DIY Mini Oscilloscope using Arduino Nano

Project Overview

An Arduino oscilloscope is an essential electronic test device that monitors the steady change of electrical voltage using two-dimensional graphs, displaying voltage changes over time on the vertical Y-axis. While oscilloscopes are crucial for electronics hobbyists and professionals, commercial models are often prohibitively expensive for students and DIY enthusiasts.

This project demonstrates how to build a simple, low-cost Arduino-based oscilloscope with a 1.3" OLED display that can visualise waveforms accurately. The project is inspired by Peter Balch's "Oscilloscope in a Matchbox" project, with modified code and hardware to suit modern requirements.

Features

• Portable Design: Compact mini oscilloscope powered via USB
• OLED Display: 1.3" OLED display for clear waveform visualisation
• Multiple Voltage Ranges:
  • DC 5V mode
  • AC 500mV mode
  • AC 100mV mode
  • AC 20mV mode
  • Voltmeter mode
• Adjustable Time Base: Multiple sweep speeds (1mS to 100mS)
• Trigger Modes: Rising and falling edge triggering
• Test Signal Generator: Built-in test signal output
• Button Controls: Two tactile switches for parameter adjustment

Components Required

Qty	Value	Device	Package	Parts	Description
2	-	Tactile Switch	TH	S1, S2	Tactile switch / Buttons
1	-	Arduino Nano	ARDUINO_NANO	ARDUINO_NANO1	Arduino Nano Board
4	0.1uF / 16V	Capacitor	TH	C1, C2, C3, C4	0.1uF/16V/Ceramic Disc
1	100K	Resistor	TH	R2	100K/1/4W/TH
1	10K	Resistor	TH	R7	10K/1/4W/TH
1	1K	Resistor	TH	R3	1K/1/4W/TH
2	1M	Resistor	TH	R6, R8	1M/1/4W/TH
2	270K	Resistor	TH	R4, R5	270K/1/4W/TH
3	4.7K	Resistor	TH	R1, R9, R10	4.7K/1/4W/TH
1	LM358	Op-AMP	DIL08	IC1	LM358 Dual Op-Amp
2	PIN1-2	Pin Header	TH	Display / Input	4Pin / M/F
1	-	OLED Display	I2C	-	1.3" OLED (SH1106)

Circuit Diagram

The circuit design is straightforward and requires only a few components:

Key Circuit Features:

1. Operational Amplifier Stage:

   • Uses LM358 dual op-amp IC
   • Both op-amps are configured for AC coupling
   • Gain setting of x5 with negative feedback
   • Reference voltage for signal offset (adjustable via 100K potentiometer)

2. OLED Display Connection:

   • Connected via I2C interface
   • SCL pin: A5 (Arduino Nano)
   • SDA pin: A4 (Arduino Nano)
   • Pull-up resistors: 4.7K ohms

3. Input Signal Processing:

   • AC input signals are processed through the op-amp stage
   • Offset adjustment allows proper signal centering
   • Multiple voltage ranges supported

4. Control Interface:

   • Two tactile switches for parameter adjustment
   • Button 1 (Pin 4): Horizontal/Time base adjustment
   • Button 2 (Pin 7): Vertical/Gain and mode selection

5. Power Supply:

   • USB powered (5V)
   • Simple and portable design

Software Requirements

Required Libraries:

1. Wire.h - I2C communication (built-in)
2. SimpleSH1106.h - Fast OLED library for SH1106 chipset (custom library by Peter Balch)
3. limits.h - Standard C library (built-in)
4. math.h - Mathematical functions (built-in)

Key Code Components:

1. Mode Selection

enum Tmode {DC5V, AC500mV, AC100mV, AC20mV, mLogic, mVoltmeter, maxMode1};

Supports different voltage ranges and measurement modes.

2. ADC Initialization

The analog-to-digital converter is configured with:

• Proper voltage reference selection
• Left-adjusted results for 8-bit operation
• Appropriate prescaler settings

3. Waveform Display

• 128-sample buffer for waveform storage
• Real-time drawing on OLED display
• Grid and graticule overlay
• Automatic triggering system

4. Button Interface

• Long press: Opens main menu
• Short press: Cycles through settings
• Debouncing implemented in software

5. Trigger System

• Rising edge and falling edge detection
• Free-run mode for continuous display
• Hysteresis for stable triggering

Installation & Setup

Step 1: Hardware Assembly

1. Solder all components on perfboard according to the circuit diagram
2. Connect the OLED display via I2C (A4/SDA and A5/SCL)
3. Install tactile switches on pins 4 and 7
4. Verify all connections

Step 2: Software Setup

1. Download and install Arduino IDE
2. Install the SimpleSH1106 library (available in project files)
3. Connect Arduino Nano to your computer via USB
4. Open the oscilloscope sketch in Arduino IDE
5. Select Tools → Board → Arduino Nano
6. Select the correct COM port
7. Upload the code

Step 3: Testing

1. Power the oscilloscope via USB
2. Use the test signal output (Pin 3) to verify operation
3. Adjust time base and gain using the buttons
4. Connect external signals to the input

Operating Instructions

Main Menu Navigation

Access the main menu by holding either button for 1 second:

Menu Options:

• Time Base: 1mS, 2mS, 5mS, 10mS, 20mS, 50mS, 100mS
• Gain/Mode: 5V DC, 0.5V AC, 0.1V AC, 20mV AC, Voltmeter
• Trigger: Rising or Falling edge
• Test Signal: Various frequencies (31Hz to 31250Hz) or Off
• Vcc Display: Shows supply voltage

Button Functions

Horizontal Button (Pin 4):

• Short press: Change time base
• Long press: Enter menu

Vertical Button (Pin 7):

• Short press: Change voltage range/mode
• Long press: Enter menu

Waveform Display Features

The oscilloscope displays:

• Waveform trace: Real-time signal visualization
• Grid lines: Vertical and horizontal references
• Scale labels: Voltage and time scales
• Trigger indicator: Shows trigger point

Testing & Calibration

Built-in Test Signals

The oscilloscope includes a test signal generator that can output:

• Square waves at various frequencies
• Useful for testing and calibration
• Available on Pin 3

Verifying Operation

1. Enable test signal in menu
2. Connect Pin 3 to input
3. Adjust time base to view complete waveforms
4. Verify trigger functionality

Sample Waveforms

The oscilloscope can display various waveform types:

• Sine waves: Smooth periodic signals
• Square waves: Digital signals and PWM
• Triangle waves: Ramp signals
• Complex waveforms: Audio and modulated signals

Specifications

Parameter	Specification
Display	1.3" OLED (128x64 pixels)
Input Channels	1 (single channel)
Voltage Ranges	20mV/div to 5V/div
Time Base	0.1mS/div to 20mS/div
Input Impedance	~1MΩ
Sampling Rate	Up to 1 Msps
Buffer Size	128 samples
Power Supply	5V USB
Trigger	Rising/Falling edge

Troubleshooting

Common Issues:

1. No Display Output

• Check I2C connections (A4, A5)
• Verify OLED power supply
• Check SimpleSH1106 library installation

2. Incorrect Waveform Display

• Adjust trigger level
• Check input signal amplitude
• Verify ground connections

3. Erratic Behavior

• Check power supply stability
• Verify button connections
• Update code if using modified version

4. Compilation Errors

• Ensure SimpleSH1106.h library is installed
• Check Arduino IDE board selection
• Verify all library dependencies

Upgrades & Modifications

Possible Improvements:

1. Add BNC Connector: Professional input connector for better signal integrity
2. Battery Power: Add rechargeable battery for portable operation
3. Dual Channel: Expand to two-channel operation
4. Higher Sampling Rate: Optimize code for faster sampling
5. FFT Analysis: Add frequency spectrum display
6. Data Logging: Store waveforms to SD card
7. USB Communication: Send data to PC for analysis

Project Resources

• Original Article: DIY Mini Oscilloscope using Arduino Nano
• Inspiration: Peter Balch's "Oscilloscope in a Matchbox"
• Related Projects:
  • Raspberry Pi Based Oscilloscope
  • Serial Monitor Arduino Oscilloscope
  • Arduino Projects

Code Structure

Main Components:

1. Global Variables & Constants

   • Mode settings, buffer arrays, display parameters

2. Image Data

   • Menu graphics stored in PROGMEM
   • Waveform icons and UI elements

3. Display Functions

   • drawScreen(): Renders waveform and graticule
   • drawBox(): Creates menu borders
   • drawMainMenu(): Main menu interface

4. ADC Functions

   • initADC(): Configures ADC registers
   • GetADCSamples(): Captures waveform data
   • SendADC(): Processes and displays samples

5. Control Functions

   • setSweep(): Adjusts time base
   • setMode(): Changes voltage range
   • CheckButtons(): Handles user input

6. Utility Functions

   • readVcc(): Measures supply voltage
   • myDelay(): Non-blocking delay
   • Timer and interrupt handlers

Safety Considerations

⚠️ Important Safety Notes:

1. Maximum Input Voltage: Do not exceed 5V DC input
2. AC Signals: Limited to specified ranges (500mV, 100mV, 20mV AC)
3. No High Voltage: This is NOT suitable for mains voltage measurements
4. ESD Protection: Use anti-static precautions when handling components
5. Power Supply: Use regulated 5V USB power only

License

This project is based on Peter Balch's work and is subject to the GNU General Public License.

Contributing

Feel free to contribute improvements, bug fixes, or additional features. Submit your ideas and modifications through the Circuit Digest forums.

Acknowledgments

• Peter Balch: Original "Oscilloscope in a Matchbox" project creator
• Circuit Digest: Project documentation and testing
• Arduino Community: Libraries and support

Support

For questions, suggestions, or troubleshooting help:

• Visit the Circuit Digest Forum
• Check the original article for detailed explanations
• Join the Arduino community for general Arduino support

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Last Updated: 2024