Automatic Hand-Washer

Introduction

Nowadays, you might have observed that hand washing in a wash basin has become automatic. You need not turn or even touch the tap to open and wash your hands. Automatic hand washers are common in leading restaurants and hotels. After you eat, you go near the wash basin and hold your hand just in front of the tap. Automatically, the tap dispenses water for a few seconds, sufficient to wash your hands properly. 

As such, this is not a luxury fitting, as it saves water wastage and prevents wear and tear of tap valves. The automatic dispensing of water for a few seconds is conveniently controlled by electronic circuits fitted just behind the water taps in the wash basin. We are going to discuss such automatic water controllers and learn how to assemble such a circuit for your domestic purpose. 

In this write-up, we will discuss the circuit schematic, design, components, spares needed and assembly steps in a simple PCB. 

Know your circuit

Kindly go through the circuit schematic of the automatic water dispenser circuit and understand the connections of the main items, namely the sensor and the control unit.    

Know your Design

IR is the infrared sensor module, and IC 555 is an important component that handles the automation.

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 send a low pulse signal to pin 2 of the NE555 timer to trigger it. This activates the NE555, and its output pin 3 goes high for 20 seconds. The flush LED1 connected to pin 3 of the NE555 glows for 20 seconds. During this time, you can wash your hands until LED1 turns off. Also, if one wants, a buzzer can be connected to pin 3 of IC1 for audio indication. This may be an additional option to alert the user.

The circuit works on a 5V DC power supply. It can be a power adaptor connected to the circuit.

Spare Parts List

IC 555 (Timer IC).................................................1 no.

IR =3pin FC-51 IR sensor Module...........................1 no.

LED=RED ...........................................................1 no.

R1=1K ohms resistor............................................1 no.

R2 = 10 K resistor................................................1 no.

R3 = 180 K resistor............................................ .1 no. 

C1=0.01MFD capacitor..........................................1 no.

C2= 100 MFD 16V electrolytic capacitor..................1 no. 

S1 on/off switch..................................................1 no.

5V DC power supply. ...........................................1 no. 

IC socket 8-pin....................................................1 no. 

Know your assembly

The circuit can be easily assembled on a general-purpose printed board. The unit can be nicely cased in a glass enclosure and kept just over the tap, so that the sensor is visible to the hand placed in front of the tap to dispense water from the tap.   

Conclusion

A simple DIY project you can try and at the same time it has a great utility value. Kindly record your comments.