From Eric

Galvo

A "laser scanning galvanometer" (or "galvo" for short), is a piece of hardware to display patterns, texts, etc. on walls using a laser beam.

Objectives

As a followup to my previous efforts to control a CRT, I have resurrected a setup that I did quite a long time ago to control a laser beam. I have done several attempts, using a handmade galvo and a moving mirror.

Here are picture of the two setups:

There are also two short videos here and there .

Needless to say, these attempts were unsuccessful.

The first solution was much too non linear (and slow, but at that time, my idea was simply to point a laser beam to some moving object, so the reaction time was not that of a problem...). The second solution was pretty nice, but the position control was a bit weak. In any case, the speed would have been much smaller that can be achieved using an industrial product (even a very cheap one).

So I ended up buying a readymade mage galvo from China (simlilar to this one, seach for "laser scanning galvanometer"). The galvo comes with a +15/-15v power suply and two drivers (one for each mirror).

The only things that remain to be done are

to generate the ILDA signals to drive the mirrors (via the drivers) from two 0-5v signals generated by an Arduino micro and a couple of DACs (this is explained below).
to write the piece of software to the generate patterns to display.

Schematics

The schematics is basically the one proposed at [1].

Please note that the 5V used for the microcontroller / DACs is obtained from the 15V power supply. I am not sure that a genuine 7805 will appreciate the 10V shift... So I'll use some of the nice 3-pin step-down replacements such as: