PIEZOELECTRIC CERAMIC KEYBOARD TRANSDUCERS. PHASE 1.
ARMY ELECTRONICS COMMAND FORT MONMOUTH N J
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Solid-block piezoelectric ceramics were cut and tested under controlled conditions simulating impacts on a light-touch typewriter keyboard. Test setups were developed to provide a controlled mechanical impact and to monitor the resulting electrical output. Tests were applied to plastic-bonded, epoxy-bonded, and unbonded elements, and to several different configurations of single and paired elements. Comparison were in terms of absolute system efficiency based on the assumption that there was a single dominant mode of a damped sinusoidal output signal appearing across the terminal and load capacitors. Results show that plastic-bonded structures are very lossy and are also non-linear. Unbonded, clamped elements are linear over a range greater than 101 in input energy, and are also more efficient. Paired elements provided peak outputs in excess of one volt-milliampere for periods over 25 micro-seconds. Preliminary experiments indicate that flatting of mating surfaces results in improved output, and that shape approaching a cube is most efficient. There was little difference between epoxy-bonded units, clamped units, and bonded units with pyramid-shaped anvils. Author
- Electrical and Electronic Equipment