FIRE is my first microcontroller based robot, incorporating sensors to interact with the environment, and control the robot behavior accordingly. Finally, my thirst to make a big robot has been quenched.

To watch the video click on the links below
Video 1
Video 2
Video 3
Video 4
Video 5

This robot has taken more than necessary time to be built, approx. 8 months. Now that is what happens when things are planned inefficiently. What started out as an 8 motor walker later became a 4 motor walker, then a 2 motor walker and now a roller. Thats what I call reverse evolution. The primary problems for such a transition has been the motors. I jumped into buying wiper motors which were quite expensive(Rs.300 each, I got four of them). This is where all my problems started.

Firstly, the motors had a design where the shaft is on one side of the central axis. So when I had to do the mechanics, I had to keep weight imbalances in the mind. The most successful designs I made required a lot of machining of metal parts for which I didnt have enough resources. This way I had to do lot of tiring mechanical work which ultimately ended up no where because as work progressed, I seriously doubted the ability of my motor to make a walker. The only solution left was to use the motors for a roller. Again output shaft position was a problem. Initially I was not satisfied with any of the mechanical designs. In fact I reached a stage when I decided to remove the gears in the motors just to get the central axis shaft to do the work for me. After removing all the inbuilt gears in 2 motors, I fixed the chain sprocket of a bike to make the wheels. This looked cool and I had almost decided to remove them from the other 2 motors to make a 4 motor roller, with the front motors chained to the back ones to make it look like a battle tank. Unfortunately the wheels were too fast and did not have enough torque to carry even 200 grams more than its weight. One motors weighs 900 grams.

This meant some type of coupling with gears or a belt drive to increase torque. All this was taking me nowhere and I was running out of time to submit this as my final year project. Thats for the mechanics alone. As for the electronics, initial plan was a nervous network processor. But as designs changed and time ran out I had no time for testing with nervous networks. Ultimately I had to use a microcontroller for quick results. For sensors I used 2 touch sensors for obstacle detection and Infrared for edge detection. This was based on the edge detection circuit of Bruce Robinson's Hider.

Overall I have had a great time doing this project. I have learnt a lot in robotics, strengthened my knowledge of linear and digital circuits and surprisingly also in nervous networks even though I used them only in the IR circuit. This was because of the initial research I did to decide the circuits for all the walkers. Thanks to all the failures now I know what not to do. Sometimes I think that the robot was made by trying everything that didnt work. Then only that what works was left and suddenly there is this robot that works. Also in the process I realized that a lot of things are available in India contrary to what I thought. Only thing is they are found only in very few shops with the problem being the shopkeeper having no idea of the specifications, especially if it is an electronic component.

FEATURES

· 8051 Microcontroller system

· High torque motors

· L298 Motor drivers for high current

· Simple design

· High load carrying capacity

MECHANICS

· Aluminium Body for light weight

· Cast Iron for stronger joints

· 12V DC Shunt Motor drawing 4A under full load

· 5V DC Gear motor for surveillance camera movement

· Custom made nylon wheels for strength and lesser weight

ELECTRONICS

1) MICROCONTROLLER:

ATMEL AT89S8252

· 8051 Compatible

· USART Serial Interface

· 8k Flash Memory (Downloadable using Serial Interface)

· 2k EEPROM

· 256 bytes RAM

· Four 8-bit Bi-Directional ports

· 5 Interrupts

2) MOTOR DRIVER:

a) L298 Dual Full Bridge Driver

· Operating supply voltage upto 46V

· Total DC current upto 6A

· Low Saturation Voltage

· Over temperature protection

· High Noise immunity

· Parallel connection per motor for higher current

b) 74HC245 Octal Tranceiver

· Four pins in parallel 140mA per motor terminal

· Wide power supply range 2-6 V

· Low quiescent current

3) POWER SUPPLY

L7805CV Positive Voltage regulator

· Output current up to 1.5 A

· Thermal Overload Protection

· Short Circuit Protection

· 2 X 6V, 4.5A Lead Rechargeable Battery

4) SENSORS

· Touch Sensors

· Infrared Edge Detection

BLOCK DIAGRAM