Automatic hand dryer circuit diagram

The infrared emission part uses a 555 time base circuit to generate a square wave signal with a frequency of 5kHz and a duty cycle of 50%, which drives the infrared emission tube to emit infrared rays.
When the hand is placed on the lower part of the hand dryer, due to the reflection of the infrared ray by the hand, the PH302 in the receiving circuit converts the received infrared ray into an electrical signal. The output signal is amplified by the frequency selective amplifier composed of IC1, IC2 and IC3. , shaping and filtering into a DC signal entering the comparator IC4. The threshold voltage of the comparator is 7V, which is set higher to improve the anti-interference ability of the circuit. When the input level of IC4 exceeds 7V, its output changes to low level, triggering the IC5 timer to start timing. At the same time, pin 3 of the timer changes to high level, causing 3DG130 to conduct, and the relay contact closes. Turn on the resistance wire and fan. A manual switch S1 is set on pin 2 of the timer, which can be operated manually, and cold air or hot air can be selected through S2.