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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.
Posted ….(designed by David A. Johnson) |
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Simple blown fuse indicator sounds an alarm - 07/10/08 EDN-Design Ideas: A simple
blown-fuse-indicator circuit sounds a buzzer and flashes an LED when a fuse
blows.....(design idea added 009/08) |
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Simple Fix Adds Door Chime Repeater - 05/13/99 EDN-Design Ideas:.....(design idea
added 11/05) |
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Simple Siren - This project is built on the third section of the PC board,
identified by "SIREN" and "Project 5." You will notice the similarity between this
circuit and the LED FLASHER circuit from project 2. The only differences are the LED
has been removed and the 22R resistor has been replaced by a mini speaker....(design
added 04/09) |
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Siren circuit (page 84) - This circuit was requested by several correspondents.
Its purpose was to obtain more power than the siren circuit already available on ...
(added 07/07/07) |
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Timed Beeper - Beeps 7.5 seconds after a preset Time Adjustable Time settings:15
sec.30 sec.1 min.2 min. & others (added 9/04) |
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Two Tone Generator - This two-tone generator includes 3 ICs NE555 Astable
Multivibrators. You can vary the duration of each tone by changing the 10k resistor or
100MF capacitor at IC1 or changing resistors and capacitors at IC1/2 for higher or
lower tone. Designed by Andrew R. Morris (added 6/03) |
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Under-/Over-Voltage Beep for Manual Stabiliser - (electronic Circuit / Schematic
added 10/04) |
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Universal Ding-Dong - One frequently finds gongs or chimes for sale in antique
shops or Eastern markets. But supposing one would want to wire these to a pushbutton
at the front door to create a ding-dong doorbell? How would this be done? Or consider,
for a moment, more creative possibilities. How would one e.g. cause wine-glasses or
African drums to resonate when a doorbell is pressed? The circuit shown in Fig. 1
provides a mechanical means of striking two gongs or chimes in sequence -- one when
the doorbell is pressed, the other when it is released. This it does by briefly
activating two solenoids in... |
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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. ….(designed by David A. Johnson) |
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Wailing Alarm - (schematic / circuit added 10/02) |
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Warble Alarm - (Tony van Roon's circuits added 08/09) |
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Whistle Responder - Beeps when hears your whistle A gadget suitable for
key-holders, games etc. (added 9/04) |
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Whooper Alarm, #2 - Destroyer Whooper alarm using 5 transistors (Tony van Roon's
circuits added 08/09) |
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Wireless Doorbell - The transmitter circuit is made up of two building blocks, the
303MHz RF oscillator and the 32kHz crystal controlled oscillator. The 303MHz
oscillator consists of a self-oscillating circuit made up of the coil….(diagram added
05/07) |
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You've Got Mail - 08/19/99 EDN-Design Ideas: Many e-mail programs provide a "beep"
or a pop-up message box signaling the user that a new e-mail message has arrived. If
you are too far from the computer to hear the audible signal or if the monitor is
turned off, then.....(design idea added 4/02) |
