a pendulum assembly.

The assembly won't move more than a few centimeters in any direction, but the force that moves it will be very slight, so whatever mechanism I attach to it to measure the deflection will have to be light, if it has too much resistance then the pendulum will stop moving. I guess I'm looking at some sort of linear encoder.

The total movement of the pendulum would be no more than 10 cm end-to-end, and I'm hoping to get a resolution of 1/2 a millimeter or better.

I had considered attaching the pendulum to a large linear potentiometer and using it as a simple voltage divider to get the position, but I think the resistance of the pot. would restrict the movement of the pendulum.

I'm now thinking I'll have to use some sort of optical method, any suggestions?

Cheers

2

A high quality ball bearing shaft encoder should work well, but might seem a bit expensive. The Bourns ENS series takes a vanishingly small amount of torque to turn and provides 360/1024 degrees of resolution: http://www.digikey.com/product-detail/en/ENS1J-B28-L00256L/ENS1J-B28-L00256L-ND/1089392

3

The AS5040 is a hall effect rotary shaft encoder. Being coupled magnetically there is no friction. I used it on this project:-
Harmonograph

4

AS5040 is a hall effect rotary shaft encoder

I think that should do the trick.

I used it on this project:-Harmonograph

I followed the the link, cool project!

Thanks

P.S. I always had you down as being a teacher, I always felt my posts were being marked with a red pen whenever you reply :smiley: