Class Notes

FALL 2007 - February 12 -- Anees

• Kits section now has a long list of websites / products.

FALL 2007 - February 05 -- Anees

• Links to relevant projects.
• You can download a flash swf file (drag it into your browser window) of the presentation I made on basics of electricity. Available on the course blackboard, under the item named Intro to electricity.
• Zip file containing pdfs of MKE and CRFT mags. They have some interesting and do it urself articles. Check out: CRFT vol.1 page 55 (nice low-tech project), page 153 (how to connect an array of LED's and embed them in a fabric); MKE vol. 5 page 163 (intro to sensors by Tom Igoe). (Note: references are for pdf page numbers, not actual magazine page numbers). Available on the course blackboard, under the item named diy.
• The Arduino microprocessor: Developers, Board schematic, Guide, Sparkfun online seller.
• This is the ITP Physical Computing Servo Motor Control Lab tutorial that I used for the demo at the end of the class.
• Another site to visit: Natalie Jeremijenko's work.

FALL 2006 - April 17 -- Anees

I uploaded some pages from a book on solar cells. It has tips on soldering, configurations, simple and advanced circuitry (charging batteries, reversing motor direction, reflective concentrators, solar engines).

Also, in the circuitry essentials section, I added a link to Tom Igoe's site where he explains how to use relays and transistors. This is a bit advanced, so it should only be relevant if your project requires that you have a second circuit that needs a much higherr voltage/current than what a solar cell array can provide.

FALL 2006 - April 14 -- Anees

Refer to the ciruitry essentials section to see the pdf's added that explain how to use the supplied solar cells, and how to set them up in a breadboard circuit. Remember, they really only work under direct sunlight, so substitute them with your switchable AA battery supply when working indoors. Incandescent light, when bright really close to the cell, however, will give it some energy, but maybe not more than 15 or 20% of what the sun would. Also, while it is possible to cut one cell into strips (only in a certain way), it makes it difficult to connect things, because then you have to reconstruct a parallel cell configuration using the cut strips. Soldering is the best way to attach wires to the terminals, though careful not to melt the material.

FALL 2006 - April 11 -- Anees

Working together with your classmates in the beginning might be a good idea, so you can help one another. And to reiterate what Laura said, try to just work with what you know and what we've demonstrated.

You have the following items as a kit of parts. For sensors/effectors, pick what you like to work with:

Circuitry Essentials

1. Relays and Transistors: Refer to Tom Igoe's Controlling high-current devices from a microcontroller to learn about relays and transistors. This is a bit advanced, so it should only be relevant if your project requires that you have a circuit that needs a much higherr voltage/current than what a solar cell array can provide. So The solar cell circuit acts as a switch to turn on the higher-power circuit.
2. Using the Powerfilm Cells: Refer to this pdf containing info abbreviated from the original tech spec sheet.
3. Breadboard set-ups: Refer to this pdf adapted from a website I found.
4. Wiring 3-Legged Sensors: You've seen how to connect a 2-legged light sensor, but some sensors have three legs: one is voltage in, one is ground, and one is voltage out. In the 2-leg version, you just have voltage in and voltage out. To connect a potentiometer, see image.
5. Caution: In order to prevent a short circuit (i.e. smoke and fire), a circuit must contain something to use the electricity like a light bulb or a resistor or a buzzer. These are termed loads.
6. Tip: An LED in series with a 220-ohm resistor is a wise thing to add to every circuit board you build. It will let you know whether you have power to the board correctly, regardless of what else is wrong on the board.
7. Tip: A multimeter is an indispensable tool for measuring circuit parameters like voltage, resistance, and current. It can be analog or digital, but digital makes life simpler. Using a multimeter to test for continuity is the easiest way to make sure that there is no break in your circuit. Good video tutorial from MAKE. Also, you can see the Mutlimeter Tutorial from northwestern.edu, and Using A Multimeter from doctronics.
8. Basic Sensor Circuits: This page explains how to use voltage divider circuits that incorporate various sensors (photoresistors aka photocells or light sensors, thermistors (temperature sensors), and acoustic sensors). You want more light hitting the photoresistor to result in more voltage output, or in less? Check here for the answer.
9. Power: batteryuniversity.com section explains power source configurations according to series or parallel connection of similar cells (batteries or solar cells). In short: in series, you maintain the amperage value of a single cell but add voltages; in parallel, you add amperages but maintain the same voltage as one cell.

Online helper applications

1. Resistor color decoders: See UPenn's and Danny Goodman's. Or Download and install this free application on a Windows system. Or print out my lovely chart.
2. LED circuits: LED series/parallel array wizard: This will recommend a circuit design for you. You'll need to know that a typical LED has a voltage rating of 2v and operates at 24 milliamps. Resistor Calculator for LED's: This one will give you the option to choose what kind of circuit you want: single LED, LED's in series, and LED's in parallel.
3. Voltage Divider Calculator: Bill Bowden has a Java applications here.

Sensors

1. Three-legged sensors: How do I connect a potentiometer to a circuit? See image. The Sharp IR Proximity sensor, which also has three connections, is connected in a similar way. Ask A for help with connecting it to the breadboard.
2. Reports on sensors from ITP/NYU class
3. Spectra Symbol: membrane switches and linear position sensors
4. Sensors page from Roboworld

Effectors (or Actuators)

1. About motors: specs and characteristics to know about when looking for a motor. types of motors: DC regular motor, stepper, gearhed, servo.
2. Shape Memory Alloys (muscle wires) These strand-like metal wires can be cut to desired length. (Jameco)

Kits

1. Kits list: Take a look and see if there is a kit that relates to your peoject ideas. Ideally it would be as simple and cheap as possible because you're likely going to be tweaking it. Note: This list is meant as a suggestion and I can't vouch for most of these sites (except ones I have tried myself: jameco's robotstore.com, acroname, and hvwtech) - Anees.

How things work

1. Electronics: Quick and easy (uky.edu); Electronic Circuits (Wikipedia); All About Circuits
2. Light Emitting Diodes (LED's): Working with LED's, from The Electronics Club. How light-emitting diodes (LED's) work (from howstuffworks.com)
3. The photocell: aka photoresistor (Wikipedia)

Online stores for electronics

1. Jameco
2. DigiKey
3. Allelectronics
4. Radioshack

General Links

1. Sustainability technologies (Tom Igoe)