Arduino project · Light sensing · Easy

Light Meter on the LCD

The LCD shows how bright it is, from 0 to 100 percent.

What you will learn

How an LDR changes with light
How to print a live value on an LCD
How a voltage divider reads resistance

How it works

The LDR and a fixed resistor share the 5 V. In more light the LDR resistance drops, the voltage at the middle goes up and the reading rises. The LCD is refreshed every 300 ms.

Try this next

Add a message "DARK" below 30 percent.
Add an LED that lights when it is dark.
Log values to the Serial Monitor.

The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.

1Choose your Arduino board

2Build the circuit

Parts: sensors and actuators (tap to show or hide)

Speed Power Buzzer sound

Try the inputs (virtual sensors)

Pins (you can change them)

Part	Arduino pin (change it here)	How to wire it

Every wire, one by one

Red rail = 5 V from the Arduino 5V pin. Black rail = GND. The coloured wires carry signals. Match the wire colours on the drawing to this list.

#	Colour	From (part and leg)	To

3Define the sequence

Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.

4Arduino code

Add Serial Monitor printing

5Parts list and where to buy

Quantities come from the parts you added. The store links open a search for that item on Robu.in, Amazon.in and ThinkRobotics, so you always see what is in stock today. Check the model, voltage and price before you order.

#	Item	Qty	Search term	Buy / compare

6Export

Project titlePrepared by (optional)

Open project file

The PDF has the circuit sketch, pin table, every wire, sequence, full code, the parts list with store links, do’s and don’ts for each part, and the safety notes. The project file lets you come back and keep editing.

7Learn: do’s, don’ts, cautions and tips

In the real world

Day and night at the window

Move the light slider. The sun rises and sets, and the room gets bright or dark.

Tip: use the gold tab at the bottom of the circuit drawing to pull the real-world view up over the Arduino board. Your parts stay visible above it, so you can press a button and watch the real scene react.

Light sensor = daylight