# LIGHT INTENSITY METER

399

1

## Introduction: LIGHT INTENSITY METER

All of us are prone to lights whether it be normal obsolete filament bulbs or ubiquitous led lights . But do we actually know the types of lamps available and can we measure the intensity of light . So Hang on!!! In this article I will give you some background about the types of lamps and create our own LIGHT INTENSITY METER !!

SO LET'S GET STARTED!!!!

## Step 2: UNITS OF LIGHT

Basically light is measured in LUX or LUMENS/sq. m or illuminance per unit area . Light is radiation that can be perceived by human eye.

Other units include candlepower or candela.

## Step 3: TYPES OF LAMPS

There are five main basic types of lamps

TUNSTEN FILAMENT
HALOGEN
GAS DISCHARGE

FLUOROSCENT LAMP

XENON LAMP

TO UNDERSTAN HOW THEY WORK AND MORE DETAILS WATCH THE VIDEO PROVIDED ...

## Step 4: CIRCUIT OF LIGHT INTENSITY METER

So first to sense the intensity of light we have to use and LDR (light dependent resistor) which changes the resistance with the amount of light incident on it .

Now the main thing is to separate different light levels .

But for that we can't solely use resistance so we have to convert resistance into voltage levels and compare it with different set voltage levels using a COMPARATOR .

Now we will use a voltage divider of 50K and LDR initially which has a drop of 3.5V when there is less light or basically no light and the voltage divider is connected to the inverting terminal of Comparator IC and the other voltage divider set has 3.2V connected at non-inverting terminal and when thelight is incident on LDR the resistance of LDR decreases so does the voltage drop

Now the OUTPUT goes HIGH because the voltage on non-inverting terminal exceeded the voltage at inverting terminal which inturn triggers the base of transistor and turns the LED on.

THIS same arrangement is used for other 3 COMPARATORS according to light intensity the led level is set

If fulll light is incident all 4 leds glow if a little less light is incident 3 leds glow and even less then 2 and finally 1 and then no led glows if dark enough .

## Step 5: PRACTICAL ON BREADBOARD

Then after the theory out of the way I started creating the circuit on the breadboard by first fixing the voltage dividers then the IC and finally the leds and transistors .

And now you can see in the video that the meter works perfectly.

## Step 6: LUX Vs RESISTANCE GRAPH

But you might this I am joking that this is not it .

So for clarification you can see that the datasheet of LDR provides tons of useful information.

But the most important is the LUX versus RESISTANCE chart.

The light intensity is highest when the resistance is approximately 0.1ohm

And there is also a chart of illumination : the highest luminosity is of sunlight around 30,000 lux and moonlight has the lowest 0.1 lux.

## Step 7: BUILDING THE ENCLOSURE

But now finally after testing and trials it was time to make the enclosure or housing for the light intensity meter

So I took a scrap box and marked the distance for fitting the leds and gathered all the components and started soldering them on a piece of prototype board and the build was complete .

## Step 8: BUILD YOUR OWN

Subscribe to my YouTube channel and stay tuned for more videos like this maybe next project will be making the light intensity meter digital.

Thank you for reading and supporting hope you like it !!!!

30 4.3K
49 10K
164 25K
166 14K