Duty Cycle Selector

Duty Cycle Selector

Here is a unique project, duty cycle selector because duty cycle of pulse generated by this circuit can be varied from 10% to 90% in different 9 steps in the difference of 10%. The two complementary outputs and the sum of their duty cycle is always 100% make duty cycle selector more versatile.

Circuit description of duty cycle selector

The duty cycle selector circuit only two low cost CMOS ICS (CD4001 and 4017). The NAND gate N1 with N2 is configured as oscillator and generate frequency (ten times of output frequency) is given to pin 14 of IC2. IC2 divides the input frequency by a factor of 10. The output frequency is determined by oscillator and be in range between 0.1 Hz to 50 KHz.

The value of generated frequency is determined by the formula

F = 1/2.2R2C1.

This formula is only verified when R1 = R2 and the value of R1 is not less than 10 KΩ


Resistors (all ¼-watt, ± 5% Carbon)

R1 = R2 > 10KΩ

C1 = Determined by output frequency


IC1 = CD4001

IC2 = CD4017


SW1 = 9-way rotary switch