[Laser] Stepper motor control of laser communication unit

[Jim Moss]

Kerry,

The stepper motor approach works pretty good.
I use a pair of "BIG" compumotor drives that were used for disk drive servo
writing. I put a pair of mirrors (x,y) and used them for pointing the beam.

The 1/10000 of a turn (0.6mR)is still a bit course.  
Typical beam divergence is about 2mR (0.1 degrees). 360 degrees = 2*PI radians.
If you run thru a 10:1 beam expander, divergence will drop by 10 to 0.2mR.
So you might want to use some mechanical leverage to reduce movement.

I ran my 1/50000 steppers into a leadscrew system that stepped it down to 10uR.

Jim
N9JIM/6
 
--- Kerry Banke <kbanke at qualcomm.com> wrote:

> Chuck (WB6IGP) & I recently picked up some surplus  Oriel StepperMike 18503 
> units. These are basically  stepper motor replacements for standard 
> micrometer heads.  I just recently finished a breadboard to drive a pair of 
> these units using the Allegro 5804 ICs.  The driver breadboard  provides 
> Az/El  control using either  a joystick or automatic  raster scan mode. 
> Last night I  replaced the manual micrometers on my laser communicator with 
> the Steppermikes and  played a bit. These units are everything I had hoped 
> for & more. Talk about smooth & precise  control of pointing!  I'll  put 
> together a short Word document soon including the schematic & a few 
> pictures of the unit and will send it upon request. Measuring the 
> motion  with a digital indicator, the linear motion is about 1/10000 " per 
> step.    If anyone is serious about making such an addition to their  hobby 
> optical communicator unit, contact either Chuck or myself. Were looking at 
> laying out a crude circuit board to ease duplication.
>   - Kerry N6IZW -
> 
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