Quick test for servo characteristics

I got some new servos and wanted to see what their range and noise was like. Running a looping test is not very informative, and typing commands over and over is tedious. I like interactive stuff.

So I wrote up a quick program in Processing to allow you to use the  mouse or keyboard to set the angle of a servo on any pin. You just move the mouse within a white box to set the angle, or use keys for more fine control (if you're Michael J. Fox, for example). You move the mouse quickly up and down in the box to get an idea of how fast/responsive the servo is.

I hope someone finds this useful. The Processing PDE source file is pasted below. There's no code for Arduino, just the bitlash library.

Requires:

• Arduino IDE
• Bitlash Arduino library: a command-line-like interface to arduino functions and pins - http://bitlash.net/wiki/start - I used 1.1, there is also a new 2.0 RC4 which may be compatible.
• Processing IDE - processing.org

 Caveats:

• Only works for angles between 0 and 200. every servo I've ever used only has a range of at most 170 degrees, usually starting 5 - 20 degrees, ending 165 - 180 degrees. It's not hard to change if you have special servos. Using this program I have determined my new Dynam 34g servo's range to be 5-175 degrees, but I would limit it to 10-170 in order to avoid damaging them.

Possible improvements:

• Allow individual, or simultaneous control of multiple servos; the standard arduino can control up to 8, and so the bitlash code only supports 8. The Mega can control more, but this requires a small change to the bitlash servo example. There are also shields and other things which can expand the servo control capabilities, which would require more extensive changes in bitlash; in fact with a large number, it might be worthwhile developing a custom protocol.
• Put it in source control for shared access and versioning. Link to that instead of pasting source here. 

Source for ServoTestBitlash.pde:

/**
  * Quickly test servo min and max angles, speed, torque and noise, using Arduino with Bitlash library.
  *
  * 1. upload bitlash servo code to arduino (part of library examples).
  * 2. configure the variables below for the pin your servo is on, and serial port.
  * 3. run it.
  *
  * The angle is initialised to 90 degrees (roughly center).
  * Move the mouse cursor up and down in the white area to change the angle.
  * The current angle is shown at the top.
  * For more fine control, move the mouse off the screen and press W and S to increase and decrease the servo angle.
  *
  * Author: Joel Byrnes, December 2011.
  * email: arduino (at) adeptusproductions.com
  */

import processing.serial.*;

/***** modify this for your setup ******/

int servoPin = 9;
String serialPort = "/dev/tty.usbserial-A700eEtE";

/***** end modify part *****/

int pos = 90;
Serial port;
int lastMouseY;
  
void setup() {
  port = new Serial(this, serialPort, 57600);
  port.write("\n");
  setPos(servoPin, pos);

  size(350, 350);
  noStroke();
  frameRate(50);
}

void draw() {
  if (mouseY != lastMouseY) {
    if ((mouseY-50) < 0 || (mouseY-50) > 200) return;
    lastMouseY = mouseY;
    pos = mouseY - 50;
  }

  background(0);
  rect(50, 50, 250, 250);
  text("0", 10, 50);
  text("200", 10, 300);
  setPos(servoPin, pos);
}

void keyPressed() {
  if (key == 'w') {
    pos++;
  } else if (key == 's') {
    pos--;
  }
  else return;
 
  setPos(servoPin, pos);
}

void setPos(int pin, int position) {
  println(pos);
  text("angle: " + pos, 150, 25);
  port.write("servo(" + pin + "," + position + ")\n");
}