Ask MetaFilter posts tagged with led

Why can't I make this work? LED angst inside

puckish — Mon, 11 Aug 2008 23:54:52 -0800

Using a AA battery, two pieces of speaker wire and an LED, I am trying to make a simple circuit. I am meeting with complete failure. Help! I read books for a living. I do not program computers, wire electronics, play with oscilloscopes, or regularly work on projects that require modulating a radio frequency. That said, I'm bored for the summer and looking for new projects. Choice A is a neat LED nightlight, and so I find myself (once again) trying to teach myself simple electronics, and (once again) meeting with middling levels of success.

Basically, I'm trying to wire an LED to a battery. I am following this instructable. I am using a 1.5V AA battery and a 1.7V LED, using a lower-level power supply on the assumption that I don't yet have to learn how to wire a resister. I realize that there are TWO steps to this process - making the connections, and putting the LED in one of two orientations. And yet...my LED fails to light.

I realize that this is possibly the most basic question I can be asking here, but does anyone have thoughts on what I might be doing wrong? Pictures here

Scrolling LED message sign

msacheson — Tue, 22 Jul 2008 14:13:33 -0800

Where to buy electronic scrolling LED message sign ... in person? I can find what I *think* I want to buy online, but this is something I really want to see in person before ordering, so I know what I'm getting. I don't want to be like a bride on her wedding night who opens the big package and says, "Is that what I ordered?" you get the idea.

More info: I want a scrolling message sign to use in my 6th-grade math classroom. Put students' names on there for good achievements, birthdays, whatever. You know, for the kids.

Is there any way to get an l.e.d. readout to stop fading?

quintno — Sat, 19 Jul 2008 07:13:18 -0800

I have a GE remote temperature sensor that uses an LED screen for a readout (black numerals against a grey background). REcently, the lines making up the numbers began to disappear. I replaced the batteries, but they still kept disappearing to the point that nothing is visible on the screen at all. Is there a solution to the problem or is this the end of the unit? For some reason, I thought these kind of readouts lasted forever.

Where can I find people who like to know 'how stuff works' in socal?

tarthur — Sat, 19 Jul 2008 00:46:18 -0800

Where around socal can I meet other aspiring electronic do-it-yourselfers? [backyard imagineering] I'm having a hard time finding fellow young folks (I'm 21) who read and understand the liking of MAKE magazine... people who like to take things apart and play with electronics.

Looking for others interested in figuring out Arduino boards, LEDs and automation stuff and I desperately need someone who can teach me some new tricks.

Any ideas where I can find (remotely) normal people with similar interests? Are there any user groups or something a bit less geeky?

Best LED flashlights?

Irontom — Wed, 09 Jul 2008 08:44:41 -0800

Best LED flashlights? After having yet another cheap flashlight bite the dust, I have decided to replace all of our old flashlights with LED ones. However, the range of choices is daunting. Does anyone have recommendations for good, reasonably priced all-purpose LED flashlights?

Help me whimsically prank some folks.

doift — Fri, 20 Jun 2008 05:39:43 -0800

Where can I find some small, cheap flashing lights? It doesn't really matter what kind of light they are as long as they flash, a variety of colors would be nice but not necessary, the ability to turn them on and off is nice but not necessary, they shouldn't require a cumbersome power source but they don't need to last much longer than ten minutes, and I need to be able to obtain them by tomorrow (Saturday) in NYC. From what I can gather, tiny LEDs seem like they might fit the bill, but I know nothing of how one obtains or works with them. (Or even if they flash.)

How can I hide the light under a bushel?

Don-da-lah — Wed, 07 May 2008 11:39:39 -0800

I have a motherboard in my PC, with 3 extremely bright blue LED lights. I can't disable them, because they show whether or not there is a problem with the CPU, RAM, etc. Would putting something like Blutack over them damage them? As far as I can tell, it's inert and nonconductive, but I'm concerned about the amount of heat that the LED gives out. I don't want to physically remove them, because they do perform a useful function. I just want to cover them up and stop them lighting up the room at night while I'm trying to sleep (yes, they are that bright).

So, would Blutack do the job? Or is there something more suitable that I could use?

LED Assistance

madmamasmith — Sat, 29 Mar 2008 18:55:24 -0800

I am trying to buy a LED headlamp on ebay...they range in brightness from 8 to 30+ and the one I want is 8. Is that goint to be bright enough for pitching a tent in the dark? I tried to look up LED levels on the inter-web but all I found was scientific mumbo jumbo, can someone just tell me which one to buy please!? Thanks

Visual Alarm

edmz — Sat, 29 Mar 2008 16:57:18 -0800

I need to design/buy a visual alarm for use with a PC. I'm writing a small software application that will be installed in about 200 places. The main task of this application is to monitor a database. When there is an important change in the database, the person closest to the PC needs to interact with the software.

I need a visual alarm because of 2 things I cannot change: the places were these computers are installed must be completely silent and the people working near the PC usually are at least 10 feet away and looking the other way. This means that I cannot use speakers nor headphones to notify the users that they need to check the computer.

Currently, I can only think of building a bright led that I can control via USB. This LED will be placed (using a long cable) where everyone could see it. My software could make the LED blink whenever I wanted to.

I can write the software to control this USB controlled LED and, maybe, I could find someone to design this USB led.

But, before doing that, I just need any ideas or comments you might have about my problem and idea to solve it.

Whatever the solution it must not be expensive (less than 20USD per unit) since we need to buy build at least 200 of them.

Thanks!

Getting my email LED working with Outlook/GMail

d7415 — Wed, 05 Mar 2008 09:07:50 -0800

I am trying to get the Email Indicator LED on my Acer Aspire laptop working with GMail and/or Outlook 2007. The easiest way seems to be with some sort of POP emulator/pass-through. Other than accessing the LED directly (there seems to be some work on this in linux - http://code.google.com/p/aceracpi/), the laptop came with "Launch Manager" software, which will check a pop server every x seconds, and flash the LED if and when there is a new email waiting.

My problems with this are:
1) Most importantly, the program is limited to POP3 access, without any SSL/TLS support, and without the ability to change the port number.

2) It can only check one pop account (I have 2, plus an IMAP and GMail, the last 2 being the important ones)

3) When outlook fetches the mail, which it does every two minutes, the light will clear. If I set outlook to leave messages on the server, the light will remain on after I have read them.

So, I need this program to access something, looking like a regular POP server, which can tell it there are new messages if there are unread messages, and that there are not if there are not. I assume the easiest way would be to use GMail as the "master" account, but I am not sure.

At my disposal, I have:
- a laptop, running Vista Business and Outlook 2007 and is effectively always on
- a (well, 2) linux-based, always-on server, with Sendmail installed and configured and no GUI installed.

I can't seem to find any "fake" POP servers, let alone anything that will provide the pass-through needed.

Thanks for reading, and for any help!

A Light to Charge By?

notyou — Sun, 10 Feb 2008 09:37:00 -0800

How do I light the inside of a box? Cheaply. Efficiently. Blue-LEDly. AC 120ly. I made this box and shelf to hide my cellphone charger brick and to have a convenient place to stow the phone.

I wired a switch into the extension cord and I'd like to wire the light into the same cord so that it can indicate when power's on and when power's off. Space is tight in the box (it's 2 1/2 X 2 1/2 x 11 1/2) -- there's room for another thin brick and not much else.

I've googled and etc and the results haven't been bright. So far my options appear to be 1) wire the LEDs myself (which is beyond my electrical know-how); 2) stuff something big in there (which is beyond the capacity of the box).

Any bright ideas?

Go towards the light Carol Anne!

Pollomacho — Sat, 22 Dec 2007 05:38:01 -0800

Is Al right? Am I really saving the environment by switching to CF bulbs? My wife and I, like most folks, have jumped on the compact flourecent bandwagon. In doing some more research, I've come to find out that while, yes, you can save a ton of energy in your home by switching, there is, like most things, more to the story.

The Energy Star folks tell us to leave the bulbs running for at least 15 minutes per use even if I would normally just switch the light off when I was leaving the room. There's mercury in them (yeah, there's mercury in coal, but only half of US electricity generation is coal fired). There are more parts to them requiring more energy to produce them. My house's heater has to work harder to make up for the loss of incandecent bulb heat (inversely of course the AC works less)...

So, what's the deal? Is there definative, accurate, mostly unbiased information that compares the actual and entire environmental impact of the various forms of lighting available, incandecent, flourecent, LED, halogen, big red tallow candles mounted on human skull sconces, etc...?

Please scienticians, male answer syndrome sufferers, environmental wack-os, global warmng deniers of the hive mnd set me on the right path!

Need a place to purchase around 50 LEDs in San Francisco

agenais — Wed, 05 Dec 2007 11:46:04 -0800

I need to purchase 30 to 50 orange or red LEDs by this Friday. Where can I get them as cheaply as possible in/around San Francisco? I need these lights for a project that has to be completed by the end of this week. I've purchased this set of lights from eBay a few days ago, but I doubt they're getting here in time.

The lights should be orange or red. Diffused/wide angle LEDs preferred, but not necessary. Size isn't important, but around 10mm sounds good. Purchasing 50 lights from Radio Shack is pretty pricey. I considered cannabilizing a set of LED Christmas lights, but it might be a pain in the arse to extract each light individually.

Do I have any other cheaper options for getting these lights in San Francisco? Are there awesome electronic stores that sell them in bulk, or should I suck it up and hit up all the Radio Shacks in the city?

Simple, small, cheap accelerometer/LED?

Zarkonnen — Tue, 13 Nov 2007 12:41:16 -0800

I'm looking for a simple, small and cheap way of measuring acceleration. Basically, I want to make a set of LEDs light up if they are accelerated significantly, becoming brighter the faster the acceleration happens. Searching the web yields only very expensive ($300) three-axis accelerometers that are way too sophisticated for my plans. Is there some simple solution, some widget that produces voltage roughly proportional to acceleration?

Looking for certain kind of RS232 LED sign.

prggr — Fri, 05 Oct 2007 14:37:27 -0800

I'm looking for a small-ish (under 12") LED/message board sign that I can drive from a computer (RS232) that would allow me to change the messages in real-time. All the ones I've found either run off 12v or are battery powered. Bonus points if it can beep on command, too. I'm more or less trying to find some way of creating a visual cue that can be triggered by a computer to signify some action has been completed. I'm going to have three of these on one computer. Each display would probably say something like "YES", "NO", or "ERR" and possibly flash if possible. Making it beep would also help. I can't use the standard PC speakers as I don't think I can get three separate channels on three different speakers without any overlap.

LED T shirts!

modernsquid — Wed, 15 Aug 2007 11:23:39 -0800

LED Shirts! NYC? I need to get about 8 LED tshirts, FAST (by tomorrow morning). These need to be programmable. In New York City.

Anyone know of a place? I vaguely remember that *maybe* they might have them in chinatown but i need a more solid answer than that.

Thanks!!

Where can I get a battery-powered LED clock?

ManInSuit — Mon, 06 Aug 2007 14:53:45 -0800

Where can I get a battery-powered LED clock? I'm looking for a cheap LED clock, ideally with a big bright display, that I can use for an outdoor sign I'll be putting up for a one-time project.

I’ve looked around and found lots of LED clocks w. battery backups, but from what I’ve been able to discern, the battery backup just keeps the clock running, it doesn’t actually keep the numbers lit.

Ideally, what I’m looking for would be something like this:

- Cheap (Say, less than $25)
- Big display would be great (over, say 2” high), though I guess not totally critical.
- Bright and visible in the evening (so, I guess: LED not LCD)
- Ideally, can run easily on standard batteries, but if it requires super-minimal hardware hacking, (assembling an external battery pack, cutting a wire or two) that might be okay, too.
- Battery life isn’t a super-big deal I don’t think. The sign will only be up for 12 hours or so. It’s not the end of the world if we have to change the batteries once or even twice during that time.
- I’m in Canada, so- bonus points for naming a supplier who happens to be here, and special Canadian sadness if you name a supplier who won’t ship here.

(For background – I’m doing a series of performance events for Nuit Blanche, an all-night city-wide art event here in Toronto. I want to be able to make a sign that says “next performance at 9:20 [or whatever] with a clock built into the sign, so people can know exactly how long till the next performance. It’ll be nighttime, so I’m imagining an LED clock is the best way to go. But If anyone has other ingenious ideas, I welcome them…)

Need some help designing and building LED light strips for an interactive table

warhol — Sat, 03 Mar 2007 20:31:08 -0800

Need some help designing and building LED light strips for an interactive table -- help me select 880nm IR LEDs, understand the circuitry, and figure out how to deal with power. As part of the table we need to build a couple of LED light strips making use of high output 880nm IR LEDs (yes, it's an FTIR table). One strip is 4' long, the other is 3' long and the LEDs are probably going to be 1" on center. Ideally, I'd like to power the strip from regular wall current.

So, the questions:

- Are there LED strips that I can readily adapt to this task?

- I love / hate digikey. For a novice, there's too much information. Can you help me find what I mean when I say "high output 880nm IR LED"? (I'm just thinking little bulb shaped guy with the 2 leads sticking out the bottom...)

- What do I need to do resistor-wise? The LEDs are going to be in series... Should I just be doing 1 stronger resistor at the end of the series or little ones in-between?

- How do I deal with the power? Is there a power brick that'll get me down into the range that I need or is will it end up being something custom?

Will dimmer switches dim LEDs?

twine42 — Tue, 20 Feb 2007 06:06:42 -0800

If I replace halogen bulbs with LED clusters, will my dimmer switches still work? Our house has a collection of halogen light fittings which look very cool but which seem to use a lot of power as well as loosing a lot as heat.

I'd like to replace these bulbs with LED replacement sets that replace a single halogen with a cluster of white LEDs. They tend to run on standard 230v mains lighting circuits, so I assume they have some sort of circuitry inside to back it down to a handful of volts.

The question is, how will these interact with the dimmer switches already on the circuit? Will the LEDs dim like the halogens do, or will the just shut off, or is the transformer like circuitry likely to stabilize the voltage to 5v regardless of the incoming voltage?

Flashlight up my sleeve?

ostranenie — Sun, 17 Dec 2006 08:55:42 -0800

Help me find a wristwatch with a built-in LED flashlight. I've found this and this but I'm looking for a digital display if possible. Preferably with a metal band. Thanks!

What does this do?

HSWilson — Sun, 03 Dec 2006 02:58:52 -0800

Does anyone know what this is? I found it on the ground in a casino. It is just under 1" long and .5" in diameter. It is powered by a single G3-A CNB Micro Cell battery. The battery is usually used in laser pointers and probably LED device. This thing does not emit any light, but the battery might be dead. The only moving part is the clip. More photos here, here, and here.

Where's my future-car?

limeonaire — Sat, 25 Nov 2006 13:54:43 -0800

It seems that taillights have evolved rather radically from their humble origins, now featuring LED configurations spanning cars' entire back ends. Why hasn't this kind of innovation been seen with headlights? I thought of a few questions along these lines last night while sitting in the back of a friend's van, watching the headlights around us on the highway.

Specifically:

1. Why don't car manufacturers use fluorescent or LED bulbs (backed by reflective material, just as incandescent bulbs are) in headlights? It seems to me that they'd be just as sturdy as incandescent bulbs, and probably provide brighter light with less energy required.

2. Are there practical reasons why car manufacturers continue to stick to the tried-and-true "two headlights, one on the left, one on the right" configuration, rather than using, say, a centrally mounted light bar? (Think something like the Millennium Falcon's propulsion bar, only on the front of the car and used solely for lighting purposes...) Or is it just convention?

When I discussed this with my friends, we speculated that it could be an issue of redundancy—i.e. if one gets knocked out, you still have one left. But then, I countered, couldn't that be addressed by mounting, say, two or more fluorescent tubes in the "light bar"? Or if fluorescent tubes are too fragile, perhaps multiple tiny white LEDs?

We also speculated that perhaps it was just a design/functionality issue, wherein, say, the grill is a standard air intake area for the engine, and it's easier to keep it there, rather than trying to create a radically new air intake system.

Any ideas which, if any, of these issues have curtailed the introduction of new forms of headlights?

LED replacement for bike light bulb

primer_dimer — Mon, 23 Oct 2006 07:30:22 -0800

Replacing a halogen bike light bulb with LED I've got a cheap 10 Watt rechargeable halogen bike light that came with a heavy SLA battery pack. I've been thinking about building a nice light NiMH battery pack (6V) to make it a bit more portable this winter. The bulb is a standard MR16 6V 10W bulb. Out of interest I had a look online to see if you can get LED replacements for these and it turns out you can. Is there any reason I can't drop in on of these (the 3 watt luxeon mr-16 builb) and build my battery pack to 12V instead? Anyone care to take a guess at whether this would be brighter / dimmer than my current bulb? I've seen it claimed that a 2W LED puts out the same amount of light as a 20W halogen bulb, but I doubt it's that simple (although I'd be delighted to learn that it is!). Since the LED bulb draws ~300mA rather than ~2A I could make a lighter battery pack for the same runtime, even though I'd need double the voltage.

How to invisibly provide power to an LED?

Ookseer — Sat, 02 Sep 2006 10:02:24 -0800

How could I have LED's on a pane of glass light up with no visible contacts like This amazing table? At an Ingo Maurer exhibit this weekend I saw a glass bench and table embedded with white LED's. This is the first thing I've ever seen with LED's that I would ever call elegant or beautiful. However the table and bench are essentially not for sale.

Is it possible for a non-international artist to recreate this effect? I looked very closely at the table and bench and couldn't find any obvious way that the electricity was being transmitted, not even thin traces like the ones you can barely see in transparent LCD displays.

Lighted LED color display base WANTED

america4 — Wed, 02 Aug 2006 22:24:01 -0800

Help! Trying to locate an LED display color light base to light up a hand blown glass globe (to sit on top of the lighted base); attached find a link (http://www.ccl-light.com/docs/indoor/undercab/ledlight/ql-07c/index.html) for EXACTLY what i'm looking for, but they have a $100 minimum order and they won't let me just buy 1, and I can't locate anything similar anyplace else. I do want colored LED lights. Ideas?