Many devices use multi-digit seven-segment LED indicators with dynamic indication. Usually they are connected to the ports of the microcontroller or to specialized driver ICs, such as the MAX7219.

I needed a simple LED indicator showing that a particular voltage level had been reached—specifically, that a capacitor had charged to a particular potential. I was convinced that there must be a way ...

This circuit is a bit of a departure from the rest of the content in this chapter, inasmuch as the appliance I describe here is not part of the E-2 project. The reason I have included this section is ...