HomeRaspberry PiLight sensor modules KY-018 and LM393 (3 and 4 pin) for a...

Light sensor modules KY-018 and LM393 (3 and 4 pin) for a Raspberry PI or Arduino

Tech details:

  • Comparator output, signal clean, waveform, driving ability, more than 15 mA. ( light sensor LM393  KY-018)
  • Potentiometer to adjust the sensitivity of a light sensor (LM393)
  • Working voltage of 3.3 V – 5 V (LM393 & KY-018)
  • Output form: digital switch output (0 and 1) (LM393 – 3 pin) and analog (KY-018), both (LM393 4 pin)
  • Wide voltage LM393 comparator used  (LM393)

Connectivity:

3 pin connector, pins as follows:

  • VCC: 3.3 – 5V Supply
  • S/DO: Output (Analog, Digital)
  • GND: 0V Ground

This module requires stepping down to 3.3V if connected to a 5V power source.

What does it do?

light sensor table

Thanks to the cheap photoresistors we can respond to light conditions. These two light sensor modules are based on a photoresistor which changes the voltage of the circuit depending on the amount of light getting to it. To give you an idea how light would affect the resistor here is a short table:

KY-018 Analog light sensor module

KY-018

The KY-018 is an analog module, and you will be able to read the voltage on the output pin from 0V-3.3V or 5V depending on the power source used. This range brings us to the sensitivity issue. Each module is capable of measuring light changes within a specific range. In theory, you can tune in this range by adding an in-line resistor of specific value. In practice,  the module is already equipped with the R103 SMD resistor, and capturing the changes in the bright light levels won’t be possible, however, the light sensor will be more sensitive to the changes in the dark spectrum of the light levels. The lower the resistance of the linear resistor, the better sensitivity in bright conditions.

LM393 Digital light sensor module (3-pin)

LM393

The LM393 works like a digital switch. Its output will be set to LOW or HIGH on the DO (Digital Output) pin. The sensitivity of this module can be adjusted by turning the built-in a potentiometer to the desired value. Due to the design of the module, it would be acting as a switch, as an analog pin is not available.

LM393 Digital light sensor module (4-pin)

This light sensor module combines both the KY-018and 3-pin design of LM393 to create a universal module that can act as a digital switch if connected to DO pin or as an analog sensor if connected to AO (Analog Output). In addition to this, you can calibrate the sensor using the potentiometer, to adjust triggering sensitivity or shift the sensitivity spectrum towards dark or bright levels.

How to use it?

Untitled Sketch_schem

If connected to a 3.3V power source, you can connect the modules directly to the GPIO on your Raspberry Pi (LM393). If you have 5V power supply use a logic level converter to step it down and protect your pins. The power source is connected to the VCC pin on the modules (+ on KY-018). Ground pin should be linked with  (-) on the KY-018 or GND of the LM393. The signal is received from the sensors are linked to your free GPIO (or ADC chip for KY-018 more on that later) and this is DO pin on LM393 and middle (or S) pin on KY-018.

Raspberry and analog input

Method 1

Untitled Sketch_bssb

Since the LM393 provides us with a digital output – the case is fairly easy – pretty much plug and play. With KY-018 we need to convert this analog output into a digital information that Raspberry can read. To do this we have to employ the power of ADC and SPI interface. To hook up your light sensor using an analog output use analog pins on the  MCP3008 8 Channel A/D Converter with SPI Interface chip. A really good hookup guide is here.

Method 2

Untitled Skesstch_bb

Another way is to introduce a capacitor to the circuit and calculate the voltage on the resistor pin by timing the charge/discharge cycle of the capacitor. The complete setup guide can be read here. You will need a capacitor and some math to be done on the paper.

t = RC
where t is time,
R is resistance (ohms)
and C is capacitance (farads)

Sample code:

These two pieces of the code can be used to test the modules:

Spoiler title
Method 1Method 2
import spidev
import time
import os

# Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)

# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7
def ReadChannel(channel):
    adc = spi.xfer2([1,(8+channel)<<4,0])
    data = ((adc[1]&3) << 8) + adc[2]
    return data

# Function to convert data to voltage level,
# rounded to specified number of decimal places.
def ConvertVolts(data,places):
    volts = (data * 3.3) / float(1023)
    volts = round(volts,places)
    return volts

# Define sensor channels
light_channel = 0

# Define delay between readings
delay = 5

while True:

# Read the light sensor data
    light_level = ReadChannel(light_channel)
    light_volts = ConvertVolts(light_level,2)

# Print out results
    print "--------------------------------------------"
    print("Light: {} ({}V)".format(light_level,light_volts))

# Wait before repeating loop
    time.sleep(delay)
import RPi.GPIO as GPIO, time

# Tell the GPIO library to use
# Broadcom GPIO references
GPIO.setmode(GPIO.BCM)

# Define function to measure charge time
def RCtime (PiPin):
    measurement = 0
# Discharge capacitor
    GPIO.setup(PiPin, GPIO.OUT)
    GPIO.output(PiPin, GPIO.LOW)
    time.sleep(0.1)

    GPIO.setup(PiPin, GPIO.IN)
# Count loops until voltage across
# capacitor reads high on GPIO
while (GPIO.input(PiPin) == GPIO.LOW):
    measurement += 1

    return measurement

# Main program loop
while True:
    print RCtime(4) # Measure timing using GPIO4

Shop with to support:

client-image
client-image
client-image
client-image
client-image
client-image

Other reviews

Are remotes still relevant? SofaBaton X1S

0
SofaBaton X1S one universal remote to rule them all? They think so. I'm about to find out how it works for me

Small, but featured: Wanbo New T2 Max

0
It's small but packs a bunch of features and supports 1080P natively - close look at Wanbo New T2 Max projector.

Every portable monitor needs this

0
Uperfect Ucolor panel looks great in 4K but there are limitations that you should be aware of - let's take a closer look at this portable display.

The mini version of my favourite gimbal

0
I have a smaller version of my Feiyu Scorp Pro gimbal to test - lighter, more porable but equally capable? Check out Feiyu Scorp Mini 2

Backpack for techies? Samsonite SPECTROLITE 3.0

0
On my second trip to LA, I decided to treat myself to a backpack upgrade. It was an unexpected, impulse buy. It was either that or meet the city of Angels with an old backpack full of holes. Is Samsonite Spectrolite 3.0 a backpack for tech people?

Half the DJI’s price, just as nice? Hohem Mic 01

0
I have been enjoying my DJI Mic, and you can attest to its quality in my videos, but Hohem decided to undercut them with Hohem Mic-01 that cost 3 times less! Have I overpaid? Let's see what can you do with this little microphone.

The holey GravaStar Mercury M2

0
Has GravaStar outdone itself again and produced a gaming mouse that catches your eye with unique design without sacrificing features? GravaStar Mercury M2