Light Emitting Diode (LED) circuits can be created with only a few simple components and can produce brilliant light in any colour of the spectrum with very little power consumption. The advantage of LEDs over incandescent light is that LEDs are more efficient at converting electricity to light. In simple circuit building, LEDs are used as indicator lights or flash lights but in more advanced applications, they can be used in device displays and fibre optic communications.
The most basic LED circuit contains a power source, a resistor and a LED. The resistor is necessary to reduce the voltage of the power supply down to the operating voltage of the LED. Each LED has a specific operating voltage and current that will determine what type of resistor should be used. Ohm's Law says that voltage equals current times resistance (V=I R) and provides all the information needed to create a basic LED circuit.
The voltage in this case will be the voltage that needs to be resisted for the LED to work properly. If the power supply is 6V and the LED is rated at 2V then the voltage needed to be resisted is 4V (6V-2V). The current in this case will be the operating current of the LED. If the operating current of the LED is 0.05A then the equation will be 4V = 0.05A times R. Solving for the resistance, R = 4V/0.05A = 80 ohms. An 80 ohm resistor is needed to run a 2V LED off a 6V power supply.
Assembling the Circuit
The LED circuit described above is assembled by first connecting the positive terminal of the 6V power supply to the positive terminal of the LED. The positive terminal of the LED will be the longer of the two wire leads coming out of the LED. Connect the negative terminal of the LED to either end of the resistor and connect the other end of the resistor to the negative terminal of the power supply. The circuit is now complete, and the LED should be illuminated.
More than one LED may be integrated into the circuit by splicing them in between the original LED and the power supply. Adding an addition LED to the circuit will change the operating voltage of the LEDs and require a different resistor for the circuit to operate properly. If two LEDs rated at 2V and 0.05 A each are added in series, then the voltage in the equation V = I R becomes V = 6V - (2V + 2V). The new voltage that needs to be resisted is 2V and the resistance that is required is now R = 2V/0.05A = 40 ohms.