Team Alpha
White Line Following
Welcome to White Line Following
The agenda behind this task was to demonstrate that the micro mouse must be capable of following a 50mm white rectangular track, which was layered out on a matte black rectangular background. The white line sensor was used to stipulate whether the micro mouse was on the white/black area of the board. Hence, if the white line sensor were located on the white rectangular track, then the sensor would light up, indicating that it’s on the right space. Thus, with the increase in illumination, the resistance value would reduce by a few hundred ohms, and also the Vout would below as well.
However, when the white line sensor falls on a black surface, not much light falls on the LDR; hence its resistance is high, and the Vout is also high.
Furthermore, a potential divider was used to convert the change in resistance to a change in Voltage. To give a clear 0/1 indication, the Vout was connected directly to the analogue inputs of the microcontroller. A decision could only be made in the software if the Vout was greater or lesser than the threshold, corresponding to a black or white surface. The threshold means the Voltage at which the white surface changed into a black surface.
Initially the plan for the micromouse was to have three LDR sensors, one in the left,right and middle. Joe designed the circuit for the breadboard and gathered the voltage output values ready to be computed into the threshold values for the code. See below:
Once we had established these values it was time to implement the circuit onto the micromouse. To save time we decided just to simply transfer the circuit onto a piece of veroboard and use that to get the micromouse following white lines. Once the circuit was built it was mounted and we tested it on the demo board available in the laboratory. During testing the mouse did follow the line however very sporadically and often went of the line and over corrected itself. We tried changing the position of the sensors, the height they were from the ground and even slowed down the mouse to give it more time to correct itself however it was too no avail. We think that the issue was to do with code being that as there were 3 LDR's rather than 2 that the additional scenarios created by the additional LDR's were not accounted.
Never the less, the team went back to the drawing board and Tom suggested creating a new PCB with both the Obstacle avoidance and White line following circuit on it. This idea had been chucked around before however we thought it would take too much time but this time we decided to run with it. The new design would mean a much more low profile and streamlines micromouse which we all as a team wanted as the end result from day one.
Tom preceded to modify the pre-existing obstacle avoidance circuit on the proteus system by adding the white line following circuit. The circuit was not only added but also modified so that it gave us 5 LDR's to play with rather than the original 3. These modifications would mean a much more accurate and potentially winning micromouse if implemented correctly. Below you will see the modified circuit (left) and the protues design (right).
As you can see the board has been designed in a very neat and organised manner and was checked over by the head lab technician who said it should work well and was impressed with the design. There were a few acute angles which may have hindered performance but there were no issues that weren't a quick and easy fix. A 3D render was also produced of the proteus PCB design alongside a video showing the entirety of the design. Note: the capacitors at the top of the PCB are acting as place holders for what would be LDR's.
As you can see this design would easily allow the design of a low profile mouse as previously mentioned and we as a team were very excited to see it come to life. The extra LDR's would have made for a much more accurate micromouse and possibly allowed us to take home the trophy. Overall as a team we were very happy with it; unfortunately due to unforeseen circumstances progress on the micromouse project had to be halted, we had almost finished populating the PCB. Never the less we were still very proud of what we had made and are confident it would of worked well.
The image below shows how far we had achieved in populating the PCB before work had to be stopped.