Introduction: "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.

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

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

A 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.

Step 1: 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