Simple short circuit, open circuit multi-channel audio alarm circuit diagram
As shown in the figure, it is an open circuit and short circuit multi-channel audio alarm circuit. The alarm consists of a rectified power supply, an audio part, a five-way short circuit, and a five-way open circuit alarm and control circuit. The rectified power supply is composed of D11~D14, R11, C11, D10, etc. The audible alarm circuit is composed of IC2 (NE555) and IC3 (NE555). IC4 (BA532) is a power amplifier integrated circuit with an output power of up to 5W. The short circuit or touch alarm part is composed of six inverter IC1 (CD4069) and BG1, BG2, etc. When the human body touches either end of A to E, since the input end of the non-gate is low level, the high level of its output makes Transistors BG1, BG2, etc. are turned on, D7 is turned on, BG5 is turned on, relay J is sucked and self-locked, and the sound of the audible alarm circuit and IC4 power amplifier is turned on, and a police car alarm sound is issued. The circuit breaker is composed of R1 to R5, LED6 to LED10, BG3, and BG4. Under normal circumstances, the points a, b, c, d, and e are connected to the ground by a thin metal wire. Once it is broken, BG3 and BG4 are turned on, and BG5 is turned on, so that the relay J is attracted, and the sound circuit can also be The power is on. IC2 and R6, W1, C1, etc. form a multivibrator. The frequency corresponding to the parameters shown in the figure is l~15Hz, which can be adjusted by potentiometer W1. In addition, the charge and discharge sawtooth wave on capacitor C1 is applied to the control terminal of IC3 (555) via the emitter follower to change the reference voltage value inside the IC3 integrated block to generate a signal of the oscillation frequency that varies with the sawtooth wave. After the IC4 is amplified, it pushes the speaker to emit a tone-changing alarm sound. In the case of low power requirements, the speaker can be directly connected to the IC33 pin output (through a DC blocking capacitor), the bipolar 555 output drive current up to 200mA. Switches K1 to K10 are used for debugging each circuit.
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