Project in need of a clear front panel - Page 1
Forum section: electronics / general

author: cosmicray
author_rank: Frequent Contributor
timestamp: November 27, 2024, 05:28:06 pm
content: A few years back, I started this project. The original intention was to see how far I couldpush the envelopeof LED efficiency. The original (and current) test bed is a 100mm x 100mm board from JLCPCB. Flash forward to 2024, For a variety of reasons, I decided back in March that the time had arrived to move from car-brain to bike-brain. As part of that, I found that forward illumination was needed for my recumbent trike. Most bicycle lighting is built for two-wheels with a steering post front and center. Then I thought about what could be accomplished with the light panel test board.What was needed was a project box to hold a 100mm x 100mm PCB, and some form of clear front. 3D printing of opaque items is mostly straight forward, but printing transparent less so. On Aliexpress I found some 115mm x 115mm ABS boxes. Depth seemed to be sufficient, so I ordered a few. Today they arrived. As expected the PCB will not fit squarely (because the clearance between posts is 97mm), but as I crossed my fingers and hoped for, the PCB will fit slightly rotated. The rear of the PCB is a solid blank solder mask, so mounting the PCB with some double sided sticky pads doesn't bother me.My question now has to do with the front. The existing front panel is the same opaque slightly off white plastic. Maybe 60 miles from me is a place  that seems to have an extensive selection of clear plastic sheeting. What I need to know is which of these is most likely to be UV resistant, and will remain transparent when subjected to sunlight. Two of these boxes will be mounted on the front outriggers on my recumbent trike. The expectation is to cut the clear plastic to 115mm x 115mm, drill four holes, then use something similar to caulk, but not caulk, to assist in sealing the two layers together.Total power dissipation (including the light output) is about 2.2w per PCB, so I'm not expecting heat build up to be an issue, but I do want to drill a very small weep hole on the bottom to allow any accumulated moisture to escape.Looking for any other thoughts or ideas.https://sibe-rplasticssupply.com/

author: themadhippy
author_rank: Super Contributor
timestamp: November 27, 2024, 05:46:45 pm
content: hows about replacing wot you got with a " junction box with a transparent lid" as an added bonus some are even ip67 rated

author: cosmicray
author_rank: Frequent Contributor
timestamp: November 27, 2024, 08:33:50 pm
content: Quote from: themadhippy on November 27, 2024, 05:46:45 pmThat was my original intention, but (1) could not find one in the size I needed and (2) none of them discussed UV resistance (only visibility).

author: tooki
author_rank: Super Contributor
timestamp: November 27, 2024, 09:00:54 pm
content: Quote from: cosmicray on November 27, 2024, 08:33:50 pmThe ones made for outdoor use (IP67/68/69, made of polycarbonate) have to be UV-resistant because that's part of being outdoors.Just don't buy them from AliExpress -- not only is it a gamble whether it is what it purports to be, but with enclosures, shipping costs quickly eat up any cost savings compared to just buying a proper brand from a regular distributor.

author: thm_w
author_rank: Super Contributor
timestamp: November 27, 2024, 10:14:53 pm
content: You probably won't like my suggestions but:- Don't worry about the box and just clear coat it. Though you want a non-yellowing coat, I think it was SDG youtube had some videos on this- Start from scratch, a LED panel array is not really a useful front bike light. Its very good for accent lighting and side visibility, so if you want it for that thats fine. But its not good for casting light onto the road in a useful pattern. For that you need a lensed LED with a cutoff or a horizontal feature.

author: themadhippy
author_rank: Super Contributor
timestamp: November 27, 2024, 11:40:23 pm
content: get in quickhttps://www.eevblog.com/forum/chat/arrow-electronics-having-50-75-off-mostly-nrnd-and-obsolete-componentshardware/msg5729151/#msg5729151before smoky buys em all

author: Kean
author_rank: Unknown
timestamp: November 28, 2024, 03:53:31 am
content: There are IP rated boxes with clear lids like the Gainta G278CMF-IP67 at 120x120x60mm that might suit.https://www.gainta.com/en/g278cmf-ip67.htmlBut the corners of your PCB won't fit, and you can't use the mounting holes, so you'd likely want to redesign and remake the LED PCB.Available from TME in Polandhttps://www.tme.com/au/en/details/g278cmf-ip67/multipurpose-enclosures/gainta/Ideally you should be designing it with some kind of lensing to control the beam. I'd probably buy an off-the-shelf spotlight and (if needed) design my own PCB to go inside.There are 3D printing services that can do clear parts, but I am pretty sure they are not UV rated.

author: cosmicray
author_rank: Frequent Contributor
timestamp: November 28, 2024, 03:24:45 pm
content: Quote from: Kean on November 28, 2024, 03:53:31 amThat, and many others, were discarded because excessively deep. The ones I have are 28mm deep, and even then I have space to play with.QuoteAnd therein is the conundrum, My first cut is baby steps. I want to prove that it works, ride the bike during pre-dawn darkness, and see what results I get from the existing approach. 3D printing is certainly not a choice, because getting transparent parts to be transparent is more difficult than printing opaque parts. If I wanted a lensing arrangement, I would begin looking at taking existing acrylic or PC sheets, and have them formed into a lens. But that is several steps along the highway.

author: cosmicray
author_rank: Frequent Contributor
timestamp: November 28, 2024, 03:31:34 pm
content: Quote from: tooki on November 27, 2024, 09:00:54 pmI understand why people think and say this. I have been burnt a few times. Aliexpress is a small quantity B2C or B2B sales platform. Sometimes it's barely worth the checkout cost, then other times it very much is. This morning, a bike valve core (purchased from AE) allowed me to limp home 3 miles to be able to replace the failing tube. For what I paid for those valve cores, not having to push the trike for 3 miles paid for itself. My hunch is that many things sold on AE, are also available on Alibaba in larger quantities, at a better price, and almost exclusively B2B.

author: thm_w
author_rank: Super Contributor
timestamp: November 29, 2024, 10:21:19 pm
content: Quote from: cosmicray on November 28, 2024, 03:24:45 pmNothing stops you from just trying this now with no enclosure and just zip tying it in place or whatever. Just make sure the wires won't come loose.I/we give this advice because we know what the end result is, we've tried it. There is no point in using a monster lens in your existing design, what you'd want is a new design with a lens per LED and one or two powerful LEDs.Lens can be had for 50c or so:https://www.aliexpress.com/item/32869283072.htmland the mount for the lens can be 3D printed.You can also get mini LED lenses but you'd use a ton of them:https://www.aliexpress.com/item/32972935458.htmlyou could leave a few lenses off to preserve the wide angle visibility.

author: tooki
author_rank: Super Contributor
timestamp: November 30, 2024, 03:54:07 pm
content: Quote from: cosmicray on November 28, 2024, 03:31:34 pmI know what AliExpress is, I’ve ordered from it many times. I am not so sure that you understand what I said and why I said it.I wasn’t commenting on AliExpress as a whole, but rather on why buying enclosures there is a bad idea:1. No guarantee that the material is what it claims to be2. Shipping costs. I have looked at enclosures on AliExpress in the past, and quickly determined that it was not really any cheaper than buying from western distributors. (And that was a while ago, before the shipping costs from China started rising!) It simply doesn’t make sense to spend more on shipping from China than it would cost to buy the enclosure locally.

author: wraper
author_rank: Unknown
timestamp: November 30, 2024, 04:09:17 pm
content: For UV resistance you need acrylic (PMMA) which is nearly immune to UV. Polycarbonate will become yellowish and opaque under sunlight. Some polycarbonate may have UV protective coating but it's still a far cry from acrylic UV resistance. Note that box itself may not be UV resistant and become fragile after a few years, especially if there is no dark pigment in it. With no UV resistance data from manufacturer chose ones made of plastic that is inherently UV resistant even without additives.

author: cosmicray
author_rank: Frequent Contributor
timestamp: November 30, 2024, 06:48:41 pm
content: Quote from: wraper on November 30, 2024, 04:09:17 pmThank you, I kinda suspected that might be the case. Always good to know the hidden details.

author: jduncan
author_rank: Regular Contributor
timestamp: November 30, 2024, 09:36:51 pm
content: Quote from: tooki on November 30, 2024, 03:54:07 pmThese are silly things to say, since there's a complete spectrum of sellers on Aliexpress - from official storefronts of billion dollar corporations like Espressif to shady shops selling counterfeit or salvaged parts. Similarly, each seller decides the shipping options they will offer and what they cost - some offer free shipping, others mark it up to balance sub-market pricing.

author: ebastler
author_rank: Super Contributor
timestamp: December 03, 2024, 08:17:24 am
content: Quote from: cosmicray on November 27, 2024, 05:28:06 pmI don't think your LED panel will work well for that. Without any collimating optics (lens and/or concave reflector) the bare LEDs will have an emission cone of ~120°, so the light gets distributed over a large area very quickly. This geometry would work well for e.g. workplace illumination, where you want to illuminate a nearby area evenly, but I can't see it illuminating the road ahead of your trike.Regarding an enclosure, for outdoor use I would look for one with an O-ring seal between the body and lid. Finding a good enclosure may be challenging. I would definitely start with that, and then design a PCB to fit.But as a first plausibility check, I would suggest that you just take the existing bare LED PCB, connect it to a power source, and take it out on a quick test drive at night. Real roads, real riding speed, to give you an idea of the illumination you get from it. My guess is that you will want to pivot, and either find a different use for the existing PCB or develop a new light source for your bike. For a headlight, you typically want a point source (one very bright LED, or a small number grouped tightly together) plus collimating optics.

author: thm_w
author_rank: Super Contributor
timestamp: December 03, 2024, 09:34:31 pm
content: Quote from: wraper on November 30, 2024, 04:09:17 pmWe use polycarbonate in direct sunlight and its fine for 5+ years. Probably depends on supplier though."Reputable polycarbonate manufacturers apply a very thin UV protective layer to the sheets. This layer is invisible to the naked eye and does not impact the physical and optical characteristics of the material. But it does secure the performance of the sheet throughout its lifetime, even under harsh sunlight exposure conditions such as those found in the Southwestern part of the United States, most of Australia, and the Middle East. A UV protection layer can be applied either on one side of the sheet or on both sides."https://www.palram.com/blog/construction-architecture/polycarbonate-and-protection-from-uv-radiation/https://www.tekra.com/products/films/polycarbonate-films/weatherable-polycarbonate-filmQuote from: ebastler on December 03, 2024, 08:17:24 amYes this is what I keep saying multiple times.

author: wraper
author_rank: Unknown
timestamp: December 03, 2024, 10:43:06 pm
content: Quote from: thm_w on December 03, 2024, 09:34:31 pmIt's about cellular polycarbonate. Only one side is UV protected which is marked on removable protective film.

author: tooki
author_rank: Super Contributor
timestamp: December 04, 2024, 11:48:37 pm
content: Quote from: jduncan on November 30, 2024, 09:36:51 pmYes, but let’s be real: the vast majority of stuff on there is from fairly random sellers. And the official storefronts tend to not be among the lower-priced options most people go to AliExpress for. (I mean, a lot of espressif stuff is the same or more expensive on their AliExpress shop than it is on DigiKey, and DigiKey offers free shipping to Europe with a very reasonable minimum order size, which espressif does not. And DigiKey ships customs precleared.)And whether the price of shipping is rolled into the item price to give free shipping or not, the cost of shipping rises dramatically with volume and weight. I have yet to see any enclosures on AliExpress larger than a TV remote where the shipping didn’t make it unattractive.