An Arduino drives the switch-mode power supply, offering dimming thanks to PWM, and the ability to automatically switch the light on and off using an RTC chip with a battery backup. The sketch ...

A PWM-controlled regulator, this time using a logic gate IC, op-amp, and resistors and capacitors to buffer the PWM signal.

However, he found that even with a large capacitor, his underpowered power supply would droop before the PWM cycles were complete. So instead of PWM he decided to experiment with pulse density ...