An adjustable duty cycle in the range between 5 and 95 percent can be: obtained from this circuit.
Also, the frequency range is adjustable betweem 0.1 and 5 Hz.
Cl can be altered to change frequency range, also R2 and R4 can be altered to change duty cycle range.
The circuit can be powered from supplies ranging from 6 to 12 V, and the output power is sufficient to drive incandescent lamps up to 1 A.
This circuit works as follows: C1 charges through R3 and R4 and discharges through R1 and R2.
Thus, R1 controls the discharge or through of the low output pulse, and R2 controls the length of the high iniput pulse. IC 1-b, c, and d are used to drive the power output stage.
A schematic diagram of the lamp flasher is shown in Fig. 1.
Transistor Q1 must be mounted on a heatsink.
Polarized components must be in their proper positions.
The lamp must be mounted in a base. For experimental purposes, the E-10 base is suitable.
The circuit also operates with LEDs. A large number of LEDs can be controlled, using appropriated resistor to limit the current.
IC1 - 4093 CMOS integrated circuit
Q1 - TIP120 N PN Darlington power transistor
L1 - 200 mA to 1 A, 6 V or 12 V incandescent lamp (see text)
D1, D2 - 1N4148 general purpose silicon diodes
R1, R3 - 2,200,000 (2 potentiometers)
R2, R4 - 100,000 9, 1/4 W, 5% resistor
R5 - 2,200 Ω, 1/4 W, 5% resistor
C1 - 0.22 µF or 0.47 µF ceramic or metal film capacitor
C2 - 100 1uF, 16 WVDC electrolytic capacitor
