Moving servo with potentiometer

Using Arduino Programming Questions
1

Does this code look right?

#include <Servo.h>
Servo servoMain;
int potPin = 2; // Analog port of potentiometer
int maxRot = 160; // Max rotation of Servo
int maxReadPot = 1023; // I read up that the analog ports read values from 0(0V) to 1023(5V)
float conv = maxRot/maxReadPot; // Converting the maxReadPot into angle measure for servo
int val = 0;

void setup()
{
servoMain.attach(3); // servo on digital pin ~3
}
void loop()
{
val = analogRead(potPin);
servoMain.write(val*conv);
}

So my issue is that no matter what rotation I turn the pot to, the servo is at 0 degrees.

Note: I'm a beginner, and if this code is correct, I'm going to assume my wiring is funky.

2

You do not say which Arduino you have, but pin 2 is unlikely to be an analog port. Perhaps you intended A2? It would help if you would:

  • Tell us what Arduino you have
  • Show us in a schematic or diagram how you have hooked things up.

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Good Luck!

3

Serial.println the Val. That will let you know if your pot is wired properly.
In setup, after you attach, servo.write(180) then delay(1000) then servo.write(0) then delay(1000)
That will let you know if your servo is wired properly

Are you powering the servo from the arduino 5v? This is troublesome at best. The arduino cannot provide the current a servo requires. Power the servo separately with common grounds.

4

Thanks, Vaj, I will take that into consideration on my next post.

I did manage to fix the issue, I changed these lines of code:

val = analogRead(potPin); 
servoMain.write(val*conv);

to:

val = analogRead(potPin);
val = map(val, 0, maxReadPot, 0, maxRot);
servoMain.write(val);
5

Make life simple.

analogRead() produces a value from 0 to 1023.
servo.Write() needs a value from 0 to 180 - about 1023/ 6
servo.writeMicroseconds() needs a value between 1000 and 2000

so either

val = analogRead(potPin);
servoMain.write(val / 6);

or (more accurate and faster)

val = analogRead(potPin);
servoMain.writeMicroseconds(val + 1000);

Avoid floating point maths wherever you can as it is very slow on an Arduino.

...R

6

FYI : When you divide 160 by 1023, both integers, the result is 0. When you assign that to the float variable 'conv' it gets changed to a float: 0.0. If you don't want the result to be truncated you have to convert one or both of the int values to float BEFORE the division.