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Broz

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I'm looking for a high brightness red LED. There are tons of them out there, however most of the high brightness stuff is in surface mount packages. I need a through hole package because I want the LED to shine at a right angle to the board. My plan was to solder the LED in the board upright and just bend the leads over so it's at a right angle to the board. The problem is I can only find one through hole high brightness red LED and it seems a bit large. Here is the one I found:

Digi-Key - 67-2061-ND (Lumex Opto/Components Inc - SSL-LX100T123SIC)

If you notice the thing is 10mm in diameter. I need something more like 5mm in diameter as I'm trying to save weight and space. I would go with one of the small surface mount units if they could somehow be mounted at right angles to the board.

Anyone have any suggestions?
 

Broz

New Member
Harvey, wow, that's a good find, thanks. Are they really that bright at only 20mA?
 
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Broz

New Member
Thanks Mickster, I've got some options now. I guess I need to expand my parts searches. I usually use Mouser and Digikey. I probably need to expand my searches to companies that specialize in what I'm looking for. Thanks again.
 

Mickster

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Google and the correct keywords usually produces the goods. :)
 

HarveyH42

Banned
Harvey, wow, that's a good find, thanks. Are they really that bright at only 20mA?
I have no way to actually measure the output, other than my eyes, but yes they are a lot brighter than any other 5mm, 20 mA LED I've seen. I know a lot of people have a bug about Chinese products and companies, but this one is great. I've been buying most of my LEDs from them for a few years now, never an issue, and pleased with what I get. Shipping is actually less than more than a few domestic sources, and less than 2 weeks (USPS delivery).
 

audioguru

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Most Helpful Member
Some of those cheap Chinese LEDs might last for longer than a couple of days.
Notice that the beam is a very narrow 20 degrees angle and will be bright only if it shines directly at you.
 

Broz

New Member
Some of those cheap Chinese LEDs might last for longer than a couple of days.
Notice that the beam is a very narrow 20 degrees angle and will be bright only if it shines directly at you.
You know, I read Harvey's post and saw the 70 degree viewing angle but it does say 20 degrees. I need these things to be visible from 100 ft away in a well lit gymnasium at various angles. I have some surface mount LED's that would do the trick, they can take up to 500 mA but they were bright enough at 250 mA that I couldn't look at them directly with unshielded eyes, and they have a fairly large veiwing angle. I wish I could find something that bright in through hole that's about 5mm in diameter with a good size viewing angle. I have a feeling I will have to order bunch of LED's and test if their quality suits my needs. That or figure out a neat trick to mount surface mount LED's at right angles to the board.
 

HarveyH42

Banned
Your right about the 20 degrees, my mistake. I took a look around while getting the link, guess the 70 stuck in my head. I've got some hooked up to a Tiny13, Knight-rider style, that comes on at night (well about 30-40 minutes before, need to adjust that sometime...). They can be seen easy across the street, even about a block and a half down the street. Then trees block the view. Guessing well over one hundred feet from the side, but maybe not as brightly lit as your gym.

What exactly are you trying to do? It's tough to help, if we can only guess. The high wattage emitters need a heatsink or they burn out quickly. Also a series resistor isn't the best current limiter for these. I don't think PCB copper would move the heat away quick enough.
 

Broz

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They're going on an indoor RC aircraft. I don't want to give the details away just yet, but I'll post some video when I get it working. They will not be on continuously and will only flash for about 1/4 of a second and be off for about a 1/2 second between flashes and the flashes will come in bursts of 5. There will be plenty of time between these bursts (about a minute or so, more details I don't want to give away yet). So I don't think heat will be much of a problem.

I have the circuit working with low power LED's right now controlled with the PIC 10F206. I'm using a 9 volt power supply with a 5 volt regulator in the circuit. As I'm doing my part search now for the finished product I realize I might have a problem. I'll be powering this device with a single 3.7V LiPo cell with a 2.5V LDO regulator. When I factor in the drop across the transistor and the LED, I won't have anything left. I suppose I can power the LED from the unregulated voltage but even then I won't have much left. I guess I better go find some small 2 cell LiPo's.
 

Broz

New Member
Looking at the transistor I've selected, it has a Vce of 0.8V and most of these high brightness LED's drop 2V. Using the unregulated voltage would give me just under a volt to play with at full charge, and will of course drop off in use. I guess I won't need much of a current limiting resistor.
 

audioguru

Well-Known Member
Most Helpful Member
If you properly turn on a transistor, its Vce is 0.1V or 0.2V at 25mA.
A red LED might be 1.8V, 2.0V or 2.2V. The manufacturer does not guarantee the voltage. They spec a range of voltages.

If you don't limit the current for an LED then when the battery is fully charged, the LED will instantly burn out.
 

Broz

New Member
Don't get me wrong, I plan on using a current limiting resistor, it's just it will be around 3.6 ohms though. Once I decide on the parts, I'll pick a middle range value to take into account a fully charged and partially discharged battery. Because there is not a continous current, I could probably go with a lower wattage transistor and get the Vce down to what you're talking about. I have some darlington pair Zetex's laying around that I used on my breadboard prototype. I was planning on using that same type in an SMT for this project but there is no reason I shouldn't be able to go with a lower wattage transistor that would give me a lower Vce. That would help alot. Part searches are the hardest part of building a project in my opinion.
 

Sceadwian

Banned
Their service is crap but Futurelec has some nice 'value packs' that give you a variety of common components at a very low prices for a lot of parts. Nothing fancy but a lot of common transistors/linear IC's and capacitors/resistors IC sockets LED's and the like.
 
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Broz

New Member
Well, I ordered some various LED's and nothing stacked up to the surface mount high brightness LED's that I had. Still, I needed them to shine at right angles to the board so I decided trying to solder the SMD LED to a two pin header and it was quite easy to do. If I make a little jig for it, I could do quite a few in short order. Just thought I would post so if anyone needs an LED to shine at a right angle to the board and you can't find any suitable through hole LED's or right angle SMD LED's soldering to a header is an option.
 
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