ONE DAY OF ROBOTICS

#1 DC MOTOR CONTROL

COACH MICHAEL

[THIS BOOKLET FOR USE WITH SciBOT + DC MOTORS]

A rapid introduction to the world of robotics and mechatronics where you learn to write and

upload text-based programs to a pre-built robot to control its movements, and participate in

a robotics challenge to inspire you to consider a career in engineering

NOTES

ONE DAY OF ROBOTICS

CONTENTS

PART 1: Getting Connected

PART 2: Upload LED code

PART 3: Motor Control

PART 4: Moving Forward

PART 5: Turns and Pivots

PART 6: Mini Challenge

NOTES

ONE DAY OF ROBOTICS

CODING AND ROBOTICS WITH ARDUINO

INTRODUCTION

How much robotics can be taught in a just a few hours? Quite a lot.

Participants, equipped with quality notes, can quickly acquire skills in this exciting field through tackling

challenges that are difficult, but not impossible.

OUTCOMES

• Learn how to operate a small desktop robot.

• Write and upload program code on a computer.

• Upload the code to an Arduino PRIMO robot

• Control the speed and direction of rotation of motors to control movements of the robot.

• How does a robotics challenge work?

• What is a competition maze?

• Learn how to navigate using a simple method called dead reckoning.

• Write program code to get through the maze.

• See how far into the maze on can get, can one complete?

Robot motors

Coding session

Challenge

Break

Robot Sensors

Coding session

Challenge

www.robotscience.co.za

www.youtube.com/electronicsafrica

NOTES

1 DAY OF ROBOTICS: PART 1 – CONNECT THE PRIMO ROBOT TO PC WITH USB

Welcome to ONE DAY OF ROBOTICS where you learn to write a few lines of code to control the movements of a

small desktop robot with the minimum of code. By learning how to change the numeric values in the code, and

observing the effect of the changes on the movements of the robot every time you upload the new code, you

can control the distance the robot travels in a straight line and even make it execute some turns and drive into

a maze.

Using the “trial and error” method you can learn how to control the robot without too much difficulty. Pay

attention and understand the notes … after the “code and upload” session there’s a navigation challenge.

If you read these notes very carefully – and take your time to properly understand the explanations of how the

code [and especially the numbers contained in the code] control the hardware – you should be able to

complete the mission.

SciBOT is based on a microcontroller programming board called Arduino UNO. More than 10 million Arduino

UNO controllers have been bought by professional electronics engineers [and hobbyists] over the past decade

making Arduino the most widespread controller in the world. Arduino can be programmed with C++ type text

code using a free software integrated development environment [IDE] and there’s an easy graphics code

option.

When you connect the robot to the computer, it’s always a good idea to first start the Windows Device

Manager to see which COM port the robot is on. You should see these screens:

Before uploading your Arduino program to the robot, in the Arduino code editor click on the <TOOLS> menu,

then <PORT> and make sure the active COM port is selected, and is showing a check mark like this screenshot:

If there’s more than one active COM port, and you’re not sure which one the Arduino is connected to, then

disconnect and then re-connect the robot and observe which COM port vanishes and comes back. That’s the

COM port you need to select in the Arduino IDE.

If you open Device Manager and look at Ports (COM & LPT) and you’re not seeing the COM port as per above

right Device Manager screenshot, or there’s an exclamation mark with a yellow triangle, speak to your

instructor because they will have to check the correct driver for your USB adapter is installed.

When you upload code to the robot, if the screen turns orange at the bottom, that means there are error

which can be mistakes in your code, etc.

Check your code very carefully for wrong characters and brackets and semicolons and keep trying until it

compiles without errors. Speak to your instructor if you can’t find the error.

1 DAY OF ROBOTICS: PART 2 PROGRAM TO FLASH LED ON ARDUINO D13

The brain of your robot is a microcontroller chip ATMEL ATMEGA 328P-PU. The ATMEGA 328 is the heart of the

Arduino UNO system which is an open source prototyping controller that allows you to control a range of on-

board and off-board systems. There is an on-board LED on the Arduino UNO, the motors on the robot are an

off-board system.

The Arduino UNO has a huge community of users around the world, many of whom help beginners get started

with online forums, there are almost endless low cost accessories, and if you wanted to invent something it’s

quite likely someone somewhere in the world might be able to help and advise you.

If you look carefully at the robot you will see it has ON-OFF switches for POWER and MOTORS. When you

connect the robot to the computer used to program it make sure the MOTORS switch is in the OFF position.

In the image on the previous page there’s a green POWER LED on the left and a red MOTORS LED on the right.

The middle LED is orange and is connected to digital pin 13. There is a breadboard where you can put

electronic parts which we will learn more about in a future robotics session.

To upload your first program to the robot go to the <FILE> menu at the top of the Arduino IDE, scroll down to

the <EXAMPLES> option and then <BASICS> and finally select the program called <BLINK> which should look

like this:

EXAMPLE CODE to MAKE LED ON D13 FLASH ON AND OFF

// FLASH LED ON D13

void setup() {

// initialize digital pin 13 as an output.

pinMode(13, OUTPUT);---

}

void loop()

{

digitalWrite(13, HIGH); // turn the LED on (HIGH is the voltage level)

delay(1000); // wait for a second

digitalWrite(13, LOW); // turn the LED off by making the voltage LOW

delay(1000); // wait for a second

}

Change the above code’s “delay” time (the numeric values you see are in milliseconds) and re-upload to the

Arduino PRIMO controller to see what happens. Remove the code from the loop and paste it into the setup

function to see what happens. Make sure the code is nested inside a set of curly brackets so you don’t get error

codes.

Watch some YouTube videos to learn more about the examples code in the Arduino IDE.

www.robotscience.co.za

www.youtube.com/mikerobotscience

www.youtube.com/electronicsafrica

NOTES

1 DAY OF ROBOTICS: PART 3 – HOW DC MOTORS WORK

In mechatronics [a fancy word for robotics] movement is produced using motors or actuators.

The robot does not have a steering mechanism like in a regular car, but turns using ‘differential

steering’ which is where the wheels turn at different rates just like an army tank in the illustration.

When the wheel on one side of the robot turns at a faster rate than the other side, then the robot

will pivot towards the side where the wheel is rotating slower. The motors on the robot have two

wires, black [or brown] is GND or 0 volts, the red wire is positive [+ or 5 volts].

Explanation of DC motors here.

CONTROLLING MOVEMENTS OF THE ROBOT

Because the servo motors are mounted on opposite sides of the PRIMO, in order to get the robot to

move forward both wheels need to turn the same way but because the motors are mounted on

opposite sides of the robot one motor will in fact be counter-rotating when compared with the other.

If you are looking at an electronic version of this page imagine folding it down the middle between

the motors to visualise how the wheels are actually rotating in the same direction. If you have a

photocopy in front of you then fold it down down the middle between the servos to see which way

the wheels are rotating on the robot.

NOTES

1 DAY OF ROBOTICS: PART 4 – PROGRAM PRIMO ROBOT TO MOVE FORWARD

In the previous section we understood how HIGH pulses control the speed and direction of the wheels. The ball

is at the back of the robot, and follows the driven wheels. If you put the ball in front it tends to force the robot

off course, which makes accurate and repeatable robot movements hard to achieve.

TEST EXAMPLE CODE THAT SHOULD DRIVE THE ROBOT FORWARD FOR TWO SECONDS:

// this code is for the yellow Keyes L298 motor shield

// this code will run the motors FWD for 1 second

// this code runs to motors at 50% duty cycle

// code last tested 20 sep 2025

int DIRA = 12; // rotation direction depends on whether this pin is HIGH or LOW

int DIRB = 13; // rotation direction depends on whether this pin is HIGH or LOW

int ENA = 3; // PWM signal is addressed to the enable pin [3]

int ENB = 11; // PWM signal is addressed to the enable pin [11]

void setup()

{

delay(2000); // STARTING WAIT-OR-DELAY

// ------------- STAGE 1 --------- drive robot forward -----------------

digitalWrite(DIRA, LOW);

analogWrite(ENA, 99); // 0 = 0% 128 = 50% 255 = 100%

digitalWrite(DIRB, HIGH);

analogWrite(ENB, 99); // was: 200

delay(1000); // original value: 1000

analogWrite(ENA, 0); // was: 200

analogWrite(ENB, 0); // was: 200

}

void loop()

{

// one shot program so nothing required here

}

ARDUINO TWO WHEEL DIFFERENTIAL STEERING ROBOT WITH DC MOTORS

If the robot reverses when you upload the drive forward program from the previous page into the PRIMO then

you need to swap the wires around, in other words the plug of the motor that is connected to D10 needs to

move to D11 and the plug of the motor that is connected to D10 needs to be connected to D11.

1 DAY OF ROBOTICS: PART 5 CONTROLLING PRIMO ROBOT: PIVOTS + TURNS

Once you have tested the code and understand how to move the robot forwards, it’s a good idea to learn how

to execute pivots + turns. If you can drive forward and turn left and right you will be able to navigate a course.

PROGRAM 1: ROBOT DRIVES FORWARD, THEN TURNS:

// this code is for the yellow Keyes L298 motor shield

// this code will run the motors FWD for 1 second

// this code runs to motors at 50% duty cycle

// code tested 20 September 2025

int DIRA = 12; // rotation direction depends on whether this pin is HIGH or LOW

int DIRB = 13; // rotation direction depends on whether this pin is HIGH or LOW

int ENA = 3; // PWM signal is addressed to the enable pin [3]

int ENB = 11; // PWM signal is addressed to the enable pin [11]

void setup()

{

delay(1111); // STARTING WAIT-OR-DELAY

// ------------- STAGE 1 --------- drive robot forward -----------------

digitalWrite(DIRA, LOW);

analogWrite(ENA, 99); // 0 = 0% 128 = 50% 255 = 100%

digitalWrite(DIRB, HIGH);

analogWrite(ENB, 99); // was: 200

delay(1111); // original value: 1000

analogWrite(ENA, 0); // this line of code stops the PWM function

analogWrite(ENB, 0); // this line of code stops the PWM function

delay(1000); // original value: 1000

// ------------- STAGE 2 --------- pivot robot to the right -----------------

digitalWrite(DIRA, HIGH);

analogWrite(ENA, 99); // 0 = 0% 128 = 50% 255 = 100%

digitalWrite(DIRB, HIGH);

analogWrite(ENB, 99); // was: 200

delay(300); // original value: 1000

analogWrite(ENA, 0); // this line of code stops the PWM function

analogWrite(ENB, 0); // this line of code stops the PWM function

delay(1000); // original value: 1000

// ------------- STAGE 3 --------- drive robot forward -----------------

digitalWrite(DIRA, LOW);

analogWrite(ENA, 99); // 0 = 0% 128 = 50% 255 = 100%

digitalWrite(DIRB, HIGH);

analogWrite(ENB, 99); // was: 200

delay(555); // original value: 1000

analogWrite(ENA, 0); // this line of code stops the PWM function

analogWrite(ENB, 0); // this line of code stops the PWM function

delay(1000); // original value: 1000

// ------------- STAGE 4 --------- pivot robot to the right -----------------

digitalWrite(DIRA, LOW);

analogWrite(ENA, 99); // 0 = 0% 128 = 50% 255 = 100%

digitalWrite(DIRB, LOW);

analogWrite(ENB, 99); // was: 200

delay(300); // original value: 1000

analogWrite(ENA, 0); // this line of code stops the PWM function

analogWrite(ENB, 0); // this line of code stops the PWM function

delay(1000); // original value: 1000

}

void loop()

{

}

To control the DC motors you use HIGH and LOW commands to switch the power ON and OFF.

The reason why one motor needs to be run forwards and the other back is because they are mounted on

opposite sides of the robot, if you send both motors the same values the robot will pivot instead of driving

forward. Now it is your turn – see if you can make the robot drive a square and triangle.

www.robotscience.co.za

www.youtube.com/electronicsafrica

www.youtube.com/mikerobotscience

1 DAY OF ROBOTICS: PART 6 ROBOTICS MAZE AND CHALLENGE RULES

1. The objective of the challenge is to evaluate the training and confirm newly acquired skills.

2. The challenge consists of a table with a start and an end point to which the robot must drive

autonomously.

3. The winner of the challenge is the robot that completes the maze first.

4. Alternately, the winner of the challenge will be the robot that drives deepest into the maze.

5. A team consists of a group of learners with one robot.

6. The competition will start at the designated time, which will be signalled by the whistle.

7. The competition will end at the designated time, when the whistle blows.

8. During practice teams will bring their robots to the competition table, and without delay place their

robot on the table and trigger the execution of the program once.

9. If a team wishes to re-test their robot [without going to their base to change and re-upload their

program] that team must go to the back of the line of teams waiting to test robots at the maze.

10. The objective of Rule 8 is to ensure everyone can access the maze without undue delay.

11. During the competition the teams will bring their robots to the competition table, and without delay

place their robot on the table and trigger the execution of the program.

12. Each team will get one start, if things go wrong and that team decides not to go back to their base to

change their code that team must go to the back of the line of teams waiting at the maze.

1 DAY OF ROBOTICS: PART 7 USING STRATEGY TO CONQUER THE CHALLENGE

Now you can move the robot forwards, and execute turns and pivots, it’s time to test your skills against the

maze challenge. There are many ways to conquer the maze, follow this method or try your own approach.

One method, that has proven effective for many teams that succeeded at this challenge, is to break your code

up into stages. Code the robot to drive forward just one fwd stage, and the first turn [Stage 2]. Upload the code

to the robot and take it to the maze and place it on the start markings. Place the robot in exactly the same

place every time you take it to the maze when testing your code. Start the robot. Observe the robot carefully.

When the robot stops after executing the first two stages it should be pointing to the next stage.

Add one more stage, then re-test the robot taking note of where it ends up. Calling out each stage of the

program code as the robot travels into the maze helps identify a stage that may require adjustment. Turns and

pivots are also stages...

Resist the temptation to add a whole bunch of stages in a hurry thinking that will save time and somehow you

will be able to unscramble the code. Yes, there is pressure because you’re competing against other robots, but

it is best to resist the temptation to simply dump a whole bunch of untested code into your robot. Rather add

one stage at a time, making sure each new stage is correct before adding the next. Below is an example of what

the starting code might look like, on the next page is an example of what the code might look like once more

stages have been added.