Well, for those of you who want to make a small project, this alarm may be an option for you. This circuit will generate the canary chirping sound. The chirp sound of a canary is generated by the oscillation process by resistor R1 and capacitor C1. The capacitor, having a capacitance value of 100 uF, is charging through the resistor, having a resistance of 4.7 K ohms. During this stage, R1 is the bias for the transistor making it operate in the cut off. When the transistor is in cut off mode, the base-emitter voltage is very minimal for any considerable current to flow. This mode triggers the oscillation to end but will start again once the capacitor discharges across the transmitter’s base-emitter circuit.
The frequency of the chirp may be modified by changing the values of the resistor and capacitor. The charging of the capacitor occurs when operating the push button switch. By releasing the button, the chirping runs quicker whilst the oscillation weakens.
The loudspeaker is being driven and coupled to the circuit by the miniature audio transformer of LT700 which having a frequency of 1 kHz. This circuit can be supplied with 9V battery.
Electronic chirping canary circuit source: http://www.elecpod.com/circuit/av/2010/03011410.html
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