Create a functional circuit diagram that makes an instrument controlled by brightness of light!

This is one of the 48 projects for our Instructables: Made In Your Mind (IMIYM) exhibition at the Children’s Museum of Houston showing from May 26, 2012 - November 4, 2012. Produced in partnership with Instructables, IMIYM is an exhibit where families work together to build different fun, toy-like projects that help construct knowledge and skills related to science, technology, engineering, and mathematics while instilling a “do-it-yourself” attitude in kids so they feel empowered to explore, tinker, and try to make things themselves. To learn more, check out the article here.

For this project, we were inspired by the How to Make an Easy Phototheramin Instructable created by TigrisLi (which, as I discovered is based on the Audible Light Probe by Forrest M. Mims III of Radio Shack books fame) , but there may be others on Instructables that are also similar. Often, the materials and process for building our projects are designed for use with a large number of visitors (we see over 800,000 annually) and the need to ensure safety in a mostly non-facilitated environment (in other words, no soldering). So, yes, many of these projects have room for improvement in both materials and methodology, which is PRECISELY what we want to encourage the kids to do. So please do share your ideas for improvement and modifications!

Step 1: What You Need

We are selective in our materials for cost, ease of use, and safety due to our high traffic (800,000 visitors annually). So, for our purposes, this design worked best. But you may have other ideas - please share! Most of the electronic components you should be able to get at Radio Shack or similar, but I've listed below where we purchase ours in bulk
  • 1 - 2N3904 Transistor (we buy ours from Jameco)
  • 1 - 2N3906 Transistor (again, from Jameco)
  • 1 - 0.1μf Ceramic Capacitor (once again, Jameco)
  • 1 - Photocell (yup - Jameco)
  • 1 - 40Ω 0.2W Speaker (this is from All Electronics)
  • 2 - CR2032 Coin Battery (from Batteries and Butter)
  • 36 inches – Copper tape (you can get this from craft stores that sell stained glass supplies. Since we need so much, we purchased ours through Amazon)
  • 1 – Phototheramin Template (see attached file below - the project can be done without the template, but it helps, especially if you aren't familiar with circuits)
  • 1 – 5”x7” Chipboard (cereal box cardboard will work, but we purchase ours in bulk from U-Line)
  • 1 – 1” Double-sided foam tape (for most people, just pick up a roll. We purchase individual squares from U-Line to help reduce waste 
  • Scissors
  • Masking Tape
  • Hole Punch

<p>Cool project. Kids will learn so much from this DIY project.</p>
<p>Would a piezo buzzer work in place of the speaker? Thank you in advance...</p>
I couldn't get this working with the copper tape either. Has anyone figured out how to make this circuit without solder?
Sorry you're having problems. Three possible issues and solutions: <br>1. We've discovered is that sometimes people get the transistors in the wrong place or backwards. Check to make sure they are put in correctly. <br>2. Sometimes leads are corroded or otherwise don't have good conductivity. Sand them gently to remove any corrosion and make sure to tape them on tight. <br>3. Some tape is conductive on both sides while others are conductive on one side (sadly, no packaging to tell us). So, where the tape must overlap to create a completed circuit, it doesn't work (I'm hoping that makes sense). My suggestion to solve this is to use wire to connect separate strips of tape instead of overlapping strips of tape. <br> <br>I hope one of these solutions works out!
<p>Actually the 3904 transistor on your build sheet is in backwards. The circuit is a type of relaxation oscillator, the collector of the 3904 should be connected to the base of the 3906. I tried it both ways and it is much louder if you flip the 3904 180 degrees, pin 3 to middle pin of 3906 and pin 1 to ground.</p>
I REALLY wanted this to work! Auugh, I'm sitting here with my attempt at this project and it is not working. Would love to do it with Middle School students, but if I can't do it, I can't expect a classroom to do it. <br> Would love to see how you do this project with museum participants.
Super instructable! <br> <br>One question though: can you give me more specifics about the photocell? <br> <br>I can only find really expensive ones online. <br>And I don't know much about electronics.. <br>So can you help me out?!
Great Instructable. Well done mate.

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