Police siren using NE555

jacky January 27, 2014 16 Comments
Description. A lot of electronic circuits using NE555 timer IC are already published here and this is just another one.Here is the circuit diagram of a police siren based on NE55 timer IC. The circuit uses two NE555 timers ICs and each of them are wired as astable multivibrators.The circuit can be powered from anything between 6 to 15V DC and is fairly loud.By connecting an additional power amplifier at the output you can further increase the loudness. IC1...
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Ding-Dong sound generator

john April 7, 2010 13 Comments
Description. This is the circuit diagram of a ding dong sound generator based on two NE555 timer ICs.The circuit is designed to toggle between two adjustable frequencies to produce the ding dong sound. The first NE555 (IC1) is wires as an astable multivibrator operating at 1Hz. The frequency of the second NE555 (IC2) is modulated by the output from the first IC. This is attained by connecting the output of first IC to the control pin (pin5) of the...
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Two transistor siren

john April 7, 2010 9 Comments
Description. Here is the circuit diagram of a simple two transistor alarm circuit that can be operated from a 9V PP3 battery. Here the two transistors are wired to form an oscillator whose frequency increases when switch S2 is pressed and decreases when S2 is released. In order to attain this the base of Q1 is biased from an RC circuit comprising of R2 and C1.When S2 is pressed C1 is charged through the resistor R2.As the voltage across...
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Police siren

john April 7, 2010 14 Comments
Description. The circuit given here produces an alarm similar to the police siren. When you press the push button switch S2 capacitor C1 will charge and this will make the transistor Q1 to ON slowly. When the switch S1 is released the C1 will discharge and the transistor Q1 will become OFF slowly. When the Q1 is switched ON, its collector voltage falls and makes the transistor Q2 ON. The capacitor C2 will be charged almost to full supply...
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Whistle to beep circuit

john April 7, 2010 8 Comments
Description. This simple circuit produces a beeping sound that lasts for around 3 seconds whenever you make a whistle. The CMOS Hex inverter CD4049 is the heart of this circuit. Out of the six inverters in CD4049, U1a is wired as an audio amplifier which amplifies the signal picked up by the microphone M1.The U1b is wired as a band pass filter with center frequency around 2KHz.The filter is necessary in order to pass the frequency corresponding to whistling...
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Canary chirp generator

john April 7, 2010 1 Comment
Description. This is a simple electronic alarm circuit that imitates the chirping of a canary. The circuit is nothing but a Hartley oscillator with few more passive components added. As the capacitor C1 charges through the resistor R1 and the transistor Q1 is driven to cut off. This makes the oscillations to stop. As the capacitor discharges through the Resistor R1 and base emitter junction of the transistor the oscillation start again. Actually the R1 and C1 are the...
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Touch controlled musical bell.

john April 7, 2010 4 Comments
Description. This circuit produces a musical tone whenever someone touches the touch point designated as TP in the circuit. The circuit works from two AA cells and produces enough sound. The circuit uses IC UM 3481 commonly used in musical circuits. The IC contains a ROM with 512 musical notes, tone generator, rhythm generator, modulator, run off control, oscillators, frequency divider and preamplifiers,.  So a very few number of components is  required for this circuit.C1 and R1 act as ...
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Water Sensor Circuit with Alarm

john October 12, 2012 17 Comments
If you are looking for a Water level indicator or a Water level controller, there are pretty good circuits we have developed. This one is just a fun project made for hobby purpose! You can call this a water sensor circuit for sure! Description. This is a simple musical alarm circuit which produces a musical tone when water or some conducting liquid comes in contact with the two sensor wires provided. The circuit is based on four transistors and...
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Metronome generator circuit.

admin April 7, 2010 2 Comments
Description. Here is a simple circuit using IC NE555 that can be used to generate metronomes.Such a circuit is very useful to those who learns music. The circuit is nothing but an astable multivibrator wired around NE555 .The components R1,R2&C1 determines the output frequency. Circuit diagram with Parts list.  Notes.  The circuit can be wired on a general purpose PCB or common board. The circuit can be powered from a 9V PP3 battery. The POT R1 can be used...
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Musical horn circuit.

admin November 10, 2011 24 Comments
 Description. Here is a simple circuit diagram of a simple musical horn using two NE555 ICs. Two ICs are wired as astable mutivibrators. The output of first multivibrator is given to the discharge (pin 7) of the second astable multivibrator. The combined effect of the astable multivibrators produces a musical tone at the output.  Circuit diagram with Parts list. Notes.  The sound effect can be adjusted by varying the POTs R2&R5. The speaker can be a 8 Ohm tweeter....
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