LED strip changing colour according to temperature

Using Arduino LEDs and Multiplexing
1

I'm essentially trying to code my Arduino Uno to change the colour of my WS2812B Led strip according to the temperature reading on my LM35 temp sensor. I've got a code using Adafruit_Neopixel but the lights don't seem to be changing, instead just taking the top value from the code.

2

Maybe you could post that here - in code tags.
(Look up 'Code Tags' before posting.)

3 
#include <Adafruit_NeoPixel.h>

float temp = 0 ;
float NtomV;
const float VREF = 1050;

#define PIN  8
#define NUMPIXELS 20  
Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
#define DELAYVAL 50 

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
  pixels.begin();
  analogReference(INTERNAL); 
  NtomV = VREF/1023;
}

void loop() {
  // put your main code here, to run repeatedly:
int temp_val = analogRead(A1);
float mv = (temp_val/1024.0)*5000;
float cel = mv/10;
temp = cel;

if (temp = 37){
    // pixels.Color() takes RGB values, from 0,0,0 up to 255,255,255
    for(int i=0;i<20;i++)
    pixels.setPixelColor(i, pixels.Color(0, 20, 0));// Green
    pixels.show();
    } 
  else if (temp >38){
    pixels.clear(); // 
    for(int i=0;i<20;i++)
    pixels.setPixelColor(i, pixels.Color(50, 0, 0));// Orange
    pixels.show();
    } 
  else if (temp <36){
    pixels.clear(); 
    for(int i=0;i<20;i++)
    pixels.setPixelColor(i, pixels.Color(50, 0, 0));// Orange
    pixels.show();
    } 
  else if (temp <35){
    pixels.clear();
    for(int i=0;i<20;i++)
    pixels.setPixelColor(i, pixels.Color(70, 0, 0));// Red
    pixels.show();
  } 
  else if (temp >39 ){
    pixels.clear(); 
    for(int i=0;i<20;i++)
    pixels.setPixelColor(i, pixels.Color(70, 0, 0));// Red
    pixels.show();
  } 
  delay(5000);
}

I'm hoping I've posted this right...

4 
  if (temp = 37)

This is the cause of the problem. You are setting temp to 37 rather than comparing it with 37

5

You did well.
Establish ranges to yield the results.
if ((temp >= 34) &&(temp < 35))

if ((temp >= 35) && (temp < 36))

if ((temp >= 36) && (temp < 37))

6

How would I go about fixing this so that the command reads if the temp is equal to 37?

7

I've changed it to have the ranges but the light still just remains as one colour with the top line (if temp = 37) rather than changing according to the ranges. The temperature on the LM35 doesn't read 37 yet it's still lighting according to temp = 37

8

Change it to
if (temp == 37)

9

Thank you so much! Got it working now.

10

Use

if (temp == 37)

instead of

if (temp = 37)
11

Cheers, got it working now!

12

Gotta ask the "elephant" question. :sunglasses:

Why are you using an LM35? :roll_eyes:

13

I'm actually looking to replace it with a non-contact temperature sensor. Are there any you'd recommend?

14

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