2PCS Automatic Leveling Module Film Pressure Probe Type Auto-Leveling Sensor (Suitable for Makerbot nozzles)

Light-dependent resistors or photoresistors are a staple of electronics. If you need a way to sense the level of ambient light then there is no easier way to do it. As the light on the sensor increases then the resistance across the two leads decreases. If you have a rear view mirror that darkens when its hit buy headlights you can check in the little hole on face of the mirror and you’ll see those wavy lines of photoresistor!