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.
<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>This isn't quite correct... 1.7V(in)-1.7V(f)=0V, 0V/0.02A=0 Ohms. It should be fine without a resistor, though a resistor won't hurt if your voltage source has potential to spike.</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>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>I don't understand why people recommend microcontrollers. It's stupid and a waste of money, just get a small electrical switch and solder the power cable to it. Doesn't get much simpler than that.<br>Not sure if these switches are toggle or hold:<br></p>
<p>A microcontroller with 4 outputs can go for as little as 50 cents (if you have the software/hardware to upload). Here's an example[http://electronics.stackexchange.com/questions/74201/is-there-an-ic-chip-to-toggle-through-three-outputs] without microcontrollers. You can also build toggles using simple circuits like JK Flipflops, or buy toggle switches.</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>I hope I may ask a question, I have a led light that I recycled from a spot lamp that packed it in. the original unit was 6volt but I do not have a 6 volt power source I do however have a 9 volt one. is there a way to use this power source for that led pack? or would I burn them out. I have basic knowledge of electronics but Im unclear on how much these lights would draw if they would take what they need and disregard the rest </p>
<p>There's a circuit called a voltage divider. It's made by placing two resistors in series, then connecting a wire to the center of this series. Look it up, perform calculations to figure out which resistors will split the voltage into 6V, and use it.</p>
<p>I never knew you could connect resistors in parallel or series being I was always told it didn't matter which way I orientated it since the polarity was the same on both sides. Could you please help in explaining how I would connect in series or parallel? </p><p>Not trying to be an arse just very curios. Thank you.</p>
<p>The resistor itself allows electricity to travel in either direction through it, much like a door. Putting 5 doors in 1 hallway slows down people more than spreading 5 doors in 5 different hallways. Resistors are kind of the same idea, so connecting them in parallel increases resistance less than in series.</p>
<p>Two resistors connected in series: R total = R1 + R1. Two resistors connected in parallel: R total = R1R2/(R1+R2). This has nothing to do with how your orient the resistors when you connect them. This is for changing to the value of the total resistors to achieve a desired voltage drop or share. </p>
<p>Ok, let me see if I've got this straight. </p><p>I want to do 50 LEDs in parallel. They're all 3v, 20mA. Assume they're all pretty well matched.</p><p>If I wanted to use a 5V power supply, and just use 1 resistor, my math would look like this:</p><p>50 * .02A = 1A (total current)</p><p>R = (5Vpower supply - 3Vload) / 1A</p><p>R = 2V / 1A</p><p>R = 2&Omega;</p><p>Also, 3V * 1A = 3Watts, </p><p>so I would need a 3W 2&Omega; resistor, correct? </p>
<p>Nooo. First rule of leds is that they each need a resistor in parallel.</p><p>In parallel, the variance in forward voltages (differences from specification) becomes very exaggerated, so they will all draw different currents. In fact, the majority of the current will travel through the led with the lowest voltage drop, and burn it out. This will occur for every led until eventually none of them work. In series, this problem is more or less solved because there's just one voltage drop (across multiple leds) for one resistor.</p><p>For each parallel circuit, the voltage will be 5V. The voltage after travelling through the led will be approximately 2V(+-variance). </p><p>V=IR</p><p>V=5V input - 2V consumed by loads</p><p>R=V/I</p><p>R = 2Volts/0.02Amps = 100 Ohms</p><p>Each led in parallel will require at least 100 Ohms of resistance.</p><p>You could also do 25 parallel circuits of 2 leds in series. Each pair of leds would then require only a 50 Ohm resistor.</p><p>5V - 4V consumed = 1V, 1V/0.02A = 50 Ohms</p>
<p>I preface this with, my dad was an electrician and I wanted nothing to do with his long drawn-out lectures on the theory of electricity when i was a kid....</p><p>I'm helping my son with a project. His assignment was to build a 3-story building with 7 rooms. Each room has to have 2 lights and an independent switch but all seven rooms have to be powered by one power source. We bought these battery powered tea lights that come with a CR2032 battery and removed the battery (http://www.hobbylobby.com/Home-Decor-Frames/Candle... and then soldered pairs of two in series (7 pairs in total). I can't find any specifications for the lights as far as voltage so the only information I have is what a CR2032 battery provides. These only have to stay powered for a few minutes while the teacher gives the structure an &quot;earthquake resistance test&quot;. Any help or ideas on an appropriate power source?</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>just buy LED Christmas lights and implement it into your project. Easy,peasy,lemon,squeezy.</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>What would cause my LED to take a while to reach full brightness?</p>
<p>do you have it connected straight to a power supply? With or without a resistor? If you have it connected straight to a power supply maybe the supply itself is the issue. Try changing to a different one. If you have it connected with a resistor maybe the value are too small or too big. It could also be the led itself. I once used led's from Christmas light who had a chip in them to blink and get brighter and brighter as time went by so you should check where the LED came from or the manufacturer. </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>how many volts do I need to power 40 leds in series and what resistors/how many do I need</p>
<p>see my reply up above </p>
<p>how many volts do I need to power 60 leds in series and what resistors/how many do I need</p>
<p>how many volts is each led and you would need 60 small resistors(one for each led) or one big one(enough resistance to keep the power/voltage stable) for all. Like what you would find in an led light bulb. </p>
<p>I have 3 strings of 10 LEDs each powered by two AA batteries. I believe they are wired in parallel (2 wires in 2 wires out).</p><p>Being green minded, I don't want to add to the trash all the used batteries. I would like to connect them together and power them ( now 30 LEDs) using a DC transformer. I'm thinking a 5V transformer, properly stepped down would do the trick but I'm not sure what current rating it should have. Any advice would be appreciated</p>
<p>what sort of wire would you recommend ?</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>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>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>

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