Description

As you fly around a Google Earth, the pinwheel spins in proportion to your horizontal speed.

Components

• DC Motor
• Transistor
• Resistor
• Diode

Arduino Code

I reused some code from some of the lab examples in my Arduino code

// serial input vars

char serInString[100];

char cmd;

int motorPin = 9; // select the pin for the Motor

int val;

void setup() {

  Serial.begin(9600);

  analogWrite(motorPin, 0);

}

void loop() {

  readSerialString(serInString, 100);

  cmd = serInString[0];

  if (cmd == 's') { // if we should spin

    val = atoi(serInString+1);

    analogWrite(motorPin, val);

    Serial.print("Spin: ");

    Serial.println(val);

  }

  resetSerialString(serInString, 100); 

  delay(100);          // Python does weird things if the lines come in too fast

}

//read a string from the serial and store it in an array

//you must supply the array variable

void readSerialString (char *strArray, int maxLength) {

  int i = 0;

  if(!Serial.available()) {

    return;

  }

  while (Serial.available() && i < maxLength) {

    strArray[i] = Serial.read();

    i++;

  }

}

void resetSerialString (char *strArray, int length) {

  for (int i = 0; i < length; i++) {

    strArray[i] = '\0';

  }

}

Python Code

Requires the pyserial module for Python (http://pyserial.sourceforge.net) and the appscript module (http://appscript.sourceforge.net) . . . and a computer running OS X. Many thanks to Hannes Hesse for showing me how to control Arduino with Python (my code was partiall lifted from his). I should also point out that this code works fine, but freezes after a few minutes and leaves a process that seems unkillable.

from serial import Serial

from appscript import *

from math import sqrt

def normalize(x):

    """Normalizes x to a value in the 0 to 255 range"""

    n = x / 1 * 255

    if n > 255: n = 255

    if n < 0: n = 0

    return n

if __name__ == '__main__':

    ser = Serial('/dev/tty.usbserial-A4001nLM', 9600)

    gearth = app('Google Earth')

    viewinfo = gearth.GetViewInfo()

    lastx = viewinfo[k.longitude]

    lasty = viewinfo[k.latitude]

    while 1:

        viewinfo = gearth.GetViewInfo()

        currx = viewinfo[k.longitude]

        curry = viewinfo[k.latitude]

        currvelo = sqrt(abs(currx - lastx) + abs(curry - lasty))

        print 'current velocity: %d' % currvelo

        ser.write('s%d' % normalize(currvelo))

        lastx = currx

        lasty = curry

    ser.close()

Picture

WindyFlight