What it shows
Sumo robots search for an opponent, push it out of a black ring and stop at the white border. This needs edge detection with reflective sensors and distance sensing, with simple decision priority in the code.
The science
A TCRT5000 sends infrared light and measures how much returns. Black reflects very little and white reflects a lot, so an output that jumps when the sensor crosses the white edge tells the robot to reverse. The ultrasonic sensor finds the opponent within 30 cm. The priority is: edge first, then attack, then search by turning. A robot must never forget the edge, so the edge check is the first test in every loop.
Materials
Cost: under Rs 1,500. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- An Arduino Uno or Nano
- Two TCRT5000 reflective infrared sensor modules for the edge
- An HC-SR04 ultrasonic sensor for the front
- An L298N motor driver and two gear motors with wheels
- A 7.4 V two-cell lithium pack with a switch
- A chassis with a front scoop made from a thin metal or plastic sheet
- A black board with a white edge about 80 cm across
Safety
For this project: Charge lithium cells only with a proper charger and an adult. Keep hands off the robot during a match. Sharp metal edges on the scoop must be filed smooth.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Fix the two edge sensors at the front corners of the robot, pointing down about 5 mm above the floor.
Connect the sensor outputs to pins A0 and A1 and read them; note the value over black and over white.
Mount the ultrasonic sensor at the front and connect it to pins 9 and 10.
Connect the L298N to pins 5, 6, 7 and 8 and to the battery.
Write the sketch: if either edge sensor sees white, reverse for 300 ms and turn away from that side.
Otherwise if the front distance is below 30 cm, drive forward at full speed to push.
Otherwise spin slowly on the spot to search.
Test on the ring with a cardboard box as the opponent, then tune the speeds and the turn time.
What you should see
The robot stays inside the ring, locates a box and pushes it out of the ring.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1How does the edge sensor tell white from black?
White reflects much more infrared light than black.
2Why check the edge first?
Falling out of the ring loses the match even if the opponent is ahead.
3Why is the scoop low?
It slides under the opponent and lifts the front so its wheels grip less.
4Why do robots use a spin to search?
It covers all directions quickly from a fixed place.
Take it further
Add two side sensors so the robot can see an opponent that attacks from the side.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
Robotics
Build an Obstacle-Avoiding Robot
An ultrasonic sensor robot that finds its own way, step by step
Robotics
Robotics and Electronics Basics Study Book
The complete study notes, practice questions and glossary for Robotics and Electronics Basics