I found this.

https://www.instructables.com/id/HOW-TO-MAKE-ADVANCED-LASER-PROJECTOR/

On its face it looks pretty simple as there are few components. But I the instructions are HORRIBLE! I have seen some really bad Inscrutables before but this one takes the cake.

For starters he doesn't even have a proper BOM. No quantity for most items. He lists transistor but doesn't even give NPN or PNP let alone a part number. There are no dimensions for anything.

He shows what looks like a low current general purpose transistor but I have no idea what he is doing with it.

Anyone have any idea there?

And then there are the mirrors. He never explains how they are attached to the motors. And why are they being spun if they are mounted in the center? What is going on there?

 

Ohh it's a box-o-mess!

in this case, you just want to take the basic idea and make a better one.
It's a bunch of mirrors mounted helter-skelter on little DC motors, bounce the laser beam between the mirrors, vary the motor speed to create various patterns. The key is getting the mirrors mounted so they don't vibrate too much, with a little bit of tilt, to modulate the beam position.

I'm sure it's actually quite cool looking and fun to play with.

 

OK so that is it then. They are not mounted flat?

What is the deal with the transistor??? I would think those motors would take too much current for that transistor.

And that is the plan to make it better.

 

I'll bet the transistor is for a crap-tastic speed regulator for the motor, probably an emitter-follower buffering the voltage from a pot.

If you mount the motors flat, they do nothing, the magic is the slight tilt angle.

 

I'll bet the transistor is for a crap-tastic speed regulator for the motor, probably an emitter-follower buffering the voltage from a pot.

If you mount the motors flat, they do nothing, the magic is the slight tilt angle.

Mount the motor at an angle or the mirror? Wouldn't the mirror need to wobble when it spins?

 

You do want the mirror to wobble, but still be centered, so it doesn't vibrate like crazy.