Week 6: Sensor Input and Calibration

Assignment Overview

This week’s tasks involved creating and configuring sensors to measure physical quantities using a microcontroller. The focus was on avoiding the delay() function and utilizing timers, as well as employing C++ class structures.

Capacitive Sensor Design

• Setup: I used two pieces of copper separated by a piece of velostat for the capacitive sensor. This setup is shown in the image below:

  

• Functionality: I connected one side to a pin for digital writing and read the difference from the other pin, similar to tx-rx sensing as outlined here.

• Schematic: The schematic for the sensor setup is shown below:

  

• Calibration: I calibrated the sensor using the number of nuts as a unit of measurement, with the experiment setup shown below where essentially I used number of nuts as the weight:

  

  The results indicate an exponential decrease in readings with larger weights, aligning with the expected behavior of tx-rx sensors because the difference between the input signal and output signal decreases as the pieces of copper become closer together.

  Number of M2 Washers	Reading
  0	47000
  1	46000
  2	45000
  3	43000
  4	32000
  5	17000

Thermistor Setup

• Circuit: I followed the wiring instructions from class for the thermistor setup. The circuit is depicted in the image below:

  

CNC Preparation

• CAD Files: Prepared CAD files for CNC week, considering both 2D DXF files for routing sheet material and 3D STL files for milling 2.5D shapes.