Question

I have just gotten started with Arduino and barely have any idea about more of the advanced stuff. It seems pretty straightforward. Now I’m one who usually likes to integrate two devices together, so i was wondering if i could control a servo with the computer’s keyboard or two hardware push buttons attached to the Arduino board.

In case it helps, I’m using an Arduino Uno board. Here is the example code i am using to sweep the servo for now

// Sweep
// by BARRAGAN <http://barraganstudio.com> 
// This example code is in the public domain.


#include <Servo.h> 

Servo myservo;  // create servo object to control a servo 
            // a maximum of eight servo objects can be created 

int pos = 0;    // variable to store the servo position 

void setup() 
{ 
  myservo.attach(11);  // attaches the servo on pin 9 to the servo object 
} 


void loop() 
{ 
  for(pos = 0; pos < 45; pos += 1)  // goes from 0 degrees to 180 degrees 
  {                                  // in steps of 1 degree 
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(10);                       // waits 15ms for the servo to reach the position 
  } 
  for(pos = 45; pos>=1; pos-=1)     // goes from 180 degrees to 0 degrees 
  {                                
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(10);                       // waits 15ms for the servo to reach the position 
  } 
}

1. Now, let’s say I wanted to change the servo’s angle via pressing the
   left/right arrow keys on my computer’s keyboard. How would i go
   about doing that?

2. Alternatively, what if i attached two push buttons to the Arduino,
   and pressing one would move the servo either left or right depending
   on the the button. Which ports would i plug the buttons into? Any
   code samples or diagrams would greatly help!

Answer 1

To move a servo attached to an arduino attached to a computer you will need two components.

You will need software on your computer to accept keyboard commands and send commands to the arduino via the serial port. I would recommend a language like python or java to do that as a simple app can written quite easily.

Check this playground link for an example of using Java. And for an example in python check out this project.

There is a bug/feature built into the arduino that will give you grief as you go on here. The arduino is designed to auto reset when a serial connection is made to it via usb. This page has a detailed description of the issue and cites several ways to deal with it.

You will need to modify the sketch on the arduino to listen to the serial port and adjust the servo’s position based on the commands received from your computer. Check out the python link above. It is an complete (hardware, pc software and arduino sketch) project designed to do something very similar to what you are trying to do.

I recommend you start with either component and try to get it going. As you run into problems, post your code and someone will be glad to help further.

As for the second question, adding buttons to the arduino is fairly simple. You will connect them to digital inputs. There are hundreds of examples on the web. Search for “add button to arduino” and see what you get. (lol… 1.3 million hits). Here again, try it and post specifics for more help.