Auto saving alarm working principle circuit

Published:2011/11/4 1:34:00 Author:May | Keyword: Auto saving alarm | From:SeekIC

Working principle: When people arewalkingor working,thebody will move more or less, when wearer is faint or totally stops movement, the saving alarm can auto emit sound call for help. Saving alarm consisits of signal source, sensor circuit, amplifier, alarm power control circuit and sound alarm circuit. Circuit principle is shown in the first diagram. The four operational amplifiers A1, A2, A3, A4 in the circuitatr four operatational amplifiers. A1, A2 separately make up two wien bridge oscillators which isusedas signal source,and C11 and C6 are coupling to alarm and sensor circuit. After human body stops move, sensor circuit bridge is in balance state, then the difference amplifier A3 has no fluctuation signal output, comparator A4 generates a steady +0.4V voltage. After comparator rollback, beacause R16, C10's delay effect, after 5s, C10 voltage drops to +3.5V, it makes voltage regulator diode 2CW9 breakover, the alarm circuit emits alarm signal. Alarm circuit consist of sound integratedblock TB4100. The 1KHz sound frequency signal generated by A1, then it is coupled to TB4100 through capacitor C11.



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