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555 Multi-vibrator with an Adjustable and Independent Charge

2015-02-06 13:26  
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555 Multi-vibrator with an Adjustable and Independent Charge time
As shown in the picture3-13, base biasing circuit of VT1~VT11 has added 11 binary data, it has 2048 compounding. If any of them becomes low-leveled, the relevant VT pipe will conduct, and C2 charges it through RA+RB, RA refers to the equivalent resistance value of these conduction pipes, its oscillation frequency can be calculated according to the following formula: f=1.44/(RA+2R2)C2 Values of R1~RA1 can be assumed as 7.21k,14.8k,29.8k, 59.8k, 120k, 240k,481k, 902k, 1.9M and 7.7 M. Only when these 11 values are high-leveled, f is equal to 413Hz. If the least significant bit reaches the highest level, f is equal to 0.4Hz. With 2048 mixes, frequency of the circuit ranges from 0~825Hz, different frequencies can be obtained according to different values of N, and the frequencies will change evenly.