How to implement LEDs in my design?

[dreaquil]

Hi,

So I recently started working on a frequency counter using a pic18f and two 4 Digit 7 Segments and decided it would be a nice project to put into an enclosure so I got onto ebay and ordered the following enclosure like Dave had recommended on the blog. http://www.ebay.com/itm/231422367563?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Now I'm gonna be cutting a rectangular hole for the seven segment to poke out the top and I need to add a few LEDs (maybe 4 or 5?) and I was wondering what the best way to do that is. I've never used light pipes so don't really know how to match them up. The LEDs will be right below the surface soldered onto the board face where i need them to be, so the way I see it is that my options are to use light pipes or to poke out some through hole LEDs and give the pins some kind of support. Any thoughts or other suggestions? I live in europe and will be probably placing an order with Mouser or Farnell Export.

[ajb]

You have a couple options:
- Use a TH LED, installed at the appropriate height.  For best results, use an LED spacer to hold it the appropriate heght.  Height is measured from the bottom of the LED to the top of the board.
- Use an SMD LED with a suitable board-mount lightpipe.  here are some vertical options, Lumex make a bunch of other shapes, as do other manufacturers.
- Use a panel-mount lens and lightpipe assembly.  Here are some lenses, if you look at the datasheets you'll find there are lightpipes that snap into the rear of some of them to conduct the light into the lens from an LED mounted further back in the enclosure.  You can also use these with a through hole LED as above, with the LED stood off from the board to land at the right point inside the lens.  The lenses give a very nice, finished look to an enclosure, and can off increased viewing angle over a standard LED that just pokes through the panel.

[dreaquil]

Thanks for the reply. Might go for the through hole design as it seems to be the easiest to implement while having room for error. If i were to go for a light pipe, do i need the exact size or can they be bought longer and then shortened?

[ajb]

Light pipes are typically polycarbonate, so could certainly be cut short, but a cut end won't be as efficient as the factory end, which typically has a bit of a convex shape or a slight texture to improve illumination. You'd probably need to sand if not polish the cut end to restore efficiency.