This is a very simple Electronic Alarm Circuit Project of piezo alarm circuit, which will generate a sound around 110dB can be designed using this diagram. This Piezo alarm siren circuit project use two piezo sounders with high efficiency and can be powered from a wide input voltage , between 5 and 15 volts .
This circuit is very easy to build , maybe you will have a little trouble with the T1 and T2 autotransformers . Both autotransformers used in this project are the same type and require between pin 1and 2 1500 turns of 44 SWG wire and 220 turns between 2 an 3 using 40 SWgG wire.
Piezo Alarm Using 555 Timer Circuit Diagram:
In this circuit the IC1:B closest to the piezo elements is set to oscillate around their resonant frequency. The frequency is then varied via input pin 11 from the other 555, IC1:A. This modulating input is a low frequency oscillation. However, instead of using the square wave output from the first 555, the step function is converted to a triangular wave by the RC network R3 & C3 . The result of this is a frequency swept output which ensures that the output frequency definitely passes through the resonant frequency of the piezo elements sometime during each modulation cycle.
This circuit is very easy to build , maybe you will have a little trouble with the T1 and T2 autotransformers . Both autotransformers used in this project are the same type and require between pin 1and 2 1500 turns of 44 SWG wire and 220 turns between 2 an 3 using 40 SWgG wire.
Piezo Alarm Using 555 Timer Circuit Diagram:
In this circuit the IC1:B closest to the piezo elements is set to oscillate around their resonant frequency. The frequency is then varied via input pin 11 from the other 555, IC1:A. This modulating input is a low frequency oscillation. However, instead of using the square wave output from the first 555, the step function is converted to a triangular wave by the RC network R3 & C3 . The result of this is a frequency swept output which ensures that the output frequency definitely passes through the resonant frequency of the piezo elements sometime during each modulation cycle.
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