Homebrew PCBs

I went ahead and placed an order for some as well. 

I am wondering if just doing simple current limiting resistors is
sufficient or if a proper LED driver chip would be the better way to
go. From what I have read, at least for visible LEDs, you want to
match the current in the LEDs to ensure that they all shine evenly.




--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@...>
wrote:
>
> Markus Zingg wrote:
> > 
> > 
> > Adam,
> > 
> > I do have a 20mm grid spacing, and I'm so far satisfied. Even
though it
> > never formed a problem of any kind, one can SEE the grid on the
> > resulting exposed laminate. It's seen like kind of darker and lighter
> > circular shaped areas on the exposed resist. Again, developping the
> > result always worked excellent with no irritations in the result
whatsoever.
> 
> That's good to hear it works despite the visible pattern. What is your 
> space between the LED and PCB ? I guess the larger the distance the 
> greater the light overlap of adjacent LED's and possibly better
uniformity.
> 
> > At the very surprisingly low prices of these LEDs, I would consider
> > using an even more narrow grid. My box (kingbright leds, with what I
> > understand only 160mcd typical) result in a one minute exposure time.
> 
> The BestHongKong ebay seller Tom pointed out had the better specs 
> (tighter spectrum tolerance, polar plot). Interestingly , some LEDs are 
> rated in mcd while others rated in mW. BestHongKong 5mm UV LED's are
all 
> 11mW 20 degree. I think I'll get these. But might also get $11 ones
from 
> Winsome House Store just for fun.
> 
>  >.... I would spend the time to build a complete exposure unit to make
> > sure they work.
> 
> For sure. Some preliminary testing will soon give me estimate of 
> exposure times vs grid spacing and test non-uniformity.
> 
> I'll be sure to let others know how it goes.
> 
> Adam Seychell
>