Introduction: Critical Hand-washing Step Teaching Machine

This is a machine that reminds the user about the steps when he/she needs to wash his/her hands.

This machine’s purpose is to help people understand how to wash their hands properly in an effective way. During epidemic or pandemic prevention periods, the government often tells citizens to wash their hands properly, yet they do not tell the citizens the exact steps precisely, making it hard for the people to really wash their hands in the correct way. My project is a simple yet effective way to remind the users of the steps needed to effectively wash their hands, mainly by using a drawing and indicating lights. If users can wash their hands according to the steps and required time for each step, then the device can help in the prevention of diseases.

Here is a link to the video of the device working properly:

Here is the link to the PDF file from the government showing the correct steps for washing your hands(Chinese):

Here is the link to the PDF file from the government showing the correct steps for washing your hands(English):

Step 1: Preparing the Supplies

The supplies used:

(1) Arduino Leonardo*1 Buy here

(2) Ultrasonic sensor*1 Buy here

(3) Wires Buy here

(4) USB-A to MicroUSB cable*1 (To connect the Arduino board to the computer) Buy here

(5) Portable power bank*1 (Can be replaced by a phone charger or any safe and useable power sources)

(6) Cardboard (For the body of the device. Can be replaced by any strong material)

(7) Glue and tape (Can be replaced by an adhesive or other tools able to connect the material used for the body of the device.)

(8) LED lights*5 (colors can change according to the user’s favor) Buy here

(9) Button*1 (The button used in this project consists of two wires instead of four as indicated in the diagram)

Step 2: Assembling the Arduino Circuit

Materials needed: Arduino Leonardo board*1 LED lights*5 Wires Ultrasonic sensor*1 Laptop or any computer capable of running Arduino.


(1) Connect the button onto the breadboard

(- of the button-->GND, and the input, which is 2 on the Arduino board)

(+ of the button-->5V in the Arduino board)

(2) Connect the ultrasonic sensor to the Arduino board

(GND→GND on the Arduino board)

(Echo→~6 on the Arduino board)

(Trig→7 on the Arduino board)

(VCC→5V on the Arduino board)

(3) Connect the wires of the LED lights to the breadboard and the Arduino board

(All of the negative, which are the shorter legs of the LED lights, should be connected to the negative row on the breadboard, which will then be connected to the Arduino board by one single wire.)

(Positive end of top left LED→12 on the Arduino board)

(Positive end of the top middle LED→~11 on the Arduino board)

(Positive end of top right LED→~10 on the Arduino board)

(Positive end of the bottom left LED→~9 on the Arduino board)

(Positive end of bottom right LED→8 on the Arduino board)

(4) Make sure that the cables are arranged in the correct order so that no technical errors or dangerous malfunctions occur before advancing to the next step.

(5) Connect the USB cable to the Arduino board and prepare to connect it to the power bank.

Step 3: Assembling the Machine

(1) Draw a diagram that clearly states the five important steps needed while washing your hands. After drawing the diagram, poke five holes corresponding to the positions of the LED placements. If you decide to stick the LEDs on a breadboard, which is not recommended, then you will have to measure the exact distance between the LEDs and cut those exact positions. The proper steps in the picture are drawn in Chinese, for the device will be placed in a Chinese environment. The steps will be stated below in English.

1. Use warm water at approximately 35~40 degrees Celsius to rinse your hands for at least 5 seconds.

2. Use soap and spread it on your hands. This step should also take about 5 seconds.

3. Fully spread the foam on your hands and focus mainly on these five positions:

[1] Wrist

[2] Palm

[3] Between your fingers

[4] In the gap of your fingernails

[5] The back of your hand

This step will take up to 20 seconds, longer if possible.

4. Rinse your hands using clean tap water, also at about 35 degrees Celsius. The time on the device for this step is also 5 seconds, yet you can change the time to a longer period if possible.

5. Wipe your hands using a clean towel. After this step, you will be finished with clean hands.

(2) Make a container using the material prepared with two holes on the side for the ultrasonic sensor, five holes on the front of the container, and another hole on the other side to let the USB cable out of the device.

(Make sure that the sensor points to the side and is facing the direction in which people coming towards the sink will pass.)

(Make sure that you leave enough space to put the actual soap dispenser into the container without harming the Arduino circuit.)

(3) Tape the diagram onto the container with corresponding positions.

(4) Put the Arduino device assembled in the previous step into the container with the ultrasonic sensor in the holes on the side and with the USB cable coming out from the other side, and with the LED lights poking out of the front.

(5) Make sure to seal the container, to keep all of the LED lights visible, and keep it as stable and in one piece as possible.

Step 4: The Code

Please use the code given below to finish the project.

Click me to get to the codes

Please remember to use a computer that can run the Arduino program.

(An example of computers not able to run the program is a MacBook with a macOS Catalina system.)

Step 5: Test Running and Safety Precautions

Test run the whole process and make sure no machinery malfunctions occur, also add any stabilizing improvements to ensure the quality and safety of the device.

Do not change the codes for the LED lights to a long period of time. The light itself may burn up, and it will be a waste of material.

Enjoy the project!