Servo Motor Control with Arduino
*Great writeup on using a servo with Arduino and it has pictures and schemas!
* Two Arduino code examples from ITP. The first one shows one servo motor being controlled and the second one shows two being controlled.
The problem with both of the links above (which actually all are based on the exact same code) is that it assumes you have a potentiometer attached, and the servo timing is based on that. The first step would be a new function that strictly turns a servo:
int minPulse = 500; // Pulse for minimum servo position (microseconds)
int maxPulse = 2500; // Pulse for maximum servo position (microseconds)
int refreshTime = 20; // the time needed in between pulses (milliseconds)
int servoPin = 2; // you decide which pin to put the servo on!
int nowPulse = 500; // nowPulse will always store the current pulse that we're giving to the servo
int temp; // always good to have a temp variable
// this function stands on its own... all you have to do is make sure the "nowPulse" variable is updated and that it equals something between "minPulse" and "maxPulse"
function doServo() {
// pulse the servo again if rhe refresh time (20 ms) have passed:
if (millis() - lastPulse >= refreshTime) {
digitalWrite(servoPin, HIGH); // Turn the motor on
delayMicroseconds(nowPulse); // Length of the pulse sets the motor position
digitalWrite(servoPin, LOW); // Turn the motor off
lastPulse = millis(); // save the time of the last pulse
}
}
// replace this with whatever you want... read an analog sensor, arbitrarily choose a number, do something based on time... whatever. I'm choosing to listen to the computer for an instruction.
void calculateNowPulse() {
while (Serial.available()>0) { // while there are bytes to read
temp = Serial.read(); // read one
nowPulse = minPulse + 15*temp/2; // this seems arbitary but its actually just approximately precalculating: nowPulse=minPulse+temp*(maxPulse-minPulse)/255
}
}
void setup() {
pinMode(servoPin, OUTPUT); // Set servo pin as an output pin
pulse = nowPulse; // Initialize the motor position value
Serial.begin(9600); // let's get this PC connection party started
}
// the loop is super simple... figure out how long the pulse should be and then doing servo stuff
void loop() {
calculateNowPulse();
doServo();
}Submitted by seandockray on 14 February 2007 - 1:06am.
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