Let's Make Robots!

Easy Arduino Robot Tutorial - Part I

Seeks Light

UPDATE: I decided to remove the H-Bridge part, now the motors are directly connected to the AA batteries, and the Arduino is connected to the 9V battery. This little bot will move only forward.

In Part II, I will add an H-Bridge and two SPDT Bump Switches. The robot will move in both directions and void obstacles.


Hi! And Welcome to the Easy Arduino Robot Tutorial - Part I !!
For your own sake read this before you move further : ]


1 - Introduction
2 – Before Start
3 – Parts List
4 – Hello Hardware!
5 – Assemble Process
5.1 – First Car
5.2 – Second Car
5.3 – Servo and front wheels
5.4 - Batteries
5.5 - The Circuit
5.6 - The Servo
5.7 - LDR
6 - Program!!!


1 - Introduction

In this tutorial you will see that you don´t have to be an electronic guru, or a super skilled programmer to make a simple, easy and funny robot.

It won´t have any IR sensor or ultrasonic.

So what will this robot do.. you may ask..
It will be an insane light seeker!!


If you decide to follow this tutorial, at least you should be able to use a breadboard, and if possible to do a little solder, and a bit of hot glue.


2 – Before Start


Have you ever used one BREADBOARD ?

Here you have a nice tutorial and explanation on the way it works:


In section 4 I will show you how to read analog inputs and how to make one servo move but..

If you don´t know:
-    how to blink an LED;
-    read a potenciomenter analog input;
-    use the Serial command;
-    understand the basics of OOP (Object Oriented Program).

I advice you to visit this links:

Getting Started with Arduino

Here is a nice set of tutorials:




Always take one step at the time. Every time you assemble something test it, and if successful, move to the next step.
This is a good practice, and it will make you save precious time and patience.


3 - Parts list:

Generic parts:

1 Arduino Diemicila
1 Breadboard
1 Servo
2 LDR (Light Dependant Resistance)
2 10k resistors
2 On / off switchs
5 - 1 Ohm resistor
Prototype Wires (colored if possible)

Customizable parts:

Batteries - it depends on your motors needs

I will use:

1 9V battery  with power plug to connect to the Arduino
3 AA NiMh to power the motor


I choosed to use toys instead of premade parts. It is faster to get them and they are also cheap, and fun to work with, the other reason is: it enhances your criativity and you get used to be a solution finder.


In 1 Euro stores, or chinese stores you can find lots of cheap toys, waiting to be vandalized!  : )

This was 5€ and I will use it´s chassis as platform


This little car was 2€ and I will use it´s front wheels for steering.


4 - Hello Hardware:

LDR - Light Dependant Resistors

This part is for beginners in Arduino, I will show briefly how to move a servo, and read analog inputs through LDR´s.


Reading LDR analog inputs:

The LDR can be placed in either way and also the resistors. This means they don´t have a + or - .


Take one wire and connect into one Arduino Analog Pin of your choice



Now for the Servo:

Before you use the servo code, you must install Servotimer1 library. Unpack it into your hardware/libraries folder to add the library. Then restart the Arduino Software.

Take the black wire that comes from the servo and plug it into the black line on the breadboard, the Red wire into the red line on the breadboard, and the Yellow wire into the Arduino pin 9.

Take two more wires and connect the 5V on the Arduino into the red line on the breadboard and the GND on the Arduino into the black line on the breadboard.

The Arduino can be powered from USB cable.



Now that you are more familiar with Arduino bits and bytes, LET THE FUN BEGIN   :D


5 – Assemble Process

5.1 – First Car

Disassemble the car wich will provide platform for components and also traction system, and remove all the parts except the rear wheels and the motor.


Solder two cables to the motor pins.


Also soldered one black wire to the Ground pin on the battery case and one red wire to the power switch.

This was the first and the last time you see solder in this tutorial.     :)


5.2 - Second Car


Another little car was vandalized, this time I will use the front wheels to have the steerings.


5.3 - Servo and Front Wheels:


This is not a very pretty glue work i know..  try to center the wheels the best you can.

Next, I used hot glue to place the servo next to the chassis.

ATTENTION: Certify that both wheels touch the ground when turning, otherwise you might have problems.


Left wheel doens´t touch the ground = PROBLEM


Both wheels touch the ground = Problem solved      : ]


5.4 - Batteries

I was lucky with this little car. The 9V battery fits perfectly inside the chassis,  and I can use the 3 AA batteries case, and save space to put the breadboard on the top.



5.5 - The Circuit

The Arduino is plugged from the 9V battery.
Red and black wires connect the 5V and Ground from the Arduino to the breadboard main row´s.


Now connect the Red wire from the AA batts into one row of the breadboard


Next, I will use five resistor´s of 1 ohm between the motor and the 3 AA batts.

This is low value resistors, each one of this resistors will make the motor go slower.

I could use only one resistor of 5 ohms, but using five of 1 ohm, I can have more control on the motor power.

If I want less or more motor power, I will remove or add another 1 ohm resistor.

This way the motor won´t burn out and it still have a good speed.


Note the Ground wire is connect to another row.


And this way I connect the motor wires. Turn on the power and see if it moves forward and if has enough power to drive your robot.


5.6 - The Servo


Connect the Servo to the breadboard.


Grab two wires and connect it into the breadboard main row´s 5V and Ground.
Grab another wire and connect the Servo Signal wire into Digital Pin 9 on the Arduino.


5.7 - LDR

Final step:

Place the LDR and resistors, they don´t have + or -. So you can place them in any direction.

The green wires to connect them into the Arduino Analog Input Pins 4 and 5.


( test the LDR as you did before)


This is the final look of our circuit.
Every physical steps are done! So now let´s upload some code into the Arduino.


6 - Program!!!

Robot Program


I´ve made the LDR antennas longer so it can be more sensitive to light variations.


I hope you find this tutorial usefull!!  And I hope to see your Arduino robots posted soon  ;)

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Thank you for your answer

Where do you buy your resistors of 1 ohm ? 

anywhere else you can buy resistors from. I even have supposedly 0 ohm resistors (in reality, just a piece of wire with a resistor casing on it, it does of course have a resistance, its just low)

iam beginner with arduino, have a small issue. Seems as if only one LDR is sensing. IN console I can see deflections in reading, when light falls on the LDRs, but servo is taking only one direction. When I point light on second LDR, servo doesnot show only movements. Please help.....!!

Does it make a difference if i use an arduino uno rev3 atmega328 instead of the diemicila? 

did u try it on Rev 3?

i have a big problem too!!!

what about the code?

hey dude, so i'm still in the process of buying all the stuff, but i notice some errors whenever i try to verify the program

but if you know a little bit about programming, i think it's possible to see what's wrong and try to fix it :/

As for the code, all you have to do to make it compile (at least - I don't say work because I haven't tested it) is:
on line 33 change the "#include <ServoTimer1.h>" to "#include <Servo.h>" and
on line 34 change the "ServoTimer1 servo;" to "Servo servo;"


i tried to make those changes you said, on line 33 and 34

But i'm still facing erros. 

What kind of errors does it give you?
What version of Arduino IDE are you using?

I am using v1.0 and it compiled without any errors.