Considering a different approcah to protruding LEDs

[PeterPan]

Among several projects I'm hoping to test market soon one thing is common, they all have some LEDs. As I've gotten better at making control panel labels, I'm starting to see my simple protruding LEDs as a little less "pro" looking than most of my store-bought gear.  Below is one such item in the works. These have several 3MM LEDs that simply protrude through the top, and my question is whether any of you has pioneered other methods of having visible LED indications, maybe without them actually sticking through the surface.

For example, maybe I can punch my holes in the label, but then get some thick flexible plastic (like they use for desk blotter covers) for a "top coat" and NOT punch the LED holes there at all. maybe I can just push the LEDs up against that plastic, so the surface is flush. In most of my "store bought pedals, . the indicators are flush with the top. I can't afford custom light pipes or rectangular leds cutouts, but at least a flush top appearance might be nice.  I'm thinking it would mean one less way for spilled liquids to enter the device, but I don't know that it will look decent when the LEDs actually light. Has anyone tried anything like I'm thinking here?

[R.G.]

One thing I've done several times is to modify the LED so it sits flush.

Most through hole LEDs have a flange to keep them from going entirely through a panel hole. Calculate the panel thickness, drill holes matching the mounting holes in a steel strip of the same thickness as the panel. Stick in an LED and run a cutter/abrasive over the LED to cut the plastic package down to level. Repeat. LEDs can now be simply glued into the final panel holes with your choice of adhesives. I like non-corrosive-curing RTV. This would also waterproof. Your packages look like they need a PCB under them, so you could make the modified LEDs up into a baby PCB and glue that in. Standoffs also work, but do not waterproof and require more fasteners.

There are LEDs that exist that are already set up as flat tops for such use, but the panel thickness choices are limite.

There are LED "light pipe" mounting devices that are intended to do what you have described while leaving the LED on the PCB, and these exist for both through hole LEDs and SMD.

There are...

This just goes on and on.    There is google.

[italianguy63]

I've also seen where the LED is below the hole in the enclosure, and there is a mylar decal over the enclosure.  The LED shines through the color of the decal.  MC

[PeterPan]

Filing the LED smooth is a good idea! I'll have to try that.

My bigger question I guess is about things like the Mylar Decal. I really would like a top plastic (or mylar, or whatever works best) over the whole label, covering my now "flush" LEDs too. I just wonder if it will look decent though. If the light from the LEDs get scattered and refracted around the added clear surface, instead of providing a crisp indicator, then I'll have defeated my purpose of looking more pro. I guess i'll just have to try it and see, but I'm hoping for some pointers on exactly what i can use for my thin plastic top coat. I mean, can you get something strong like Plexiglass in really thin sheets (like maybe 10 mills?)

[digi2t]

Why file? That will only mess up the nice glossy finish of the LED. Flat top LED's already serve that purpose.

[deadastronaut]

^ yep...i have those now..

[R.G.]

Why file? That will only mess up the nice glossy finish of the LED. Flat top LED's already serve that purpose.

It depends on how you want it to look. An LED with a smooth top has a viewing angle of whatever it has. One with a frosted/random top has a viewing angle of nearly 180 degrees.

If you're viewing from a limited position, the "projector" style is good. If you're looking at it from a bigger set of directions, you may want frosted/diffusing.

[PeterPan]

Why file? That will only mess up the nice glossy finish of the LED. Flat top LED's already serve that purpose.

Ha! Those are nice. I do have a constraint though... the MCU I'm using to drive my LEDs is only good to about 4MA per I/O line. I'm currently using those little 3MM LEDs that only require 2MA. I'll look at the company you linked, but I'm finding most specialty LEDs are standard 20MA (not to mention pricier).

[davent]

Ultrabrites you can go down less then 1mA and still find them bright enough.

[aion]

Ha! Those are nice. I do have a constraint though... the MCU I'm using to drive my LEDs is only good to about 4MA per I/O line. I'm currently using those little 3MM LEDs that only require 2MA. I'll look at the company you linked, but I'm finding most specialty LEDs are standard 20MA (not to mention pricier).

Keep in mind the actual current draw of an LED is based on the current-limiting resistor used. So even if the datasheet says 20mA, you might find that it draws less than 2 if you use a 4k7 or 5k6 resistor.

[~arph]

Or use a transistor

[PeterPan]

In any case, whatever LEDs I use, my bigger issue is what to use for a transparent cover.

[R.G.]

Clear, non-glare mylar in about 0.008" to 0.012" thickness, held on with transparent permanent pressure sensitive acrylic.

An alternate might be clear silicone rubber film, but unless you get moderate durometer stuff, it'll tear more easily.

Mylar will be more durable.

[duck_arse]

so everyone noticed that the "Sound Man" has an "RG" setting, but you all left it to me to mention, right?

perhaps your mylar label could be printed with the level numbers as clear, then the led lights through the number itself.

[edit :] oh alright, the sound man on the right of the picture.

[Mark Hammer]

Looking at those particular units, it occurred to me that having any light source so close to any other, AND being mounted so that it does not protrude through the top of the chassis, may risk light "bleeding" from one LED through the opening of an adjacent one.

Of course, not knowing anything about either the brightness, the proximity, or the colour scheme, I may be over-estimating the risk.  Still, do consider that just because we want the light to be visible on the outside, doesn't mean the light declines to exist on the inside.

If I've understood RG's earlier suggestion accurately, having some sort of spacer on the inside, such that the LED flange butts up against the spacer, and the entire path for the light to the outside world is bounded by the spacer and the wall of the chassis, will virtually eliminate any risk of "light bleed" from one LED to another "escape route".

[PeterPan]

Thanks everyone!

More progress... I did find some 0.020 " thick PETG plastic on ebay, for what i would call a decent good price (compared to widget-works anyway). Here's a link in case any of you want any. Even it's just a temporary ebay lin, it might be worth noting the seller, because it looks like he has a huge roll of this stuff.

http://www.ebay.com/itm/330578441634?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
better view-> http://i.ebayimg.com/00/$%28KGrHqJ,!j!E3Rg%29BzkQBN-87Yb+z!~~_35.JPG

I have vacuum formed stuff made of this same gauge of PETG and I have to tell you... for something only .020 thick, the thermoforms I've made have been incredibly rigid and strong. And this stuff is flexible enough to punch holes in without shattering, and is rigid enough to make a surface that should not require adhesive all over its surface. I've ordered some and I'm really excited to see it. To my advantage, all my enclosures have a .030 recess area for a label, and my actual label material is only a few mills thick. So cutouts of this stuff should fit well.

Tot he light bleed issue, I'll have to wait and see. The enclosure plastic is pretty think (made by POLYCASE.COM, their LP series). So clean holes where the label LED holes are should help with the light bleeding, especially with something as super clear as this PETG stuff.

For adhesive, this is still my big unknown. it would be really nice if there were some way to just put a thin line of adhesive around the edge, between the clear cutout and the deep recess. I THINK it would be wise for me to avoid coating the whole bottom with adhesive and press it up against the label, don't you? There's a good chance that this adhesive will leave air gaps, possibly take a long time to dry ( and so eventually attack the label ink), and one single bit of adhesive over the LEDs would turn my clear top into a muddy matte finish, that would look crappy and perhaps add to the light bleed situation.

So all this to say, I think this PETG stuff might be my best solution, but how I make it stay put is still a big question mark.

[karbomusic]

but at least a flush top appearance might be nice.  I'm thinking it would mean one less way for spilled liquids to enter the device, but I don't know that it will look decent when the LEDs actually light. Has anyone tried anything like I'm thinking here?

Well, I typically drill a hole then a hole slightly bigger from the inside that doesn't go all the way through which makes the LED effectively flush. It works great, I can still see the LED and you'd never push it through unless it was extremely deliberate.



I also use EnviroTex as a finish which makes the surface a higher altitude than the LED. Though I didn't do it above, on my next build I'm going to pour the EnviroTex with the LED in place which will make it completely flush on top. With such a small surface area the LED will still be removable after the fact if needed. If that works it will be completely impervious to spills and 100% flat above the LED. However, since I place a small ring of epoxy around the LED on the inside when I glue it, it's water proof anyway.

[PeterPan]

I also use EnviroTex as a finish which makes the surface a higher altitude than the LED. Though I didn't do it above, on my next build I'm going to pour the EnviroTex with the LED in place which will make it completely flush on top. With such a small surface area the LED will still be removable after the fact if needed. If that works it will be completely impervious to spills and 100% flat above the LED. However, since I place a small ring of epoxy around the LED on the inside when I glue it, it's water proof anyway.

Envirotex? Interesting. You pour it and then it hardens? Guess I'll have to GOOGLE it! :-)

[karbomusic]

Envirotex? Interesting. You pour it and then it hardens? Guess I'll have to GOOGLE it! :-)

Yep, there are various brands of it but it is a two-part perfectly clear epoxy, like the stuff they pour on restaurant tables. It's not for everyone but I happen to love it due to its durability and wow factor. You may be able to see its qualities a little better in this pic:

[PeterPan]

Envirotex? Interesting. You pour it and then it hardens? Guess I'll have to GOOGLE it! :-)

Yep, there are various brands of it but it is a two-part perfectly clear epoxy, like the stuff they pour on restaurant tables. It's not for everyone but I happen to love it due to its durability and wow factor. You may be able to see its qualities a little better in this pic:

Definitely cheap enough to warrant a try, and some experimenting. I spoke earlier about a 0.020" thick coating would be ideal, and had I not seen what you were doing, I'd have thought something like this was only good for much thicker applications. And I guess you just mask-off holes and such? Do you have some control over its consistency? I'd think both of our requirements for a thinner coating, it might help if there were product variations that were a little lower viscosity to work with?

if I do use the PETG coverings anyway, maybe this would work as a cover-all adhesive between the label and the PETG. I was concerned about a regular adhesive attacking my labels, bur since this is an epoxy resin, there won't be any danger of it never really drying.

Thanks for the tips. If I had a dime for every good product I learned about on these forums, I think I'd have a nice bankroll saved up!