Homebrew PCBs

What's your objective?
If it's aligning the drill, you might find it easier to project
crosshairs onto the board.
mike

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" <stefan_trethan@g...> wrote:
> 
> Hi everyone,
> 
> remember some time back we talked about PCB drill viewing mechanisms.
> 
> I want to make one for a pivoting drill stand, with the drill from the top.
> 
> I think, please correct me, it could work by illuminating the PCB with  
> bright light from below, then taking that reflected light and sending it  
> through a convex lens which sends it to the projection screen. a mirror  
> will be required too.
> 
> i'm not too good with optics, but i took a lens, illuinated a piece of  
> newspaper and tried to project the image, which worked to the extent you  
> can expect from a flashlight.
> 
> Now i wonder where to put the screen, it could be under the atual drill  
> table, on the front of the machine.
> Not ergonomically ideal but if the machine is positioned relatively high  
> it might be acceptable (the screen could be angled to get a better view).
> 
> Another option would be to have a slightly tilted-down screen on the top,  
> back of the srilling machine.
> the image would be projected diagonally up through the work surface of the  
> machine (cutout).
> 
> Each setup requires a lens and a mirror, but the screen-on-top version has  
> a much longer optical path.
> 
> How can i work out which lens size and focal length i need?
> 
> ST