This instructable is based on Fred Sena project that can be found on Fred Sena project.
It uses 2 steppers from CD ROM drives, an amplifier, a LM317 constant current limiter and a red laser pointer.
You can source materials from:
Amplifier Around $4
LM317 Around $3
Laser pointer Around $9, any will do but more powerful more visible and more dangerous. Use Laser safety procedures. Consider your self warned.
CD steppers FREE, dismantle preferably two identical CD ROM drives
Scanner mirrors FREE from dismantled scanner
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Principle
Principle is surprisingly simple.
Unlike common projects found on the net which use HDD heads as actuators that need some kind of mechanism to reset it to middle, usually its a rubber band, this setup doesn't need it and is more precise.
It works by energizing one set of coils by constant with LM317 and varying the other set with audio amplifier. The energized set of coils acts as aforementioned rubber band but with addition that we can varying the K factor, or how elastic the rubber band is.
Common CD ROM steppers have very small number of steps per revolution, some as low as 14 steps or around 25 deg per step.
By energizing both sets of coils the stepper shaft is set to middle and has about from 9 to 12 deg wiggle room both ways.
Step 2: Setup
CD steppers have 4 pins.
Use multimeter in continuity mode to find which pins are paired. On one CD stepper connect one pair to Left channel on the amplifier. Repeat on other CD stepper but connect it to Right channel.
You are now left with on set of unused pins on both CD steppers. Connect them to LM317. The one used has two output terminals but you can use two LM317 for better control over the CD steppers. So you could varying the elasticity of individual CD steppers.
Setup used here sets both CD steppers to same elasticity.
The polarity is not that important.
Step 3: CD Stepper Setup
Print out the attached STL. It enables you to attach CD steppers in proper orientation.
Now, mirrors are from old scanner. This is somewhat important as normal mirrors can be used but they have mirror surface behind the glass and laser beam refracts and as mirror moves it smudges the beam.
Scanner mirror has mirror surface in front of glass and has no such issue.
Cut mirrors to size.
Before hot gluing the mirrors power everything up with 5V power supply (excluding the laser) and connect the amplifier to sound source. Place a piece of sticky tape as flags on the CD steppers instead of mirrors to see in what orientation they are and try to make them at 45 deg and 90 deg to each other. Reference picture is attached.
Once satisfied hot glue the mirrors and cautiously power up the laser to check your work. Use laser safety glasses while doing this.
And that is it. Use line out from computer as input to amplifier.
With music is playing turn on the LM317 board, laser and together with amplifier slowly increase the power until you see laser dot moving.
Step 4: Additional
For more control over the laser you could use Two Channels Frequency Generator v.1.2.
Decrease frequency to 100 hz on both channels and increase the volume. Play around with Phases for both channels to get nice patterns. This will produce deep sounds and I would suggest lowering your volume on speakers.