Does any one know what happen if multiple FSR connected in series?
The fsr’s down the line will negate any effect that the activated one has.
You’ll see some drop in resistance, but not enough to trigger a digital input when using the internal pullup. They’ll work better wired in parallel.
I’m thinking of making a back to back FSR on each ear so total using 4 FSRs
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Why on earth would you want to do that?
The FSR adapter boards (analog to digital conversion) uses 3 FSR sensors each separate. The way it works is that any one triggers the output rather than multiple being required.
I’m tapping into all possible force contact points. And it seems to me the back of that FSR could use some reading
That’s not how they work. Put a flat surface on the back and a convex surface against the front to concentrate the force enough to trigger it (but not enough to poke a hole in it). If you stack two of them, that’s like stacking two springs. The effect will be that the stack compresses twice as much as a single FSR would before anything triggers.