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How to Wire LEDs: A detailed tutorial
Posted: 20 November 2007 08:30 PM   [ Ignore ]
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Please refer to the Wiki version of this Tutorial here. The Wiki version is constantly updated and is more complete than this tutorial. Thank you.

This a tutorial I wrote for an Xbox 360 modding forum about a year ago. I didn’t see a tutorial on this site and thought it might help out some people. The Resistor Calculator section of this tutorial was written for a calculator that isn’t online anymore but it might still help. I will include a link to a new, much easier to use calculator at the bottom of the section.

Many people on these forums ask “How do I wire LEDs?”. I decided I would write a brief tutorial so they will understand how to wire and the different methods of wiring. I will also explain the resistor calculator because it seems some people don’t understand how to use it. Let’s begin with the various wiring methods.

There are three different wiring methods. These methods are single (for one LED), series (for multiple LEDs) and parallel (for multiple LEDs). I am only going to talk about series and parallel circuits.

SERIES
When wiring in series the voltage of the source is dispersed equally throughout all of the LEDs. In order to find out how much power will be going to each LED you divide the voltage of the source by the number of LEDs. In a hypothetical situation, we have a 12V source and 6 LEDs (each requiring 2V to run off of). Divide the voltage source by the number of LEDs and you will get 2V, which means that 2V will be going to each LED. Great, each LED works perfectly and has the required voltage needed to run.

What happens when you have 3 LEDs (requiring 3.7V to run) and a 12V source? You will have too much power going to each LED. Divide 12V by 3 (LEDs) and you will get 4V going to each LED. Because there will be to much power going to each LED you will most likely smell something burning and will have to go out to buy a new LED. To fix this problem a little thing called a resistor was invented. A resistor is a “circuit component which offers resistance to the flow of electric current. A resistor also has a powerhandling rating measured in watts, which indicates the amount of power which can safely be dissipated as heat by the resistor.” In order to figure out what kind of resistor you will need you will need to know several things about the LED and the voltage source:

A) What is the voltage of the power source?
B) How many LEDs will you be wiring?
C) What wiring method will you be using?
D) What is the voltage drop of the LED (How much power does it take to run it)?
E) What is the recommended milliamps (mA)?

Once you know these things you will be able to use a resistor calculator to calculate the resistor that you need (I will go into more detail about this later).

When wiring LEDs together in series you wire from the - leg on one LED to + leg on another (the longer leg on the LED is the + leg). Here is a diagram courtesy of LsDiodes that will clarify what I am trying to say.

LEDSeriespicture.jpg

If you place an LED backwards nothing bad will happen. The LEDs just won’t turn on. If you need resistor wire this into the circuit before the LEDs. Wire to your power source and a ground to finish up your circuit. Now your circuit is complete and your LEDs will work just fine. I would recommend using electrical tape or shrink tubing to put around your soldering joints to prevent a short.

PARALLEL
Now on to a parallel circuit! A parallel circuit allows you freedom when choosing how many LEDs you would like to wire. Many people wire in parallel because of this “freedom”. This kind of circuit works great if you have a small voltage source and need multiple LEDs. If you had a 5V source and wanted to wire 3 LEDs (requiring 2V to run off of) there wouldn’t be enough power to power your LEDs. That’s true with a series circuit, not so with parallel. A parallel circuit works like so: “while every LED receives the same amount of voltage, the current of the source is dispersed between the LEDs.” What this is saying is that you will draw more power from you source. When wiring to a point on the XBOX 360 this won’t be an issue, only if you were getting your power from batteries or a similar power source that couldn’t replenish itself would you possibly need to consider this.

Because parallel doesn’t have any tricks for finding out how many volts is going through each LED I am going to skip to how to wire it. When wiring in parallel you always need a resistor. When wiring in parallel you wire the + legs together and the – legs together. Here is another diagram courtesy of LsDiodes.

Parallel.jpg

RESISTOR CALCULATOR
Now that you know about the various wiring methods I am going to talk about resistor calculators. In order to use a resistor calculator you need to know several things (I mentioned these above but here they are again):

A) What is the voltage of the power source?
B) How many LEDs will you be wiring?
C) What wiring method will you be using?
D) What is the voltage drop of the LED (How much power does it take to run it)?
E) What are the recommended milliamps (the desired current)?

Do you know this information? If so lets move on. I am going to be explaining everything from here on, based on this particular resistor calculator. Find on the page the wiring method that you will be using (series is in the middle and parallel is towards the bottom). Enter in the information that it asks (that would be my A,B,D,E). Double check the information that you have entered and hit “Click to Calculate”.

The information that you are looking for is this, the “Nearest higher rated 10% resistor” and also “Calculated Resistor Wattage” and “Safe pick is a resistor with power rating of”. When purchasing a resistor I look for a resistor that has an ohmage of the “Nearest higher rated resistor” and a wattage between the “Calculated Resistor Wattage” and the “Safe pick”.

NEW RESISTOR CALCULATOR

That concludes my tutorial. If you have questions please feel free to ask.

Pictures from LSDiodes.com
Other reference sites used: connectors.tycoelectronics.com/glossary/glossary-r.stm
Resistor Calculator: http://metku.net/index.html?sect=view&...dcalc/index_eng

O’Malley

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How to: Wire LEDs

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Posted: 21 November 2007 09:47 AM   [ Ignore ]   [ # 1 ]
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Thanks O’Malley, looking good

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Posted: 21 November 2007 12:20 PM   [ Ignore ]   [ # 2 ]
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Nice article O’Malley.

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Posted: 21 November 2007 05:17 PM   [ Ignore ]   [ # 3 ]
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Thanks for the feedback. Let me know if there is anything you think I should add.

O’Malley

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Posted: 06 December 2007 05:01 PM   [ Ignore ]   [ # 4 ]
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Really nice tutorial grin But as you said the Resistor needs to be wired before the LEDs. Though the diagram shows the Resistor being wired after the LEDs, in both cases serie and parallel. I know that in theorie diagrams like these show the electricity going from + to -, but it’s actually the other way around. You probbably know this, but why do the diagrams show the power going from + to - anyway? If I’d wire my circuit like this the resistor wouldn’t be really usefull. rasberry

But good guide though!

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Posted: 06 December 2007 05:58 PM   [ Ignore ]   [ # 5 ]
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I’m sure you can wire the resistors before or after the LED’s

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Posted: 06 December 2007 07:13 PM   [ Ignore ]   [ # 6 ]
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Despite what I wrote I’m almost certain that the resistor can either go before or after the LEDs…

O’Malley

Conventional current, the idea of electricity flowing from + to - is wrong, electricity does flow from the - to +, but it doesn’t make a difference. When working with electronics you always use the idea of conventional current.

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Posted: 09 February 2008 02:54 PM   [ Ignore ]   [ # 7 ]
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I went ahead and posted this tutorial up on the NUI Group Wiki with some modifications. Check it our here.

O’Malley

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Posted: 13 February 2008 06:34 PM   [ Ignore ]   [ # 8 ]
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This rulz.. thanks you very much smile

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Posted: 24 February 2008 12:36 PM   [ Ignore ]   [ # 9 ]
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The resistor can go anywhere in the serial circuit, btw. wink
(Not just before and after.)

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Sebastian Hartman

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Posted: 24 February 2008 12:54 PM   [ Ignore ]   [ # 10 ]
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Thanks Seb. I’ll go ahead and make that correction on the Wiki.

O’Malley

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How to: Wire LEDs

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Posted: 27 March 2008 04:42 AM   [ Ignore ]   [ # 11 ]
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Here is a great LED calculator that I use

http://ledcalculator.net

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Iyad Marzouka
http://ledcalculator.net

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Posted: 27 March 2008 01:37 PM   [ Ignore ]   [ # 12 ]
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Great find imarzouka. Thanks for the post. I will add this to the Wiki right now.

O’Malley

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Posted: 03 April 2008 04:28 PM   [ Ignore ]   [ # 13 ]
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Serial vs. Parallel

Devices placed in serial will have the same current but possibly different voltages.
Devices placed in parallel will have the same voltage, but possibly different current.

The tutorial shows both parallel and serial, AVOID THE PARALLEL CONFIGURATION! Even though they do include a caveat that the LEDs must be of the same color and specs, this can not be certain since of manufacturing variations.

The parallel configuration does not provide any over-current protection. It is possible for a single device to draw more current, get hotter, draw more current, get hotter, etc.

Besides, it is easier to run at higher voltages (12vdc) and lower current than at lower voltages at higher currents!

In my opinion, the parallel configuration should be removed from the tutorial.

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Posted: 04 April 2008 09:12 AM   [ Ignore ]   [ # 14 ]
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rogerj - 03 April 2008 04:28 PM

In my opinion, the parallel configuration should be removed from the tutorial.

Even if there is only one person who would like to know about the differences between serial and parallel for any reason, whatsoever, then the parallel verion should be in the tutorial aswell. Mostly a combination between parallel and serial makes the best LED module. Removing the information about a parallel circuit is a bit ridiculous.

Nice article, helped me quite a lot building my illuminator. smile

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Posted: 05 April 2008 02:08 PM   [ Ignore ]   [ # 15 ]
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Nice article, helped me quite a lot building my illuminator.

Glad to hear it helped!

Rogerj, I disagree. I have only ever dealt with wiring LEDs in parallel and frankly try to avoid series configuration as its just a pain. On all of the modding communities and DIY forums that I have seen people wire LEDs they almost always wire in parallel, many of them with backgrounds in the electronics field. To avoid this problem couldn’t you use simply wire each LED with its own resistor in a parallel configuration?

O’Malley

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