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Picture of LEDs for Beginners

This instructable shows how to wire up one or more LEDs in a in a basic and clear way. Never done any work before with LEDs and don't know how to use them? Its ok, neither have I.

***If you have wired up LEDs before, this explanation might seem overly simplistic. Consider yourself warned.***

Step 1: Get some LEDs

Picture of 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.

 
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vu2aeo9 hours ago

"Once I knew that I needed a resistor of 140 ohms to get the correct amount of voltage to the LED"

I think you mean to say that the resistor ensures that the CURRENT flowing through the circuit does not exceed LED's CURRENT rating of 20 mA. In your previous step...if you had an LED rated at 1.5 volts and you used a 1.5 volt battery WITHOUT a resistor, your applied voltage would be perfect but you would burn out the LED since the current flowing through it would be extremely large.

SalM320 hours ago

The link below calculates LED resistor values for series or parallel arrays of any amount, color, and desired voltage.

http://led.linear1.org/led.wiz

JohnM1233 days ago

Thank you so much for your very good Instructable on LEDs!

I need to build a large array of IR emitter LEDs to light my yard at night and use a CCD camera to catch a jerk who's been Night Golfing in my yard. I have a collection of about 15 golf balls he's left behind Good ones, Titlist and Nike, mostly. I may start selling them on the Internet..... (This reminds me of "Mitch Cumstein" from Caddyshack!)

I plan to get a perfboard and solder it up, using your information and a nice adequate power supply. I'll have to calculate the value of the total load at operation levels, so as not to over drive them, and burn them out early... I plan a white reflector behind the array as my house is white and it would camouflage it from being seen at night. They won't t see the IR anyhow, only the CCD camera can.

One place you CAN get lots of good stuff (I DO NOT WORK THERE OR HAVE TIES WITH THEM) is a place I have bought the odd hard to find part from is a company in Miami called Dalbani Electronics. They have the run of the mill stuff too! They can get almost ANYTHING. And their prices are NOT astronomical, and are way more reasonable than at ShadyoRack. (I used to work for them, and won't buy there ever again.) I went by to find the price of a 357 button cell for a TI-30XA calculator. They sell for $5.99 for ONE. I found a five pack at Dollar General... Mercury Free, $1.00 for five.... Never pay retail if you can help it. For the two I needed, I could have bought a new calculator....

Some other alternate sources for electronic components: MCM Electronics, Jameco Electronics, Mouser Electronics. I have purchased supplies from all three of these sources over the past 40 years and find them all equally reputable.

I frequently buy at Tayda Electronics

grt57yesterday

I dig it... well done. I'm going to share to a group that likes to build models of space ships, as I often hear people ask how someone lit up a kit...

JohnM123yesterday
GrinninSam questions, "If I have a 3 terminal fixed voltage regulator, how do I make that adjustable? There is no Vref pin."

There are variable Voltage Regulation IC's that have what would seem to be a potentiometer inside them which is be adjusted within the stated range of the package. See the catalogs from Dalbani Electronics (Miami Florida), they'll mail you one. Or search their online catalog.

The fixed ones can be regulated in the fashion that Lee Wilkerson suggested.

Hook it up, pull out your DVM and adjust it to the voltage you need.
It's almost like a 'volume' knob for the voltage.
DarrenW8yesterday

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JohnM1233 days ago

The only other suggestion I might make is to use a voltage regulator (triple lead IC like device) that will keep your voltage relatively constant, and avoid resistor mis-identification problems.

You can eliminate the resistor and go forward safely. They come in values in the range you need for this. They have a range of input voltages, and will put out a steady voltage (some can be had that are variable for more money). I stick with fixed values.

Any regulator IC (fixed or variable) can be used as a variable voltage regulator by varying the voltage at the reference pin with a potentiometer. Use a parallel resistor to limit maximum excursion. The resistor values will (similar to the 'ible) vary according to voltage/current requirements for the particular IC in question. If you acquire the spec sheet for the IC you intend to use, there will almost always be a variable voltage output circuit somewhere on the page.

?? If I have a 3 terminal fixed voltage regulator, how do I make that adjustable? There is no Vref pin.

michaelb23 days ago

A usufull addition to this article is how to determine the voltage of a radom LED in the junk bin

If you can access a variable voltage supply and an ammeter (if not supplied with the VVS) and a small supply of different resistors, the LEDs will be readily testable. Connect the ammeter in series with the supply resistor and the load (+ goes toward source +) then bring the voltage up slowly. Use a voltmeter paralleled with the LED in question to monitor Vf (Forward voltage drop) and watch the ammeter carefully. If the current starts to climb rapidly after the LED is lit, turn the voltage back down to limit it.

Arturisk28 days ago

So, I'm about to begin an LED project in my car, running sets of 4 LED's(3-3.2v, .02a) in series from a transistor connected to the dome light. After much reading on many sites, there's a question I can't seem to find an answer to.

The math I'm coming up with is R=(12v - 12v)/.02a

R=0

From what I can tell, this would mean a resistor wouldn't be needed, am I correct?

One thing you will need to keep in mind in an automotive setting is that the non-charging voltage is 12V., but the charging voltage will range between 14.4 - 14.8V. A fully charged lead-acid battery voltage is 2.4V - 2.47V per cell times 6 cells. You will want a resistor value which looks at the worst case scenario. Hence I would go with the understanding that the voltage supplied may go as high as 15V.

JohnT4 Arturisk23 days ago

Hey bro, your math is correct, you do not need a resistor if your supply is 12v and your led requires 12 volt.

Mark 42 JohnT43 days ago
If you have a 12V LED, it has a resistor built in somewhere.

His maths is correct, but his electronics is not!

No. An LED is basically a current-operated device;the voltage of 3.2v is the forward biased voltage that will appear across the LED when a current of 0.02amp is passing through it. You always need a supply voltage which is greater than the forward voltage of the LED with a resistor in series. You could put two LEDs in series with a series resistor of (12-6.4)/0.02 ie 280 ohms (270 is the nearest preferred value). A 1/8 watt resistorwould be adequate, but I would be safer and use 1/4 watt. You can then duplicate that for the other two LEDs.

chintans2 days ago

Can I use 5mm LED with 1V 1A load?

You can use whatever size, voltage rating, and current rating you desire. All you need to remember is to make resistor changes according to voltage supplied, voltage required, and current required.

Very nice job. You have managed to take a lot of the guesswork out for some people. I would point out: when you insert the resistor in series with 1.7v LED and 4.5v power supply, check the voltage at the LED to make sure it is going no higher than around 1.65v.

I've played with LEDs, batteries and small motors with my kids in making circuits but I don't recognize the beige block you're using with the holes in it. Where does the soldering come in? I am apparently even more beginner than you. :)

https://en.wikipedia.org/wiki/Breadboard

No soldering necessary!

You can find them online and cheapest from Chinese sites

Thank You! Between what I've learned from you, and about throwies, and about bristle bots....my Girl Scout troop is well on its way to making wonderful things.

1$ or 2$ per led? you can find 100 5mm leds with 2-2.5$ on ebay

Kaarst2 days ago

very nice lesson for me, thanks

chintans2 days ago

Can a 5mm led take 1v 1a load?

ktalex5 years ago
so if i use a 3v led and running 5v as power what resistor should i use? im noob sorry.
JimR2 ktalex2 days ago
3 volt will just make your led put out more light but shorten it's lifetime :-)

Search on google for ohm voltage calculater. Don't invent the wheel tvice as one says. :-)

There is no such thing as a 3v led! If you have a led with a forward voltage of 3v it is presumably a high intensity led with a rated forward current of about 20mA (0.02A). With those figures the resistor would be (5-3)/0.02 ie 100 ohmsrated at least at 0.04 watt (2 x0.02)

a resistor with color code brown, black, brown, gold would break even but brown, brown, brown, gold would be a better choice
EfrainM12 days ago

that is very truth...NEVER SOLDER INTO A BATTERY!!! EVER!

If you can find some LM3909 chips it will give you a lot more options

tonep2 days ago

There is no accounting for human beings' facination for lights! This Instructable was published 9 years ago. More than 2 million views and 675 comments later this thread is still alive, with some commenting 2 hours ago to comments that were written 7 years ago. Fascinating!

Nicely written Instructable, noahw. Just a few relevant points regarding wiring up LEDs:

1. Never connect an LED to a power source (battery or other power supply) without a series resistor. The internal resistance of the battery as a series resistance is a good excuse for omitting the resistor, but as long as you haven't measured the actual internal resistance, you don't know how much current is flowing through the LED - it can easily be close to burning point of the LED. NEVER OMIT THE SERIES RESISTOR.

2. You don't need to bother yourself calculating the series resistance value. Just google for a "LED resistance calculator". They are all easy to use. Just enter the voltage and current of the LED and how many are in series/parallel and you get the resistor value. To be on the safe side, use a value that is on the higher side of the calculated value. Some even have a table to guide you with the various voltages and currents of LEDs based on colour.

3. If you are using many LEDs of different colours make sure that all the same colours are wired together (series or parallel - depending on your circuit).

4. If you have a fixed low voltage power source (e.g. 3V battery) and you have to wire a few LEDs together, consider using a parallel circuit. Use one resistor for each LED. If you have all the LEDs connected togetler in parallel and one series limiting resistor to the power source, if one of the LEDs goes open the current through the remaining LEDs increases and another one may blow after some time.

5. If your power source is to be decided by you, e.g. 9V or more, consider a series (or series/parallel) connection. See Berrydueds below.

I hope this helps.

NoelT13 days ago

Basics, like this article are great for those of us who would like to try messing around with electronics but don't know anything. Your style of explanation was very easy to follow, great article and very helpful.

Jamebonds13 days ago

I would recommend you to using three resistor for three LED in parallel. It is better than just one resistor. As for programmable chip, they all need have all LED's own resistor each. As if only one light are lit while 9 out of 10 are not lit, it won't limited to 20mA.

I have 3 packs of 2700 ohm 1/2 watt 5% tolerance resistors , what I can I do with that and LEDs?

sko565 years ago
The only reason the LED doesn't Fry from adding 1.5V is because the Alkaline Battery has an internal resistance. Ohms Law Holds true I (current) = V(volts)/R(resistance in Ω) . If there was no resistance the current would be near Infinity causing the Wattage to go through the roof as well (W=I^2*R). same reason a "throwie" works without a resistor.
How do you make an ohm's symbol on a keyboard?
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