How to Wire LEDs

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I hope this tutorial is helpful for everyone that passes through the NUI forums or Wiki. This article was originally written for an Xbox 360 modding forum but applies to all types of LEDs. I have seen several articles on here that address certain aspects of wiring and resistors but not one that encompasses all aspects and effectively teaches the reader how to wire LEDs and how the wiring works. I will try to keep this article updated for everyone with any new information I learn or corrections that need to be made. Please feel free to add information. I will try to combine some of the other articles on here with this one to give everyone one place to find and read about the LED hardware aspect of this project. - Luke O'Malley

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

LEDs in Series
LEDs in Series

When wiring in series the voltage of the source is divided equally throughout all of the LEDs. In order to find out how many volts will go to each LED you simply divide the voltage of the source by the number of LEDs (this is because the total voltage of the circuit is found by adding together the voltage required by each component). In a hypothetical situation, we have a 12V source and 6 LEDs (each requiring 2V to run off of). Divide the voltage source (12V) by the number of LEDs (6) and you will get 2V, which means that 2V will be going to each LED. Perfect! Each LED has the required voltage needed to run. However, this is an idealized system.

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 too much power going to each LED the LEDs will burn out and you will have to replace them. To fix this problem a circuit component called a resistor is used. A resistor is a “circuit component which offers resistance to the flow of electric current. A resistor also has a power handling rating measured in watts, which indicates the amount of power which can safely be dissipated as heat by the resistor.” This ultimately means that the resistor will use up some amount of the voltage and turn it into heat, reducing the amount of available voltage that can go to the LEDs. The power handling rating simply describes how much heat the resistor can dissipate. 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 (the following information applies both to series and parallel):

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 (the shorter leg marked by a flat side on the LED) on one LED to the + 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.

If you place an LED backwards nothing bad will happen. The LEDs just won’t turn on. If you need a resistor wire this into the circuit anywhere. 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

LEDs in Parallel
LEDs in 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 through a series circuit (refer above). However this is not true with parallel circuits. 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 current from you source. When using a power supply or a wall unit to power your LEDs 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 should you 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:


When wiring in parallel please be aware that each LED in a specific set needs to have the same electrical specs otherwise the LEDs needing the lower power will light and blow out due to the increased current. When wiring in parallel keep the number of LEDs in a given set down (no higher than 10 but lower is highly recommended). Alternatively you can wire a resistor in for each LED, rather than the resistor going before all of the LEDs the resistors attach to the legs of the LEDs and all of the resistors are linked to the power source (+) or ground (-). This method will keep the heat produced by a resistor down and eliminates the risk of any potential problems down the line.

RESISTOR CALCULATOR

NOTE: This section is based on an older resistor calculator that no longer functions. The information may still be useful, I have just removed information that directly refers to the old calculator. I will include a link to a new and much easier to use resistor calculator at the end of the section.

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):

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

Do you know this information? If so lets move on. The process from here is very straightforward. It is only a matter of entering the correct information in the corresponding sections. If you are using the resistor calculator below I recommend using the advanced section as it will allow you to find exactly what you are looking for. You may need to tweak and play with the number of LEDs you are using to find a resistor that you can easily buy or that exists (some values I have found I could not find a corresponding resistor anywhere).


1st RESISTOR CALCULATOR - Courtesy of imarzouka

2nd RESISTOR CALCULATOR

LED/Resistor Array Wizard

If you have any questions please feel free to ask them on the NUI Group forums. Thank you.

Pictures from LSDiodes.com Other reference sites used: connectors.tycoelectronics.com/glossary/glossary-r.stm

Originally written by Luke O'Malley