Part 1: Getting Started

Design Decisions:

My goal for this project was to have a real word physical object that connected to the internet and displayed information. I liked the idea of the blink(1), but since it required a host computer and cost $30.00 a pop it seemed kind of expensive based on the cost of the components. Instead I oped for a Raspberry Pi and an RGB LED strip, which I could reuse for other projects.

I liked the Raspberry Pi model A, since it was a full fledged computer and only cost $25.00 USD. ** NOTE ** Since the Raspberry Pi model A only has 256MB RAM, I noticed that it would crash when I loaded a GUI text editor, like Geany. I would recommend using command line based editors when doing development on the Raspberry Pi model A. Being new to the Raspberry Pi I wanted to learn Python, and there seemed to be a large community of Python developers, so this seemed like a logical choice. I started out developing with Python 2, but soon realized that if I wanted to use interrupt driven GPIOs, to reduce CPU polling overhead, then I would need to use Python 3. There may be interrupt based Python 2 GPIO examples out there, but I didn’t see any. Using Python 3 caused some problems for me initially, since my WS2801 chip based LED module(pigredients) wasn’t written using Python2. So I forged ahead and modified it to use Python 3. Along the way I needed to use another SPI implementation(spidev) since it was developed using Python2. I eventually settled on quick2wire’s SPI implementation written in Python3. The good news is that all of the functionality I wanted requires only about 1% CPU and 3% of the memory of a Raspberry Pi model B rev 2.

Materials Needed
  • Electronics
  • Raspberry Pi model A $25.00 USD + S&H (Model B is OK too, it just costs more)
    – 4 GB or larger SD Card for the OS $6.00 USD or more
    Edimax WiFi EW-7811Un $9.99 USD
    – Raspberry Pi case $6.50 USD (optional, but useful for insulating the Raspberry Pi from the steel outer casing)
    Panel Mount USB extension Cable $3.95 USD
    WS2801 IC based RGB LED Strip $24.99 USD + 5.00 S&H or daisy chain a couple of WS2801 Breakouts $4.95 ea + S&H

    click here to daisy chain a couple of these together.
    Inline Fuse Holder $1.97 USD ensures that if a short occurs the fuse will blow
    – Inline AC switch to remove power when needed
    – Old IDE Hard Drive cable
    – Old Computer speakers (Amplifier, Speaker)
    – 1 foot long 1/8″ male to male stereo jack. My amplifier requires a male adaptor, in addition to the Raspberry Pi
    Cable strain relief for AC power cord $5.00 USD I recommend black, since it’s less obtrusive
    solderable PCB Breadboard $3.00 or less
    push button tact switches $6.00 USD or less
    – misc 1/4 watt resistors
    3mm LED $8.00 USD or less
    – soldering iron, solder, wire, wire cutters/strippers, electrical tape or heat shrink tubing

  • Enclosure
  • Stainless Steel Wine Cooler $19.99 USD
    Silver Round Tin with Window $2.99 USD
    – Miscellaneous screws and nuts for USB extension cable and pushbutton/LED PCB
    – Plexiglass and sandpaper, a halved ping pong ball, or a section of a plastic milk jug to act as LED diffusers
    – Dremel to cut out USB port hole in Stainless steel wine cooler
    – 5/32” drill bit for push buttons and small LED
    – Large drill bits to make hole for power supply cable.

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