Tag Archives: lux meter

chipKIT Project 4: Digital light meter

A light meter is used to measure the intensity of illumination in a given area. It is widely used in schools, warehouses, factories, hospitals, office buildings, museums, art-galleries, parking garages, stadiums, and many more, to measure and maintain proper lighting levels. The intensity of illumination is usually expressed in Lux or foot-candles. As the 4th project in our chipKIT tutorial series, today we are going to build a digital light meter using the chipKIT Uno32 board and the BH1750 digital light sensor. This project uses Digilent’s chipKIT Basic I/O shield for displaying the measured light intensity in Lux, foot-candles, and Watts/m^2 units.


Digital light meter using chipKIT Uno32

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Building a simple digital light meter using Arduino and BH1750FVI sensor

A light meter is a device that measures the intensity of light. It finds applications in schools, hospitals, production areas, passageways and more to measure and maintain proper lighting levels. It is often used by photographers to determine the proper exposure for a photograph. Today we are going to build a simple light meter using an Arduino board and a BH1750 digital light sensor. The measured lighting level or intensity is displayed on eight seven segment LED displays, in both Lux and Foot-candle units.

Digital Light Meter using Arduino and BH1750FVI sensor

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Another LUX meter using MAX44007 ambient light sensor

In his digital light meter project, Shawon Shahryiar demonstrated a technique of using a normal LDR to construct a simple LUX meter that outputs the ambient light conditions on an LCD display. While this technique is simple and cost-effective, it requires an additional reference photometer to calibrate the LDR first adding an additional step. I came across this another LUX meter project on University of Wisconsin-Superior website that eliminates the need of external calibration and provides very precise measurement of illuminance in the range of 0.025 – 99999 LUX.

Digital LUX meter using MAX44007 (Source: http://mcs.uwsuper.edu/sb/Electronics/Lux/)

This project uses Maxim’s MAX44007 ambient light sensor which features an integrated photodiode with onboard ADC and I²C digital output. The sensor is designed to operate from a 1.7V to 3.6V supply voltage and consumes only 0.65µA in full operation. It has an extremely large dynamic light range that extends from 0.025 lux to 104,448 lux. The microcontroller used in this project is Silicon Laboratories C8051F304, but the sensor can be interfaced to any other microcontroller with I2C capability.

Building a digital light meter with a calibrated LDR

Measurement of light intensity is a prime necessity in several occasions.  The diversity of such needs make their way to various branches of physics and engineering as well as in media. For instance, in engineering, such kinds of measurements are needed to design optimum lighting conditions of a room. In photography, light intensity measurements ensure good quality pictures by determining the right exposure. Wiring a phototransistor or a light-dependent-resistor (LDR) with an analogue LED voltmeter chip like the LM3914 or even to a microcontroller and displaying the ADC values is a pretty simple technique of measuring light intensity. The bad part of this technique is that these simple and amateur-level devices can only measure relative intensity of light and are unable to provide measurements on an absolute scale. However, with a precise knowledge of the transfer characteristic (resistance vs light intensity) of the LDR it is possible to relate the LDR output to the intensity of light in standard unit. In case the LDR characteristic is unknown or unreliable, you can still calibrate the sensor output by using a variable light source and an external reference photometer. This project is about a microcontroller based light intensity meter where an LDR light sensor is calibrated against an external photometer to obtain the intensity of incoming light in the unit of lux. The lux is the SI unit of illuminance and luminous emittance, and measures lumens per square meter (lm/m2). The microcontroller used in this project is ATMega8L and its firmware is written using mikroElektronika’s MikroC Pro for AVR compiler.

AVR based LUX meter

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