Design Evaluation

The design of the buggy was good and unique in the fact that it was Lego with a acrylic base for reinforcement. It was suited for the task but could have been improved in the following ways:

1. The Lego could have been glued together to prevent breakages when the buggy was running.

2. The circuitry could have been built on strip board or PCB (printed circuit board) this would have reduced the size of the buggy, which would make it lighter.

3. The variable resistors could have been mounted on the top of the buggy in order to make tuning the circuitry to follow the lines easier.

4.  A cover could have been built in order to cover all the electronic parts using Lego doors in order to access switches and battery compartments.

5. The trolley wheel could have had a better design as it did not suit its purpose and would not swivel as intended causing the buggy to deviate from its intended route.

Overall we believe the design was good and was easy to adapt due to the fact that it was Lego and if something didn’t fit it could be rearranged in order to fit it in, allowing from extensive development during testing.

Tuning

GO buggy GO

Lego design so Far

Motor Testing

Code used to test the motors:

main:

high 1
low 0
high 2
low 3
pause 5000
low 1
high 0
low 2
high 3
pause 5000

goto main

this code was used to make both motors head in the forward direction and after 5 seconds go in the reverse direction.

Software Update

Problems Faced

• Reed switches were not sensitive enough for magnetic tape.
• Only 3 analog to digital converters on chip.

Actions on Problems

• Changed code to suit LDRs.
• Chose to not use the ADC's and plan to use the LDR's digitally. If they provide a voltage of over 2.25V then PICAXE will read as logic 1. If under 2.25V then logic 0 will be read.

Future Intentions and Learning Outcomes

• LDR's will need to be calibrated for light conditions in the room.
• Debug code on buggy testing in order to remove faults and include possible failsafe.
• Include extra code for unique additional functions which will be revealed on competition day.

Current Situation

• Code for both line following and signal reading modes is complete, tested and fully operational.
• Input output variables may change but are easily edited in the code.