Oversized 7-segment display

[sunray]

That's true for lamp-style LEDs which have lenses. For the flat surface mount 5050 type there is no lens so it makes no difference.

No lens? I'm surprised, I've only handled tape a couple of times but the SMT LEDs I've used have lenses and assumed tape used the same devices.

 

What makes them directional?

 

Well they aren't really directional. The output angle is probably 120 degrees or more. They just have a flat window with the LED die slightly recessed behind it. A lot of the high powered ones are the same, a separate lens or reflector is placed on the flat window to control the light.

I'm not disagreeing with you as I haven't done this with tape.I made up a board with SMT LEDs, Little rectangular blocks with a window one side. tried it to make sure it worked and did what was required then potted the whole thing in crystal clear resin to waterproff it and suddenly the LEDs were all but invisible. Just like happened when I potted standard 3mm leds. I doubt it was to do with the clarity of the resin as component details were clearly visible and readable.

MK2 was rings of clear silicone sealant formed around each LED then applying a sheet of perspex (so each LED had a pocket of air) before potting PCB with resin against the perspex. It looked ugly and there were lots of air bubbles, it did work but there was a certain amount of light reflected back onto the board.

I'd assumed the tape is made using 'standard' SMD LEDS

 

[alistermorton]

If you buy a retail pack of tape it usually comes with a short length (3 LEDs) with a battery to indicate the colour, and often this tape has no silicone on it. You can clearly see that the LEDs have no lenses.

[TomHoward]

I'll post some pictures later, but I've just done a very rough test rig, the resin hasn't gone off yet but lenses or no pouring resin over the bare silicone-less 5050 tape definitely affects the output of the LEDs and they are like little RGB spots rather than a mixed colour.

I might try with some of the silicone covered tape, I prefer the bare stuff myself but I don't know whether pouring over the stuff that is already silicone covered might fare better.

[musht]

 

As these are going to be outside for a long time, I don't know if the print material will matter - I don't want to be remaking them in a year if they've fallen apart..

 

 

With reflective or transparent body can mount the tape round the inside edge side firing, making the centre squares of the 7 seg figure 8 to a divisable, ie 150mm for 9 LEDs per side on 60leds/m tape. of the tape spacing so can wrap a single strip round top part of 8 and a U round bottom part. Less joints is good.

 

PLA is OK if coated, PETG much better, ASA best but hardest to print,

[canoemoose]

I'll post some pictures later, but I've just done a very rough test rig, the resin hasn't gone off yet but lenses or no pouring resin over the bare silicone-less 5050 tape definitely affects the output of the LEDs and they are like little RGB spots rather than a mixed colour.

I might try with some of the silicone covered tape, I prefer the bare stuff myself but I don't know whether pouring over the stuff that is already silicone covered might fare better.

 

I'm keeping an eye on this thread with interest - I'd always previously assumed that there was a tiny lens cast into the top of the SMD5050 package, seeing as manufacturers can offer tape with different "beam angles" - which from experience are definitely real, rather than marketing!

 

Although, conversely, 5+ years ago I was involved in an install in a bar in which some LED tape had resin slopped over it to offer some protection against the corrosive effects of coke et al and I don't recall the outputbeing effected...

[mikienorth]

Having had my hands on this stuff a few years ago:

 

https://fireflylighting.com.au/lighting-products/neon-flex/

 

I seem to recall it pretty much being LED tape inside a translucent silicone 'thing'

 

Might translucent silicone, or making a resin pour 'cloudy' create a waterproof diffused cover that, even if the point sources of the LED are wiped out by resin, make the whole shape glow?

 

By translucent I mean 'clear' like B&Q mean clear silicone sealant... Clear 'ish'

[Brian]

Anything over the front of an LED will affect the radiation pattern as you're making an additional lens. It has nothing to do with how 'clear' the added material looks; it's down to its refractive index.

[timsabre]

I'll post some pictures later, but I've just done a very rough test rig, the resin hasn't gone off yet but lenses or no pouring resin over the bare silicone-less 5050 tape definitely affects the output of the LEDs and they are like little RGB spots rather than a mixed colour.

I think the LED output does bounce around inside the cavity of the LED body and so to the eye it looks like a larger spot. As Bruce says with resin over the window the light will pass out into the resin rather than bouncing around so you won't get that internal illumination of the body, just the direct output of the LED dies. The actual light output will be much the same though and at a distance it will look similar. A piece of frost gel in front of the LED would get you back to the "diffused" appearance at the expense of reduced contrast if the sun shines on it.

I would avoid the silicone covered tape as the silicone goes yellow and opaque after a couple of years.

 

[TomHoward]

I'm not a fan of the silicone covered tape either, as I find the sticky glue on the back can't take the weight so prefer the uncovered stuff, but also I've found it burns the back of the silicone where it touches the chip over time and what looks like the LED output reducing is actually just burnt silicone blocking the output. If you pull the silicone off some tape with high hours you can clearly see the black and tape looks a lot brighter.

 

Here's my rather shabby test rig - built up with hot glue and then poured in.

 

With the uncovered tape, when poured on, the output is reduced, or at least the focus is knackered:

(With this image, the tape is running at about 5% level for the photograph, at 100% the image doesn't photograph well but it is still visible to the eye)

 

I didn't have any silicone covered WS281x tape to test, so I had to use RGB silicone tape.

However I didn't have a dimmer for this set up, which means I just ran 12V into it so it's at 100%.

The effect is pretty much as bad when poured in resin as the uncovered tape, which I wasn't expecting, I thought the silicone tape wouldn't be effected as badly.

You can see 'haloing' around the LED, which you can see by eye as well.

If you view it from a shallow angle there are sudden 'bright spots' when you're looking from the side, so I think it's the beam angle being totally knackered and the output prismed into it's component colours.

 

So, given the trouble with pouring resin over, we are likely to look at laser cutting 2mm Acrylic sheet or similar for the top, and then print a lip for that to sit into and seal it with a small bead of silicone / glue etc.

 

Given the segments are going to be used in full sunlight, and are supposed to be visible from 100m+ away, I'd rather keep the contract as high as possible, so I'd rather use black tape on a black background facing straight out than rely on any reflection off a white surface, or add white diffusion or similar over the top and rely on the illumination through it - as I imagine the sunlight reflecting off the diffusion from the front will also light it up and reduce the contrast.

I don't know whether using a colour for the pixels as opposed to white might increase visibility also.

[timsabre]

Interesting photos. I can't decide if the apparent dimness of the LEDs in the resin is an optical illusion due to the point source of the led die vs the larger circle of the window, or if the light is getting lost. The actual light emitting from the LEDs can't be changing so where is it going?

 

Anyway, back to your plan, you are right to keep it as a clear window with black inside rather than an internally lit segment with a diffused/white surface, sunlight would wipe that out.

[TomHoward]

I concerned about even being able to read an LED when it’s fully on, but we’ll see.

 

I think it’s refracting within the LED, the 3rd image with what looks like lens flare and refracted colours, it actually looks like that in the flesh, if you turn the part 90degrees to the desk you get a few hard lines of individual colour coming out, something’s going wrong in the beam angle for sure.

[musht]

Depends on the resin, slight difference in refractive index will turn the interface into a near perfect mirror.

 

Wide variety of clear potting resins available and clear silicones.

 

As suggested above LED neon https://www.aliexpress.com/item/4000074841092.html

[timsabre]

Led neon won't be visible in direct sunlight.

[gyro_gearloose]

Are you sure about that? I’ve seen it used on a few shows and seems quite bright. If neon flex isn’t visible in direct sun light, then I’m not sure that LED tape will be either. I do know that these LED clusters are visible from some distance outside. Maybe 3 or 4 per segment would work depending on how big you need the characters to be.

[timsabre]

Are you sure about that? I've seen it used on a few shows and seems quite bright. If neon flex isn't visible in direct sun light, then I'm not sure that LED tape will be either. I do know that these LED clusters are visible from some distance outside. Maybe 3 or 4 per segment would work depending on how big you need the characters to be.

 

OK no I haven't used the exact product so I might be wrong. But I have made a sign where we attempted to use a material with a diffused surface, like the surface of the LED neon, and when the sun shone on it you could not tell whether it was lit or not. However using LEDs which were directly viewable, as in the clusters you suggest, the difference between lit and unlit was much more obvious.

I think if you could put sections of WS2811 tape arranged in 7-segment format behind a waterproof panel then that would work. Maybe a black foamex back board with the tape stuck on and clear acrylic sheet for the front sealed round the edges with silicone or resin. For maximum prettyness backprint the acrylic in black with windows for the LEDs to hide the tape and wiring.