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Transistor based Security Siren - This circuit was requested by several correspondents. Its purpose was to obtain more power than the siren circuit already available on this website (One-IC two-tones Siren) and to avoid the use of ICs. A complementary transistor pair (Q2 & Q3) is wired as a high efficiency oscillator, directly driving the loudspeaker. Q1 ensures a full charge of C2 when power is applied to the circuit __ Learning Electronics
Twilight Lamp Blinker - During sunset or sunrise, the ambient light is not adequate to lead you through the open doorway or make your way around obstructions. To avoid any mishap, here is a twilight __ Electronics Projects for You
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
Two-Tone Siren - This circuit is intended for children fun, and is suitable to be installed on bicycles, battery powered cars and motorcycles, but also in models and other games. With SW1 positioned as shown in the circuit diagram it reproduces the typical dual tone sound of Police __ Contact: Flavio Dellepiane, fladello @ tin.it
UM3561 Siren Generator Design - UM3561 is an excellent ROM IC that can generate Multi siren tones simulating Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. This 8 pin low power IC can work down to 2.4 volts. The UM 3561 is a low cost siren generator designed for use in toy applications. The IC has an inbuilt oscillator and tone __ Designed by D Mohankumar
Under- /Over-Voltage Beep for Manual Stabiliser - Manual stabilisers are still popular because of their simple construction, low cost, and high reliability due to the absence of any relays while covering a wide range of mains AC voltages __ Electronics Projects for You
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 __ Designed by Jospfh
Unplugged Appliance Alarm - I received a call from an administrator at a large prison. He told me that he was having problems with inmates who keep unplugging refrigerators, vending machines and microwave ovens in a commons area. He wanted a battery-powered device, which could be mount. . . Circuit by David Johnson P.E.-April, 2010
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. . . Circuit by Dave Johnson P.E.-February, 2009
Very Loud Beeper Circuit - This circuit generates a continuous tone instead of a pulsing one for your hobby project. 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 maxim . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000
Very Loud Pulsating Beeper - Many battery powered alarms draw excessive current when operating. Some of the most attention-getting noise makers, such as the unit shown below, use piezo 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. . . Circuit by David A. Johnson P.E.-October, 2010
Wailing Alarm - This circuit provides a warbling sound to any alarm circuit. IC2 is wired as a low frequency astable with a cycle period of about 6 seconds. The slowly varying ramp waveform at C1 is fed to PNP emitter follower Q1, and is then used to frequency modulate alarm generator IC1 via R6. IC1 has a natural center frequency of about 800Hz. __ Designed by Tony van Roon VA3AVR
Warble Alarm - The circuit above provides a 'warble' alarm-call generator that simulates the european 'dee-dah-dee-dah' type sirens used in several european countries __ Designed by Tony van Roon VA3AVR
Well Pump Flasher & Beeper - Several years ago I installed a box on my water well pump head. At the well head, the solar powered box flashed a very bright LED light and chirped a very load siren, whenever the pump motor was in operation. After many years of service, the box finally became corroded from rain water and died. So, I thought it was time to redesign the circuit and build up a replacement. . . . Circuit by David Johnson P.E.-July, 2017
Whistle Responder - This device beeps intermittently for about two seconds when a person in a range of around 10 meters emits a whistle. The first two inverters contained in IC1 are used as audio amplifiers. IC1A amplifies consistently the signal picked-up by the small electret-microphone and IC1B acts as a band-pass filter, its frequency being centered at about 1.8KHz. __ Learning Electronics
White LEDs powered by 24V - 24vac is a popular voltage. It is often used in low voltage lighting systems and industrial controls. It is much less dangerous than 120vac/240vac line voltages. The circuit below is one method to efficiently power a cluster of 7 white LEDs from 24vac. . . Circuit by David A. Johnson P.E.-December, 2009
Whooper Alarm, #1 - If you've ever watched any TV at all and seen those old WWII navy movies, you've heard that distinctive "whoop-whoop-whoop" as a destroyer sliced through the waves, guns blazing, and everybody yelling "battle stations!" __ Designed by Tony van Roon VA3AVR
Whooper Alarm, #2 - Destroyer Whooper alarm using 5 transistors. __ Designed by Tony van Roon VA3AVR
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. __ Contact: Collin Mitchell
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 by Gary Kath and Craig Bishop, Scotch Plains, NJ |
