Homebrew PCBs

On 08/05/2011 12:55, DJ Delorie wrote:
>
> James English<jimenglish123@...>  writes:
>> Does anyone out there have experience with exposing a photosensitive
>> board through a negative to sunlight?
>
> Sunlight is very variable, but in general, anyone doing UV exposure
> should have a "transmission step wedge" - this is a plastic film with
> various calibrated shades of grey printed on it.  Using this, you can
> calibrate *any* UV source and, with a little math, figure out the ideal
> exposure time in one trial run.

I found the optimum exposure for my process by sliding a piece of 
cardboard across a test piece of laminate with a test piece of artwork, 
moving it at 1 minute intervals.

Leon
-- 
Leon Heller
G1HSM