Automatic Disinfection Unit – COVID-19 Period

Overview
During the COVID-19 pandemic, we designed and built a simple automatic disinfection unit to provide contactless hand sanitization. The system consisted of a metal enclosure, a liquid reservoir, a small water pump, and a motion sensor that triggered the spray automatically when a hand was detected.

1. Defining the Requirements

The main goals for this device were:

Enable touch-free disinfection to reduce the risk of virus transmission
Use readily available, low-cost components
Make the system compact and easy to install in different locations
Provide reliable and repeatable spray of disinfectant solution

2. Mechanical Design – Metal Enclosure and Reservoir

I designed a simple metal box to house all components:

The metal enclosure protected the electronics and pump from accidental contact and provided a clean, robust exterior.
Inside the box, I mounted a bottle/reservoir containing liquid disinfectant (e.g., alcohol-based solution).
The enclosure was designed so that only the spray nozzle and sensor area were accessible from the outside, keeping the rest of the system safe and enclosed.

3. Fluid Delivery System – Pump and Nozzle

For the disinfection mechanism:

We used a small water pump to draw liquid from the bottle and deliver it to the outlet.
The outlet was connected to a nozzle that sprayed the disinfectant onto the user’s hands.
The tubing and nozzle were chosen to provide a short, controlled spray pulse rather than a continuous flow, which helped to reduce liquid consumption.

4. Sensing and Control – Motion Sensor Activation

To make the unit fully automatic and touch-free:

A motion sensor (IR-based presence sensor) was mounted on the front of the box.
When a user’s hands entered the detection zone, the sensor sent a signal to the control circuit.
The control logic then activated the pump for a short, preset time, creating a single disinfection burst.
After the spray, the system automatically reset and waited for the next detection.

5. Assembly, Wiring, and Safety

I assembled the pump, reservoir, motion sensor, and wiring inside the metal box.
The electrical connections were kept isolated from the liquid lines to ensure safety.
A main power switch and basic protection components (fuse) were included to prevent electrical faults.

6. Testing and Use

After assembly, I tested the system to:

Adjust the sensor range and spray duration
Ensure consistent spray volume for each activation
Verify that the device operated reliably with repeated use

The final unit provided a low-cost, automatic disinfection solution that could be deployed quickly in the lab or office environments during the COVID-19 pandemic.

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