Nuts and Volts - July 2014

Lab 4: Pot Motion Control

Now that we have a way to read an angle (not precisely but close), we will add the servomotor with the angle dial and pointer. We will then use the pot to control the position 10 times per second, and thereby control the motion of the servomotor.

Parts required:

1 Arduino 1 USB cable 1 Arduino proto shield and jumper wires 1 Potentiometer 1 100 Ω resistor

Check off when complete:

■ FIGURE 19: Servo and pot dials.

1 Potentiometer dial angle image

1 Servomotor

1 Servomotor angle dial image

1 Servomotor angle pointer image

❏ Place the following program into the Arduino IDE: ■ FIGURE 17: Pot motion control schematic.

Estimated time for this lab: 30 minutes

❏ The images for the pot dial, servomotor dial, and pointer are shown in Figure 19. You can reuse the servomotor dial and pointer from Chapter 5 if you have it. Construct the dial and pointer as discussed in Chapter 5.

❏ Assemble the servomotor dial and pointer, then plug it into the Arduino proto shield breadboard as in Figures 1, 16, and 17.

// A101_ch7_pot_motion_control 5/7/14 Joe Pardue
 
#include <Servo.h>
 
Servo myservo;  // create servo object to control a
 // servo
int sensorPin = A0;  // analog input pin
int zero = 0; // calibration reading for 0 degree
int oneeighty = 0; // calibration reading for 180

■ FIGURE 18: Pot motion control test.

void setup() {
  // attaches the servo on pin 9 to the servo
  myservo.attach(9);
 
  Serial.begin(57600);
  Serial.println(“Pot motion control rev 1.0”);
}
 
void loop() {
  int val;
 
  if(Serial.available())
  {
 char c = Serial.read();
 
 if(c == ‘a’) // get the zero degree calibration value
 {
 // read the value from the sensor:
 zero = analogRead(sensorPin);
 Serial.print(“You set 0 degree to: “);
 Serial.println(zero);
 }
 if(c == ‘b’) // get the 180 degree calibration value
 {
 // read the value from the sensor:
 oneeighty = analogRead(sensorPin);
 Serial.print(“You set 180 degree to: “);
 Serial.println(oneeighty);
 }
  } delay(100);