1. using servos

2. DISCLAIMER & USAGE
The content of this presentation is for informational purposes only and is intended only for students attending Louisiana Tech University.
The author of this information does not make any claims as to the validity or accuracy of the information or methods presented.
Any procedures demonstrated here are potentially dangerous and could result in injury or damage.
Louisiana Tech University and the State of Louisiana, their officers, employees, agents or volunteers, are not liable or responsible for any injuries, illness, damage or losses which may result from your using the materials or ideas, or from your performing the experiments or procedures depicted in this presentation.
If you do not agree, then do not view this content.
The copyright label, the Louisiana Tech logo, and the “living with the lab” identifier should not be removed from this presentation.
You may modify this work for your own purposes as long as attribution is clearly provided.

3. wires to power & control servo
white = signal
red = 5V
black = Gnd
output shaft

4. servo components small DC motor
gearbox with small plastic gears to reduce the RPM and increase output torque
special electronics to interpret a pulse signal and deliver power to the motor

5. which way to spin & how fast to spin
types of servos
continuous rotation
standard
can only rotate 180 degrees
can rotate all the way around in either direction
pulse tells servo
which position to hold
pulse tells servo
which way to spin & how fast to spin

6. full speed counter clockwise
Arduino programming
these lines of code make the servo go full speed counter clockwise
void loop()
{ digitalWrite(7, HIGH); delayMicroseconds(1700); // hold pin 7 high for 1700μs or 1.7ms digitalWrite(7, LOW); // hold pin 7 low for 20ms
delay(20); }
full speed clockwise
pulse width
(μs)
servo action
1300
full speed CW
1400
½ speed CW
1500
stopped
1600
½ speed CCW
1700
full speed CCW
pulse width varies between 1.3ms and 1.7ms
time (milliseconds)
voltage (V)
5V -
0V -
full speed counter clockwise
20ms
speed not linear with pulse duration

7. wiring servo to breadboard

8. wiring servo to breadboard
Since the servos will likely be hooked up for a while, it is worthwhile to keep the wiring tidy, cutting short jumpers from the power bus.

9. using the servo library
both programs below cause a servo attached to pin 7 to continuously spin full speed CCW
put this statement in your program to use library don’t forget the space
void setup(){
pinMode(7,OUTPUT); }
void loop() {
digitalWrite(7, HIGH);
delayMicroseconds(1700);
digitalWrite(7, LOW);
delay(20);
#include <Servo.h>
Servo myservo1;
void setup() {
myservo1.attach(7); myservo1.writeMicroseconds(1700); }
void loop() {
“declare” the name of your servo as “myservo1” can choose any name
indicate that servo will be wired to pin 7
send a pulse of 1700 μs or 1.7ms out pin 7
this program continues to send pulses to the servo so that it continues to run
almost all of the execution time is spent on the delay(20) function and you can’t do anything else while this is happening
writeMicroseconds(1700) continues to send pulses to the servo unless the myservo1.detach() function is called
you could also send writeMicroseconds(1500) to stop the motion of the servo without detaching it
when using the servo library, you can do other things, like check whisker status, while the servo is running

10. using functions (experiment on your own to control robot path)
#include <Servo.h>
Servo myservo1; // declare servo 1
Servo myservo2; // declare servo 2
void setup() {
myservo1.attach(7); // attach right servo to digital pin 7
myservo2.attach(8); // attach left servo to digital pin 8 }
void loop() {
forward(); // go to forward function
delay(1000); // wait 1 second stop_robot(); // go to stop_robot function delay(500); // wait for 1/2 second
void forward() { // declare function named forward
myservo1.writeMicroseconds(1445); // spin right wheel counterclockwise
myservo2.writeMicroseconds(1550); // spin left wheel clockwise
void stop_robot() { // declare function named stop
myservo1.writeMicroseconds(1500); // stop left wheel
myservo2.writeMicroseconds(1500); // stop right wheel