2: LED with Button

Now you will add a button so the LED only turns on when you press it.

This is the same basic LED circuit as circuit 1, but with a switch added. A pushbutton is a temporary switch: when you press it, it connects two points and completes the path.

Along the way you will practice:

• what a switch does (open path vs. closed path)
• how parts in series must all be connected for current to flow

Learn more (optional):

• A circuit needs a complete path
• Series and parallel

Goal

Make the LED light only while the button is pressed.

Parts you need

• 1 LED
• 1 resistor
• 1 pushbutton
• jumper wires
• breadboard
• RP2040-Zero

Build idea

You are adding a switch into the path:

3V3 -> button -> resistor -> LED -> GND

When the button is not pressed, the path is open.

When the button is pressed, the path closes and the LED can light.

Build steps

Try each step, then check your work with the blurred photos below. Did you connect it the way you meant to?

1. Place the RP2040-Zero into the breadboard.
2. Place the pushbutton so it bridges the center gap of the breadboard.
3. Place the LED so its legs are in different rows.
4. Put the resistor between one side of the button and the long leg (+) of the LED (in series).
5. Using a jumper wire, connect 3V3 to the same row as the button leg that shares a row with the resistor.
6. Using a jumper wire, connect the short leg (-) of the LED to GND.
7. Plug the board into USB, then test the button.

The LED should light only when the button is pressed.

What to notice

• The button is acting like a temporary bridge.
• If the button is turned the wrong way on the breadboard, the circuit may stay open all the time.
• This is still a circuit, just one you control with your finger.

Try this next

What do the different pins on the pushbutton do, if you connect the resistor or power to it?

• ← 1: Simple LED
• Next up 3: Two Buttons OR →