Builders guide robot pacman.pdf

8.4 RegulatorsRegulators were added to provide a constant output voltage to the variable load onboth robots. On Pac-Man, we used a LM7805 5V regulator to power all thecircuitry. This included the RF receiver module, the obstacle sensors, contactsensor, micro-controller, stepper motor driver chips, the LCD, and the beaconcircuit. The total amount of current consumed by all circuits is less than 1A,which was enough to meet the regulator’s specifications.On the Ghost, we decided to experiment with a 5V switching voltage regulator tosend power to the micro-controller, obstacle sensor, contact sensor and beaconcircuits. See Figure 48 for the circuit set-up. The switching regulator contains a52kHz internal frequency oscillator that allows it to output the input power as apulse. The regulator controls the pulse duration by using feedback as shown inFigure 49. The width of the pulse changes based on the amount of output powerrequired. When the output power is small, the pulse duration is narrow and whenthe output power is large, the pulse duration is wider.Figure 48. LM2575 Circuit SchematicFigure 49. LM2575 Circuit Block Diagram39