Lithium
A Micromouse is an autonomous robot designed to solve a maze comprises of 16 x 16 unit squares that are 18 cm x 18cm, and reach the center as fast as possible.
The user programs the Micromouse using high-level programming language on the PC. After cross-compiling the code, the executable file is then stored on an EEPROM. The CPU reads and performs in the instructions stored the EEPROM. The CPU then pulses the infrared LEDs. The infrared detectors placed around the mouse pick up the infrared light bounces off the walls of the maze, and output an analog voltage between 0.5 to 4.5V. The A/D converter reads the voltage and outputs an 8-bit number. Based on the value of the numbers from the detectors, the CPU decides whether there are walls present. The CPU then executes the “flood fill” algorithm to find the shortest path to the center of the maze. Then the CPU moves the stepper motor to move a predetermined location.
Hardware Design
Power Circuitry: Four Sony US18650S rechargeable lithium ion batteries were placed in series to provide 16.8V DC. This voltage was then stepped down to 5V using a MAX744AEPA switching voltage regulator. The unregulated voltage from the batteries was used directly to power the stepper motors.
Supervisor: The Maxim MAX707CPA microprocessor supervisor provides power on reset and manual halt and reset of the MC68EC000.
MC68EC000: This microprocessor is a high-performance embedded controller that is object-code compatible with the Motorola MC68000. It’s also relatively low-cost and has low power consumption.
EEPROM: The erasable programmable read only memory is an Atmel 29C256 flash EPROM. I installed a switch that allows me to also use the 28C256 EEPROM.
SRAM: The static random access memory is a CY7C199-12PC from Cypress Semiconductor Co. that supplies 32K of RAM.
Address Decoder: Address decoding was accomplished with the EMP7064SLC44-10 PLD from Altera.
Motor Driver: The stepper motor driver is the UCN5804B from Allegro Micro. It can supply up to 35V @ 1.5A.
A/D: The Maxim MAX118EPI converts the voltage from the infrared sensors to 8-bit binary values. It has 8 input channels and is running in pipeline mode.
LED/DIP: The LED was connected to the CPU in a parallel fashion through an Octal D flip-flip. The DIP is the input parallel port connected through an octal bus transceiver. They’re used to test and debug the Micromouse.