555 calculator/stopwatch convertor circuit

Published:2011/6/7 2:11:00 Author:TaoXi | Keyword: 555, calculator, stopwatch, convertor | From:SeekIC

As the figure 15-29 shows, the convertor is composed of the time-base pulse generator and the photoelectric isolating device. The astable multivibrator is composed of the 555 and the R1, R2, RP1, C1, the oscillation frequency f=1.44/(R1+RP1+2R2)C1, by adjusting RP1, you can make the frequency to 60Hz. The output of pin-3 adds to the photoelectric coupler through the current limiting resistor, and the output also adds to any calculator buttons which have the automatic constant, so it can be used as the stopwatch.



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