I am attempting to make a temperature monitor based on these links:
1. https://bitbucket.org/pschow/rpiadctherm/src/dbfe8101eeb4/basiclogmcp.py?at=master
2. https://www.paulschow.com/2013/08/monitoring-temperatures-using-raspberry.html
Using a MCP3008 and a thermistor. I have enabled the SPI interface, installed spidev, and I have rewired my circuit several times using different wires. I have also used a voltmeter to test connections and I am getting voltage across my voltage divider. I have a wire connected between the thermistor and resistor to Channel 0 on the MCP3008. I get this error when I run my code:
%Run Thermistor.py
Traceback (most recent call last):
File "/home/pi/Desktop/Thermistor.py", line 54, in <module>
print(temp_get(0))
File "/home/pi/Desktop/Thermistor.py", line 23, in temp_get
ohms = ((1.0/volts)*3300.0)-10000.0 #calculate the ohms of the thermististor
ZeroDivisionError: float division by zero
I want to see if I am even getting any output from the MCP3008 (like you can on arduino). My code is the following:
import spidev
import math
import time
spi = spidev.SpiDev()
spi.open(0, 0)
# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7
def readadc(adcnum):
# read SPI data from MCP3208 chip, 8 possible adc's (0 thru 7)
if adcnum > 7 or adcnum < 0:
return -1
r = spi.xfer2([1, 8 + adcnum << 4, 0])
adcout = ((r[1] & 3) << 8) + r[2]
return adcout
def temp_get(adc):
value = readadc(adc) #read the adc
volts = (value * 3.3) / 1024.0 #calculate the voltage
ohms = ((1.0/volts)*3300.0)-10000.0 #calculate the ohms of the thermististor
lnohm = math.log1p(ohms) #take ln(ohms)
#a, b, & c values from http://www.thermistor.com/calculators.php
#using curve Z/D (-4.4%/C @ 25C) Mil Ratio B
a = 0.001124753301019
b = 0.000234813406978
c = 0.000000085355035
#Steinhart Hart Equation
# T = 1/(a + b[ln(ohm)] + c[ln(ohm)]^3)
t1 = (b*lnohm) # b[ln(ohm)]
c2 = c*lnohm # c[ln(ohm)]
t2 = math.pow(c2,3) # c[ln(ohm)]^3
temp = 1/(a + t1 + t2) #calcualte temperature
tempc = temp - 273.15 - 4 #K to C
# the -4 is error correction for bad python math
#print out info
print ("%4d/1023 => %5.3f V => %4.1f Ω => %4.1f °K => %4.1f °C from adc %d" % (value, volts, ohms, temp, tempc, adc))
return tempc
while True:
print(temp_get(0))
time.sleep(1)
