PB Fortich

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  • Digital Stop Watch

  • Created: Sep 11, 2014

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The design is a simple application of astable multivibrator with 7-segment display in 4 digit counting. It has high segment current that is approximately 40mA and noise immunity of 0.45Vcc which is more than enough to drive four 7-segment display components. It features durability against possible chip heating.

The design is comprised of MM74C926 4-digit counters that drives the four 7-segment display. It uses LM555 to generate oscillation in which it operates in astable mode. The BJTs are used for switching and amplification of signal while the different types of switch are used for rotary switching(S1), start/stop switching(S2), and Reset switching(S3). The segment resistors dissipates power and control the heating of the driver IC.

It is suitable for low cost digital timing application that can handle different system configurations as timer. It can be developed as part of a larger system or a stand alone timer device. It is also a good reference for developing more sophisticated timing circuit.



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