Strain@ Weight@
Measuring air pressure from human breath
Russell McMahon suggests
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Strain gauge Fairly cheap Needs extra
instrumentation.
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Bimorph Piezo elements (Radio
Shack has these)
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Smothered hot wire? Just a thought - a heated resistive element whose
ability to cool is reduced as key is depressed against a spring.
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Spring with optical obscuration as key descends. Could be quite cheap.
Use eg LED source and LDR (!) or phototransistor plus a shaped mask which
progressively obscures light path.
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Crimping a pipe with airflow therein. plastic / rubber / ??? Or block
/ open an orifice as key moves. Could be very small at key itself Needs air
source and pressure sensor. If this is for University experimental use rather
than production purposes this could be quite viable. A fishtank air puimp
good for a few psi can be bought for about $NZ10 (20?) This could supply
a number of switches - especially if the key opens rather than closes an
orifice. Airflow might also be able to be measured by "interesting" means
- eg turbine/interrupter. Pressure driven pot? - getting desperate now :-)
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Linear pot spring loaded.
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Capacitance !!!! (or other proximity) Could
eg drive oscillator and measure frequency.
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Linear Hall switch and magnet.
Archive:
Annie Ogborn says: I just
had a discussion with a coworker about piezo devices. He emphasized checking
temperature range before applying one, they have narrow temp. bands