Here is a low-cost and simple Automatic Hand Wash Timer that uses a timer at the heart of the circuit. NE555 timer is used in monostable mode along with an IR sensor to trigger it. The FC-51 IR sensor module has an inbuilt transmitter and receiver.
When you stand in front of the washbasin and place your hands near the IR sensor module, the sensor detects your hands. The detection makes the sensor to send a low pulse signal to pin 2 of the NE555 timer to trigger it. This activates NE555, and its output pin 3 goes high for 20 seconds. The flush LED1 connected to pin 3 of NE555 glows for 20 seconds. During this time, you can wash your hands until LED1 turns off. Also, a buzzer can be connected to pin 3 of IC1 for audio indication.
The whole circuit can be assembled on a general-purpose PCB or veroboard. The author’s prototype assembled on the veroboard is shown in Fig. 2. The prototype kept in a glass near the washbasin during hand-wash is shown in Fig. 3.
Shashank T.S. is an embedded engineer at Adappt Intelligence, Bengaluru. He has a keen interest in robotics and AI