CU ATLAS Practical electronics Motion and Servos Wayne Seltzer – Mar 20, 2017

Learning Objectives Consider how physical motion is created and managed in electronics projects Introduction to servo motors Construct a circuit to control a servo Think about how servos may be used in your project(s)

What are some types of physical motion? In small groups, discuss how motion is a part of your ATLAS project(s) or future project ideas. What type of motion? (Linear, rotational, …) What electrical/electronic devices could create this motion? How is the motion controlled?

Servos Servo motors are an easy way to add motion to your electronics projects. Originally used in remote-controlled cars and airplanes, they now crop up in all sorts of other applications. You can instruct these small motors how far to turn, and they do it for you. Most hobby servos use a standard type of 3-pin plug, with the same control signaling, which makes RC servos reasonably interchangeable. Controlled by a pulse train signal between 1 and 2 milliseconds in width. The Pulse Width Modulation hardware available on a microcontroller is a great way to generate servo control signals. Servos (and other motors) can use a lot of power, so be careful about your power supply selection. Source: https://learn.sparkfun.com/tutorials/hobby-servo-tutorial

Pulse Width (milliseconds) SERVO MOTOR SG90 Pulse Width (milliseconds) Angle Position 1.0 ms 0˚ Counterclockwise stop 1.5 ms 90˚ Middle 2.0 ms 180˚ Clockwise stop Source: http://www.ee.ic.ac.uk/pcheung/teaching/DE1_EE/stores/sg90_datasheet.pdf

555 servo controller Servo 5 volts (+) 56Kresistor (green, blue, orange) Servo 100K potentiometer 3.3M resistor (orange, orange, green) 0.022 uF capacitor labeled “223” Ground (-) Source: http://www.555-timer-circuits.com/servo-tester.html

Arduino servo controller Source: https://www.arduino.cc/en/Tutorial/Knob

Arduino servo controller File … Examples … Servo … Thumb #include <Servo.h> Servo myservo;  // create servo object to control a servo int potpin = 0;  // analog pin used to connect the potentiometer int val;    // variable to read the value from the analog pin void setup() {   myservo.attach(9);  // attaches the servo on pin 9 to the servo object } void loop() {   val = analogRead(potpin);            // reads the value of the potentiometer (value between 0 and 1023)   val = map(val, 0, 1023, 0, 180);     // scale it to use it with the servo (value between 0 and 180)   myservo.write(val);                  // sets the servo position according to the scaled value   delay(15);                           // waits for the servo to get there } Source: https://www.arduino.cc/en/Tutorial/Knob

Discussion Topics How might you use a servo in your project(s)? What would the servo(s) move? How would the servo(s) be controlled? Analog vs. Digital controller tradeoffs? What other components might you consider? (motors, stepper motors, solenoids, electromagnets, …)

Resistor Color Code https://learn.sparkfun.com/tutorials/resistors The first two bands indicate the two most-significant digits of the resistor’s value. The third band is a weight value, which multiplies the two significant digits by a power of ten. The final band indicates the tolerance of the resistor. The tolerance explains how much more or less the actual resistance of the resistor can be compared to what its nominal value is. No resistor is made to perfection, and different manufacturing processes will result in better or worse tolerances. For example, a 1kΩ resistor with 5% tolerance could actually be anywhere between 0.95kΩ and 1.05kΩ. Example 4.7kΩ resistor with four color bands Yellow = 4, Violet = 7, Red = 100 multiplier 4700 Ω (= 4.7kΩ )