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Circuit design for a 1W LED lamp project
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This circuit prototype uses a rather uncommon but brilliant design that combines both simplicity and efficiency! (At least when power factor isn't considered). More details about this project here.
Instead of using a 3W resistor to limit the current I'm going to use a X2 class capacitor from an old power supply to limit the current by capacitive reactance to ~11mA. PF is horrible (22%) but even then this design remains twice more efficient than using a 3W resistor!
The final lamp is going to have 20 LEDs, but I only have 9 in stock at the moment LOL.
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@Mike, your school schould have used this instead lol.
Weird, those retrofit lamps you linked are usually pretty good. I have a few pictures of exit signs with horrible retrofit lamps, transparent tubular ones with little 3mm LEDs.
@ Vince; The retrofits work but they're so dim. On a sunny day and when all the hallway lights are on (sometimes every third light is off for whatever reason lol) you can't even tell the signs are lit. Plus a good portion of the exit signs at my school look like this one here. As you can guess, the red light behind the face makes the EXIT face illegible so it's actually even harder to read. I don't know how they even pass fire code.
The Cranston Public Schools is trying to get a $15 million grant for the schools and half of that will be getting the schools up to fire code. So if the exit signs aren't up to par they'll probably just replace them. And since it's a grant they'll smash up the old exit signs even though they're probably worth a hundred bucks each and I'd probably kill somebody to get my hands on one lol.
When it comes to exit signs it seems everyone maintains them their own way LOL. I've seen some very well maintained and regularly relamped, others not taken care of at all! In my school again, I know a few exit signs that never got relamped since my first day in that building, in 2010! But that building's exit signs aren't the best maintained anyway LOL.
as for my middle school, i actually forget what kind of exit signs they used. I know they were LED though and they must not have been very attention-worthy or I'd remember them more lol.
Some parts of the school that were added in the 90s have plastic LED exit signs and I SWEAR they don't light up. I bet they were brighter when new but you seriously cannot tell they're lit unless you really study them closely. Some have missing front covers too so it's just an open box with a faint red light lol. They replaced one exit sign in the gym that was victim to a ball I suppose and it's nice and bright! though it too has no cover and simply has an array of red LEDs on the bottom inside of the sign. At least you can see that it's lit lol.
I'd sure like to see your concept put into use. My guess is that red and blue LEDs are the cheapest and that's why they're used instead of white. (i heard green exit signs actually use blue LEDs, but have only ever seen red exit signs except for the green edge-lit signs at the Showcase near me).