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.***
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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:
Power supply


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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DerekP8 days ago

I am new to electronics, and I have a Nintendo 64 that I want to wire roughly 16 LEDs into. I have seen many people use a 5 volt power output on the board. Should I wire the LEDs in parallel or series?

Hi can you tell me if this is correct - I purchased these 50 LEDs connected in series powered by 3 x AA batteries (4.5V) i want to switch to a 4.5V multivoltage adapter instead of batteries but need a resistor to prevent dimming and dieing of the leds.

I know the Voltage is 4.5v and the Current is 10mA so using Ohms Law would i be right in saying that based on a "white" LED generally having a forward voltage (vF) of 3.3V i would need to take the 3.3v from 4.5v to give 1.2v for ohms law

Resisance = 1.2 (v) / 0.01 (10mA)

This gives me a 120 resistor.

adding this in the series would this help? or am i totally out lol

Thanks :)

i have 3x6v led lights that each take 4x1.5 AA battery's

im wanting to wire them to all up so they can be powered by a wall adapter

what power size adapter would i need to do this


Maybe someone on here can answer this for me. I have aftermarket headlights (spec d) on my car. Had em for 2 years and now I have two leds blown out that are part of the eyebrow on the lights. They are wedge style leds with one led on each light. There are 5 LEDs wired in series for each eye brow. You can't buy the LEDs from the company they don't sell them and they won't tell me where to get them. My problem is I tried a 12v led and it wouldn't light up. I checked the voltage and each led in the series only uses 3volts. Where can I find a 3volt wedge (looks like t10) led?!?? Email me at
Rushmoore20 days ago

This was so awesome! Very clear and easy to understand! I had been looking at other sited the whole morning and this was the only explanation that made sense. Thanks you!!

i take an led dim light an remove the 2 resisters and plugged on the switch i can see a lightinig!! and it stoped what does it mean???

You probably blew the LED because of too much power going into it. Try again with a new LED and a bit more resistance.

ahwang4 years ago
I have a question but btw, you have an awesome website for ppl like me who's interested in learning to light up some LEDs!!!

Forward voltage: 3.0-3.2
Current: 20ma
Battery: 6V

1. Following your instruction, I first tested my 2 of my LED, in a series without any resistors to my 6V and baam! it lit up! thanks!
but after about 20 secs, the LEDs started to get hot. Is that normal? I don't think I'd need any resistors or I wouldn't even know how since I would get 0 ohm resistor value

2. My project is to light up 8 LEDs. 4 pararell LED each side, then 2 of 4 pararell LEDs in series. so like. (1+1+1+1) + (1+1+1+1).
so I'm thinking (3V, .08ohm) + (3V, .08ohm) so it would be 6V with .08ohm right?
then it would require no resistor since 6v-6v=0 right?
Or would that get too hot and require resistors?

any help is appreciated!!!

do the first one with resistor, u were giving the led toooooooooooooooooooooooooooooooooooooooooooooo mich current abd volts

ronym83 ahwang7 months ago

6 volt battery sometimes have more than 6 volt

( it's depend on battery state... it's full... or near empty )

so we must measure the exact voltage of battery using volt meter

if the voltage of battery is... say 6,5 volt

devide it by two we get 3,25 volt...

that's why your LED are too hot... because you over voltage it


just like 12 volt battery which can be 10,7 to 12,8 volt

( it's depend on charge state of battery )

it also can be 14 volt ( if the battery are connecting to the charger )

cellis6 ahwang3 years ago
LEDs power is based on Amperage not Voltage, that's why they are getting hot. Think of them like a resistor, when you put 2 resistors in series, you drop voltage each resistor but Amperage never changes.

So if your LED requires Forward Voltage of 3.0-3.2Vf, and 20mA, and you want to run it off 6V. If you were just trying to power one LED it would be (6V-3.2V)/.02mA. Meaning you'd need a 140 ohm resistor before attaching the LED to power.

As far as hooking them up in series/parallel, you should be able to do it with one resistor at the beginning of each series of 4 of 140 ohms. Which would make each series 20mA and 3.2 Volts after the resistor. Hope this helps.
johnefrancis3 months ago

We built a couple 76 IR Led lights to run off 12 volt batteries for a portable surveillance system. Once the voltage of the battery drops after several hours the led's fade a bit and then go out but the camera continues to run all night because we're using a dc-dc converter to drop the voltage down to 5 volts.

Is there a way to drop the voltage required for the led's down to 5 volts or even 3 volts by adding a single large wattage resistor to the system? If so what's the formula?

Our other alternative is to add a second battery is series to raise the voltage to 24 volts and then use a dc-dc converter to drop it to 12.

Thanks in advance!

give the leds their own batter... if u cant do that a high wattage resistor would also work but sep batters is the best option coz u will get xtreme runtime,... OR a sec batter and high watt resistor togehter will make the leds last longer than the camera

mizami1 month ago

Say i have 12V power supply and 15 LEDs. i decide to make three loops of parallel LEDs (3.6V each) and arrange them in series (i.e one loop has five LEDs arranged in parallel and the three loops are connected by series). This means for every loop, there is approximately 3V to power adequately.

Question is do i still need to put resistor in front of LEDs since theoretically i have used voltage power effectively? If yes, do i put the resistor in series of each LEDs or in series of every loop?

i dont thiink you would need one. but im not certain, send a pic :D

CarlosC111 month ago

I want to connect 100 pcs LEDs together, for my garage. I was planning to connect them with a cellphone charger 12v. CanI do it? And how should I wire them?

MarkJ101 month ago

Here's My question

in Parallel, I m trying to use Parallel Connection in the Resistor which means, Single Resistors on different Rows(Parallel) of Led, in my case 1 resistor on 1 Led and my Voltage Source would be 9V, My Led's are Red^4 1.6 V @ 20 mA and my Resistor is 390 ohms, is that a Good Connection? I mean they're all just the Same V and mA but with a Equal Voltage Source Flow(9v) and of course Parallel makes Led more Brighter right?

Will that Make my Battery Drain up Faster?

and Is my Circuit Good enough that my Led wouldn't burn up?

Beacause i have a Simulator,(Everycircuit) and when i Try to use Series on 4 Led's with One resistor, even if the the resistor is Correct, The first Led would Get High V and High Ma 23-27.4mA, before it go down to the exact 1.6V with under the maximum specified mA of the Led which is 18-19mA if that's the case and if that first Led Died, then the connection will die also,

by the way im using an AC/DC inverter, but my backup batt is a Standard 9V Battery

Ok, trying to light 3 x 1.5w infared leds from a USB cord (5w). What would be the best way to hook them up? Series or Para? What resisters would I need (if needed) Thanks!

ElenaG3 months ago

A novice needs help: We just bought a five piece Christmas entryway
set which includes five separate LED light strings and 5 separate
double D cell battery power supplies. I want to convert all to be
powered by one AC adapter I have which has a 12VDC and 2A output. There
is no Watt or Amp ratings on the light strings. My best guess is that
each light is .069 Watts with about 25 lights per string for total of about 125 lights. What is best way to wire these light
strings to the one AC adapter? Thanks in advance for any help

JohnL8 ElenaG2 months ago

It's a tough question because what you exactly have is unclear. You mentioned "double D cell battery power supply". Is it just one 3.6V (or other voltage value depending on the battery type) or more than one "double D cell battery" connected either in series or in parallel together? Does each LED string has any electronic components (e.g. a driver) connected or simple LED?

Anyhow, if you find some sort of circuit somewhere on the LED string, it would be complicated to make any change unless the battery power supply is in fact around 12V, then connect the 5 string in parallel. If visually you only see LED on each string and if you have a multimeter, measure the voltage of the power supply. Depending on the measured voltage, the wiring may be very easy or complicated.

Assume measured around 3V, then connect 4 strings in series, +-+-+-+-. The fifth string requirs resistor.

Assume measured around 6V, then connect each of 2 strings in series, +-+-; then connect the two "2-strings-in-series" in parallel. The fifth requires resistor. Based on the same procedures, you can figure out connections for other voltage options.

In case you want to power all the 5 strings, current-limiting resistors are needed or re-assemble the strings to have equal length unless the battey supply is around 12V.

AliS25 months ago

Thanks for this guide, very useful. I'm having an issue in following something, though - ended up burning out a couple of LEDs presumably due to a mistake I'm making.

I've got a 9v battery power source, trying to drive two blue LEDs (3.4-3.8v rated, 20mA) in parallel. I calculated necessary resistor as R = (9 - 3.4) / 0.04 = 140 ohms; to be on the safe side, I used a 180 ohm resistor (brown/gray/brown/gold) in series (battery + to resistor; resistor - to + pole/anode of both LEDs; - pold/cathode of both LEDs back to battery) on a breadboard. Upon connecting the 9V battery the first time, circuit lit; on 2nd time, it then stopped and I smelled distinct LED burnout - after which both LEDs would no longer light, even when connected individually to a 3v (2x AA) source.

Would appreciate any advise re: what I'm doing wrong. Thank you!

JohnL8 AliS23 months ago

If the 9V power supply is from battery, your connection works with drawbacks. If the two LED are from the same manufacturing batch, there will be less potential problem. If they are from different batches, one may draw more current than the other and one of LED will burn or weakened. The second time power is connected, the already-weakened LED couldn't handle more stress and blow. Now all the current will be consumed by the survived LED. With double current, it burns out as well.

In case the 9V is from an AC adapter (wall-wart), your LED may be burnt due to higher than anticipated current. A 9V AC adapter is guaranteed to provide a minimum 9V at a maximum load specified by the adapter. As the two LED only draw 40mA, the supply voltage could be 11-13V or even higher. And your LED will be blown out eventually as the current supplied to each LED is higher or way higher than 20mA. It also have the same problem as of battery.

That is why separate resistors are required to connect to every LED string connected in parallel, either each string consists of just one LED or a few LED, to avoid what you have experienced.

romanycaravan3 months ago

need help! Trying to wire up 4 led (night light brightness lights) to replace my (4) conventional lights. Would like to wire them all together and be powered by a 12 Volt adapter. I have no experience in doing this. Anybody willing to chime in? Thanks folks..

johnefrancis3 months ago

We built a couple 76 IR Led lights to run off 12 volt batteries for a portable surveillance system. Once the voltage of the battery drops after several hours the led's fade a bit and then go out but the camera continues to run all night because we're using a dc-dc converter to drop the voltage down to 5 volts.

Is there a way to drop the voltage required for the led's down to 5 volts or even 3 volts by adding a single large wattage resistor to the system? If so what's the formula?

Our other alternative is to add a second battery is series to raise the voltage to 24 volts and then use a dc-dc converter to drop it to 12.

Thanks in advance!


i need to get a contentious 2.9v,200 mah to power my digi-speedometer in bike....can i take it from bike bettery.which resistor i need to use...please help me...

Thanks in advance

banman114 months ago

Hi noahw,

Great article. I converted my outdoor garden light setup from old style halogen bulbs to LED technology. I managed to buy 12v 1 watt LED's from internet for a few bucks.

Thanks so much. :-)

BobyF6 months ago

I have one of those a newer one with a led display, I have been powering a 50w smd bead with nothing but a 24v in and a 32v out. Just make sure your input amp. is rated for the beads. Now since you are wiring it in a series be very careful with your v and amp. make sure it`s outputing a constant 3v and slowly bring it up to 3.3v the chinese buck converters will drop in voltage if the supplied amps are not enough. Also when led`s do that it means either too many volts or amps. check your resistors and see if they are smelly, kind of like a burnt carbon smell. Try adding a

DenisĐ6 months ago


I see that this topic is little bit old

But knowledge cant get old :)

my question is: what do i need for connecting few leds in parallel, on my "old" USB lamp(i want to use only housing of this lamp).

Becouase on USB power limit, parallel connection is logical way, or?

I think some kind of step down module is needed that drops 5v to desired 3-3.3v that is needed for led's, for ex.

Power souce is wall socket->USB 5v 1A,

led's are 5730 3-3.3v 150mA,

or 1W beads 3-3.6v 300-350mA.

Is it ok to connect 6 of 5730 led's, and/or 3 of 1W led's in parallel?

Is there something else needed for make this working?

P.S. this "old" usb lamp has 13 led's(those small ones) and each has resistor in front, but after short time they start to rapidly blinking and at the end stop working. What that mean, led's are dead, or resistors are not ok, or what?

tnx, and sorry for a little long post :)


killrsheep8 years ago
Am i the only Electronic-Loving guy whou wonders WHY? Why god Why! why would you wire Leds in series?! LOL, but seriopusly, i just want to recommend to those who want to build Led projects to try and use paralell everytime, if for any reason something gets messed up the whole set wont light, if a Led gets shorted you will get a higher current than the one you calculated, Paralell sets are independent from each other, have a nice day, i didnt mean to sound like a "know it all" its just that electronics is the one subject im not faling this semester, thats why i love em
because if you want to power 4 leds, why waste a resistor if you're using a 12 volt input and your leds take 3 volts?
wow, that comment is really old XD Now that i see the instructable again, its actually pretty well written and it does involve ohms law to make everything safe and functional, so yeah it does get a 5/5 however if you have 4 led that consume exactly 3 volts each (wich they dont) and you hook it up to exactly 12 V (wich is hard yet not impossible to achieve with the proper circuit) and we hook it up to a mm lets say car battery... im sure your LED's will light pretty bright for an instant and then die, im not encouraging anyone to do it, but if you do maybe some heat resistant gloves are a good idea. small batteries usually cant supply enough current to destroy LED's thats the reason why led throwies etc work without the resistor

are you sure without resistor LED can burn in few second ? ever try it ?

i ever connecting 4 series of 3 watt LED to 50 AH battery for 3 hours

yes the LED is hot ( even LED are producing heat, that's why we still need proper heat sink+fan if necessary ), but they are not burn

i measure voltage in every LED... 3,0 - 3,2 volt each

so it's safe because its around LED rating at 3,0-3,7 volt


for 20mA white LED, we have different case

because it's voltage rating are only 3,0-3,4 volt


car battery have stationary voltage at 12,6-12,8 volt

so devide by 4, we get 3,15 - 3,2 volt

but if car battery jump to 14 volt ( because alternator are charging battery )

we get 3,5 volt in each LED

that's why in 20mA white LED it's a bit riskier

( 3,5 volt in 3 Watt LED it's not a big deal

because it's less than max rating of 3,7 volt )


using resistor to limiting current ?

it's useless too if battery jump to 14 volt

I = V / R

because R are constant

but V are up... so I must be up in value

( so it's not safe either just using resistor )

Can there a difference in the brightness if you use series ? say R= (6v-8.0)/.02mA
I am such a beginner!
sushil0109 months ago

actually i already got 5 led(white) in series with 4.5 power supply..and there is one resistor well i dont care about that resistor. Now the main problem is supplying 4.5v to it is really difficult for me i need to buy batteries time n again,instead of that 4.5v i would like to replace with 12 volt(lead acid)battery just to supply power,for that what resistor do i need to replace with?please help me.

djspincycle10 months ago

Hi Noah, Some LED spec sheets list "Foward Voltage" and "Reverse Voltage". Which is the voltage that is correct for supplying to the LED?

tomc53 djspincycle10 months ago

Forward Voltage is the volatage when it lights up. reverse voltage is the limit to what it can take hooked up backwards. Hint: If you want to hook an LED to AC, make sure that the forward and reverse are both 1.4X the rated AC voltage. For example, if you wnat to hook up a series of 3V leds to make christmas lights and run them off 120VAC, you could use 56 lights, or 50 lights and a resistor.

thinders10 months ago

i followed the steps in this project ....

and posted a comment (with a pic) that my LEDs have all gone "dim" ....

Can someone take a peek at what I posted and advise me on what I did wrong ...thanks

eortega81 year ago

"What that means is that if I had a 12V car battery, I could power 4, 3V LEDs (attaching a resistor to each of them)." Can someone please explain why he needs to attach a resistor to each LED if all together, the LEDS use up the 12 volts?

baecker03 eortega811 months ago

Leds work differently than incandescent lamps. first it is a semi conductor, when the voltage is applied, current rushes through the Led as if there was no resistance. incandescent bulbs increase in resistance as they warm up if I remember correctly. more current equals more power and consequently more heat. thermal runaway kills semiconductors.

dudes eortega81 year ago
Because the amps of a car battery would blow out an led instantly. It's not all about volts it's also about amps. Hope this helped.
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