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555 radio digital frequency displayer circuit

2016-12-15 23:18  
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555 radio digital frequency displayer circuit
As the figure 14-2 shows, this circuit is composed of four pieces of integrated circuits and four LED luminescence digital tubes to display the frequency of the medium-wave station, it displays the frequency accurately and the circuit is simple.IC1 uses the dual time-base circuit 556, the astable multivibrator is composed of the 1/2 556 and the R9, R10, C3, the oscillation frequency f=1.44/(R9+2R10)C3, it is about 1000Hz, the output of pin-9 adds to IC2's external scanning input port pin-4. Another half of 556 (1/2 556) is connected as the trigger, the output of pin-5 adds to the luminescence digital tube. The IC2(MC14553) is a BCD code 3-bit counter. The AND gate is composed of the D9 and D10. When the pin-1 and pin-15 have the low electrical level, the VT3 and VT4 conduct.