Using Hobby Servos with the Arduino living with the lab © 2012 David Hall

living with the lab 2 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. DISCLAIMER & USAGE

wires to power & control servo 3 living with the lab red = 5V black = Gnd white = signal output shaft

servo components 4 living with the lab 1.small DC motor 2.gearbox with small plastic gears to reduce the RPM and increase output torque 3.special electronics to interpret a pulse signal and deliver power to the motor

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

Arduino programming 6 living with the lab void loop() { digitalWrite(3, HIGH); delayMicroseconds(1700); // hold pin 3 high for 1700μs or 1.7ms digitalWrite(3, LOW); // hold pin 3 low for 20ms delay(20); } these lines of code make the servo go full speed counter clockwise time (milliseconds) voltage (V) 5V - 0V - 20ms full speed clockwise full speed counter clockwise pulse width varies between 1.3ms and 1.7ms pulse width (μs) servo action 1300full speed CW 1400½ speed CW 1500stopped 1600½ speed CCW 1700full speed CCW speed not linear with pulse duration

wiring servo to breadboard 7 living with the lab 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. The red wire from the power bus should go back to Vin or 5V, and the black wire should go back to Gnd.

playing around with programing 8 living with the lab “for” loop executes 200 times i = 0, 1, 2, 3, 4, void setup() { pinMode(3, OUTPUT); } void loop() { int i; for (i=0; i<200; i++) { digitalWrite(3, HIGH); delayMicroseconds(1300); digitalWrite(3, LOW); delay(20); } delay(1000); for (i=0; i<400; i++) { digitalWrite(3, HIGH); delayMicroseconds(1700-i); digitalWrite(3, LOW); delay(20); } } this for loop causes the servo to go from full speed CCW (pulse width = 1700  s) to full speed CW (pulse width = 1300  s) create a square wave with a pulse width of 1300  s followed by a 20ms pulse wait one second