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

Lesson Overview:

Now we'll learn about circuits in series!

## Step 1: Series Circuits

Once you’ve tired of pressing the button to turn the light on, it’s time to shake things up by adding a second button.

In this lesson you will connect buttons in series. Components in series come one after the other - they share a connection at one terminal. Check out the circuit diagram below, showing the buttons in series. The components have the same electrical current flowing through them and they both have to be pressed in order to complete the circuit to turn on the LED!

1. Continue to the next step.

## Step 2: Add a Button

Before moving on, stop the simulation (or remove your power source on a physical kit).

Bring another button into the Workplane, then rearrange and re-connect them IN SERIES as shown in the figure below.

The circuit from the previous lesson is already in the Workplane. You can follow along with your physical kit, as well.

1. Start by deleting all of the red wire connections, except for the power line form the Arduino.
2. Move the LED to the right by four sockets to make room for another button.
3. Drag another button into the Workplane, and place it between the current button and LED.
4. Create a wire connecting the right terminal of the 1st button and the left terminal of the 2nd button. Now the buttons share one connection, so they are in series.
5. Next create a wire connecting the right terminal of the 2nd button to the left terminal (cathode) of the LED.
6. Finally, re-connect the right (anode) terminal of the LED to the power rail.
7. Continue to the next step.

## Step 3: Use It!

Simulate the circuit! (Or plug in your Arduino Uno)

In this SERIES circuit, the same electrical current flows through both of the buttons.

This means you must press both buttons at the same time to light the LED. While this is very easy to do on a physical kit because you can simply press each button with a finger from each hand, in a virtual world you only have one mouse, so we will introduce a new way to press momentary buttons.

The instructions below explain how to do this.

Let's test out the circuit!

1. Click the Start Simulation button or plug in your Arduino board.
2. Try pressing one button at a time, or both buttons to turn on the LED.
3. Pressing both buttons in the simulator requires a special method! Hold down the shift key and press the each of the buttons. Holding the shift key turns the switch into a "latching switch" that stays closed after you have pressed it. You will see a green circle appear on each, indicating that the button is closed.
4. Continue to the next lesson to learn about buttons in parallel.

Next Lesson:Build a Parallel Circuit