Published June 26, 2020 © GPL3+

Touchless Hand Sanitiser

An inexpensive way to kill germs instantly without spreading them first.

IntermediateFull instructions provided1,330

Things used in this project

Hardware components

Arduino Nano R3

Can be used interchangeably with Arduino UNO

SparkFun Dual H-Bridge motor drivers L298

9V battery (generic)

Rocker Switch, SPST

Ultrasonic Sensor - HC-SR04 (Generic)

Submersible DC Pump

Jumper wires (generic)

Software apps and online services

Arduino IDE

Story

Introduction

This is a device that dispenses just the right amount of hand sanitiser without the user even touching it. It prevents the transmission of germs by contact, and thereby controls the spread of diseases like COVID-19.

It is portable and lightweight, and can be hung from a nail or simply kept on a table or any other surface.

Building the Exterior

The container can be made easily at home with commonly available and inexpensive materials, most of which are generally discarded as waste. The outer casing is made using an ordinary cardboard washing powder carton, waterproofed for outdoor use with regular enamel paint. The hand sanitiser is stored in an airtight 500mL plastic jar with a screw-on lid. Holes are poked for the aquarium tubing, and the body of a gel/ballpoint pen squirts out the hand sanitiser.

Assembly

Cut holes in the painted carton for the switch, ultrasonic sensor and pen body. Use a warmed screwdriver to poke two holes in the lid of the plastic jar, and push a piece of aquarium tubing into the larger hole. Attach the end inside the jar to the pump, and the end outside to the back of the pen body. The tube will remain firmly attached without using any tape or glue. Put the pump in the jar, and push the connecting wire out through the other hole. Fill the gap (if any) around the tube and wire with a few drops of hot glue or m-seal. Connect the electronics. Attach a wire loop to the carton if needed to hang it.

Handy Tips

When the device is not in use (eg; at night), the tip of the pen body can be covered with the cap of the pen to prevent evaporation of hand sanitiser. A switch is also included to prevent unnecessary battery consumption.

Code

Touchless Hand Sanitiser

// Touchless Hand Sanitiser
// by CookerBird

int enA = 13;
int in1 = 12;
int in2 = 11;
int trigPin = 5;
int echoPin = 6;
int Speed = 255;
int onTime = 300;
long duration = 0;
long distance = 0;

void setup()
{
  pinMode(enA, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}

void checkHands()
{
  distance = 0;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration*0.0343/2;
}

void pumpSanitizer()
{
  analogWrite(enA, Speed);
  digitalWrite(in1, HIGH);
  digitalWrite(in2 LOW);
  delay(onTime);
}

void pumpOff()
{
  digitalWrite(in1, LOW);
  digitalWrite(in2, LOW);
}

void loop()
{
  checkHands();
  if (distance > 0 && distance <= 10)
  {
    pumpSanitizer();
    pumpOff();
    delay(2000);
  }
  else
  {
    pumpOff();
  }
}