Works with Arduino (5V) and Raspberry Pi (3.3V) TTL.” The IR Detector proximity sensor is not just limited to the applications mentioned above.

The coaster uses a TMP006 infrared temperature sensor which measures the temperature of whatever you place on the coaster indirectly. It also doesn’t use much power.

The part list consists of one Arduino, two resistors, and one IR emitter. That’s right, an emitter. When an LED (IR or otherwise) is reverse biased it can act as a light sensor.