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.
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<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>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>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>What would cause my LED to take a while to reach full brightness?</p>
<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>
Very informative , I liked iy.
<p>The link below calculates LED resistor values for series or parallel arrays of any amount, color, and desired voltage. </p><p><a href="http://led.linear1.org/led.wiz" rel="nofollow">http://led.linear1.org/led.wiz</a></p>
<p>I was just about to post this link. I've been using it for years, such a great source.</p>
<p>Nice to see a real close up of the insides of one. :)</p>
<p>i liked the explanation of the wiring system rely helpfull </p>
<p>Step 6 got me thinking about wiring batteries in parallel. If I wanted to go longer between replacing batteries how could I get 4.5V from AA batteries?</p><p>For example, wiring six 1.5v batteries. 3 in series wired to 3 in parallel. </p>
<p>Nice instructable! Playing with LEDs is one of my favorite activities. I like the fact that you paid attention to voltage and current ratings - good advice for the beginners. One thing to note: you didn't use blue or white LEDs; people that do choose to play with these might use a little caution - they tend to be more sensitive to over-current and static electricity. It's a bummer to burn out a $5 LED right off the bat...</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 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>If you intend to crank as much light as possible out of a LED, (without burning it) you should probably pulse it and limit the temperature.</p><p>For regular signal LED's, it's not so important, but the optimal driving scheme is a current source. Without aktive components (transistor and Zehner diode), a current source is done by a high voltage and a high impedance(high resistor).</p><p>This way, it isn't that important, what the voltage of the LED is. With a active current source, it even doesn't matter if you have multiple LED's in series, as long as the supply voltage is high enough.</p>
<p>Thank you so much for your very good Instructable on LEDs!<br><br>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 &quot;Mitch Cumstein&quot; from Caddyshack!)<br><br>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.<br><br>One place you CAN get <strong><em>lots of good stuff</em></strong> (<u>I DO NOT WORK THERE OR HAVE TIES WITH THEM</u>) 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....</p>
<p>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.</p>
<p>I frequently buy at Tayda Electronics</p>
<p>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... </p>
GrinninSam questions, &quot;If I have a 3 terminal fixed voltage regulator, how do I make that adjustable? There is no Vref pin.&quot;<br><br>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.<br><br>The fixed ones can be regulated in the fashion that Lee Wilkerson suggested.<br><br>Hook it up, pull out your DVM and adjust it to the voltage you need. <br>It's almost like a 'volume' knob for the voltage.
<p>Impressed! It&rsquo;s been a long time that I got interest to read what others write to have useful information that I further discuss among my gathering and it makes our time good. We make cross questions and answer them but for all that I read articles and this site has been on top of my list for providing such information. &lt;a href=&quot;http://www.fjackets.com/categories/Shop-By-Character/&quot;&gt;comic character jackets&lt;/a&gt;</p>
<p>A usufull addition to this article is how to determine the voltage of a radom LED in the junk bin</p>
<p>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.</p>
<p>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. </p><p>The math I'm coming up with is R=(12v - 12v)/.02a</p><p> R=0</p><p>From what I can tell, this would mean a resistor wouldn't be needed, am I correct?</p>
<p>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.</p>
<p>Hey bro, your math is correct, you do not need a resistor if your supply is 12v and your led requires 12 volt.</p>
If you have a 12V LED, it has a resistor built in somewhere.
<p>His maths is correct, but his electronics is not!</p>
<p>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.</p>
<p>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.</p>
<p>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. :)</p>

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