Sunday, 24 April 2011

Build a Simple LED Circuit

Simple LED circuits are not so hard to build. An LED (Light Emitting Diode), is a very low current light source that is safe and durable for use in your project. This article will show you how to make a very simple LED circuit. 
The LEDs you purchase online will usually have several important pieces of information written about them, like angle, intensity (mcd), wavelength(nm), power consumption, size.
Here is a list of some led vendors:

1.    In the first step you must select the types(brightness and color) of leds that you are using and how many leds you want to light up. In this simple circuit you will be in one way limited by the amount of voltage that can be safely provided for your project.

2.    Find out how big voltage you will have or need from your power supply, than you should take a look for the diodes voltage specification on the manufacturers site or on the packaging.
In case that you don’t find this information you can estimate:
Blue (430 nm) 4.6 V
White 3.3 V
Blue 3.3 V
True Green 3.3 V
Green 2.2 V
Yellow 2.1 V
Red or Orange 2.0 V

For example if you would like to have 3 White Leds in your simple led circuit, than you will need 3 x 3.3V = 9.9V.

3.    In these step we will choose from where will we power up the simple led circuit:
         a.    DC voltage, where you can use 9V, AA or AAA batteries which are easy to find, cheap and you can than move around with your led circuit.
         b.    AC voltage, from where you can get constant power and the simplest way is to use a wall plug. But first you must cut the end of the plug and using a multimeter, you must see which is the negative and positive wire.
AC voltage may even be designed in the circuit. AC will only drive the LED half of the time since the voltage travels in waves. A full-wave bridge rectifier can be used to fully power LEDs. This is fundamentally what the wall wart is doing for you.
You must find a power supply bigger than the calculated voltage (>9.9V) and if you are driving a big number of leds than current can be also important.

4.    LED's cannot be connected directly to the battery or power supply. The LED will be instantly destroyed because the current is too big. The current power must be reduced. The simplest way to do this is by using a resistor. Calculate the LED resistor value with the following formula:

LED Resistor Value, R=(supply voltage - LED voltage) / LED current

Supply voltage - The voltage obtained from a power source for operation of a circuit

Led voltage - look at step 2
LED current - is 20 mA (this is a typical value if not specified else by the manufacturer)

If the resistor value is not available, then pick the nearest greater standard resistor value. In case you require to increase the battery life you can select a higher resistor value to reduce current. The reduced current will lead to a dimmer LED.

5.    You can soldier the wires directly together, use crimp connectors, or use a tiny circuit board. Choose the best technique based on the size of your project.

6.    The final step is to mount the LEDs in your project. Radio Shack and others sellers sell plastic or chrome LED holders that make a professional looking mount easy. You can add momentary push buttons or on/off switches to your simple LED circuits.

Building a simple LED circuit is an easy project.


  1. Wow! That's really amazing and informative post for me as a pcb manufacture. I will try my best to design this custom PCB.

  2. Anybody have any recommendations on cheap pcb assembly? I need 3 boards assembled. I'm in the US but don't mind shipping internationally.

  3. LED lights for cars are also shatter proof and free from Mercury, making them much safer for home and the environment.


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