The project was designed as an AVR witch timer that can turn OFF lamps after a minute of exposure on a UV exposure box for PCB prototyping. The old good ATmega8 microcontroller was used in this ...

Most switch-mode power supplies rely on a PWM (pulse-width-modulated) output that is controlled via voltage feedback. A 555-timer IC can inexpensively perform PWM. The circuit in Figure 1 shows how to ...