This week we learned about pulse width modulation (PWM). This is where we use a digital signal to act like an analog signal. This happens by changing the frequency of digital pulse's through our system (which obviously corresponds to width of pulse). To learn more about PWM, duty cycle, and extended information about using digital signals to communicate in an analog world, check out this article.
This lab was really exciting for me as it was the first time we used a transduced input and used it in such a way as to immediately affect our world in a physical manner. This was really fun and I am excited about using multiple arrays of servos + motors + gears to create mechanically robust entities.
/*
Servo control from an analog input
The minimum (minPulse) and maxiumum (maxPulse) values
will be different depending on your specific servo motor.
Ideally, it should be between 1 and 2 milliseconds, but in practice,
0.5 - 2.5 milliseconds works well for me.
Try different values to see what numbers are best for you.
This program uses the millis() function to keep track of when the servo was
last pulsed. millis() produces an overflow error (i.e. generates a number
that's too big to fit in a long variable) after about 5 days. if you're
making a program that has to run for more than 5 days, you may need to
account for this.
by Tom Igoe
additions by Carlyn Maw & Rob Faludi
Created 28 Jan. 2006
Updated 10 Jun. 2008
*/
int servoPin = 2; // Control pin for servo motor
int minPulse = 500; // Minimum servo position
int maxPulse = 2500; // Maximum servo position
int pulse = 0; // Amount to pulse the servo
long lastPulse = 0; // the time in milliseconds of the last pulse
int refreshTime = 20; // the time needed in between pulses
int analogValue = 0; // the value returned from the analog sensor
int analogPin = 0; // the analog pin that the sensor's on
void setup() {
pinMode(servoPin, OUTPUT); // Set servo pin as an output pin
pulse = minPulse; // Set the motor position value to the minimum
Serial.begin(9600);
}
void loop() {
analogValue = analogRead(analogPin); // read the analog input
pulse = map(analogValue,0,1023,minPulse,maxPulse); // convert the analog value
// to a range between minPulse
// and maxPulse.
// pulse the servo again if rhe refresh time (20 ms) have passed:
if (millis() - lastPulse >= refreshTime) {
digitalWrite(servoPin, HIGH); // Turn the motor on
delayMicroseconds(pulse); // Length of the pulse sets the motor position
digitalWrite(servoPin, LOW); // Turn the motor off
lastPulse = millis(); // save the time of the last pulse
}
}
