Light Emitting Diodes (LEDs)

LEDs (that’s “ell-ee-dees”) are a particular type of diode that convert electrical energy into light. In fact, LED stands for “Light Emitting Diode.” (It does what it says on the tin!) And this is reflected in the similarity between the diode and LED schematic symbols. 

In electronics, polarity indicates whether a circuit component is symmetric or not. LEDs, being diodes, will only allow current to flow in one direction. And when there’s no current flow, there’s no light. Luckily, this also means that you can’t break an LED by plugging it in backward. Rather, it just won’t work.

The positive side of the LED is called the “anode” and is marked by having a longer “lead,” or leg. The other, negative side of the LED is called the “cathode.” Current flows from the anode to the cathode and never in the opposite direction.

In short, LEDs are like tiny light bulbs. However, LEDs require a lot less power to light up by comparison. They’re also more energy-efficient, so they don’t tend to get hot as conventional light bulbs do. In electronics, heat usually means wasted energy.

The brightness of an LED is directly dependent on how much current it draws. That means two things. The first being that super bright LEDs drain batteries more quickly because the extra brightness comes from the extra power being used. The second is that you can control the brightness of an LED by controlling the amount of current through it.

How they Work

A Light Emitting Diode (LED) is an electronic component that can emit light when the electric current is passed through it. LEDs are made with semiconductors. When the electrons in the semiconductor recombine with holes then it released energy in the form of photons. The color of the light is determined by the energy required for electrons to cross the energy bandgap of the semiconductors. Early LEDs produced only red light, but modern LEDs are made like that they can produce different colors such as yellow, green, blue. 


Basically, LEDs are used for indicators( such as power on/off lights) in electronic devices. Other applications of the LEDs are in electronic signs, clock displays, and flashlights. The LEDs are consumed very low energy than the old bulb, CFL, so it is largely used in lighting purposes. A newer use for LEDs is TV and other device screens. LED's have gotten very small and using different intensities of RGB LED's packed closely together the screens can make a variety of images. 


If you connect an LED directly to a current source it will try to dissipate as much power as it’s allowed to draw and it will destroy itself. It is important to limit the amount of current flowing across the LED. For this, we employ resistors. Resistors limit the flow of electrons in the circuit and protect the LED from trying to draw too much current. 

For more information on LEDs and a few experiments to build to further understand them, check out our page on Resistors in a Circuit where we will first go over the impact of how circuits are built and LEDs on MakerLessons.