Controlling Servos with the Arduino

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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

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

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

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.

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); }

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); }

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

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, . . . 199 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)