Controlling a servo motor with a touch sensor

Question

I want to modify my code to move a servo motor only for the duration of time that the sensor is touched and stop moving immediately when the sensor is no longer touched. The code I have moves the sensor from 0 to 90 and back. That motion is completed even when you remove your finger. I want it to be such that if you remove your finger before the servo reaches 90 degrees the servo stops. And the servo starts up again toward 90 when touch resumes. This is the code I currently have:

//when signal output is high the sensor is being pressed

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
int pos = 0;    // variable to store the servo position
int sensor=11; //initialises component to arduino digital pins
led=13;

void setup() {
        myservo.attach(9);
        pinMode(led,OUTPUT);
        pinMode(sensor,INPUT);
        Serial.begin(9600);
}

void loop() {

        int value=digitalRead(sensor);
        if(value == HIGH){
                digitalWrite(led, HIGH);
                for (pos = 0; pos <= 90; pos += 1) {
                        myservo.write(pos);              // tell servo to go to position in 
                        variable 'pos'
                                delay(15);                       // waits 15ms for the servo to reach the 
                        position
                }
                for (pos = 90; pos >= 0; pos -= 1) { // goes from 90 degrees to 0 degrees
                        myservo.write(pos);              // tell servo to go to position in 
                        variable 'pos'
                                delay(15);
                }
                Serial.println("TOUCHED ");
        }else{
                digitalWrite(led, LOW);

                Serial.println("NOT TOUCHED ");
                delay(500);
        }
}

Answer 1

To solve your problem, you need to take a tiny step into real time programming. Most Arduino programs deal with one issue or action at a time. Your simple twist to interrupt and action "i want it to be such that if you remove your finger before the servo reaches 90 degrees that's where the servo stops" requires you to continuously monitor your input (touch switch) while changing your output (next servo position).

You can go about this 2 ways. You can use interrupts to inform you when the state of the touch switch changes. This is challenging. Many find it difficult to conceive of what might happen if their program were to be interrupted at any and all possible points in its execution. A mistake here can lead to unexpected results.

Or you could take turns polling the state of the touch switch then making a small adjustment in the position of the servo. When the state of the touch switch changes from active to not-active, exit the loop you are using to change the servo position.