Project Hub /Basic Analog & Power Electronics/Power Supplies & Voltage Regulators/Simple Touch-Free Automatic Handwash Dispenser

Beginner

ANALOG / DISCRETE

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

Simple Touch-Free Automatic Handwash Dispenser

A simple touch-free automatic handwash dispensing machine built using recycled household materials and an IR proximity sensor to prevent the spread of infections.

Originally published on ElectronicsForU

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

IR Proximity Sensor Module With Pot Rs. 55.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
10pcs 5mm RED Diffused Light Emitting Diodes - LEDs Set Rs. 39.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
5V 1 Channel Relay Module Rs. 45.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: Water Pump / Valve
Pipes / Tubing / Hose / Fittings
Enclosure / Box / Case
Transistors (BC547 / 2N2222 / TIP / MOSFET)
Diodes (1N4007 / 1N4148 / Schottky / Zener)
BC 547

Browse all components

How It Works

The Simple Touch-Free Automatic Handwash Dispenser operates by combining infrared proximity detection with a transistor-driven relay circuit to pump liquid soap without physical contact. At the heart of the detection stage is an IR Proximity Sensor module, which continuously emits infrared light and monitors for reflections caused by a user's hands entering its field of view. When an object is detected, the sensor outputs a control signal that biases the base of a BC547 or BC549 NPN transistor through a 100-ohm current-limiting resistor. As the transistor turns on, it completes the control circuit for a 5V electromagnetic relay, energizing its coil. The 1N4007 diode is placed in a flyback configuration across the relay coil to suppress voltage spikes and protect the transistor from inductive kickback when the relay switches off. Once activated, the relay's contacts close, routing power from the 220V AC to 5V 1A DC power supply module to the 6V DC mini submersible pump. The pump then draws liquid soap from the plastic container and pushes it through the 10mm diameter plastic flexible pipe to dispense it externally. A 5mm green LED, also integrated with a 100-ohm resistor, serves as a visual indicator to show when the system is actively powering the pump.

Why Build This

Design and implement a practical, contact-free automated public health utility suitable for deployment in high-traffic undergraduate campus facilities or healthcare environments.

Gain hands-on experience integrating solid-state proximity sensing with electromechanical relay switching to control higher-load DC actuators from low-voltage logic signals.

Apply fundamental analog circuit principles, including transistor biasing, inductive load protection via flyback diodes, and linear DC power conversion.

Real-World Application

Deployed in hospitals, government offices, and public areas to provide touch-free hand sanitization for visitors and frontline healthcare workers, helping prevent the spread of contagious viruses like coronavirus.

Skills You'll Learn

Infrared proximity sensing

transistor switching circuits

electromechanical relay control

inductive load flyback protection

DC motor actuation

power supply integration

Safety Precautions

Ensure proper insulation when working with the 220V AC to 5V DC power supply module to avoid electrical shock.

Technology Tags

IR PROXIMITY SENSOR

TRANSISTOR

RELAY

SUBMERSIBLE PUMP

POWER SUPPLY

AUTOMATION

Frequently Asked Questions

Why is a 1N4007 diode necessary across the relay?

The 1N4007 acts as a flyback or freewheeling diode, protecting the BC547/BC549 transistor from high-voltage inductive spikes generated when the relay coil turns off.

Can I use a different transistor instead of the BC547 or BC549?

Yes, as long as the replacement is a general-purpose NPN transistor with sufficient collector current ratings to drive the specific 5V relay coil you are using.

How does the IR proximity sensor trigger the pump without a microcontroller?

The IR sensor module features onboard comparison circuitry that outputs a direct digital or analog voltage level change when an object reflects its infrared beam, which is strong enough to bias the NPN transistor directly.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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