You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
138 lines
4.6 KiB
138 lines
4.6 KiB
#!/usr/bin/python
|
|
#
|
|
# Creates a C code lookup table for doing ADC to temperature conversion
|
|
# on a microcontroller
|
|
# based on: http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
|
|
"""Thermistor Value Lookup Table Generator
|
|
|
|
Generates lookup to temperature values for use in a microcontroller in C format based on:
|
|
http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
|
|
|
|
The main use is for Arduino programs that read data from the circuit board described here:
|
|
http://make.rrrf.org/ts-1.0
|
|
|
|
Usage: python createTemperatureLookup.py [options]
|
|
|
|
Options:
|
|
-h, --help show this help
|
|
--rp=... pull-up resistor
|
|
--t0=ttt:rrr low temperature temperature:resistance point (around 25C)
|
|
--t1=ttt:rrr middle temperature temperature:resistance point (around 150C)
|
|
--t2=ttt:rrr high temperature temperature:resistance point (around 250C)
|
|
--num-temps=... the number of temperature points to calculate (default: 20)
|
|
"""
|
|
|
|
from math import *
|
|
import sys
|
|
import getopt
|
|
|
|
class Thermistor:
|
|
"Class to do the thermistor maths"
|
|
def __init__(self, rp, t1, r1, t2, r2, t3, r3):
|
|
t1 = t1 + 273.15 # low temperature (25C)
|
|
r1 = r1 # resistance at low temperature
|
|
t2 = t2 + 273.15 # middle temperature (150C)
|
|
r2 = r2 # resistance at middle temperature
|
|
t3 = t3 + 273.15 # high temperature (250C)
|
|
r3 = r3 # resistance at high temperature
|
|
self.rp = rp # pull-up resistance
|
|
self.vadc = 5.0 # ADC reference
|
|
self.vcc = 5.0 # supply voltage to potential divider
|
|
a1 = log(r1)
|
|
a2 = log(r2)
|
|
a3 = log(r3)
|
|
z = a1 - a2
|
|
y = a1 - a3
|
|
x = 1/t1 - 1/t2
|
|
w = 1/t1 - 1/t3
|
|
v = pow(a1,3) - pow(a2,3)
|
|
u = pow(a1,3) - pow(a3,3)
|
|
c3 = (x-z*w/y)/(v-z*u/y)
|
|
c2 = (x-c3*v)/z
|
|
c1 = 1/t1-c3*pow(a1,3)-c2*a1
|
|
self.c1 = c1
|
|
self.c2 = c2
|
|
self.c3 = c3
|
|
|
|
def temp(self,adc):
|
|
"Convert ADC reading into a temperature in Celcius"
|
|
v = adc * self.vadc / (1024 * 16) # convert the 10 bit ADC value to a voltage
|
|
r = self.rp * v / (self.vcc - v) # resistance of thermistor
|
|
lnr = log(r)
|
|
Tinv = self.c1 + (self.c2*lnr) + (self.c3*pow(lnr,3))
|
|
return (1/Tinv) - 273.15 # temperature
|
|
|
|
def adc(self,temp):
|
|
"Convert temperature into a ADC reading"
|
|
y = (self.c1 - (1/(temp+273.15))) / (2*self.c3)
|
|
x = sqrt(pow(self.c2 / (3*self.c3),3) + pow(y,2))
|
|
r = exp(pow(x-y,1.0/3) - pow(x+y,1.0/3)) # resistance of thermistor
|
|
return (r / (self.rp + r)) * (1024*16)
|
|
|
|
def main(argv):
|
|
|
|
rp = 4700;
|
|
t1 = 25;
|
|
r1 = 100000;
|
|
t2 = 150;
|
|
r2 = 1641.9;
|
|
t3 = 250;
|
|
r3 = 226.15;
|
|
num_temps = int(36);
|
|
|
|
try:
|
|
opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="])
|
|
except getopt.GetoptError:
|
|
usage()
|
|
sys.exit(2)
|
|
|
|
for opt, arg in opts:
|
|
if opt in ("-h", "--help"):
|
|
usage()
|
|
sys.exit()
|
|
elif opt == "--rp":
|
|
rp = int(arg)
|
|
elif opt == "--t1":
|
|
arg = arg.split(':')
|
|
t1 = float( arg[0])
|
|
r1 = float( arg[1])
|
|
elif opt == "--t2":
|
|
arg = arg.split(':')
|
|
t2 = float( arg[0])
|
|
r2 = float( arg[1])
|
|
elif opt == "--t3":
|
|
arg = arg.split(':')
|
|
t3 = float( arg[0])
|
|
r3 = float( arg[1])
|
|
elif opt == "--num-temps":
|
|
num_temps = int(arg)
|
|
|
|
max_adc = (1024 * 16) - 1
|
|
min_temp = 0
|
|
max_temp = 350
|
|
increment = int(max_adc/(num_temps-1));
|
|
|
|
t = Thermistor(rp, t1, r1, t2, r2, t3, r3)
|
|
tmp = (min_temp - max_temp) / (num_temps-1)
|
|
print tmp
|
|
temps = range(max_temp, min_temp + tmp, tmp);
|
|
|
|
print "// Thermistor lookup table for Marlin"
|
|
print "// ./createTemperatureLookup.py --rp=%s --t1=%s:%s --t2=%s:%s --t3=%s:%s --num-temps=%s" % (rp, t1, r1, t2, r2, t3, r3, num_temps)
|
|
print "#define NUMTEMPS %s" % (len(temps))
|
|
print "short temptable[NUMTEMPS][2] = {"
|
|
|
|
counter = 0
|
|
for temp in temps:
|
|
counter = counter +1
|
|
if counter == len(temps):
|
|
print " {%s, %s}" % (int(t.adc(temp)), temp)
|
|
else:
|
|
print " {%s, %s}," % (int(t.adc(temp)), temp)
|
|
print "};"
|
|
|
|
def usage():
|
|
print __doc__
|
|
|
|
if __name__ == "__main__":
|
|
main(sys.argv[1:])
|
|
|