1. Controlling Servos with the Arduino

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3. Types of Servos Continuous Rotation Standard
can only rotate 180 degrees
can rotate all the way around in either direction
pulse tells servo which way to spin & how fast to spin
pulse tells servo
which position to hold

4. Electronics to Control the DC Motor
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
Electronics to Control the DC Motor
DC Motor
Gears to Reduce RPM and Increase Torque of DC Motor

5. Wires to Power and Control Servos
Orange = Signal
Output Shaft
Red = 5V
Brown = Ground

6. Wiring Servo to the Breadboard
Since the servos will hooked up for a while, you should keep the wiring tidy, using short jumpers from the power bus.

7. Servos are Controlled with Electrical Pulses
time (milliseconds)
voltage (V)
5V -
0V -
20ms
pulse width varies between roughly between 1ms and 2ms
void setup() { pinMode(12, OUTPUT); }
void loop()
{ digitalWrite(12, HIGH); delayMicroseconds(1000); // hold pin 12 high for 1000μs or 1ms digitalWrite(12, LOW); // hold pin 12 low for 20ms
delay(20); }

8. What happens if you try above 2000ms or below 1000ms?
Discover what the pulses do with your servos
Complete Activity 1 and Activity 2 for each of your servos
Activity 1: Understanding pulse widths
Start at 1ms pulses
Let servo run
Record observations in a table
Direction of spin (forward/backward)
Speed of spin
Increase pulse width by 100μs
Repeat steps 2 and 3
End at 2000ms
Activity 2: Finding the servo’s stop pulse value
Locate range where direction changes
Start at lower end of range
Let servo run
Record observations in a table
Direction of spin (forward/backward)
Speed of spin
Increase pulse width by 10μs
Repeat steps 2 and 3
End at upper end of range
What happens if you try above 2000ms or below 1000ms?
Record the stop value for each servo. Suggestion: Write the value on a piece of tape that you put on the servo.
void setup() { pinMode(12, OUTPUT); }
void loop()
{ digitalWrite(12, HIGH); delayMicroseconds(1000); // hold pin 3 high for 1700μs or 1.7ms digitalWrite(12, LOW); // hold pin 3 low for 20ms
delay(20); }

9. Playing Around with Programing
Make your Arduino:
Go forward
Go in in reverse
Do a zero turn to the left continuously
Do a zero turn to the right continuously
Make a wide turn left
Make a wide turn right
Do a zero turn left/right for a limited amount of time (hint: for loop)
Go forward for some time then turn left/right

10. Playing Around with Programing
Discover what is happening with this code. Modify it to do more or something different.
“for” loop executes 200 times i = 0, 1, 2, 3, 4,
void setup() { pinMode(12, OUTPUT); }
void loop() { int i; for (i=0; i<200; i++) { digitalWrite(12, HIGH); delayMicroseconds(1000); digitalWrite(12, LOW); delay(20); }
delay(1000);
for (i=0; i<400; i++) { digitalWrite(12, HIGH); delayMicroseconds(2000-i); digitalWrite(12, LOW); delay(20); } }
create a square wave with a pulse width of 1000ms followed by a 20ms pulse
wait one second
this for loop causes the servo to go from full speed CCW (pulse width = 2000ms) to full speed CW (pulse width = 1000ms)