# Light-dependent Resistor with micro:bit

Difficulty
Easy
Steps
5

Light-dependent resistors are electronic components whose resistance changes with light intensity. They are also called LDRs, photoresistors, or photoconductors.

In this guide, you will learn to connect a light-dependent resistor to the micro:bit, and measure the relative brightness of the environment.

Complete this guide to learn how to use a light-dependent resistor. They are used in all sorts of light-sensing circuits; For instance, they could be used as a sensor in cameras or automatic lights that come on when it gets dark enough.

Parts Used in This Guide

## Step 1  The module

Before we begin, let's take a closer look at the light-dependent resistor module. It has four pins:

• 3.3V  : While 'VCC' stands for Voltage Common Collector, we'll connect the VCC pin to 3.3V on the micro:bit
• GND: In electronics, we define a point in a circuit to be a kind of zero volts or 0V reference point, on which to base all other voltage measurements. This point is called  ground or GND.
• Note: Voltage is the difference in potential between two points. As it is difficult to talk about voltage without a reference point, we need another point to compare it to.
• DO: Digital Output
• AO: Analog Output

## Step 2  Create the variables!

Open up MakeCode editor and start a new project.

• First, create two variables: 'sensorVal' and 'threshold'.
• As the AO pin of the light-dependent resistor is connected to Pin 1 of the micro:bit, we set sensorVal (short for sensor value) to analog read pin P1.
The third variable, "threshold" is set to 500.
• Next, add a 'show number' block and change its value to 'sensorVal'. Upload this code now, and test it. What values show across the screen of your micro:bit's 5X5 LED matrix?

## Step 3  The loop!

• The next step is to create an 'if... then ... else if ... then' loop. So drag and drop that block from the 'Logic' tab into the editor.
• To add an 'else if' block, click on the white plus (with a circular border) icon twice.
• Delete the extra 'else' block by clicking on the white minus (with a circular border) icon next to it.
• We will set two conditions here.
• If sensorVal > threshold, then use a 'show icon' block with the following pattern.
• The second condition is 'sensorVal <= threshold', use another 'show icon' block with a different pattern.

## Step 4  Upload the hex file

It's time to upload the code to the micro:bit!

1. Connect your computer to the micro:bit by using a microUSB cable
2. Click on the 'Download' button on the bottom left corner of the MakeCode editor