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Electronic Buzzer: This very simple circuit just uses a couple of resistors, a capacitor and the easily
available 555 timer IC. The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can be changed by
varying the 10K resistor. (added 6/06) |
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Electronic Canary (Doorbell): This circuit is a modified "Hartley Oscillator" with a couple extra parts. T1, the
LT700 (or equivalent, is a small center tapped (ct) audio transformer with an impedance of 1000 ohms at 1000 hertz. The secondary of this transformer has an impedance of 8 ohms.
Usually noted as 1K:8 ct. I tried a couple other models like the red and green types (taken out of a $5 made-in-china am pocket radio) and they both work good. You may have to
adjust the caps to get the sound... (added 2/06) |
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Electronic Siren #1: (electronic circuit added 7/03) |
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Electronic Siren #2: (electronic circuit (added 10/03) |
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Electronic Whistle: (electronic circuit (added 10/03) |
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Fix Adds Door-Chime Repeater: 05/13/99 EDN-Design Ideas / (added 11/05) |
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Flip Flop Flashers Buzzers Etc.: (circuit / schematic design added 6/06) |
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Personal Alarm: (project / circuit added 10/06) |
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Piezo Device Generates Buzz Beep or Chime : 04/23/98 EDN-Design Ideas / (added 05/03) 04/23/98 EDN-Design Ideas
/ (added 11/05) [Note: File contains multiple circuits scroll to find this circuit.] Piezoelectric buzzers, such as the Murata (Smyrna, GA) PKB5-3A in Figure 1, make excellent
alarms. They're compact, lightweight, efficient, and reliable. However, a piezo alarm is a dc device; it requires additional circuitry to operate from an ac source. The circuits in Figure 1
provide a simple and inexpensive way to obtain the dc drive. The W04G full-wave bridge rectifier produces a full-wave dc waveform from the 120V ac line. The 100 ohm resistor protects the
circuit from surges when you first apply power. The 5.5V 1N4733 Zener diode protects the buzzer against high-voltage excursions. The 1-µF capacitor provides filtering for the buzzer.... |
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Plane Locator Beeper #2: (schematic / circuit design added 9/02) |
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Plane Locator Beeper: (schematic / circuit design added 9/02) |
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Powerful Siren: Simple circuitry No ICs 12V Battery operation (added 9/04) |
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Remarkable R Beeper: (electronic circuit added 7/03) |
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Remote Doorbell Indicator: (electronic (schematic / circuit added 4/02) |
