Lesson 2: How to use a Breadboard

It took three wires with clips to turn on a light. If you wanted to turn on three lights, add two buttons, a speaker and nine sensors, it will quickly become a rat's nest of wires unless there is something else connecting the wires. And for that, we turn to the solderless breadboard. 

A solderless breadboard is a board is a small board with a bunch of holes in it. Each of the holes has a clip inside that will grab a wire that is put in it. The clips are wired together in different patterns to make it easy to connect wires together. We're going to go over how to use one of the most common breadboards, as shown below, which will be used in the rest of the course.


I will be referring to this as a breadboard from now on. There are a couple of useful features to this breadboard. The first is that it is the board is symmetrical, with two sections on either side, shown in green below. Each section has a plus in red and a minus in blue at the top of the breadboard. There is also a line in red or blue that runs down the length of the breadboard vertically. Remember what has a plus and minus?

Power Rails

That's right, the battery. These are called the power rails, and this is where you connect the plus and minus sides of the battery. All of the holes in the breadboard in these two sections are connected vertically. This makes it easy to connect multiple things to a battery and build multiple circuits on one breadboard. It also helps you remember which holes are connected to the plus and minus sides of the battery with the red line as a reminder that it's connected to plus, and a blue line to remind you that it's connected to minus. 

To demonstrate how the power rails are connected, we are going to rebuild the circuit from last time with the electricity going through the breadboard. We are going to use a different wire than the one with clips to connect to the breadboard, as shown below. To plug these in (and plug anything into the breadboard), push the metal part in until almost all the metal is inside the breadboard. You can push with a medium amount of force.


Once the wire is in the breadboard, it should look like this. 

wire in breadboard

Now we are going to rebuild the circuit from last time using the breadboard. The electricity will go from the plus side of the battery, through the red wire, through the LED, into the left power rail on the side next to the plus sign on the bredboard, up the breadboard, into the yellow wire (plugged into the breadboard), then into the yellow wire with clips, into the resistor, out into the green wire and back into the minus side of the battery.

 Using Power Rails

However, what happens if we plug the yellow wire into the hole on the breadboard next to the blue minus sign? What do you think?

 LED off

The LED does not turn on, because the LED is no longer connected to the yellow wire. The holes on this part of the breadboard are only connected vertically (top to bottom in the photo) not horizontally (left to right in the photo).

So that covers the two things on the side of the breadboard, what about the middle? The middle is the place where you build circuits, which we will call the build area, shown in blue below. 

Build Area

 The build area is set up like a grid with numbers going down each side and letters going across the top. You can designate what hole to plug something into in the same way that you play a game of battleship. For example, the top left corner is hole a-1. The hole on the bottom right of the build area is j-30. The hole on the top right is hole j-1. We will use these designations when plugging things into the breadboard to make it easy to follow along.

Like the power rails, the build area is separated into two parts. The divider in the middle splits the breadboard into two sections, one with letters a to e and the other with letters f to j. Each section is connected horizontally. So, the hole a-1 is connected to hole b-1, c-1, d-1 and e-1, but it is not connected to hole f-1. The hole f-1 is connected to hole g-1, h-1, i-1 and j-1. 

 To demonstrate this, we can move the circuit to connect the yellow wire to hole a-1 and one leg of the LED to hole e-1. Like the circuit before, the yellow wire and the LED are connected through the breadboard, so electricity can flow from the plus to minus side of the battery, and the LED turns on.

build area

However, if we plug the LED into hole f-1, the LED does not turn on, because the yellow wire and the LED are no longer connected.

Sad LED is not on

To summarize, the holes in the breadboard are connected in the same pattern as the printed circuit board below, shown side by side next to the breadboard.

Breadboard Connections

Now that you know how to use a breadboard, we are going to build the same circuit that we made with alligator clips on the breadboard. First, plug the plus and minus sides of the battery into the plus and minus power rails. 

Next, plug a red wire from the plus power rail to a-4.

Next, plug the long leg of the LED into e-4 and the shorter leg into e-5. You will have to bend the legs of the LED so that they are pointing in the same direction, as shown below.

Bend LED

Next, plug one end of the resistor into b-5, and the other end of the resistor anywhere on the minus power rail. You will need to bend the resistor's legs so that they are facing the same direction, as shown below.

 Bend Resistor

And that's it. The LED should turn on. When you are done, your circuit should look similar to the one below.

Circuit on breadboard

Here is a close up of the breadboard so you can see where things are connected.

close up

Power goes from the plus side of the battery through the red wire with clips, into the red wire that goes into the plus, or positive power rail. Electricity then goes through the positive power rail on the breadboard to the orange wire on the breadboard. It then goes through that wire to a-4, and then across the solderless breadboard to the long leg of the LED. The electricity then goes through the LED to e-5, and then through the breadboard to the resistor, on a-5. Electricity then goes through the resistor and into the minus power rail, and then back up the minus side of the power rail to the black wire, into the green wire with clips and into the minus side of the battery.

That's quite the trip. But, if you really want to test your skills at breadboarding, try to add as many wires as you can and have the electricity go through all of them to build the circuit that lets electricity go from the plus side of the battery, through the LED, through the resistor, and back to the minus side of the battery. This can get very messy very quickly, so to make sure you don't skip the resistor accidentally, I'd recommend connecting the resistor to the battery using the clips again, just in case. I had five wires on the breadboard to connect the LED to the resistor. How many can you have (and have the LED still work)?

Rat's Nest

In the picture above, the electricity goes through the re, then orange, then white, then green, then black, then yellow wires. Can you follow the path it takes through the breadboard?

Up next, adding a button to make it easy to turn the LED on or off.