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Background:
       Commercially availabe LED Backlights are very expensive.  I have long wanted to find a cheap alternative and share them with fellow makers.  In this project, I will use both polycarbonate and acrylic scrap 

Goal: 
        To design a LED backlight board so that one could use it as cut board for cutting silkscreen arts.  At the same time, be able to use it for making LED lit Commercial Sign.

Procedure & Design:
         Since polycarbonate scrap is relative cheap, we might use it for front and rear panels.  I got some thick Acrylic scrap but they are only strips.  We will cut them to form the edges.
         For portability, I chose 9v DC source because we could either use a 9v DC output AC Adapters or 9v DC Cell Battery.
I will use a DC power jack and solder all the LEDs.  The LEDs should be bright enough and evenly spread.  I think hat shape top 5mm Cool White clear glass and ultrabright are good for this application.
          To my understanding, series connection is more energy efficient.  Therefore, there would be some trial and error and verification..
         For commercial sign application, it is both common to hand draw or color printed notices and artworks   If a power source is nearby, it could be powered by using an AC Adapter.  If the sign is going to be remotely location, a 9v cell battery could last for days.  One could tape the colored sign on the LED backlight board. Alternative way is to add a clear acrylic top cover.  If sign is use on a daily basis, adding the acrylic top cover would be both elegant, professional looking and protect the artworks from the environment.
         For silkscreen work application, either power could be used but AC Adapter would save money since 9v cell are not exactly cheap.

         

Result:
       In the following configuration, I was able to lit up 28 5mm Straw Hat LEDs with one single 31-Ohm 1/2W Resistor with 12v DC power source.  Both LEDs and resistor remained cool so it is a good sign.   To fill the board fully, it would be about 4x the current configuration.


Tip:
         If we make the LED fixture replaceable, then we could play with blinking,  UVs and / or multi-color LEDs.  We will design so that one side could be remove via screws.  One side need to be glue so it would hold the frame edges together.  Since we are using polycarbonate sheets, acrylic glue won't work here.  I am not sure if super glue will.   Worst case is using epoxy glue or screws.



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