A sensor is a component that can measure things in the world around you, like light or temperature. In many cases, a sensor is a resistor that changes its value based on light level, temperature, or some other physical quantity you might want to know about.

Your finger can act as a resistor. It usually has a resistance of a few megohms (MΩ) but can vary a lot, for example, if your finger is sweaty. In this project, you’re going to use this knowledge to build a touch sensor that will turn an LED on or off.

This is a great project for practicing your soldering skills.