“Coronavirus Covid-19” 1 Meter Keep Away Alarm Gadget

بسم الله الرحمن الرحيم

This article is a demonstration of the use of the Ultrasonic Distance Sensor HC-SR04.

The sensor will be be used as a measurement device to build the 1 Meter Keep Away Alarm Gadget for distanciation purposes.

The brain of this gadget is the wonderful ATTINY85 µController powered by a 3.7V Lipo battery.

The gadget integrates the TP4056 charger.

GREEN LED lights if the measured distance from any object is greater than 120 cm.

RED LED blinks if the measured distance from any object is lower than 100 cm with a lovely (noisy) beep.

YELLOW LED blinks if the measured distance from any object is between [100,120 ] cm with a less noisy beep.


Many articles explain in details how the HC-SR04 works.

In a nutshell, The HC-SR04 Ultrasonic Distance Sensor is

1 – An Ultrasonic Transmitter – This transmits the ultrasonic sound pulses, it operates at 40 KHz

2 – An Ultrasonic Receiver – The receiver listens for the transmitted pulses. If it receives them it produces an output pulse whose width can be used to determine the distance the pulse travelled.

Components Sourcing (BOM)

A few components are needed for this simple gadget.

These components are easily accessible from Amazon, Ebay or Aliexpress.

BOM : Bill of materials

Step 2: Schematics

The Open source Schematic Capture & PCB Design Software Kicad is used.

Step 3: Pcb Design

Kicad is used to route the board.

Step 4: PCB Assembly

A few components are to be soldered for this gadget.

Be careful and patient.

Step 5: Arduino Sketch

The arduino sketch uses the famous NewPing library to read the distance from the sensor.

The NewPing Library is Open Source and very well documented.

Step 6: Arduino Sketch Flashing

The flashing of code will use the Arduino Uno itself as an ISP programmer.

Hopefully, the “ATTINY85 ISP Programmer Shield  is used to flash the board.

Remark: Read the article “Yet Another ATTINY85 ISP Programmer Shield for Arduino”

Step 7: Enjoy

In this article we have gone over all the steps to produce a funny gadget that might be helpful.

A 15 seconds home made video shows a use case.

Need more information, put a comment.

الحمد لله رب العالمين

Published by

abdelhak Bourdim

Embedded Software Engineer