| 摘要 |
PURPOSE: An alarm sound generation device gives the alarm by low cost microcomputer without an interrupt and an input capture when a car runs overspeedily. CONSTITUTION: An alarm sound generation device comprises a main timer(10), a microcomputer(11), a resister(R1), a transistor(Q1), a zener diode(ZD1), a diode(D1) and an alarm device. The main timer(11) counts the change and the level of a frequency to be inputted at regular interval. The microcomputer(11) examines the level of a frequency through the main timer(10), has no input capture and no interrupt function. The resister(R1) limits an excess current in the output level of the microcomputer(11). The transistor(Q1) is switched on/off according to a signal level inputted through the resister(R1). The zener diode(ZD1) connected with a collector of the transistor(Q1) maintains a constant voltage. The constant electric current diode(D1) is connected with a cathode of the zener diode(ZD1). The alarm device connected between the diode(ZD1) and a power step generates an alarm sound in overspeed running.
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