Lab 4 - Force Sensors and Photocells

Description

I took a little liberty with the requirement's for this week's lab.  Since we had just started using photocells and force sensitive resistors, I was itching to see if I could build my own photocell alarm clock.  The idea admittedly is not new, but now I felt like I had the tools to try building one.  The concept of a photocell alarm clock goes like this:  Instead of being woken up in the morning by a jarring buzzer or blaring music, why not wake up gradually as the sun is rising?

My photocell alarm clock demonstrates this principle by co-opting the FSR as an on/off switch and using the photocell as a volume control.  The green LED doesn't serve any purpose other than to visually inspect the analog input from the photocell.

I used Arduino to receive analog input from the photocell and control transmission of that data to the serial port.  I then used PySerial, appscript, and more Python to parse the serial volume data and play the wake-up song in iTunes.

Components Used

• Arduino board x 1
• breadboard x 1
• wires x many
• Force Sensitive Resistor (FSR) x 1
• photocell x 1
• 10k resistor x 2
• green LED x 1
• 220 Ohm resistor x 1
• catchy song x 1

Arduino Code

#!usr/bin/env python
# encoding: utf-8
"""
phot_alarm.py
Created by Emily Wagner on 2011-02-23.
"""

from appscript import *
import serial

   

def get_serial():
    ser = serial.Serial('/dev/tty.usbmodem411', 9600)
    buf = ''
    volume = 10
    app(u'iTunes').tracks[u'Here Comes the Sun'].play()
    #read from serial port
    while True:
        try:
            value = ser.read()
            if value == '\r' or value == '\n':
                volume = int((float(buf.strip())/180)*100)
                print volume
                app(u'iTunes').sound_volume.set(volume)
                buf = ''
            else:
                buf = buf + value
        except:
            continue #ignore non integer data that is not \r or \n

            
if __name__ == '__main__':
    get_serial()