I'm looking to make a timer for Rubik's Cube solving, which looks like this:
My design just has some added features and a different output type.
However, I'm not sure how best to replicate the hand sensors. They're just binary, "hand on"/"hand off". The pressure required to trigger the sensor should not be very high.
I have a couple of ideas, but I can't imagine that the actual product does any of these. Which one of these is the best, or is there a better way?
Each hand sensor is just a physical array of, say, 10 small pushbuttons laid out in a horizontal line. Each one is wired in parallel between VCC and signal so that if any are pushed, the signal is pulled high. I would have a plastic sheet over the top of the pushbuttons so that pressing anywhere (or everywhere) on the sheet will trigger multiple pushbuttons.
Have a strip of conductive metal along the bottom of the hand sensor area, and then another strip on top. Separate the two by some sort of spring, and then when pressed the two will contact. There would also be some sort of plastic sheet over the top just to make it look better.
Use capacitive touch sensing. (I'm not sure how cheap this is though, or if it works through a thin plastic sheet.)
The signals (one for each hand) just need to be read by some microprocessor -- I haven't decided on one yet, but probably some simple ATMega.