No Solder Light Organ




Introduction: No Solder Light Organ

This instructable is also known as the Audible Light Probe by Forest Mimms III and builds off of these great Instructables: Photothermin( and How to Make an Easy Phototheramin (

I made this instructable as I was looking for a cheap, impressive, easy to build and solder free electronics project for an intro to electronics. The biggest challenge was figuring out how to make this project work without using solder. The Huston Museum of Science published a nice Photothermin( instructable which has you tape your components on cardstock using conductive tape. As cool as that sounds I just could not get their project working. I also wanted to make this as cheaply as possible, which meant battery holders, solderless breadboards and on-off switches were out of the question.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1:

First Gather the materials:

Sorry but you won't all find the parts at Radio Shack as they don't sell a PNP transistor. I therefore purchased a large lot of transistors off of ebay

2n3906 PNP transistor
2n3904 NPN transistor (purchased 100 of each type from a ebay seller from China)
photoresistor (GL5537 from ebay)
.1 uF cap (ebay again)
4 Silver Plated Copper Cord End Spacer Crimp Tube Beads 1.5mm (ebay seller)
cr2032 3V coin cell
3x5 index card
.5 inches of copper tape

small 8 ohm mylar speaker

Step 2:

So first lets start out with the schematic. Forrest Mims III published it many years ago. It is a basic oscillator whose frequency is changed by the amount of light that strikes the photoresistor. The capacitor sets the frequency and I've found the .1 uf souns the best

Step 3:

Get an index card and poke holes in it for your components.

Start out by putting the transistors in. 3904 NPN is on the left and a 3906 PNP is on the right

Step 4: Step 4 Start Crimping

Connect the 3904 collector to the base of the 3906 and crimp the leads together

Step 5: Power Supply

the power supply consists of a clothespin with coper tape stickon the lest and right Josie of the part. Sandwich a wire and the battery between the copper tape.

Step 6: Now Add the Photoresistor

Oops, I put the 3906 transistor in backwards. The circuit still works but its not a loud as it should be.

Step 7: Add the Speaker

Messing up the polarity of the speaker won't cause any problems, just do whatever is easiest.

Step 8: Ready for Power

take the power supply and put the positive lead on the + sign and the negative lead on the - sign and listen to the wonderful sounds.

Be the First to Share


    • Backyard Contest

      Backyard Contest
    • Silly Hats Speed Challenge

      Silly Hats Speed Challenge
    • Finish It Already Speed Challenge

      Finish It Already Speed Challenge