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Reading light sensor value

Summary​

This is an example of reading the light sensor value using ADC. Convert the analog value to a formula and serial it with a value between 0 \ ~ 3.3V It shows on the screen through the port. Turns the LED on or off compared to the specified analog value.

Materials​

  • WIZwiki-W7500 board
  • USB cable
  • Breadboard
  • Jumper wire
  • PGM5537D (CDS Photo Resistor)

Hardware​

Schematic​

The overall circuit diagram is as follows.

Connection diagram​

Software​

Example Code​

Here is an example code.

Open the page below and compile by importing the program with "Import this program".

🌎https://os.mbed.com/teams/IOP/code/CDS_HelloWorld_WIZwiki-W7500/

Or, compile after copying and pasting the following code to main.c in the mbed environment.

#include "mbed.h"
 
DigitalOut redled(LED1); // RED
DigitalOut blueled(LED3); // BLUE
AnalogIn CDS(A0);
 
int main(/) {
    printf("Hello WizWIki-W7500!\n\r");
    printf("===========================================\n\r");
    
    int CDS_data = 0;
    double CDS_vol = 0;
    
    while(1) {
        CDS_data = CDS.read(/)*1000;
        CDS_vol = CDS.read(/)*3.3;
        
        //CDS Seneor ADC Low Data
        printf("CDS Data : %3d\r\n",CDS_data);      
        //CDS Sensor Voltage data
        printf("CDS Voltage : %3.3lfV\r\n",CDS_vol);
        printf("===========================================\n\r");
        
        wait(1);     
        //Status is bright.
        if(CDS_data < 500){
            redled = 1;
            blueled = 0;
        }
        //Status is dark.
        else  {
            redled = 0;
            blueled = 1;
        }
    }
}

Methods and results​

The following is an example execution screen. The CDS value and the CDS voltage value measured based on 3.3V are shown alternately. !

Learning materials​

Refer to the link below for the specifications of the illuminance sensor.