A simple PWM (Pulse Width Modulation) Generator by using IC-555.
The basic theury is f = .693*R1*C1. C1 capacitor Charging through D1 diode and Discharge through D2 diode. But both case in every full cycle of capacitor charging and discharging, the variable resistor R1 is used for that reason the frequency of the PWM is fixed but the Duty cycle is changing by changing the value of R1 resistor.
Frequency : 200Hz
Duty cycle : 0% – 100%