This example controls a servomotor. It moves a servomotor based on the value of an analog input. Thanks to Casey Reas for cleaning up the code. Thanks to Henryk Marstrander for the formula.
/*
Servo control from an analog input
The minimum (minPulse) and maxiumum (maxPuluse) 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
Created 28 Jan. 2006
Updated 7 Jun. 2006
*/
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
int 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 = (analogValue / 10) * 19 + 500; // 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
}
}
Here’s a version that controls two servos. Note that you have to reduce the refresh time to compensate for the pulse times of the servos as you add more servos. Thanks to Carlyn Maw for the update.
/*
Two-servo control from an analog input
Moves two servos based on the value of one analog sensor,
in opposite directions.
The minimum (minPulse) and maxiumum (maxPuluse) 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.
by Tom Igoe
Created 28 Jan. 2006
Repurposed for Dual Servos by Carlyn Maw
24 Mar. 2006
*/
int servoPinL = 2; // Control pin for servo motor - L
int servoPinR = 3; // Control pin for servo motor - R
int minPulse = 500; // Minimum servo position
int maxPulse = 2500; // Maximum servo position
long adjustedAV = 0; // Analog value adjusted for determining pulse values
int pulseL = 0; // Amount to pulse the servoL
int pulseR = 0; // Amount to pulse the servoR
int delayValueMax = 20000; // the 20 microsecond maxiumum pulse range for the servo
int delayValue = 20000; // the actual value the code should wait, determined later
int analogValue = 0; // the value returned from the analog sensor
int analogPin = 0; // the analog pin that the sensor's on
void setup() {
pinMode(servoPinL, OUTPUT); // Set servo pins as an output pins
pinMode(servoPinR, OUTPUT);
pulseL = minPulse; // Set the motor position values to the minimum
pulseR = maxPulse;
}
void loop() {
analogValue = analogRead(analogPin); // read the analog input (0-1024)
adjustedAV = (analogValue / 10) * 19; // convert the analog value to a number
// between 0-2000 (difference between min and max)
pulseL = adjustedAV + minPulse; // set value for left motor
pulseR = maxPulse - adjustedAV; // and the inverse for the right
digitalWrite(servoPinL, HIGH); // Turn the L motor on
delayMicroseconds(pulseL); // Length of the pulse sets the motor position
digitalWrite(servoPinL, LOW); // Turn the L motor off
digitalWrite(servoPinR, HIGH); // Turn the R motor on
delayMicroseconds(pulseR); // Length of the pulse sets the motor position
digitalWrite(servoPinR, LOW); // Turn the R motor off
delayValue = (delayValueMax - pulseL) - pulseR; // determine how much time you have before the 20 ms is over...
delayMicroseconds(delayValue); // 20 millisecond delay is needed between pulses
// to keep the servos in sync
}