Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> 
> On Sat, 08 Jan 2005 18:24:37 -0000, gettingalongwouldbenice  
> <gettingalongwouldbenice@y...> wrote:
> 
> >
> > What's your objective?
> > If it's aligning the drill, you might find it easier to project
> > crosshairs onto the board.
> > mike
> 
> 
> project crosshairs... hmmm... how?

My system was computerized, so I put the crosshairs a known
difference from the drill center.  Align it, then drill the hole
relative to the alignment position.

My first choice would be a laser pointer.  But I was too cheap
and mounted an incandescent at the end of a foot-long brass tube.
Soldered wires over the other end for the crosshairs.  What I got
was a "shadow" not a projection.  But if the light is far enough
away to look like a point source, it works out the same.
If you don't want to do the offset thing you can project at an angle
IFF you have fixed height off the board.  Or project two, one from
each side and make sure they align at the reaquired height.

You might consider an annular light source that converges at the
desired height.

I think projection of the alignment marks is always gonna be easier
than trying to project an image of the work.
mike


> 
> my thinking was if i project the picture on the other side of the
drill  
> onto a screen i can draw concentric rings on the projection surface
to aid  
> in aligning. also, it would have magnification, crosshairs projected
on  
> the PCB would need another means of magnification to see better.
> 
> ST