BOEBot Project

Design

General Outline Design Schematics Datasheets Bill Of Materials Code Pictures Progress-To-Date Future Expansion Conclusion Credits

Hardware: 4AA batteries on BOE drive BASIC stamp and wheel encoders 9V battery with LM7805 voltage regulator drive servos 4AA batteries powering PC-side RF module Serial (RS-232) is main communication link Obstacles: Problem: Servos causing interference with BASIC stamp and wheel encoder data processing due to voltage spikes and electrical noise. Solution: Separate power supply for (1) BASIC stamp and wheel encoders and for (2) servos. In order to fully isolate the servos from the microcontroller, an optoisolator is also needed. Problem: Negative voltages coming from PC serial RS-232 before Visual Basic program running – blew RF transmitter. Originally used DTR (4) and ground (5) from DB-9 socket to power PC RF module through LM7805. Solution: Wait until VB program is running. In future implement a switch/zener interface to safely allow only safe voltages. External power supply of 4 AA batteries through LM7805 instead of PC-powered. Problem: Could not get BASIC Stamp to properly configure LS7166 counter IC. Solution: Created a software simulation representing encoder counting and sending to PC for graphing purposes. Robot wheel distance calculation (for scaling purposes): Wheel Encoder: 200 CPR Wheel Diameter: 6.67 cm Wheel Circumference: 20.95 cm (pi * d) Distance per Count: 20.95 cm / 200 CPR 10.475 cm / 100 counts (pi * d / 2) 20.95 cm / 200 counts (pi * d / 1) 5.2375 cm / 50 counts (pi * d / 4) 2.095 cm / 20 counts (pi * d / 10) 1.0475 cm / 10 counts (pi * d / 20) 0.52375 cm / 5 counts (pi * d / 40) 0.10475 cm / 1 count (pi * d / 200) Every 200 counts ~ 20 cm (20.95cm) traveled