These light up paper circuit cards were much easier to make than I expected and only need a few inexpensive materials.

A blast from the Elektor archives: this 1998 battery tester uses a simple LED display to reveal a battery’s true condition under load — even below 1 V.

This expandable LED display for a microcontroller in Figure 1 has a simple interface with only 6 data/control wires and can be easily accommodated to a DIY design. The display has static indication.

The heart of this diy metal detector circuit is the CS209A IC. The metal detector is built with one 100µH coil that has 40 mm in diameter and is made of 50 turns/0.4 mm wire. CS209A has one oscillator ...