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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

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.

Step 2: The LED

LEDs come in different sizes, brightnesses, voltages, colors and beam patterns, but the selection at Radioshack is pretty small and so I just picked up a couple different LEDs from what they had in a few different brightnesses and voltages. I kept close track of what LED was what voltage because I didn't want to accidentally send too much current through one of the low voltage LEDs.

The first thing I did with the LEDs was figure out which wire (its called an electrode) was positive and which was negative. Generally speaking the longer wire is the positive electrode and the shorter wire is the negative electrode.

You can also take a look inside the LED itself and see whats going on. The smaller of the metal pieces inside the LED connects to the positive electrode and the bigger one is the negative electrode (see picture below). But be warned - in the LEDs I picked up I didn't always find this to be true and some of the LEDs had the longer electrode on the negative when it should be on the positive. Go figure - its OK though, if it didn't light up I just flipped it around.

Once I knew what was positive and what was negative I just had to remember what the voltage of each LED was.

All my LEDs recommended 20mA of current. 20mA is standard for most LEDs.





Step 3: Power supply

To make the power supplies I just soldered some wire onto the ends of the batteries I had bought so that I could easily attach the LEDs to them. The 9V battery served as my 9V power supply, one AA battery made a 1.5V power supply and three AA batteries bundled together made a 4.5V (1.5V + 1.5V + 1.5V = 4.5V) power supply. I didn't use alligator clips on the ends of the wire, but they would have been helpful here.

Step 4: Resistors

I opened up the assortment pack to find that resistors aren't labeled with what value they are. The pack said it contained a whole bunch of different resistors from 100 ohms to 1 Meg ohm so I set out to see what was what. When I poked around online I found that all resistors have a coding system on them that tells you what value they are.

Here are two pages which explain in depth about how to calculate resistor values.

Do it yourself
or
Have it done for you

I'll go through the examples of how I calculated the values myself in the next few steps when I start wiring up my LEDs.

For the time being I just admired their little colored stripes and moved on to trying to get just one LED to light up.

Step 5: One LED, no resistor

I thought that I would start as simply as I possibly could - just one LED with no resistor. First I had to decide what power source to use and which LED to light up. This may seem obvious, but this was my first time through so I might as well be as clear as possible...

LEDs require sufficient voltage to light them. Sometimes if you give them too little voltage they wont light at all, other times they will just shine dimly with low voltage. Too much voltage is bad and can burn out the LED instantaneously.

So ideally you would like the voltage of the LED to match the voltage of your power supply, or even be slightly less. To do this you can do a couple of things: change your power supply voltage, change the LED your using, or you can use a resistor that allows you use a higher voltage power supply with a lower voltage LED.

For now I just wanted to get one lit up so I chose my the power supply that had the lowest voltage - the single AA battery which outputs 1.5V.

I chose to light the red 1.7V LED since the battery outputs 1.5V and I knew I wouldn't kill the LED with too much power.

I wrapped my positive wire from the battery to the positive electrode of the LED and wrapped the negative wire from the battery to my negative electrode and presto - let there be LED light!

This first experiment was pretty easy to do - just some wire twisting and enough knowledge to know that the 1.5V power supply would light the 1.7V LED without need a resistor.

Step 6: One LED with a resistor

It was just a coincidence that I bought an LED that was 1.7V and that it ended up working being able to be powered by my 1.5V power supply without the use of a resistor. For this second setup I decided to use the same LED, but up my power supply to the three AA batteries wired together which output 4.5V - enough power to burn out my 1.7V LED, so I would have to use a resistor.

To figure out which resistor to use I used the formula:
R = (V1 - V2) / I

where:
V1 = power supply voltage
V2 = LED voltage
I = LED current (usually 20mA which is .02A)

Now there are lots of calculators online that will do this for you - and many other instructables reference this as a good one, however, the math really isn't too hard and so I wanted to go through the calculation myself and understand whats going on.

Again, my LED is 1.7V, it takes 20mA (which is .02 A) of current and my supply is 4.5V. So the math is...

R = (4.5V - 1.7V) / .02 A
R = 140 ohms

Once I knew that I needed a resistor of 140 ohms to get the correct amount of voltage to the LED I looked into my assortment package of resistors to see if I could find the right one.

Knowing the value of a resistor requires reading the code from the color bands on the resistor itself. The package didn't come with a 140 ohm resistor but it did come with a 150 ohm one. Its always better to use the next closest value resistor greater than what you calculated. Using a lower value could burn out your LED.

To figure out the color code you basically break down the first two digits of the resistor value, use the third digit to multiply the first two by and then assign the fourth digit as an indicator of tolerance. That sounds a lot more difficult than it really is.

Using the color to number secret decoder website found here, a 150ohm resistor should have the following color code...

Brown because the first digit in the value resistor I needed is 1
Green because the fifth digit is 5
Brown because in order to get to 150 you have to add one 0 to 15 to get to 150.
Gold - the resistors I got all have 5% tolerance and 5% is represented by gold

Check out the decoder page link above if this isn't making sense.

I looked through all the resistors, found the one that was brown, green, brown, gold, and wired it in line on the positive electrode of the LED. (Whenever using a resistor on an LED it should get placed before the LED on the positive electrode).

Low and behold, the LED lit up once again. The 150 ohm resistor stopped enough of the 4.5V power supply from reaching the 1.7V LED that it lit up safely and kept it from burning out.

This is just the process that I went through to figure out what resistor to use with my particular LED with my particular power supply. You can easily use the formula above to figure out what value resistor to use with whatever LED and power source you happen to be using.

Step 7: Wiring up multiple LEDs in series

Now that I knew how to wire one LED with various combinations of LED voltages and power supplies, it was time to explore how to light up multiple LEDs. When it comes to wiring more than one LED to a power supply there are two options. The first option is to wire them in series and the second is to wire them in parallel.

To see an in depth explanation about the difference between series and parallel check out this page. I'm going to cover wiring LEDs in series first.

LEDs wired in series are connected end to end (the negative electrode of the first LED connects to the positive electrode of the second LED and the negative electrode of the second LED connects to the positive electrode of the third LED and so on and so on...). The main advantage of wiring things in series is that it distributes the total voltage of the power source between all of the LEDs. 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). Hypothetically this could also work to power 12, 1V LEDs; 6, 2V LEDs; or even 1 12V LED if such a thing existed.

Ok, let's try wiring 2, 2.6V LEDs in series to the 9V power supply and run through the math.

R = (9V - 5.2V) / .02A
R = 190 Ohms
Next higher resistance value - 200 Ohms

Now the variety package of resistors didn't come with a 190 or 200 Ohm resistor, but it did come with other resistors which I could use to make a 200 Ohm resistor. Just like LEDs, resistors can be wired together in either series or parallel (see next step for an explanation on wiring things together in parallel).

When same value resistors are wired together in series you add their resistance. When same value resistors are wired together in parallel you divide the value of the resistor by the number of resistors wired together.

So, in the most simplified sense, two 100 Ohm resistors wired together in series will equal 1 200 Ohm resistor (100 + 100 = 200). Two 100 Ohm resistors wired together in parallel will equal one 50 Ohm resistor (100 / 2 = 50).

Unfortunately, I learned this key point after I wired my resistors together for the experiment. I had originally wanted to wire two 100 Ohm resistors together to equal the 200 Ohms of resistance I needed to protect my LEDs. Instead of wiring them in series, as it should have been, I wired my resistors in parallel (did I mention I am beginner with resistors?) So my resistors were only providing 50 Ohms of resistance - which apparently worked out OK on my LEDs in the short duration of the experiment. Having too much power getting to the LEDs would probably burn them out in the long term. (Thanks beanwaur and shark500 for pointing this out.)

I took my resistors and placed them in front of the positive lead of the first LED that was wired in series and hooked them up to the battery and once again, there was LED light!

With three different combinations of LEDs and battery power supplies and no puffs of plastic smoke yet things were looking good - aside from my little confusion between wiring resistors in series and in parallel.

Step 8: Wiring up multiple LEDs in parallel

Unlike LEDs that are wired in series, LEDs wired in parallel use one wire to connect all the positive electrodes of the LEDs your using to the positive wire of the power supply and use another wire to connect all the negative electrodes of the LEDs your using to the negative wire of the power supply. Wiring things in parallel has some distinct advantages over wiring things in series.

If you wire a whole bunch of LEDs in parallel rather than dividing the power supplied to them between them, they all share it. So, a 12V battery wired to four 3V LEDs in series would distribute 3V to each of the LEDs. But that same 12V battery wired to four 3V LEDs in parallel would deliver the full 12V to each LED - enough to burn out the LEDs for sure!

Wiring LEDs in parallel allows many LEDs to share just one low voltage power supply. We could take those same four 3V LEDs and wire them in parallel to a smaller power supply, say two AA batteries putting out a total of 3V and each of the LEDs would get the 3V they need.

In short, wiring in series divides the total power supply between the LEDs. Wiring them in parallel means that each LED will receive the total voltage that the power supply is outputting.

And finally, just some warnings...wiring in parallel drains your power supply faster than wiring things in series because they end up drawing more current from the power supply. It also only works if all the LEDs you are using have exactly the same power specifications. Do NOT mix and match different types/colors of LEDs when wiring in parallel.

OK, now onto to actually doing the thing.

I decided to do two different parallel setups.

The first one I tried was as simple as it could be - just two 1.7V LEDs wired in parallel to a single 1.5V AA battery. I connected the two positive electrodes on the LEDs to the positive wire coming from the battery and connected the two negative electrodes on the LEDs to the negative wire coming from the battery. The 1.7V LEDs didn't require a resistor because the 1.5V coming from the battery was enough to light the LED, but not more than the LEDs voltage - so there was no risk of burning it out. (This set up is not pictured)

Both of the 1.7V LEDs were lit by the 1.5V power supply, but remember, the were drawing more current from the battery and would thus make the battery drain faster. If there were more LEDs connected to the battery, they would draw even more current from the battery and drain it even faster.

For the second setup, I decided to put everything I had learned together and wire the two LEDs in parallel to my 9V power supply - certainly too much juice for the LEDs alone so I would have to use a resistor for sure.

To figure out what value I should use I went back to the trusty formula - but since they were wired in parallel there is a slight change to the formula when it comes to the current - I.

R = (V1 - V2) / I

where:
V1 = supply voltage
V2 = LED voltage
I = LED current (we had been using 20 mA in our other calculations but since wiring LEDs in parallel draws more current I had to multiply the current that one LED draws by the total number of LEDs I was using. 20 mA x 2 = 40 mA, or .04A.

And my values for the formula this time were:

R = (9V - 1.7V) / .04A
R = 182.5 Ohms

Again, since the variety pack didn't come with that exact value resistor I attempted to use the two 100 Ohm resistors bundled together in series to make 200 Ohms of resistance. I ended up just repeating the mistake that I made in the last step again though, and wired them together in parallel by mistake and so the two 100 Ohm resistors only ended up providing 50 Ohms of resistance. Again, these LEDs were particularly forgiving of my mistake - and now I have learned a valuable lesson about wiring resistors in series and in parallel.

One last note about wiring LEDs in parallel - while I put my resistor in front of both LEDs it is recommended that you put a resistor in front of each LED. This is the safer better way to wire LEDs in parallel with resistors - and also ensures that you don't make the mistake that I did accidentally.

The 1.7V LEDs connected to the 9V battery lit up - and my small adventure into LED land was completed.

Step 9: Extrapolation

While I didn't actually end up making anything besides a couple of lit LEDs, this information can be used to make all kinds of cool things!

The take away concepts hopefully were:
- Power a whole bunch of different value LEDs using the same basic principals.

- Figure out what is the positive electrode and what is the negative electrode of an LED by looking at it and testing it.

- Use resistors, or combinations of resistors wired together in series or in parallel to supply the correct amount of power to the LED.

- Make calculations to determine what resistor is needed using the formula, or using web sites that do it for you.

- Wire LEDs in series or in parallel depending on the application.

- Make LEDs light up!

This was the most basic kind of walk through for LEDs possible - and I learned a whole lot along the way. LED arrays and wiring schemes can get significantly more complicated - but for the most part, LEDs are pretty simple to work with, and with relatively little knowledge I was able to light them up - all be it if I sent a little too much juice through them towards the end of the experiment. I don't fear the LED now. They are my friends.

<p>what sort of wire would you recommend ?</p>
<p>What would cause my LED to take a while to reach full brightness?</p>
<p>You would need a microcontroller for that, and some knowledge of coding, and a adapting resistor.</p>
I think you misunderstood my question. It is doing this on its own. I do not want it to do this.
<p>Sorry then, I don't know.</p>
<p>Using one resistor to for two LEDs in parallel you would double the current in the calculation. (9-1.7/.04=182.5 ohm.) Would it be correct if you use one resistor for each LED in parallel to divide only by 20ma (9-1.7/.02=365 ohm). </p>
<p>I want to create something that uses an LED and is wired into a power cable that you plug into the wall. Can anyone point me to toward instructions on that process to I can ensure I am not missing anything or making any mistakes? Thanks. </p>
<p>Yes buy a 2 or 3 metre led strip 60 leds per metre and a strip of wood same length. get a 12V converting device and connect to strip. stick strip to wood. place in corner of room from bottom to top then you do not have to worry about fixings. </p>
<p>O the 12 V converter usually comes with the strip but it does pay off looking for them seperate as you can really save a couple of dollars on it that way. Do not buy the strip only if you have not found the converter yet. Do not use longer strips or they will fail after a while. Strips can be cut to length where it has the little scissors on the strip. connect plus to plus and minus to minus on the strip.</p>
<p>I need to make lamp battery 3,7V it should be commanded by a momentary switch </p><p>1click 1 led on, 2nd click 2 led on, 3rd click off.<br>Anyone can help me?</p>
<p>You're probably better off going to an electrical shop (a decent one) and talking to a member of staff </p>
Youre gonna have to use a microcontroller for that, an arduino should do
<p>Hello, I am looking for directions on how to hook multiple LEDs up to one 9v battery without a breadboard. Can anyone give me a hand?? I am an 8th grade student and this is for my science fair project. Thank you ahead of time</p><p>Emmaruth</p>
<p>you could just wrap the wires around the negative and positive electrodes without soldering to test them, then you can see if it works before you permanently connect them together :)</p><p>Sorry if you haven't gotten this reply in time lol ^_^</p>
<p>Which LED's are you using?</p><p>What voltage does each one need?</p>
<p>Hello i need to connect </p><p>two leds with two resistors, two push on/off switches, </p><p>where i can turn on one led while the other is off and turn on both leds at the same time.</p><p>what battery should i use? isnt ok for two 1.5volts battery??</p><p>thanks in advance</p>
<p>&quot;Once I knew that I needed a resistor of 140 ohms to get the correct amount of voltage to the LED&quot;</p><p>I think you mean to say that the resistor ensures that the <strong>CURRENT</strong> flowing through the circuit does not exceed LED's <strong>CURRENT</strong> 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.</p>
<p>I understood your post and like to ask you something:</p><p>If ideally we had a 1.7v input, a 1.7v led that consumes 20ma, which resistor you would need to securely feed the led?</p>
<p>So you need to ensure that only 20mA flows through your LED correct? What size of resistor would permit only 20mA to flow when a voltage of 1.7V is connected across its leads? R = V/I, so R = 1.7 V/ 20 mA = 85 Ohm.</p><p>So 85 Ohms is the resistor you need, choose the closest available resistor higher or equal to this value.</p>
<p>I understood your post and like to ask you something:</p><p>If ideally we had a 1.7v input, a 1.7v led that consumes 20ma, which resistor you would need to securely feed the led?</p>
<p>I thought that the LED itself can control the current passed through it when the applied voltage doesn't exceed its forward voltage? My teacher told me resistor only needed when the applied voltage exceed the forward voltage of the LED.</p>
<p>Hi... My sons Halloween costume has led lights on the chest that don't work. The board seems to be chipped. It has 8 blinking blue led lights powered by three 1.5v lr44 batteries. What can i use to supply power to the led lights. I attached a picture of the circuit board. Also, I attached a picture of the costume, the chest part is the one that's not lighting up. Thank you.</p><div><br><br></div>
<p>The black bit on the circuit board is a chip-on-board ic. It probably controlled the blinking of the leds. I am guessing it is probably busted from the board breaking. What I would do is remove the circuit board and replace it with a resistor. The leds will not blink anymore but they will light up.</p>
<p>If you want it blinking you could also replace that led with a blinking led. But it will blink independently of the other leds</p>
<p>Right, complete novice, so be gentle lol</p><p>Conflicting stories? I've read you don't need resistors, then you do, even a 5.1 Zenner diode was mentioned, don't run em in series etc. etc. </p><p>I have 2 flashing Red LEDs &amp; I want to run em off a 9v battery.......</p><p>Do you run em in series or parallel?</p><p>Do I need a single resistor or a resistor for each of the LEDs, if so, what resistors?</p><p>Regards</p><p>Tony</p>
<p>How can I connect more than 1 LED to a single switch with 3 toggles on the bottom? I know how to connect 1 LED, but I need to connect multiple ones!</p>
<p>Hi am a beginner with electronics and im wanting to make a series circuit using 2 red LEDs ( 5mm 1.85 v) and 1 white LED (5mm 3.3v). i have 2 types of resistor 1 180R and 1 220R. My power supply is a 9V battery. </p><p>My question is which resistor goes with which led?</p>
<p>R = (V1 - V2) / I</p><p>R=(9-( (2x1.85) + 3.3)/0.02 = 100 ohm</p><p>you need 100 or a bit higher. I am a bit rusty however.</p><p>see step 6 in this tutorial.</p>
<p>Totally the level I'm at. Thanks for the tutorial</p>
<p>Well...keep moving on..</p>
<p>Can I use 5mm LED with 1V 1A load?</p>
<p>It will only work if your led's forward voltage is around 1v. Most leds are not. see the attached chart for different color led forward voltages.</p><p></p><p> You want to provide the voltage where the led color you are using passes the 20mA line (or whatever forward current is specified in the datasheet) </p>
<p>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.</p>
<p>In your calculation, where did you get .02A?</p><p>I plan on making some circuits with LED's and 12v 1000ma and 2000ma power supplies.</p>
<p>Most leds run at optimally at 20 milliamps (.02A). This is called the forward current on the led datasheet if you have it.</p>
<p>Great beginners guide!</p>
I have 8mm white leds to use in different projects but I don't know what resistors to use for the same? plz help me out?
I have a 60 volts led driver and 4 smd 12 volts 10 watts led.plz would u tell me need any register....<br>
<p>Thanks for this tutorial :)</p>
<p>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. <br><br>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.</p>
<p>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.</p>
<p>?? If I have a 3 terminal fixed voltage regulator, how do I make that adjustable? There is no Vref pin. </p>
<p>The 'ground' pin is used for Vref. The regulated output voltage will be normal regulated output voltage + Vref voltage. So, for example, if you have an LM??05 and your 'ground pin' floats at 3V, then your true regulated output voltage will be 5V + 3V = 8V.</p>
<p>I'm trying to figure out why different color LEDs won't light up when i add two together onto one battery&hellip;?? i'm betting it has something to do with the amount of power needed, but would like to know if that is correct.</p>
Using this instructable I made an led that will run off an 18v battery.<br>http://m.instructables.com/id/Kayak-LED-light/
Very nice.....Thank you very much.
<p>So nice... Needs more such help....</p>
<p>Thank you very much for doing this tutorial especially in plain english. I have 2 LED lights that I need to fix, I have broken it down to the actual switch. So I found the exact same switches at Radio Shack. Now I need to get up the nerve to remove the existing switches and replace with the new ones. The wires are so tiny I find it hard to strip them with out cutting into some wires. Do you have an easier way to do this.</p><p>I would really like to keep these solar lights going for the a long time. I like to see them all lit up when I drive up the road.</p><p>Again thank you for this tutorial is was very good. I believe I have to join Pro to be able to download it to my computer so I can reference back to it when I need to.</p><p>Glenda</p>

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