Using multiple digital input

Projects Programming
1

im currently using 4 LDR sensor modules for my project which is using digital output.The LDR will then send digital output to arduino and send digitalwrite.The problem is when digitalread2 is HIGH all the output becomes high.

const int ldr_pin1 = A0;
const int ldr_pin2 = A1;
const int ldr_pin3 = A2;
const int ldr_pin4 = A3;
const int led_pin1 = 10;
const int led_pin2 = 11;
const int led_pin3 = 12;
const int led_pin4 = 13;

void setup() {
  // put your setup code here, to run once:
    pinMode(ldr_pin1,INPUT);
    pinMode(led_pin1,OUTPUT);
    pinMode(ldr_pin2,INPUT);
    pinMode(led_pin2,OUTPUT);
    pinMode(ldr_pin3,INPUT);
    pinMode(led_pin3,OUTPUT);
    pinMode(ldr_pin4,INPUT);
    pinMode(led_pin4,OUTPUT);
    Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
   if( digitalRead( ldr_pin1 ) == 1){
      digitalWrite( led_pin1,HIGH);
   }
   else{
      digitalWrite( led_pin1 , LOW);
   }
      if( digitalRead( ldr_pin2 ) == 1){
      digitalWrite( led_pin2,HIGH);
   }
   else{
      digitalWrite( led_pin2 , LOW);
   }
      if( digitalRead( ldr_pin3 ) == 1){
      digitalWrite( led_pin3,HIGH);
   }
   else{
      digitalWrite( led_pin3 , LOW);
   }
      if( digitalRead( ldr_pin4 ) == 1){
      digitalWrite( led_pin4,HIGH);
   }
   else{
      digitalWrite( led_pin4 , LOW);
   }
   

}

CODE

2

Check pins against HIGH and LOW, not 1 and 0;

Also, you can try this:

    digitalWrite( led_pin1, digitalRead( ldr_pin1 ) );
3

Try this to see if you are getting good values, add printing to everywhere and see.

   if( digitalRead( ldr_pin1 ) == 1){
      Serial.println("                                  ldr_pin1 is 1"); 
      digitalWrite( led_pin1,HIGH);
   }
   else {
      Serial.println("                                              ldr_pin1 is 0");
      digitalWrite( led_pin1 , LOW);
   }

a7

4

image
image1209×531 22 KB

5

Ummm… what were you doing to get that output?

It is time to draw a schematic and post it.

Hand drawn is easiest. Show all your parts, how they are connected and from where x they get power to operate.

Draw, snap a picture and post it.

TIA

a7

6

Post the datasheet.

7

Normally LDRs are not "simply" HIGH or LOW, but they change their resistance depending on the incidence of light.

Accordingly, they should either be read out with the ADC Conwerter or at least be connected to a Schmitt trigger to generate HIGH and LOW signals.

Otherwise, to switch LEDs on or off, depending on which LDR pin has a HIGH signal, the following code should work.


struct LdrState {
  bool isHigh;
  const byte ldrPin;
  const byte ledPin;
};

struct LdrState ldrs[] { {false,6,10}, {false,7,11}, {false,8,12}, {false,9,13} };

void setup() {
  // put your setup code here, to run once:

  for (auto &ldr : ldrs) {
    pinMode(ldr.ledPin,OUTPUT);
    pinMode(ldr.ldrPin,INPUT);
  }
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  
  for (auto &ldr : ldrs) {
    if ( digitalRead( ldr.ldrPin ) && !ldr.isHigh) {
      digitalWrite( ldr.ledPin, HIGH);
      ldr.isHigh = true;
    }
    else if (ldr.isHigh) {
      digitalWrite( ldr.ledPin, LOW);
      ldr.isHigh = false;
    }
  }
}
1 Like
8

nice interlocking, I like it :+1:

9

@paulpaulson Thanx :-).

I found LDR sensors on WokWi that are probably the same as the one TO is using.
If you start the simulation and click on a LDR, you can change the LUX number. At a certain value the LEDs go on and off. In this example they turn on at a low LUX value (< 100lux), high values turn them off.

10

These modules typically have a digital and analog output pin. The digital pin is connected to a trim pot and a comparator to produce HIGH or LOW.

1 Like
11

Thank you for the explanation. In the meantime, as written in #9, I had found such modules and experimented with them in a simulation.

12

I guess this one?

grafik
grafik805×702 106 KB

13

Here are a few explanations to be found... wokwi-photoresistor-sensor Reference | Wokwi Docs

14

i actually wanted to do this project but with 4 ldr sensor module like in this video

The Video

15

image
image1031×541 58.9 KB

16

The code from the video

const int ldr_pin = 7;
const int led_pin = 13;
void setup() {
  // put your setup code here, to run once:
    pinMode(ldr_pin,INPUT);
    pinMode(led_pin,OUTPUT);
    Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
   if( digitalRead( ldr_pin ) == 1){
      digitalWrite( led_pin,HIGH);
   }
   else{
      digitalWrite( led_pin , LOW);
   }
   
   Serial.println( digitalRead( ldr_pin ));
   delay(100);
}
17

Good, then you got a working solution in posting #7. And if you look at the simulation linked in posting #9, you can see how it works.

1 Like
18

Hello yabedibedoo

Try this simple classless object oriented multi-IO sketch to gain the knowledge how to.

constexpr byte ldrPins[]{A0,A1,A2,A3}; 
constexpr byte ledPins[]{8,9,10,11}; 
enum ledLDR {One,Two,Three,Four}; 
struct MULTIIO
{
  byte ldr;
  byte led;
};
MULTIIO multiIos[] {
  {ldrPins[One],ledPins[One]},
  {ldrPins[Two],ledPins[Two]},
  {ldrPins[Three],ledPins[Three]},
  {ldrPins[Four],ledPins[Four]},
};
void setup()
{
  for (auto multiIo:multiIos) pinMode(multiIo.ldr,INPUT_PULLUP);
  for (auto multiIo:multiIos) pinMode(multiIo.led,OUTPUT);
}
void loop() 
{
   for (auto multiIo:multiIos) digitalWrite(multiIo.led,!digitalRead(multiIo.ldr));
}
1 Like
19

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