Published February 12, 2020 © CC BY

Mini Digital LUX Meter

Sometime I need to measure the exposure of light but a lux meter costs around $30, I made it with a BH1750 sensor which cost me around $10.

IntermediateFull instructions provided3 hours1,985

Things used in this project

Hardware components

BH1750 light intensity module

OLED 0.96 inch I2C IIC Interface OLED Screen Display 4 Pin (White)

Breadboard (generic)

Jumper wires (generic)

Node Mcu

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Solder Wire, Lead Free

Story

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What is a lux meter?

A digital Lux Meter is a device to measure the intensity of a source of light. A lux meter will be used in photography to estimate how bright the flash is and also the encircling ambient lighting.

working principle of lux meter :

Most of the lux meter consists of a body, photocell or light sensor, and display. The light that falls on to the photocell or sensor contains energy that is transformed into electric current. Indeed, the measure of current depends on the light that strokes the photocell or light sensor. Lux meters read the electrical current calculate the appropriate value, and show this value on its display.

Step 1: Components Needed

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Components needed :

Step 2: BH1750 Sensor

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BH1750 is a digital ambient light sensor that is used commonly used in mobile phones to

manage screen brightness based on the environment lighting. This sensor can accurately measure the LUX value of light up to 65535lx.

Features of the sensor:

● Power Supply: 2.4V-3.6V (typically 3.0V)

● Less current consumption: 0.12mA

● Measuring Range: 1-65535lx

● Communication: I2C bus

● Built-in A/D converter for converting analog illuminance in the digital data.

● A very small effect of IR radiation

● Highly responsive near to the human eye.

This is a BH1750 light intensity sensor breakout board with a 16 bit AD converter built-inwhich can immediately output a digital signal, there is no need for complex calculations. This is more accurate and simpler to use the version of the simple LDR which only outputs a voltage that needs to be calculated to obtain meaningful data.

Board Schematic

● J1 is interfacing connector

● U1 is a voltage regulator which gives out 3V to board from 3.3-5V supply input

● Q1 is bidirectional data level translator for 5V to 3V level conversion

● D1 is unidirectional clock level translator for 5V to 3V level conversion

● Please note that the "addr" Pin is to assign a different I2C address to the sensor.

Step 3: Circuit Diagram

First, connect the VCC and GND of the BH1750 Light Sensor to 3V3 and GND of ESP 8266 Then connect the SCL and SDA pins of the sensor to corresponding pins of ESp 8266 using jumper wires.

Then, connect the SCL, SDA, GND, and VCC pin of the OLED display to the corresponding BH1750 sensor pins.

Let's talk about lux and Illuminance:

The lux (symbol: lx) is the SI derived unit of illuminance, measuring luminous flux per unitarea. It is equal to one lumen per square meter. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square meter, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used as both the singular and plural form.

Illuminance: Illuminance is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total "amount" of visible light present, and the illuminance as a measure of the intensity of illumination on a surface. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance is inversely proportional to the area when the luminous flux is held constant.

One lux is equal to one lumen per square metre:

1 lx = 1 lm/m2 = 1 cd·sr/m2.

A flux of 1000 lumens, concentrated into an area of 1 square meter, lights up that square meter with an illuminance of 1000 lux. However, the same 1000 lumens, spread out over 10 square meters produces a dimmer illuminance of only 100 lux.

Step 4: Lets Code

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Download the libraries :

We can download libraries in the Arduino IDE

steps :

Sketch -> Include libraries -> manage libraries

For this project library needed:

Adafruit ESP8266
Adafruit SSD1306
BH1750FVI

Schematics

Code

BH1750

#include <BH1750FVI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Create the Lightsensor instance
BH1750FVI LightSensor(BH1750FVI::k_DevModeContLowRes);

void setup() 
{
  Wire.begin(2,0);
  Serial.begin(115200);
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

  // Show initial display buffer contents on the screen --
  // the library initializes this with an Adafruit splash screen.
  

  LightSensor.begin();  
}

void loop()
{
 float lux = LightSensor.GetLightIntensity();
 display.clearDisplay();
  display.setTextSize(2);             // Normal 1:1 pixel scale
  display.setTextColor(SSD1306_WHITE);        // Draw white text
  display.setCursor(0,0);             // Start at top-left corner
  display.println(F("Light :"));
   display.println(lux);
    display.println(F("LUX"));
    display.display();
  
  delay(500);
}

Credits

Nafisa Anjum

2 projects • 5 followers

Computer science student who loves electronics

Mini Digital LUX Meter

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

What is a lux meter?

working principle of lux meter :

Step 1: Components Needed

Components needed :

Step 2: BH1750 Sensor

Step 3: Circuit Diagram

Step 4: Lets Code

Custom parts and enclosures

code

Schematics

Circuit diagram

Code

BH1750

Credits

Nafisa Anjum

Comments

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Mini Digital LUX Meter

Mini Digital LUX Meter

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

What is a lux meter?

working principle of lux meter :

Step 1: Components Needed

Components needed :

Step 2: BH1750 Sensor

Step 3: Circuit Diagram

Step 4: Lets Code

Custom parts and enclosures

code

Schematics

Circuit diagram

Code

BH1750

Credits

Nafisa Anjum

Comments

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