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Circuits designed by David Johnson, P.E.
Last Updated on:
Thursday, December 01, 2011 07:06 AM
Master Category List
- Dave's Circuits
Text & Graphics
Copyright © David A. Johnson, PE - ALL Rights Reserved.
LINKING to Dave's circuits is permitted but DO NOT COPY to your WEB SITE server! |
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Beeper & Buzzer Circuits |
- 24V DC
Powered Beeper with 4 Separate Inputs
24v DC is a very popular voltage used in industrial settings. The circuit
below was designed to accept four different 24v DC alarm input signals, which are
then used to drive a single low power beeper. The beeper is a magnetic type
with its own oscillator/driver. The four diodes form an “OR” gate so any one
of the four inputs will cause the beeper to make noise. A CMOS version of the
popular 555 timer is used to strobe the beeper on and off at about 1Hz.
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3V Sweeping Siren Alarm
The circuit uses a LTC1799 precision frequency
generator from Linear Technology. A 74HC14 hex Schmitt trigger from Texas
Instruments is also used to perform several other functions. One section is
wired as a simple 7Hz square wave oscillator....
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ANOTHER
VERY LOUD PIEZO ALARM BEEPER
This is yet another beeper circuit that really draws attention. It sweeps the drive
frequency slightly to produce a very annoying sound. It uses a transformer to increase
the drive voltage across the piezoelectric device to more than 200 volts peak to peak.
It cranks out an ear splitting 120db when measured at 12 inches.
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Basement Doorbell Beeper
If you can't hear your doorbell when you are in your basement try this circuit. This
circuit takes advantage of the 24vac power source located near the furnace. Using a
simple current transformer technique, the circuit sounds a beeper whenever the main door
chime is activated.
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- Basement Doorbell
This circuit will activate a beeper in the basement, whenever the front doorbell is
pressed.
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- Check Engine
Beeper
When wired into a car’s indicator light panel, this circuit will turn on a loud beeper
when the “check engine” light turns on. (added 7/06)
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- Front Desk
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
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HIGH
SOUND OUTPUT BEEPER CIRCUIT
I you need a real loud beeper, this 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. By changing the control IC
to a 74AC14, the same circuit can operate from 3v and 1.5v batteries. Published in
Electronic Design, Aug 5, 1993
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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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- 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.
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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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- 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.
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- Star Trek Doorbell:
In the Star Trek “Next Generation” TV series, the doorbell outside the private quarters
of a crew member makes a particular “beep-boop” sound. The 3v battery powered
circuit below tries to simulate this sound. The circuit uses one 74HCT74 dual D
flip/flop IC, wired as two one-shot circuits. Both are designed to produce a pulse
about one half second long. The first pulse turns on a 555 timer to form the beep
sound. The second flip/flop one shot ....
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Very Loud 3v Powered Beeper - Getting a high sound intensity from a
piezoelectric type beeper is not easy when the available DC supply is only 3v. The
circuit below is not only efficient but produces a very intense sound. The circuit
combines a voltage boost section with a resonant feedback network. The voltage
applied to the piezoelectric wafer is about 40 volts peak to peak. The result is a
circuit that generates an attention getting sound without drawing a lot of current.
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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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Very Loud Piezoelectric Beeper Circuit
This circuit is similar to circuit number 7, but 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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Very Loud Pulsating Beeper Keeps Average DC Current Draw Low - - Many
battery powered alarms draw excessive current when operating. Some of the most
attention-getting noise makers, such as the unit shown below, use piezoelectric sound
generators with a frequency sweeping tone. When operating with a 9v battery, these
units can often draw 100ma or more. In many applications, a continuous alarm sound is
not needed. Locating a balloon or a rocket are examples where you want a loud
sound but a low average power drain. To lower the average current, the device can
be pulsed with short 0.05 second chirps, once every two or three seconds. This
lowers the average current by a factor of 60. So, instead of drawing 100ma, by
chirping the alarm, the current is lowered to just 2ma. The circuit below
generates the pulse train needed for these short but very loud chirp sounds.
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