The circuit includes vibration and shock sensors, power switches, ultra-low frequency oscillators and language alarm circuits, which can be used for earthquake alarms, burglar alarms and security messages. Its circuit is shown in the figure.
The sensor consists of a tinned metal ball suspended by a metal wire and a small metal box. The ball is suspended in the center of the box. There is a gap of l-2mm between them. It does not touch under static conditions, that is, it is electrically isolated and small. The ball is connected to the power supply VDD, and the small box is connected to R1 and VT1. When there is impact or vibration, the ball under the metal wire will tremble or shake, and it will contact with the metal, so that VT1 is positively biased and turned on. Due to the connection of the C2 charging capacitor, even a slight shock vibration can maintain VTl continuous conduction, so that ICl, 1C2 get a "ground" loop, and the saturation voltage drop of VT1 is not more than 0.4V. ICl uses time base circuit 555, which forms a low frequency multivibrator with R2, R3, C3, etc., and its oscillation frequency is f=1.44∕(R2+2R3)C3.
The illustrated parameter has an oscillation period of 22 seconds and a duty cycle close to 1:2.
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