Hi
I need to count the number of turns of a shaft for a home_make coil winder I am thinking to build.
I picture a small magnet mounter on the turning shaft, such magnet is triggering a reed switch which is connected to the two terminals of an "=" button "inside connection" of a calculator.
the operator hits 1+1 and then let the shaft run and the calculator should display the number of turns.

I just opened up a cheap calculator I had but the terminals are printed circuit board. I don't have enough materials on the terminals to solder the reed switch it them.

any suggestions are welcome

thanks
Sam

 

Got some fine wire? 30 ga solid would probably solder onto those PCB pads pretty well. Tin the pads, make a tiny loop in the end of the wire, and use the iron to press the loop onto the pad. Solder the other end to the reed switch. Make the wires fairly long, so the calculator can sit in a solid location while winding.

 

I went to an "Everything's $1" store and picked up a couple of pedometers for $1 each. These things are perfect for coil winders; they are five digits. All you'd have to do is bump the thing to make it count. Hard to come up with something easier or cheaper than that.