ECE 110/120 Honors Lab Section : Capacitive Touch Numpad

Statement of Purpose

We are attempting to make a numpad addon based on capacitive touch sensors for computers without one. Numpads are frequently used in scenarios from 3D Modelling, CAD, and other complex software to daily numerical input. Many computers, restricted by their size and design methods, does not have such a convenient tool. Making the numpad addon with capacitive touch sensors particularly is for making a cool "keyless" keyboard.

Background Research

The purpose/importance of usage of this project is stated in the above section. For the similar projects, we found that no one actually made such a project. There are computers with capacitive touchscreen being its full keyboard; there are touchpads based on capacitive touch sensors but used as a numpad; there are optical keyboards that feels the same but uses a different sensors. We picked an unique combination of tech stack, size, and characteristic in the keyless keyboard projects. We hope our project to be both useful and coooooool.

Block Diagram / Flow Chart

System Overview

The general idea of the system is to take an input sensed by the touch sensor and display it on a computer. To sense a touch input, sensors have to constantly measure the voltage of the capacitive touch screen. If there is a significant increase in the voltage, then the Raspberry Pi will measure the ratio of currents on the screen and identify the location of the input. Then the location must be compared to the acceptable ranges of the various keys on the glass number pad. When the key is determined, the information should be sent to the computer to be displayed.

Parts

Raspberry Pi. (In Lab)

ITO (Indium Tin Oxide) Coated PET Plastic - 100mm x 200mm: https://www.adafruit.com/product/1309

SMT RGB LEDs: https://www.adafruit.com/product/619

Adafruit 12-Key Capacitive Touch Sensor Breakout - MPR121 - STEMMA QT: https://www.adafruit.com/product/1982

Self-designed PCB Printing

Possible Challenges

• Learning about Keyboard Interfaces / encoding protocols;
• Figure out which "key" is being pressed without having an individual pin for each key;
• Designing PCBs and manually solder everything.

References

Instructables. 2021. Optical Keyboard. [online] Available at: <https://www.instructables.com/Optical-Keyboard/> [Accessed 19 September 2021].

Dinotools.de. 2021. Use an Arduino board to emulate a keyboard. [online] Available at: <https://www.dinotools.de/en/2016/11/09/use-an-arduino-board-to-emulate-a-keyboard/> [Accessed 19 September 2021].

Randomnerdtutorials.com. 2021. Turn Raspberry Pi Zero in USB Keyboard | Random Nerd Tutorials. [online] Available at: <https://randomnerdtutorials.com/raspberry-pi-zero-usb-keyboard-hid/> [Accessed 19 September 2021].

Rototron.info. 2021. Raspberry Pi Graphics LCD Display Tutorial | Rototron. [online] Available at: <https://www.rototron.info/raspberry-pi-graphics-lcd-display-tutorial/> [Accessed 19 September 2021].

Final Project Report and Video Demo

Final Project Report: 

Video Demo: Capacitive Touch Number Pad