Light pipe/diffuser solution needed - Page 1
Forum section: electronics / projects

author: elliotb
author_rank: Contributor
timestamp: April 12, 2016, 06:38:42 pm
content: I have a project that is in a small key fob form factor. The application requires user feedback for which I use a bicolor LED. Recently the manufacturer (polycase) stopped carrying the clear polycarbonate version that I was using (fb-20-4*1). The only solution left is to use the black ABS variant which they still stock and drill a hole to let the LED shine through. I'd like to plug that hole with some sort of diffuser to give it a finished look. The ABS is probably only ~1mm thick where is it to be drilled. Doesn't seem like a press fit solution would stay. Does anyone know of another solution? Maybe a clear epoxy of the right consistency? Ideas?Thanks!

author: Kjelt
author_rank: Super Contributor
timestamp: April 12, 2016, 09:30:21 pm
content: Perhaps something like this if there is room on the pcbhttp://www.newark.com/pdfs/datasheets/Visual_Comm/LPC_Litepipe.pdf

author: rx8pilot
author_rank: Super Contributor
timestamp: April 12, 2016, 09:42:51 pm
content: How many are you needing to make? How much time are you willing to spend on each one?Sent from my horrible mobile....

author: Buriedcode
author_rank: Super Contributor
timestamp: April 12, 2016, 10:50:10 pm
content: If its a one-off, or <5 units, you'd be surprised how good hot-melt glue can be for diffusing. It's also easy to squirt into molds, and cut with a knife. It'll hold itself in place, but won't be adhered so much you can't peel it off. I realize 'hot-snot' isn't the nicest solution, but I've used it before in small areas (<5mm) and it diffused it well, and allowed plenty of light through. I let it go through the hole, then sliced it off so it was flush with the front of the case with a very sharp blade. At the back I used 4mm M8 spacers as a 'tube' so the area was only lit form an LED directly below, and not the others.A more permanent would be clear epoxy. If the LED is directly below and you don't need 90 degree angles, or wacky shapes, you can parcel tape over the hole (the brown stuff, shiney side, epoxy won't stick to it) and use something like a plastic standoff as a 'tube'. It'll be completely clear, but when roughed up with 400grit, it diffuses well.Of course, the above is very much a cheap DIY job, hardly professional. In fact out of the two the hot-melt looks the best and is the quickest to do.

author: elliotb
author_rank: Contributor
timestamp: April 12, 2016, 11:24:42 pm
content: Thank you for the solutions.@Kjelt - I don't think there will be enough space for the light pipe. There is a picture of the case onhttp://tinylabs.iobut it's an old version of the pcb without LED. The PCB sits maybe 1mm behind the case (with a hole in it and the led backfiring from the opposite side).@rxpilot @Buriedcode - Running this as a kickstarter so quantity unknown. Hopefully at least 1000 so I think hot glue might be out. I tried today with some super glue called "plastic surgery" and it looks pretty good although I had to go back to clean up some "frosting" on the front. Do you guys know of any clear epoxies that are less runny that I might try?