Ultrasonic Distance Display

ATtiny85 Ultrasound Distance Measurement project with Dual Segment LED Display

Description

This project uses the HC-SR04 ultrasonic distance module to determine distance and display the results via two 7-segment LED displays. The HC-SR04 provides readings from 2cm to 400cm (1in to 13ft).

Imperial and SI Units

In Imperial unit mode, the code is written to display distances in inches (1 to 11) for distances less than 1 foot. Once the distance reaches 1 foot, it will show feet in decimal (1.0 to 9.9) until the distance reaches 10 feet when it will display in feet only (e.g. 10).

In SI unit mode, it will show centimeters for distances less than 1 meter (1 to 99, then it will show meters with decimal (1.0 to 9.9) until the distance reaches 10 meters and will continue to show meters only.

To toggle Units: Hold the distance to 4 (either unit) for ~4 seconds and it will toggle between units. Imperial mode will flash "in" and SI mode will flash "c".

Sleep Feature

Sleep Mode: The code includes logic to turn off the display when there is no movement and power back on when movement is detected.

Circuit

A Kicad schematic is included in this project and the schematic export is listed below. The circuit is powered with a steady 5V DC supply (e.g. USB adapter). The HC-SR04 is an entry level sensor and does suffer from some fluctuation. Logic in the code attemps to stablize the measures by making multiple readings.

Components:

• ATiny85 Microcontroller
• HC-SR04 Ultrasonic Distance Sensor
• 74HC595 8-bit Shift Register (Qty 2)
• 7-Segement LED Display (Qty 2)
• 0.1uF Ceramic Capacitor
• 100uF Electrolytic Capacitor
• 5V Power Supply

Schematic

ATtiny85 Microcontroller

Prototype Example

List of Materials

Integrated Circuits

• 1 x ATiny85 Microcontroller (DigiKey)
• 2 x 74HC595 8-bit Shift Register (DigiKey)

Sensors

• 1 x HC-SR04 Ultrasonic Distance Sensor (DigiKey)

Display/LED

• 2 x 7-Segement LED Display CC (DigiKey)

Power Supply

• 5V Power Supply

Misc

• 16 x 220 Ohm Resistor
• 1 x 100uF Electrolytic Capacitor (DigiKey)
• 1 x 0.1uF Ceramic Capactior - (Amazon)

References

• Hackster, Tauno Erik, Selfmade I2C 7-Segment Display with ATtiny85 - https://www.hackster.io/taunoerik/selfmade-i2c-7-segment-display-with-attiny85-a637d0

• Instructables ATtiny85 HC-SR04 Pocket-Sized Ultrasonic Ruler - https://www.instructables.com/id/Pocket-Sized-Ultrasonic-Ruler/