Introduction: How to Use a Breadboard to Light LEDs

Picture of How to Use a Breadboard to Light LEDs

The following information is a single lesson in a larger project. Find more great projects here.

Return to Previous Lesson: How to Make a Simple Circuit with a Light Bulb

Lesson Overview:

Now we'll learn how to use a breadboard!

Step 1: LEDs and Breadboards

Picture of LEDs and Breadboards

In this lesson you are going to expand on what you learned about connecting a simple light bulb to a battery by making a multi-colored light source using small components that are similar to light bulbs but have a few special properties. They’re called LEDs (stands for “Light Emitting Diode”) and you'll be using them in many lessons.

By combining three LEDs: red, green, and blue in different brightnesses, you’ll be able to make any color of the rainbow.


  1. Continue to the next step.
  2. Stuck? HINT: If you look very closely at your TV or computer screen you’ll see very tiny red, green, blue dots next to each other – called pixels.

Step 2: Breadboard Basics (part 1)

Picture of Breadboard Basics (part 1)

In this lesson you’ll connect components with wires and with something new: a breadboard.

A breadboard is box-shaped. On the outside are hundreds of holes to plug wires into. On the inside there is a pattern of metal that connects certain holes together so you can plug in wires or the legs of components to quickly connect them without solder or tape.

When you move your mouse over a hole in the virtual breadboard all of the connecting holes highlight in green.

At the top and bottom you can see 2 horizontal rows of holes (blue and red), these are called “rails” and the blue holes on the top are all connected to each other.

The red holes on the top are all connected to each other. If you want the blue row at the top to be connected to the blue row at the bottom you need to add a wire that connects both rows. The same is true for the red rows.


  1. Move your mouse over the top two rows of holes in the breadboard, notice how it automatically highlights other holes too.
  2. Continue to the next step.

Step 3: Breadboard Basics (part 2)

Picture of Breadboard Basics (part 2)

The middle row of the breadboard is empty and separates the top from the bottom columns. If you mouse over the middle section you’ll notice for each column there are 5 rows above and below the middle empty row.


  1. Move your mouse over the holes in the middle section of the breadboard, notice how it automatically highlights other holes too.
  2. Continue to the next step.

Step 4: Breadboard Basics (part 3)

Picture of Breadboard Basics (part 3)

If you want to tell someone an exact location you can tell them a number+letter coordinate like C25. Here's how it works:

Every vertical column has a number.

The upper 5 holes of each horizontal row are labeled A, B, C, D, E and the lower 5 holes are labeled F, G, H, I, J.


  1. Continue to the next step.

Step 5: Add a 9 Volt Battery

Picture of Add a 9 Volt Battery

Now that you know that the two rows at the top and bottom of the breadboard are connected all the way across – it's time to give those “rails” some power.

Note about the battery: Batteries almost always have two places to connect to.

The red terminal is the positive ( + ) and the black terminal is the negative ( - ) or "ground."


  1. Click the \u201cComponents +\u201d menu. Scroll down until you find the 9V battery, then add it to the circuit like the image on the left.
  2. Move the battery terminals so they overlap the bottom power rails below the number "50" on the bottom rows of the breadboard.
  3. Continue to the next step.
  4. Stuck? HINT: Placing the battery right at "50" is not necessary, you may connect it anywhere along the bottom two rails as long as its + (red) terminal is in the bottom (red) rail and it's - (black) terminal is in the - (blue) power rail.

Step 6: Add the First LED

Picture of Add the First LED

Its time to add your first LED.

LEDs have special properties. One is that they are “polarized” which means they have a + and a – side, just like a battery.

The “D” in LED stands for “Diode” and what this means is that it will only allow electricity (or “electrical current”) to flow in one direction.

If you connect a LED or a regular diode backwards it will block the flow of current.


  1. Click the Components+ button and search for the red colored LED.
  2. Place the LED in the middle of the breadboard (just beneath the 123D.CIRCUITS.IO writing).
  3. Clicking your mouse to create a wire - connect a hole under the left leg of the LED (-) with the blue ground rail at the bottom of the breadboard.
  4. Connect a hole under the right leg of the LED (+) with the red power rail at the bottom of the breadboard.
  5. Continue to the next step.
  6. Stuck? HINT: Remember, if you want to change the color of a wire after it's drawn - select the wire and change its color in the element inspector (little window) that pops up when you select things.

Step 7: Turn on the Simulation

Picture of Turn on the Simulation

You have connected an LED to a battery using the breadboard.

By pressing “Start Simulation” you will turn on the circuit and current will flow through the LED. Try it.

Notice how the LED looks like it is exploding? This is because 9V batteries are too high-voltage and high current for a single LED and the simulation is showing you that if you connect a LED directly to a 9 volt battery it will be destroyed.

Next you will learn how to protect a LED and make it light up safely.


  1. Click on the Start Simulation button and observe the behavior of your circuit. The little explosion on the LED means it is getting too much current.
  2. Continue to the next step.

Step 8: Add a Resistor

Picture of Add a Resistor

To protect the LED you’ll need to add a new type of component called a “Resistor.”

Resistors are meant to do two things very simply:

lower voltage, and limit current. You can think of a resistor like a narrow tube, anything going through it must squeeze to fit through and this limits a lot of the energy trying to get from the battery to the LED.

Some of this energy gets turned into heat. Think of a light bulb. Light bulbs are special resistors that make heat and light!


  1. Delete the right side wire that connects the LED to the + rail.
  2. Click Components+ and scroll to find the Resistor. Drag the resistor to the work area.
  3. Place the resistor in where the wire used to be, it should connect the red + rail to the right side of the LED.
  4. Click \u201cSimulation Play\u201d The LED lights up!
  5. Continue to the next step.
  6. Stuck? HINT: The initial value of the resistor is fine for this step. You'll change it in later steps.

Step 9: Adjust the Resistor (part 1)

Picture of Adjust the Resistor (part 1)

Not all resistors are the same. They come in many different strengths, and in the 123D Circuits simulator you can quickly make them stronger or weaker.

The stronger the resistor the less current gets through to the LED and so it will be dimmer. Make the resistor too strong and the LED will not make any light.

The weaker the resistor the more current gets through to the LED and so it will be brighter. If you make the resistor too weak the LED will get too much current and be destroyed.


  1. Press Start Simulation so that the LED is on.
  2. Select the resistor so a little inspector box appears in the top left corner.
  3. Change the resistance value (number) to 10, but leave the units as kΩ. k stands for "kilo" which means “ times 1000” so you are changing the resistance between 1,000 and 10,000 ohms. An "ohm" is the unit of resistance.
  4. What happens to the brightness of the LED when you change the value of the resistor?
  5. Continue to the next step.

Step 10: Adjusting the Resistor (part 2)

Picture of Adjusting the Resistor (part 2)

The LED is dimmer when the resistance is higher. When you set the resistor back to 1KΩ the LED will light up, but you can make it brighter.

Notice how the colors on the resistor change when you change its value? Those colored bands on the resistor are like codes so you can tell what value they are.

Now try changing the units to see if you can get the LED brighter but not burnt out.


  1. With the simulation playing – change the value of the resistor from 1KΩ to 1Ω. The resistor is now 1000 times weaker and allows too much current into the LED – so it bursts!
  2. Change the value of the resistor between 1Ω - 999Ω. How high can you set the resistance and not damage the LED?
  3. Spend a minute changing the value. How low could you go without destroying the LED?
  4. Finally - set the resistance to 500Ω and leave it.
  5. Continue to the next step.

Step 11: Add 2 More LEDs

Picture of Add 2 More LEDs

It’s time to add two more LEDs so you have red, green, and blue.


  1. Click the Components+ button and add another LED.
  2. Place the new LED next to your red LED at the same height on the breadboard.
  3. Select the LED by clicking it once. An inspector will appear. Choose a different color from the list: green.
  4. Connect the left leg of the LED to the blue ground rail at the bottom.
  5. Add another resistor between the power line and the left side of your new green LED.
  6. Set the value of the new resistor to 500 ohms.
  7. Repeat step1-5 for the blue LED.
  8. Start the simulation by pressing Simulation Play.
  9. Congratulations! You have completed this lesson.
  10. Stuck? HINT: Did you know you can copy and paste components? You can also hold down the Shift key and select multiple components at once. Try it. Just make sure you don't delete the breadboard! If you do you can press "Undo" (the circle arrow).

Congratulations, you have completed this project!

Check out other great projects here.


dougBelcher (author)2016-11-25

I'm taking a free class (how to use a breadboard) but none of the instructions seem to work, i.e. mouse over this and it changes (doesn't), click the components+ button (can't find it), etc.

JetG2 (author)2016-10-21

Thanks for the guide really appreciate the effort :) your link to other projects doesn't work for me though :(

rafununu (author)2016-10-20

It seems your leds are inverted ! Cathode is connected to plus !

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