Class Syllabus → Class Schedule Page → Academic Integrity Policy → Piazza Page

Assignment 3: LED Circuit and Motor

due Nov. 13 (Friday) @ 11:59pm

This is a short assignment, intended to give you a chance to experiment with hardware and engage in some creative problem-solving. The writeup will ask you to describe what you did and how you solved the additional problems given. If you have elected to work with a partner, you should make sure each person has a chance to think about and understand each part of the homework, and writeups will be separate, but you can freely discuss answers.

Components

You should have the following:
  working in pairs
• 1 breadboard  
• 1 battery case  
• 1 AA battery  
• 2+ resistors
100Ω OR 1000Ω 		• 4+ resistors
• 2 LEDs • 4 LEDs
• 1 length copper wire • 2 lengths
• 1 magnet  

Steps

Step 1: Build an LED circuit board

The goal here is (1) to build a board with one or more steadily glowing lights, and (2) to add an on/off control of some sort. The goal here is not to wire in an existing on/off switch, but to come up with a creative solution of your own for activating and deactivating a light with what you have.
  1. Build a board on which one or more LEDs is glowing steadily.
    • For this, please use the components given.
  2. Manufacture some sort of on-off controller for your LED.
    • Your circuit must be in one piece whether on or off.
    • Your circuit must remain in the last state set (on or off) without being touched (e.g., no holding something down).
    • Turning it on and off cannot involve plugging/removing something from the board.
    • For this step, you MAY use other objects (except manufactured two-state switches or push buttons), but don't need to.

Step 2: Build a simple DC motor

The goal here is to build a simple DC motor that takes electricity as input and produces torque (that is, spins). There are a large number of tutorials on this exact problem available (here is one), and I recommend looking at several. The goal of this piece is to get some experience with the level of precision (and sometimes troubleshooting) building such a system can entail.

Step 3: Writeup

The writeup for this project will describe the building process for Steps 1 and 2, and answer some questions about the technology you have constructed.

1

2

  • Describe the way you constructed the motor and, especially, any problems you had. What kind of troubleshooting was necessary (unless it worked perfectly on the first try)? What changes did you make?
  • How does this motor work - that is, in your own words, how does this construction produce torque? (Basically, explain DC motors.)
  • What are a few ways you might...
    • ...improve the strength of the torque on this system?
    • ...speed up the rotation? (Are those the same thing or different problems?)
    • ...make it easier to construct and reduce errors?
    • Consider these answers in terms of physical layout (especially distances), strength of battery and magnets, specific electrical components, and the like.
  • Include a picture of the finished motor.

Both

  • The names of anyone you helped or were helped by, and a little about what the help was.
  • All sources you used (web pages, books, etc).
  • Approximately how much time you spent on each step of the process.
  • The thing(s) you found hardest and any errors/problems you ran into.

Turn in:

  1. A writeup of the process, as described in Step 3. This can be EITHER a PDF file mailed to the instructor, OR a web page, in which case you will email me the URL.
  2. A demonstration of your circuit and motor in class on the 12th, OR a video of each (including the action of the on/off mechanism) mailed to the instructor.