Finally I have got together the web page(s) describing the last of my new projects that I showed at the Maker Faire (Newcastle 2010).
Basically it is a 16 input analogue to MID converter, showing how to use analogue multiplexers.
Clever sensor idea! Always enjoy your projects. Thanks for sharing.
Question: Why do you have two resistors, a zener diode, and a capacitor on each sensor? What's the advantage of those extra parts over just one pullup resistor?
Mike you come up with some pretty trippy stuff man!
Why do you have two resistors, a zener diode, and a capacitor on each sensor?
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One pull up resistor
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Series resistor and zener for input protection - the connection goes to a socket so it is potentially liable to static pickup or being plugged into anything else. For example I used a phono sockets, if this were to have an audio line plugged into it then there would be negative voltages and possibly voltages over 5V on the input. The zener clamps this and the series resistor limits the current through the zener. It is so small in comparison to the circuit you want to measure it has no effect on this.
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Capacitor, to stop mains pickup injecting a disturbance into the measurement. The intended use required long leads from the sensor into the interface and these could pickup interference.
So they provide a bit of robustness to the design.