Automatic Hand Sanitizer Dispenser (No Arduino)

Corona Virus (COVID-19) is wreaking havoc in the world. Almost every country is suffering from the Corona Virus. WHO has already announced it a Pandemic disease and many cities are under lockdown situations and changed our lifestyle. In this current scenario of the global outbreak, it is advised by WHO (world health organization) to maintain HealthyHand Wash and Sanitation Habits, but the main problem is the way we do it, that is by physical touch. Touching alcohol containers or hand sanitizers with infected hands can spread the virus to the next person. In this tutorial, we will build an automatic hand sanitizer dispenser that uses IR sensors to detect the presence of a hand and activates a pump to pour the liquid on the hand.

You can find several Arduino automated liquid dispensers circulating the web. But my intention is to keep it simple and cheap so that anyone can replicate it. Possibly the easiest solution for this purpose is to use a simple transistor or MOSFET with an IR proximity sensor, which would also drastically reduce the costs. Obviously, the absence of a microcontroller removes control of over spilling, but using a smaller nozzle would physically limit the flow of liquid.

Before proceeding further you can watch the demo video:

The Circuit & Components

I choose a blank Horlicks Jar as container of the sanitizer. I designed the 3D encloser according to the size of the cap of the container for placing the circuit inside it. I used Tinkercad for my design and .STL file is attached in the file section.

How does it work?

The schematic is very simple and easy to understand. IR proximity sensor detects the presence of a hand and makes the OUT pin LOW. Normally OUT pin keeps HIGH. When it goes low it turns on the PNP transistor and the pump becomes on. I used the BD136 power transistor for the circuit. A 1K resistor is connected between sensor OUT and the base of the transistor. It protects the transistor from burning out.

Turn the potentiometer of the sensor from the lowest sensitivity level, and slightly increase it to achieve your desired detection range. Do NOT make it too sensitive because the pump might act spontaneously without any trigger!

For powering the circuit and the motor a 14500 Li-ion cell is used and it is connected with a USB charging circuit. For the sanitizer container, you can select any similar glass or plastic container, such as a plastic coffee storage container. My selected one is a glass Horlicks container. An encloser for the circuit is designed according to the cap size and the file is attached.

The Connection

I soldered the battery with the Li-ion charging module directly using jumper wires. The sensor was connected with the BD136 PNP transistor using jumper wire. The base of the transistor is connected through a 1K resistor.

I made a hole in the middle of the container cap and bring out the wire of the motor through the hole and soldered according to the circuit diagram. Then I tested everything is working by connecting the charger.

After confirming on the operation I added hot glue in every solder joint.

Then I placed all the circuit components in the right place and fixed in place with hot glue. I also cover the components under a blob of hot glue to keep it safe and to make it waterproof as well.

To pump out the sanitizer from the container I used a bendable stainless steel tube. Inside the container, I used aquarium tube and connected the pump and the steel tube using the aquarium tube.

The dispenser is ready. You can now fill your dispenser with whatever liquid you want. It even works with viscous liquids such as liquid soap and dishwashing liquids! I made this project specifically for hand wash alcohol and hand rub since I use it often.