LEDs for Beginners

Step 1 Get some LEDs

So I wasn't completely honest - I have used LEDs once or twice before for simple applications, but I never really knew what I was doing, and since so many projects on instructables use LEDs, I thought I might as well teach myself and post about it too.

I know that there are many projects already posted that contain information about how to wire LEDs for simple projects - LED Throwies, LED Beginner Project: Part 2 and 9v LED flashlight - teh best evarrr!, but I think that there could still be some use for a detailed step by step explanation about the basics of LEDs for anyone who could use it.

The first step was to buy some supplies and figure out what I would need to experiment with. For this project I ended up going to Radioshack because its close and a lot of people have access to it - but be warned their prices are really high for this kind of stuff and there are all kinds of low cost places to buy LEDs online.

To light up an LED you need at the very minimum the LED itself and a power supply. From what I have read from other LED instructables wiring in a resistor is almost always a good idea.

If you want to learn about what these materials are check out these wikipedia entries:
LEDs
Power supply
Resistors

Materials:

LEDs - I basically just reached into the drawer at Radioshack and pulled out anything that wasn't more than $1 or $2 per LED. I got:

2760307 5mm Red LED 1.7 V
2760351 5MM Yellow LED 2.1 V
2760036 Flasher Red LED 5 V
2760041 2 Pack Red LED 2.6 V
2760086 Jumbo Red LED 2.4V

Power Supply - I really didn't know what I would need to power them so I bought some 9V batteries and some 1.5V AA's. I figured that would allow me to mix and match and make enough different voltage combinations to make something light up - or at least burn those little suckers out in a puff of smelly plastic smoke.

Resistors - Again, I wasn't too sure what I would need in terms of resistors here either. Since I got a whole bunch of different LEDs with various voltages I knew that I would need a couple different types of resistors, so I just bought a variety pack of 1/2 Watt Carbon Film Resistors (2710306).

I gathered up a soldering gun, solder, needle nose pliers, electrical pliers, some primary wire and electrical tape too since I thought they might be useful.

Comments

[ydeardorff]

I'm trying to build an array using 2.0 vdc 15K MCD 4 post LED's.
My smaller array is fed by a 12vdc 150mA power supply using 20 LED's hooked in parallel. they hooked up using 510 ohm resistors.
I had 4 burn out while handling the unit. was this because of something I did wrong?
Im building tail lights for a custom car. so they will be fed by the cars 12 volt system.

Any help?

[PlattinumPanther]

you want to calculate 12-14VDC for an auto application as the only time you should get 12VDC is when the generator isn't running

[cyber.engineer]

Check your speck for Vd and Imax calculate using my equations below. LEDs in Parallel will not always be the "exact" same brightness. However if you put them in series one burns out they all fail if it goes open if it shorts your other LEDs get brighter and have a lower life. If it were me, I would use one resistor per each LED and quit using them in parallel. That is just a personal like. www.brainpwr.com

[sdanks]

Most LEDs want about 18 milliamps of current. So 12v/.018A = 666.67 ohms. I would use about a 680 ohm resistor in line with the LED. That would make them last longer. Max is usually around 20 mA. You were sending 23 mA through them. So just change to around a 680 ohm resistor or whatever the standard resistor value is that is cheap around that value.

[cyber.engineer]

Sdanks you are in error you must drop 2 volts and make it 10 for your equation so it will be 10V/.018A and most that I use are 20ma. some are much more and the Vd (Voltage drop is higher) www.brainpwr.com sorry, an Electrical Engineer here with 30 years experience

[sdanks]

I was just trying to help the guy that didnt know anything about electronics. But since you are an electrical engineer, lets be more accurate. Silicon voltage drop across a junction is actually .6 -.7 volts. So , 12V - .6 = 11.4 Take 11.4 volts and divide it by .018 and you get 633.33 ohms. SO, a 680 ohm resistor would work out good. 20 mA is usually Ic max with most LEDS wanting around 18 mA typical. a 680 ohm resistor would work really well. I stand by my initial statement. Different LEDS have different typical current requirements, but even at your calculations, 10/.02 = 500 ohms and he burned up 4 leds at 510 ohms, so I would STILL recommend he use 680 ohms resistors.

[pgheit01]

The charging circuit of a car typically puts out 13.6V, so 13 / 0.018 = 722.222. Sorry, but I don't know what the common size resistor is to exceed that rating. Also, the power is kinda noisy, so I'd think about transients. At the least, I would put a meter to the socket with the engine running and see what I get. Maybe even take readings at idle and with a friend stepping on the gas a little. Good luck!

[brradusvi]

how much watt does each led use, what do i need to do to convert to plug in to the wall, I bought x-mas light half price after x-mas making each led cost .45 cent , now I want to make my own lights, I figured i would use a light screw in plug so I could screw it into the lamp. and a circut board to form the light patterns put how do you convert the power

[Asbestos]

In most online places, you shouldn't have to pay more than 5-20c per LED (5mm). Of course, you have to pay a bit of shipping, so you need to buy them in bulk (say, $20 of LEDs) to make it worth it.

[SlimDan22]

Yeah, i tend to avoid radioshack for LEDs i usually order them off ebay in bulk packs of 50 for $5 from from this manufacturer in Japan

[travisabruce]

What is the name of the manufacturer?

[codongolev]

hey! I did that too! now I know they'll actually come. (I ordered them about half an hour ago.)

well, really it's coming from hong kong, so china.

well, really, hong kong is just in china, not of it.

*slaps self in face* I'll shut up now.

[think3000]

http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&categoryName=cat_15&subCategoryName=Opto%20%26%20Illumination%20%2F%20Discrete%20LEDs&category=1520&refine=1&position=1&history=me6yebna%7CsubCategoryName~Opto%2B%2526%2BIllumination%5Ecategory~15%5EcategoryName~category_root%5EprodPage~15%5Epage~SEARCH%252BNAV
 I know this is kinda long but it is a good site for leds.  The original site is www.jameco.com

[bigwhitebob]

Thanks for doing this, I do still have a question. I want to make some led earrings and I am curious how long they would stay lit with a small 1.5v button cell battery? any ideas? Thanks

[un0]

depends on what type of LED ur using. If you have only 1 LED connected to the batteryyou should get a 1.5v LED. You MIGHT be able to get of with higher voltages, but they could be poorly lit because of the lack of power.

[mark101]

don't buy from radio shack as there prices are super inflated.

[cfire]

Radio Shack is great for what it is. I need something NOW, and cannot wait for it to be delivered. It used to be the place to get all your supplies, but now they are more of a "I forgot to get a ..." type of store, as shown by the inventory they carry. They used to have entire walls of parts, now it is a small section of an aisle. They are kinda like your corner grocery store. Not a place to get all your food from, but when guests are over for dinner, and you run out of mustard, it is worth the extra price not to travel across town and wait in the long lines.

[hunter1125]

Google seach something about an LED wizard, there are programs that can calculate what resistors you need based on the LED voltage, current and battery voltage. I cant remember the website but there is a good website that can help find the right resistor.

[Coolboyme]

please tell me if led's fuse like other bulbs i have this doubt as LED"s dont have filaments

[daspoint]

You are correct - they do not have a filament. They have a "Junction". This is what makes them less prone to damage do to dropping and other abuse.... that's not to say they can not -not- be damaged in this manner-- they can . If an LED is fed to high a voltage a couple of things happen almost immediately before failure. First- They get hot ! They can get hot enough to melt the lens - Be careful !!! Second - they change colour (red turns to an orange, green turns almost yellow ) then the junction fails. Sometimes it is permanent - sometimes the damage is temporary. Hope this helps.

[demonshreder]

My first ever LED was a 3v Bright light model of blue colour for a night lamp. I just plugged it into the 9v Cell and poof.....there you go........instead of a bright blue light i got a reddish one in the "filament" thing and a good fresh smell of plastic.....thx to this guide now I know how to use LEDs without ****ing them up......

[Minifig666]

 They can sometimes explode too!

[s3ctorsev3n]

I had an electronics class in middle school.  The first thing one kid did the day we started working with LED's was run over to the wall and jam the two electrodes into a wall socket.  The resulting explosion was quite spectacular, if somewhat short lived.  Needless to say, we immediately skipped to the lecture on the importance of resistors.

[bcraun]

cool.

[Coolboyme]

Thank you very much daspoint. Your post was very Helpful.

[AmandaGbur]

Very nice instructable! Helped me learn A LOT. One question though, where can i buy red/black wire?

[demonshreder]

Dude, just go to your nearest hardware or electrical shop and ask them for electrical wire of lets say, 1 meter. Then as the shopkeepers are enlightened fellows they will give you the proper wire needed for your usage just tell them why you want the wires for if you dont know the exact technical specs....

[Virtuous]

Are there any ways to tell how much voltage an LED can take...without testing it o burn out...like if I desolder and plan to reuse LEDs out of some circuit board from some random thing, is there ne way to tell the voltage on the LEDs i salvage?

[bware]

Voltage is a function of color, as in a rainbow red=1.5v to purple=4v. White are usually 3.5v, infra-red and UV are usually fairly close to the respective ends of the rainbow.

More practically the is no danger of under powering LEDs. You can start at a low voltage (say 1v) and turn the voltage up till the LED lights at full brightness. If you burn it out before you get to the brightness you were expecting it probably wasn't a very useful LED anyway.

[DELETED_phlynx]

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[Zem]

Only if you don't have a Resistor.

[FireDragon]

Or blow them up in your face

[natethegreat88]

Sounds like an LED bomb 'ible should be made.

[mspearin]

Yeah but it doesn't blow up every time!!! :)

[grizzly g]

yeah!

[TCPMeta]

What about the small square shaped LEDs?

[sivion44]

Don't use 9V.

[spainard7445]

you say to use half watt resistors, can I use 1/4 watt resistors, and can someone explain the difference in wattages, what they mean. thanks

[Bionex]

Go Here and it tells you alot about it a nd it has a calculater so you can see what kind of resistor you need.

[alexhalford]

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