CODEWITHSUNDEEP
pythonraspberry-pi4temperature
AnonimF
AnonimF

Reputation: 1

Read analog temperature Raspberry Pi

The conversion formula does not work as expected(21.6 Celsius degree in the room but will return another value of 34 or more depending on the formula used).
I use a KY-013 temperature sensor and the mcp3008 driver. I connected the temperature sensor to the channel 1 of the driver. I connected the driver as mentioned on this website: https://randomnerdtutorials.com/raspberry-pi-analog-inputs-python-mcp3008/. I also tried with a humidity soil sensor and it works fine. The MCP3008(channel = 1) returns me a value between 0 and 1. How Should I convert it into Celsius degree?

I tried to use the formula mentioned on the datasheet:

Temp = math.log(10000.0 * ((1024.0 / RawADC - 1)));
Temp = 1 /(0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp)) * Temp);
Temp = Temp - 273.15; // convert from Kelvin to Celsius
return Temp;

But since Raspberry has value 1 when the channel does not receive anything i replaced RawADC with 1 - RawADC. It returned somewhere around 34 degrees.. but in the room, I recorded with a thermostat the 21.7 degrees. I tried other formulas similar to:

voltage = 5 * (1 - RawADC)
temp = (voltage / 1024 - 0.5) * 100
#-55 is the minimal temp that the sensor can read
#125 is the maximum
return temp-55

or something like:

delta_temp = 125 - (-55)
delta_v = 5 - 0
m = delta_temp/delta_V
b = -55 # at point 0 voltage => -55degre 
T = (1 - RawADC) * 5 * m + b

I even tried the simple rule of 3 but the result was still NOT as expected.

My current code is:

from gpiozero import MCP3008 
from time import sleep
import math


while True:
    #create an object called temp that refers to MCP3008 channe1 
    temp = MCP3008(1) 
    print(temp.value) # display 0.49 or 0.53 depending
    sleep(0.1)
    voltage = (1- temp.value) *5
    Temp = math.log(10000.0 * (1024.0 / voltage - 1))
    Temp = 1 /(0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp)) * Temp)
    Temp = Temp - 273.15 # convert from Fahrenheit to Celsius
    print(Temp) # display a value over -74

coeficients

conversion Function

main

Upvotes: 0

Views: 156

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