Siren

House Alarm Loop Circuit

This circuit offers open and closed loop contacts (switches 1,2,3) that triggers the alarm ON and stays ON for 5 -10 minutes. The trigering delay (entrance/exit) is 27 seconds. This simple alarm circuit Has also a cancel button for reseting the circuit to stand-by mode again......

Auto-Arming Car Alarm circuit

The car alarm here is a simple circuit with basic characteristics that cover all entrances at the car that has switches (doors etc).With one switch (arm-switch) the circuit waits for the sensor-switches to open and to activate it. So the horn with 1 sec pulses will sound imediatelly seconds so the driver can enter in car and disactivate the arming switch. ..

Electronic Police Siren

This circuit produces a sound similar to the police siren. It makes use of two 555 timer ICs used as astable multivibrators. The frequency is controlled by the pin 5 of the IC. The first IC (left) is wired to work around 1Hz. The 47uF capacitor is charged and discharged periodically and the voltage across it gradually increases and decreases periodically. This varying voltage modulates the frequency of the 2nd IC. This process repeats and what you hear is the sound remarkably similar to the police siren...

Electronic Siren

This circuit produces a sound similar to a factory siren. It makes use of a 555 timer Ic used as an astable multivibrator of a center frequency of about 300Hz. The frequency is controlled by the pin 5 of the IC. When the supply is switched ON, the capacitor charges slowly and this alters the voltage at pin 5 of the IC hence the frequenct gradually increases. After the capacitor is fully charged, the frequency no longer increases. ..

Advanced Electronic Siren

Voltage is applied to the chip via pins 14 and 7 so that when power is applied to the project, the high and low frequency oscillators will come into operation to produce a wailing sound from the piezo. The high frequency oscillator is the only tone sent to the piezo. The low frequency oscillator merely modifies the high frequency by putting a varying "set on the 1n capacitor via the 1M so the frequency of the oscillator changes. The low-frequency oscillator charges the 4u7 via the 1k and this voltage is passed to the 1n via the 1M. The best place to put the piezo is in the room you are protecting. ..

Electronic Siren with 2 transistors

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. Since Q1 is directly coupled to the second transistor, Q2 turns on too. When Q2 turns on, the resistance between its collector and emitter reduces and allows current to flow. This causes current to flow in the voice coil of the speaker and pulls the cone towards the magnet. ..

Siren circuit

With this circuit we can create a altered sound of siren. The oscillator IC1a-b is constituted by two gates NAND, oscillating in very low frequency. This oscillation drive the IC2, that is a electronic switch, which opens and closes in the rythm of oscillation. When closes the switch then the voltage of supply charge the capacitor C3 through the resistance R2. When switch IC2 opens, the C3 discharge through the R3. The voltage with which is charge the C3, regulates the VCO of IC3, that is PLL, so that we have in the exit his one altered sound. You can experiment with the prices of resistances and capacitors in order to you change the sound of siren. The R1, C1 check the time of operation, the R4, C2 check the frequency of produced sound and the R3, C3 check the change of sound...

Simple circuitry - No ICs.This circuit was requested by several correspondents. Its purpose was to obtain more power than the siren circuit already available on this website since many years (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. 12V Battery operation...

This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 positioned as shown in the circuit diagram, the typical dual-tone sound of Police or Fire-brigade cars is generated, by the oscillation of IC1A and IC1B gates. With SW1 set to the other position, the old siren sound increasing in frequency and then slowly decreasing is reproduced, by pushing on P1 that starts oscillation in IC1C and IC1D...

This circuit provides a good siren noise suitable for warding off robot-predators! Change the pitch by adjusting R2, and R5...

An electronic siren made from discrete components. The sound produced imitates the rise and fall of an American police siren. When first switched on the 10u capacitors is discharged and both transistors are off. When the push button switch is pressed to 10u capacitor will charge via the 22k resistor. This voltage is applied to the base of the BC108B which will turn on slowly. When the switch is released the capacitor will discharge via the 100k and 47k base resistors and the transistor will slowly turn off...

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It`s easy to use. First check that the building is secure and that the green LED is lit. Then move SW1 to the "set" position. The red LED will light. You now have about 30 seconds to leave the building. When you return and open the door - the Buzzer will sound. You then have about 30 seconds to move SW1 to the "off" position. If you fail to do so - the relay will energize and the Siren will sound...

This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike, flash the lights etc...

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It`s designed to be used with the usual types of normally-closed input devices such as - magnetic reed contacts - micro switches - foil tape - and PIRs. But it can be Easily Modified to accept normally-open triggering devices - such as pressure mats...

This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike, flash the lights etc. The circuit is designed to use an electronic Siren drawing 300 to 400mA. It`s not usually a good idea to use the bike`s own Horn because it can be easily located and disconnected. However, if you choose to use the Horn, remember that the alarm relay is too small to carry the necessary current. Connect the coil of a suitably rated relay to the "Siren" output. This can then be used to sound the Horn, flash the lights etc...