Trouble with LDR

Other Hardware Sensors
1

So I made a simple voltage divider with LDR, to let some servos do work if its dark and if it's light, I need them to stop. No problem there. However, the values that my LDR gets are always lower than 90/100. Not once has it been above that. As to my understanding the analog to digital with 5V should be between 0 and 1023. What is the problem here?

Im not sure if I can post links (whether it's allowed), but this is the circuit I have built and with the same code:
https://maker[dot]pro/arduino/tutorial/how-to-use-an-ldr-sensor-with-arduino

I have tried multiple resistors from 10k ohm to 100kohm, 2 different lightsensors, but I keep getting the same value. always below 100 (dark around 20, light around 80)

my code:
#include <Servo.h>

// create servo object to control a servo

Servo servo1; //servo1 = down
Servo servo2; //servo2 = start
Servo servo3; //servo3 = select
Servo servo4; //servo4 = a
Servo servo5; //servo5 = b

int sensorPin = A4;
int sensorValue = 0;

int minLight; //Used to calibrate the readings
int maxLight; //Used to calibrate the readings
int lightLevel;

int rest = 90;
int servo1press = 155; //155
int servo1release = 35; //35

int servo2press= 90; //190
int servo2release = 90; //160

int servo4press= 90; //25 //90
int servo4release = 90; //90
int servo5press= 90; //90
int servo5release = 90; //160 //90
int pos = 0; // variable to store the servo position

void setup() {
servo1.attach(9); // attaches the servo on pin 9 to the servo object
servo4.attach(10);
servo5.attach(11);
servo2.attach(3);

minLight=15;
maxLight=20;
Serial.begin(9600);
}

void loop() {
sensorValue=analogRead(sensorPin);
//if((minLight<lightLevel) &&(maxLight>lightLevel)){

servo1.write(rest);
delay(1000);
servo1.write(servo1press);
delay(600);
servo1.write(rest);
delay(1000);
servo1.write(servo1release);
delay(600);
servo1.write(rest);
delay(300);
servo2.write(servo2press);
delay(300);
servo2.write(servo2release);
delay(300);

servo4.write(servo4press);
delay(300);
servo4.write(servo4release);
delay(300);
servo5.write(servo5press);
delay(300);
servo5.write(servo5release);
delay(300);
sensorValue = map(sensorValue,0,1023,0,100);

Serial.println(sensorValue);
//exit(0);
//}

}

P_20180915_224506.jpg
P_20180915_224506.jpg2304×4096 1.61 MB

2

It would be much better if you post the code that you used here (follow the guidelines in the how to use this forum-please read sticky) instead of making us find it.

A photo of your setup would help, too.

3

Sounds like your setup is not wired correctly. See above reply.

4

An LDR doesn't have zero or infinite resistance, so a voltage divider with LDR is never going to return 0 or 1023.
sensorValue = map(sensorValue,0,1023,0,100); // will never be 0 or 100

Read/print the raw A/D value first, so you can map sensible values to 0-100, like
sensorValue = map(sensorValue, 225, 825, 0, 100);

Might have to use constrain() to limit A/D range before mapping to 1-100.
Leo..

5

No one can make sense of the photo you posted, and the code you posted is mostly irrelevant to the problem.

Wire up the simple setup exactly as shown in this image from the link you posted, use the very simple code from that link, and tell us what values you get in bright light and reasonable darkness.

584×600 59.2 KB

6

If you are always indoors, try a 220k or 330k resistor, the resistance of those LDRs is around 2.5k in outdoor full daylight (not pointed at the sun, of course) and over 100k in low room light.

7

Update:
Indeed my picture wasn't much help, neither was the rest of my code. However I sent it in a hurry, so my apologies, next time this won't happen. However @Wawa has helped me on the way to fix the problem, the values made indeed no sense. With a small edit as mentioned, it works now.