Lei Feng Fab Academy 2025

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Week 9: Input Devices ​

This document was generated with AI assistance based on the course outline and subtitles from the video conference session that I provided to Claude 3.7 Sonnet.

Course Overview ​

This week's course focuses on input devices and sensor technologies, teaching how to connect various sensors to microcontrollers and read data from them. The course covers a wide range of input devices, including button switches, magnetic field sensors, step response measurements, temperature sensors, light sensors, motion sensors, distance sensors, real-time clocks, position sensors, accelerometers, sound sensors, force sensors, and cameras. Students will learn how to measure physical quantities using these sensors and input this information into digital systems for processing.

Detailed Course Content ​

1. Course Introduction and Background ​

In the process of manufacturing electronic devices, input devices are key components for interacting with the external world. This week's course will explore various sensor technologies and their applications in depth. In the coming weeks, we will learn about output devices (such as motors and displays), communication between multiple processors, and how to build complete machine systems.

2. Microcontroller Input Basics ​

2.1 Datasheets and Pin Functions ​

2.2 Signal Processing Basics ​

  • Analog Comparators: Quick comparison of two voltage values
  • Analog-to-Digital Converters: Converting analog signals to digital values
  • I2C Communication: Increasingly more sensors use the I2C communication protocol

3. Buttons and Switches ​

3.1 Button Principles ​

3.2 Button Programming Examples ​

The following are examples based on ESP32-C3:

Other microcontroller examples:

4. Magnetic Field Sensors ​

4.1 Hall Effect Sensors ​

  • Principle: Hall effect sensors measure magnetic fields and output corresponding voltages
  • Directionality: Flipping the sensor can measure magnetic fields in different directions
  • Sensitivity: Sensitive enough to measure the Earth's magnetic field
  • Applications: Detecting lid closure, shaft proximity to endpoint
  • Example: hello.mag.45, Board design, Code, Video

4.2 Vector Magnetometers ​

5. Variable Resistors (Potentiometers) ​

6. Step Response Measurement ​

6.1 Capacitive Sensing Principles ​

  • Measurement Principle: Based on measuring capacitance changes through charge/discharge time
  • Application Range: Measuring resistance, capacitance, inductance, position, pressure, tilt, acceleration, humidity, proximity, etc.
  • Human Capacitance Measurement: Utilizing human body conductivity to measure contact or proximity
  • Animation Demo: Step response simulation

6.2 Self-Capacitance Measurement (Single Pin) ​

6.3 Remote Processor Measurement ​

6.4 Mutual Capacitance Measurement (Dual Pin) ​

6.5 Remote Amplifier Measurement ​

6.6 Dielectric Spectroscopy Measurement ​

  • High-Frequency Applications: Can measure material properties at higher frequencies
  • Material Identification: Can differentiate between different liquids such as alcohol, martini, beer, wine, etc.
  • References: Application Note, Theory, Measurement Methods

6.7 Application Examples ​

7. Temperature Sensors ​

7.1 Thermistor Bridge Circuits ​

7.2 Infrared Temperature Measurement ​

8. Light Sensors ​

8.1 Phototransistors ​

8.2 Synchronous Detection ​

8.3 Color Sensors ​

9. Motion Sensors ​

9.1 Doppler Radar ​

9.2 Pyroelectric Sensors ​

10. Distance Sensors ​

10.1 Laser Time-of-Flight Measurement ​

10.2 Ultrasonic Sensors ​

11. Real-Time Clocks (RTC) ​

12. Position and Time Sensors (GPS) ​

13. Acceleration, Rotation, and Orientation Sensors ​

13.1 Three-Axis Accelerometers ​

13.2 Six-Axis IMU (Inertial Measurement Unit) ​

13.3 Nine-Axis IMU ​

14. Sound Sensors ​

14.1 MEMS Microphones ​

14.2 Electret Microphones ​

15. Other Sensor Introductions ​

16. Image Sensors ​

16.1 Camera Modules ​

16.2 Artificial Intelligence Modules ​

16.3 Webcams ​

16.4 Image Processing Libraries ​

16.5 Web Image Processing ​

Assignment Requirements ​

Group Assignment ​

Probe input devices for their analog levels and digital signals:

  1. Select an input device (such as a button, sensor, etc.)
  2. Use an oscilloscope or other tools to measure its analog levels
  3. Observe and record the characteristics of digital signals
  4. Analyze signal patterns and understand their working principles

Individual Assignment ​

Measure something: Add a sensor to your designed microcontroller board and read the data

  1. Design and build a circuit board with a microcontroller and sensor
  2. Program it to read sensor data
  3. Visualize the data (through Arduino/Thonny built-in plotting tools or Python code)
  4. Document the process and write up the sensor principles, applications, and measurement results

Reference Example: Adrian Torres' Input Devices Project

Suggestion: If unsure which sensor to choose, try using step response technology, as it only requires processor pins and simple copper electrodes to create various interesting interfaces and sensors.

Learning Resources ​

References ​

  1. Input Devices Course Homepage
  2. AVR DB Series Datasheet
  3. I2C Communication Protocol Description

Programming Libraries and Tools ​

  1. Adafruit FreeTouch Library
  2. ESP32 Touch Sensor API