Hi. I work for local government and we have a land-use ordinance that regulates signs. Recently LED sign requests have been coming in and I’ve got a problem because our ordinance doesn’t allow for a sign to show the light source directly. (E.g., a neon sign must be covered by a transluscent (sp?) face so that the bulbs aren’t directly viewable.)
Specifically, I’m asking about a gasoline station sign advertising the price of fuel. The drawing says the sign is an “8.88[sup]9[/sup] configuration” and the mounting says “faces push through fascia w/cabinets secured to canopy structure.” That sounds like the diodes, which produce the light, will be directly visible. The problem is the applicant insists no light source will be directly visible, but cannot explain why.
I’ve googled and haven’t found any luck in helping me understand. To anybody who’s able, will you please help clear this up? Thanks!
Please note: since I don’t know much about this stuff, my post is most likely poorly worded. Sorry about that.
LEDs are often mounted inside a filtering piece of plastic. Sometimes it is clear, sometimes not. If a red LED has a red filtering cover, perhaps that is sufficient to satisfy this ridiculous ordinance.
LEDS are most commonly packaged in a little bell-shaped blob of epoxy; the curved front of the package acts as a lens; when you look at the illuminated LED, you’re seeing the actual emitter chip, magnified. Definitely the case if the LEDs are the more modern, ‘water clear’ packages, but if they’re the older style red(or whatever) epoxy, that may qualify as sufficiently translucent that you’re not directly seeing the emitter.
Well, you could argue that the LED itself covers the source, since all LEDs I know of have an epoxy plastic covering that the actual LED junction sits within. (LED lasers are a different breed, but you’re certainly not talking about them here).
I’ll bet the original regulation was to ensure that the light bulbs wouldn’t break and potentially send dangerous broken glass all over the place. LEDs don’t have glass, I’ve never seen one break, and they have their own built-in protective plastic cover.
You could try arguing that way, and maybe get a new regulation written to cover a new circumstance. Or you might be buried under the weight of unresponsive and stupid beaurocracy. Or you might notr say anything at all. It all depends on how responsive and intelligent the folks you’re dealing with are.
Nope, it’s because bulbs used to illuminate signs can be very bright & cause serious glare. (Indeed, LEDs can be pretty bright, too.) We’re currently revising the sign ordinance.
So we may be looking at the light source magnified through a lens? (Thus lumen output [for lack of proper terminology] is something that may need to be addressed.)
Hmmm…okay. Cool. Thanks for the help. And any more to come!
In the interest of scientific inquiry, I took a spare UV LED in a water-clear T-1 3/4 package and hit it with a hammer until it shattered. It took a lot of force–much more than a glass bulb would. The resulting pieces weren’t sharp at all. I can’t see exposed LEDs posing any sort of risk, assuming you’re correct about the reason for the ordinance.
It’s not that the light is magnified by the lens – the lens-shaped epoxy cover is meant to redirect the light so that it all comes out in the forward direction, rather than all over the place (they used to make regular light bulbs that did this, too)
In that case it’s even less of an issue – you can get LEDs in which the epoxy package does not form a lens, but it saawn off flat and given a matte surface (actually, it’s just molded that way, but that gives you an idea of the shape), so you can get LEDs with a built-in diffuser as well.
If the sconstruction of the ign is being specified here, rather than it just being a slot-in component, then yes, just do what CalMeacham and specify translucent/diffused LEDs
If a glass lens over a light-emitting semiconductor is “covering”, then so is the glass bulb that surrounds the tungsten filmament of a standard incandescent bulb. That argument won’t wash.
OP, it’s going to be your job to figure out the intent of the law and act accordingly. If it’s for breakage hazard, don’t worry, LED’s are not very breakable. If it’s for glare, again, don’t worry as most LED’s are small and poorly focused.
I suspect the law is for aesthetics, though. Exposed light bulbs are ugly and the preponderance of neon signs are beer signs which, in abundance, create an appearance of a low-rent area. Some people in your community might feel the same way about LED signs… sure, they’re nifty when somebody first erects that sign with the newest greens, blues, and violets. But when individual diodes go dark here and there, they tend not to get replaced due to expense and hassle. What was an interesting novelty starts looking cheap and distressed. So I would suggest maybe going to the community and getting your constituents ideas on the matter; after all theoretically the law is there to benefit them.
More likely, or at least, reasonable, that the regulation is to ensure that the illumination isn’t obstructive or distracting. But I have to agree with Cal’s justification; the gallium-based (or whatever doping material is used) substrate is encapsulated by a plastic cover, and that should ( ::crosses fingers:: ) satisfy the legal requirements. It’s an interesting area of applied solid state research.
Clearly, you haven’t seen Brazil as recently as I have.
There may be a very compelling reason to require a shield or cover. I use ultra-bright l.e.d.'s for something I manufacture. When off, they are clear with a clear epoxy dome. When on, they are bright red- but no place are they brighter than when viewed exactly at the nodal point. If you look straight into even one lit l.e.d. of this type, the glare is difficult to look at. Many of my clients who use this device only in dim light take a Sharpie and put a small black dot at the nodal point, dulling the hit.
A bundle of them, or a sign spelling out " 2:88.9 " would be incredibly hard to drive towards and look at, and read.
A slight diffuser placed over the l.e.d. array would alleviate this situation. Perhaps that is why it’s a good idea to require a cover or shield. Not just for breaking bulbs, but to slightly soften the (collective) hit to the eyes of dozens of l.e.d.'s.
There are several scrolling advetisement type LED signs popping up around town, and I’m here to tell you that an ordinance requiring indirect illumination is neither out of date nor stupid. These signs are SUPER bright to the point of being distracting. They’re MUCH, much brigher than neon or anything else I can think of. A few times I’ve seen a these things in the rear view mirror and for a moment thought the police were after me.
They’ve just installed one of these outside of a hotel along my route from work, and it’s glaringly bright. Vivid blues, whites and reds. Even in bright sun it’s very distracting and I could see an ordnance being written to control their placement and brightness.
In my opinion, restricting brightness by simply requiring a translucent cover is ridiculous. Attempting to restrict brightness by, say, actually putting a limit on the brightness — even a subjective one — makes more sense, solves the problem, and doesn’t need to be rewritten when technology changes.
This is why I think it wasn’t really intended to address brightness so much as ugliness. And if you regulate based on brightness, better be careful how you define it because strictly speaking, it doesn’t mean what you seem to think it does.
LEDs don’t have to be stupidly bright, and I see no reason why they can’t be used safely for traffic signs. One consideration is the viewing angle of the LED, depending on whether you want front-on visibility only, or the ability to see the sign from a side angle.
LED traffic lights are becoming popular in many countries, but you can be certain they don’t use any old LEDs, as there are local regulations about traffic light design, and in particular, the wavelength of the coloured lights.
A lot of the buses around here have LED destination signs, which have two brightness settings. The bright one is for use during the day. The dim one is for night. The bright setting is very glary and distracting during night.
Considering that a) all the traffic signals in the city of Mississauga now use LEDs, at a considerable savings in electricity over filament bulbs, and b) on the newest of the buses mentioned earlier, every external lamp except the headlights is some form of LED, I’d say that LEDs can be plenty bright.
LEDs are basically solid transparent plastic moulded around the emitter chip. No spaces, no vacuum. They can burn up, I suppose, but they won’t shatter.
js_africanus, if you are rewriting the regulation, what is its goal?
Check out the LED Museum to see just how many colours you can get LEDs in. Whee!
