Introduction

My name is Ryosuke Kamei and I am an IT consultant based on the idea of "gentle IT"! Currently, in my work, I am doing upstream processes focusing on requirements analysis and requirements definition, but I also write programs! As part of our friendly IT activities, we will introduce "Raspberry Pi 3" (commonly known as Raspberry Pi), which has the philosophy of "providing inexpensive PCs that can be programmed for education"!

This time, we will detect the brightness! For example, you can make a security light that lights up when the room gets dark! [Razpai Magazine-June 2016 Issue Special Feature 1 Akiba's Popular Parts Wiring Diagram Best 17 12 Measuring Brightness](https://www.amazon.co.jp/ Razpai Magazine-June 2016 Issue- Nikkei BP PC Best Mook -? Nikkei Linux-ebook / dp / B01EH2RX42 / ref = as_li_ss_tl ie = UTF8 & dpID = 61P3o6Agz + L & dpSrc = sims & preST = OU09__BG0,0,0,0_FMpng_AC_UL160_SR120,160 & psc = 1 & refRID = 31SKG5E0DGKBSF9BWNGV & linkCode = ll1 & tag = sr2smail-22 & linkId = 18fd04738627edef8d6fffd6c9b8f9c2 ) Is used as a reference.

procedure

Wiring
Program illuminance.py
Run the program

1. Wiring

Wiring diagram is [Razpai Magazine-June 2016 issue Special feature 1 Akiba's popular parts Wiring diagram best 17 12 Measuring brightness](https://www.amazon.co.jp/ Razpai Magazine-2016 June issue-Nikkei BP PC Best Mook-Nikkei Linux-ebook / dp / B01EH2RX42 / ref = as_li_ss_tl? -22 & linkId = 18fd04738627edef8d6fffd6c9b8f9c2) As it is.

If you get an image like this, referring to the picture of the circuit Raspberry Pi 3でpythonを使い「明るさ」を検出する！回路図.jpg

I also made a video

Text version From the Raspberry Pi side

--Raspberry Pi Pin 1 (3.3V) --AD Converter 8 Vdd --Illuminance sensor left side --Raspberry Pi 19th pin (MOSI) --AD converter 5 MOSI --Raspberry Pi 21st pin (MISO) --AD converter 6 MISO --Raspberry Pi 23rd pin (SCLK) --AD converter 7 CLK --Raspberry Pi 24th pin (CE0) --AD converter 1 CS --Raspberry Pi 6th pin (GND) --AD converter 4 Vss

From AD converter (difference only)

--AD converter pin 2 (CH0) --Illuminance sensor right side --Resistance (10kΩ)

Other

--Resistance (10kΩ) --GND

2. Program illuminance.py

Program is also [Razpai Magazine-June 2016 Issue Special Feature 1 Akiba's Popular Parts Wiring Diagram Best 17 12 Measuring Brightness](https://www.amazon.co.jp/ Razpai Magazine-June 2016 No.-Nikkei BP Personal Computer Best Mook-Nikkei Linux-ebook / dp / B01EH2RX42 / ref = as_li_ss_tl? = 18fd04738627edef8d6fffd6c9b8f9c2) is referred to.

The source is uploaded to GitHub, so please use it as you like.

`Clone with git`


$ git clone https://github.com/RyosukeKamei/raspberrypi3.git

`illuminance.py`


#Library to control GPIO
import wiringpi
#Timer library
import time
#Get arguments
import sys

# MCP3002（A/Specify the channel to which the D converter) is connected
SPI_CH = 0

#MCP3002 to be read (A/Specify the analog input channel of the D converter)
READ_CH = 0

#Specify the brightness threshold as an argument
param = sys.argv
set_illuminance = int(param[1])

#SPI initialization
wiringpi.wiringPiSPISetup( SPI_CH, 1000000 )

while True:
    # MCP3002（A/Create data to send to D converter)
    buffer = 0x6800 | ( 0x1800 * READ_CH )
    buffer = buffer.to_bytes( 2, byteorder='big' )
    
    #Get the value of CH0 using SPI
    wiringpi.wiringPiSPIDataRW( SPI_CH, buffer )
    
    #The values are sent in 2 bytes, so combine them into one value.
    illuminance_value = ( buffer[0] * 256 + buffer[1] ) & 0x3ff
    
    #Output brightness threshold and illuminance
    print ("Brightness threshold: " + str(set_illuminance) )
    print ("Illuminance: " + str(illuminance_value) )
    
    #"Bright" is displayed when the brightness exceeds the standard value, and "Dark" is displayed when the brightness falls below the standard value.
    if ( illuminance_value > set_illuminance ):
        print ("bright")
    else:
        print ("dark")
    
    #Detected by 1 second
    time.sleep(1)