By: Alan Valles (Electronics and Control)
Approved by: Ijya Karki (Project Manager)
Table of Contents
Introduction
The purpose of this blog post is to explain the function and design of the custom PCB color sensor that was made.
Analysis
This color sensor was made to meet our requirements and detect color pads below. Two version of the color sensor were made, one that was designed and laid out from scratch. The second models and updates the open source files provided by adafruit for the existing TCS34725 breakout board colorsensor[1].
Figure 1. Color Sensors.
The design created from scratch model is the one that was used in the final model since it is smaller and simpler. One update is that the drilled holes for the pin headers was very tight and would allow for more room on future builds. The LED was a PLL-C2 package and the manufacturer selected was CREE which outputted cool white. A .1uf capacitor was used as the decoupling capacitor. In the future the TCS34725 package which was designed by the division manager, Ryan Daly, would have extended copper pads to support hand soldering. The IC had the copper pads pre-tinned and then the chip was placed. Following that, the entire board was reflowed with a hot air gun.
A second board was also designed, but was not manufactured since this design was working. The adafruit design was modified to operate on a 3.3.v bus instead of a 5v bus.
Figure 2. Color Sensors.
Figure 3. Sensor Board.
The color sensor was tested and functionally worked with the Adafruit TCS34725 Library. However, in the actual readings of color there is a difference because of hue of light used and placement of light and color sensor. The same code was utilized from color experiment[2]. Overall, this custom color sensor is a smaller more compact, no frills color sensor that operates on a 3.3v I2C bus.
Conclusion
In Conclusion, the custom design color sensor outputted correct data reading using the adafruit TCS34725 library.
References
[1] https://www.adafruit.com/product/1334 [2] http://arxterra.com/fall-2016-biped-color-senor-experiment/