The SparkFun QRE1113 Line Sensor Breakout (Analog) offers a simple analog output that varies based on the amount of infrared light reflected back to the sensor—ideal for line-following applications. It’s compact and compatible with both 3.3V and 5V systems.

The onboard QRE1113 IR sensor includes an IR-emitting LED and an IR-sensitive phototransistor. When powered via VCC and GND, the LED emits infrared light. A 100Ω resistor limits current to the LED, while a 10kΩ pull-up resistor keeps the output high. As reflected IR light increases, the phototransistor conducts more, causing the output voltage to drop—a key signal for detecting surface contrast.