In the design of a circuit for PWM control, a 555 timer can be used on its own as a modulator. Unfortunately it is not possible to vary the modulation from zero to 100%, which limits its usefulness in ...

Simply adding a diode and potentiometer to a 555 timer operating in the asynchronous mode yields a pulsewidth modulator (PWM) with a duty factor adjustable from 1% to 99% (Fig. 1). Applications ...

An astable 555 multivibrator circuit, where the timing characteristics are determined by the interplay of an inductor, resistor, and diode.

The project is aimed at Arduino-based circuits, but any chip with an ADC will work. The 555 timer is used as a free running oscillator.