Arduino based applications-part 3

Servo Motors
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• A servo is a motor with a feedback system that helps to
control the position of the motor.
• Servo motors are small in size but pack a big punch and are
very energy efficient. Because of these features, they can be
used to operate remote-controlled or radio-controlled toy
cars, robots and airplanes. Servo motors are also used in
industrial applications, robotics, in-line manufacturing,
pharmaceutics and food services.
• Servo motors are great devices that can turn to a specified
position. Usually, they have a servo arm that can turn 180
degrees.

Servo Motors
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There are so many types of servo motors:

Servo Motors
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Servos are clever devices. Using just one input pin, they receive
the position from the Arduino and they go there. Internally, they
have a motor driver and a feedback circuit that makes sure that
the servo arm reaches the desired position. But what kind of
signal do they receive on the input pin?
It is a square wave similar to PWM. Each cycle in the signal lasts
for 20 milliseconds and for most of the time, the value is LOW. At
the beginning of each cycle, the signal is HIGH for a time
between 1 and 2 milliseconds. At 1 millisecond it represents 0
degrees and at 2 milliseconds it represents 180 degrees. In
between, it represents the value from 0–180. This is a very good
and reliable method.

Servo Motors
To build such application, you need the following
components:
1. Arduino Uno
2. USB cable
3. Micro Servo Motor 180 degrees
4. Jumper wires
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Servo Motors
// Include the Servo library
#include <Servo.h>
// Declare the Servo pin
int servoPin = 3;
// Create a servo object
Servo Servo1;
void setup() {
// We need to attach the servo to the used pin number
Servo1.attach(servoPin);
}
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The following code will turn a servo motor to 0 degrees, wait 1
second, then turn it to 90, wait one more second, turn it to 180,
and then go back.

Servo Motors
void loop(){
// Make servo go to 0 degrees
Servo1.write(0);
delay(1000);
Servo1.write(90);
delay(1000);
Servo1.write(180);
delay(1000);
}
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Servo Motors
10
More things about servos:
•Controlling the exact pulse time
Arduino has a built-in function servo.write(degrees) that simplifies
the control of servos. However, not all servos respect the same
timings for all positions. Usually, 1 millisecond means 0 degrees, 1.5
milliseconds mean 90 degrees, and, of course, 2 milliseconds mean
180 degrees. Some servos have smaller or larger ranges.
For better control, we can use the servo.writeMicroseconds(us)
function, which takes the exact number of microseconds as a
parameter. Remember, 1 millisecond equals 1,000 microseconds.

Servo Motors
11
• More servos
In order to use more than one servo, we need to declare multiple
servo objects, attach different pins to each one, and address each
servo individually. First, we need to declare the servo objects—as
many as we need:
// Create servo objects
Servo Servo1, Servo2, Servo3;
Then we need to attach each object to one servo motor. Remember,
every servo motor uses an individual pin:
Servo1.attach(servoPin1);

Servo Motors
12
• Continuous rotation servos
There is a special breed of servos labelled as continuous rotation
servos. While a normal servo goes to a specific position depending
on the input signal, a continuous rotation servo either rotates
clockwise or counter-clockwise at a speed proportional to the
signal.
For example, the Servo1.write(0) function will make the servomotor
spin counter-clockwise at full speed. The Servo1.write(90)function
will stop the motor and Servo1.write(180) will turn the motor
clockwise at full speed.

Relay
• A relay is an electrically operated switch. Many relays use an
electromagnet to mechanically operate a switch.
• Relays are used where it is necessary to control a circuit by a low-
power signal (with complete electrical isolation between control
and controlled circuits), or where several circuits must be
controlled by one signal.
• There are many types of relays as follows:
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Relay
How Relays work:
When power flows through the first circuit (1), it activates the
electromagnet (brown), generating a magnetic field (blue) that
attracts a contact (red) and activates the second circuit (2). When
the power is switched off, a spring pulls the contact back up to its
original position, switching the second circuit off again.
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Relay
• Normally Open (NO) relay:
Normally open relays are the most common; the contacts in
the second circuit are not connected by default, and switch on
only when a current flows through the magnet.
• Normally Closed (NC) relay:
The contacts are connected so a current flows through them
by default and switch off only when the magnet is activated,
pulling or pushing the contacts apart.
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Relay
To build such application, you need the following
components:
• Arduino Uno
• USB cable
• 5v relay
• AC power source
• A lamp (or any device that has to be controlled).
• Electrical wires
• Jumper wires
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Relay
A simple example shows how to control a lamp using
a 5v relay.
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Arduino based applications-part 3

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Arduino based applications-part 3