Programming a Servo
Learn to connect wires and write code to program a Servo motor.
If you have gone through the LED Circuit and LED Blink exercises, you are ready to move on to
programming a Servo. A Servo is a motor that is programmable. There are 2 different types of Servos
that we use here in the lab, a full rotation (or continuous) Servo and a regular (or position based) Servo.
If you purchased a kit online, it may only have come with a regular Servo, but you could buy a full rotation
Servo online for around $10 if you wanted one.
 Arduino
 Servo
 Red Wire
 Black Wire
 White Wire
1. Start by opening a new sketch and erasing everything that is already there. Also don’t forget to
connect to the right port!
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2. Coding a Servo is actually quite complicated as it needs a very unique signal in order to make it work.
However, others before us have made some shortcuts for us to make it a bit easier. They made a
Programming
a Servo
library that we can reference
that controls our Servo
more easily.
To use this library, go to Sketch -> Include Library and find and click on Servo. It should come up on
your screen as “#include <Servo.h>”. This means that we are including the Servo library in
this project.
3. Use your arrow key to arrow down so you are on the next line, and then type in “Servo
myservo;”. This names your servo “myservo” but you really could call it whatever you want.
Please note, if you decide to change the name of your servo, be sure to change it everywhere and
not just here!
4. Next press Enter twice to move your cursor down, then type in “void setup(){ “ and press enter.
When you press enter, a closed bracket “}” should appear at the bottom of the code. These brackets
are like hamburger buns, you can decide what you want to put on your burger, but you always need
a top and bottom bun. Anything you type between the open bracket and the closed bracket will be
part of the setup.
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5. Our set up has one line of code, type in “myservo.attach(9);”. This means that we will attach
the signal wire of our servo to pin 9. Keep this in mind later when we go to connect our wires! Note
Programming
Servo
that we use pin 9 because
it has the ~ symbol a
next
to it which means that it generates the PWM
signal needed for the Servo.
6. Use your arrow key to arrow down, and then press Enter twice. We want the closed bracket to
remain where it is but our cursor to move down the page.
7. Next we will code the action phase of our servo, “void loop(){ “. Again, once you have typed
this in press enter and you will get a closed bracket at the bottom of the page.
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8. The last part of the code is the motion. There are 4 lines of code that will make up the action of our
servo. The first line, “myservo.write(0);” tells the big servo to spin fast to the left and tells
Programming
Servo
the small servo to go to 0 degrees.
The next line,a“delay(2000);”
tells the Arduino to wait before
reading the next line of code (so the big Servo would keep spinning to the left for 2 seconds and the
small Servo would stay at 0 degrees for 2 seconds). Next, “myservo.write(180);” tells the big
servo to spin fast to the right and tells the small servo to go to 180 degrees. The last line,
“delay(2000);” again tells the Arduino to wait for 2 seconds before reading the next line of code
(so the big Servo would keep spinning to the right for 2 seconds and the small Servo would stay at
180 degrees for 2 seconds. So the value we put in “myservo.write( );” tells it the motion to
do and the “delay( );” essentially tells it how long to do that motion.
9. Once all of your code is written, upload the code to your Arduino. If you get any errors, see
troubleshooting below.
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1. Connect your wires toProgramming
your Servo. The red wire
connects to the red wire, the black wire connects
a Servo
to the black wire, and the white wire connects to the white wire. (Remember, the color of the
wire helps us to keep things straight. This is especially true with a Servo where the manufacturer
has made red to be positive and black to be negative.) Next, connect these wires to the Arduino.
Connect the red wire to Vin or 5V (positive), connect the black wire to GND (negative) and
connect the white wire to pin 9 (the signal). Note: in my picture the white wire is actually yellow,
but they behave the same. You may also have a brown wire instead of a black wire or an orange
wire instead of a red wire, but again they behave the same.
Your servo should now be moving. Congratulations! If you have multiple Servos, test them and see how
the same code affects the different Servos.
 If you get an error when you upload, download the “Troubleshooting” document and try to find
a solution. Most common problems: missed semicolons, missed brackets, misspelled words, and
not connecting to the board.
 If your code uploads but the servo does not move, check that your wires are all in the right place.
Next, check that your “setup” looks exactly like the code above. Often students change the
number in “myservo.attach( );” but if you change this value you will need to move your
white wire to that number. You also must choose a number that can generate a PWM signal,
these are the numbers with the ~ symbol next to them (3, 5, 6, 9, 10, and 11).
1. Try to make your big servo spin to the left for 3 seconds and to the right for 1 second.
2. Try to make your regular servo go to 0° for 1 second, 45° for 1 second, 90° for 1 second, 135° for
1 second, 180° for 1 second, and then back, stopping at each of the above mentioned degrees
for 1 second each. For example, 0°, 45°, 90°, 135°, 180°, 135°, 90°, 45°, 0°, etc.
3. Try to make your big Servo spin slow to the left forever.
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4. Try a new function, random! In myservo.write( ); type in random(0, 180) and this will give a
random value between 0 and 180, meaning that your regular Servo will go to a random degree
Programming
a Servo
and your full rotation Servo
will spin in a random
direction and speed. Keep the delay big enough
to see the effect, either 1000 or 2000, or make the delay random too!
Note: Only the loop is shown in the solutions below, as the setup and pre-setup are the same for all
solutions.
Challenge 1 Solution:
void loop(){
myservo.write(0);
delay(3000);
myservo.write(180);
delay(1000);
}
Challenge 2 Solution:
void loop(){
myservo.write(0);
delay(1000);
myservo.write(45);
delay(1000);
myservo.write(90);
delay(1000);
myservo.write(135);
delay(1000);
myservo.write(180);
delay(1000);
myservo.write(135);
delay(1000);
myservo.write(90);
delay(1000);
myservo.write(45);
delay(1000);
}
Challenge 3 Solution:
void loop(){
myservo.write(80);
}
Challenge 4 Solution:
void loop(){
myservo.write(random(0,180));
delay(2000);
}
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