| Circuits Designed by Dave Johnson, P.E. : |
- Piezoelectric Triggered Switch
Two different switch circuits are shown. One sources current and the second sinks current. Both switches are connected
to a piezoelectric wafer. When the wafer is tapped, the switches are activated. (added 7/06)
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- POWER REMINDER BEEPER
This circuit produces a short beep once each minute. It is powered directly off the 120vac power line to remind you that a device connected to the circuit is turned on. It is simple enough to be
packaged inside a small plastic box. It might be ideal for computers, printers or some test equipment that shouldn't be left on all night.
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- MACHINE POWER LOSS BEEPER
For some medical equipment it is important for an operator when power is lost to the machine. The beeper is powered from a 9v battery and requires the machine to have a power switch with a third
set of contacts.
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- Service Beeper: This device functions like a lobby desk service
request bell. A short beep is sounded whenever the large pushbutton on top of the device is pressed. Once pressed, the device will not make another beep until at least 2 minutes of
time has elapsed. This prevents impatient customers from ringing the bell over and over. NEW
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- VERY LOUD BEEPER CIRCUIT
This circuit generates a continuous tone instead of a pulsing one. The circuit delivers about 110db (12 inches away) from a 9v battery using a single inexpensive C-MOS IC. An off-the-shelf
piezoelectric beeping device is driven at resonance to insure maximum efficiency.
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