What Type of sensor is used in hand dryers?

Which sensor is used in hand dryer type of devices which does not need a pair of boxes as transmitter and receiver? You just bring your hand under the dryer and it triggers the device.

Re-design8 years ago
IR motion sensor.  THe tx and rx are side by side and the rx is reading reflected IR.  The hand is not the no reflected light.  The hand is there and reflects the IR.  Works the opposite way from the usual beam interrupted system.
Chu Guk4 years ago
Does anyone know how to make one of those sensors from scratch?
warengadia7 years ago
you have to use a vibrating sensor and you have bring youre hand to attached vibrate from your hand.
Fizzxwizz7 years ago
and if you really want to know if its IR, which it most likely is, then you can take a camera, any kind works-even your phone- and just look through you will see light, its usually light blue.