diff --git a/Marlin/scripts/createTemperatureLookupMarlin.py b/Marlin/scripts/createTemperatureLookupMarlin.py index d08abce39..f23db1393 100755 --- a/Marlin/scripts/createTemperatureLookupMarlin.py +++ b/Marlin/scripts/createTemperatureLookupMarlin.py @@ -23,68 +23,60 @@ import sys import getopt "Constants" +ZERO = 273.15 # zero point of Kelvin scale +VADC = 5 # ADC voltage +VCC = 5 # supply voltage ARES = pow(2,10) # 10 Bit ADC resolution +VSTEP = VADC / ARES # ADC voltage resolution TMIN = 0 # lowest temperature in table TMAX = 350 # highest temperature in table 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 + l1 = log(r1) + l2 = log(r2) + l3 = log(r3) + y1 = 1.0 / (t1 + ZERO) # adjust scale + y2 = 1.0 / (t2 + ZERO) + y3 = 1.0 / (t3 + ZERO) + x = (y2 - y1) / (l2 - l1) + y = (y3 - y1) / (l3 - l1) + c = (y - x) / ((l3 - l2) * (l1 + l2 + l3)) + b = x - c * (pow(l1,2) + pow(l2,2) + l1*l2) + a = y1 - (b + pow(l1,2)*c)*l1 + self.c1 = a # Steinhart-Hart coefficients + self.c2 = b + self.c3 = c + self.rp = rp # pull-up resistance - def res(self,adc): + def res(self, adc): "Convert ADC reading into a resolution" res = self.temp(adc)-self.temp(adc+1) return res - def v(self,adc): + def v(self, adc): "Convert ADC reading into a Voltage" - v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage - return v + return adc * VSTEP # convert the 10 bit ADC value to a voltage - def r(self,adc): + def r(self, adc): "Convert ADC reading into a resistance in Ohms" - v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage - r = self.rp * v / (self.vcc - v) # resistance of thermistor + r = self.rp * self.v(adc) / (VCC - self.v(adc)) # resistance of thermistor return r - def temp(self,adc): + def temp(self, adc): "Convert ADC reading into a temperature in Celcius" - v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage - r = self.rp * v / (self.vcc - v) # resistance of thermistor + r = self.rp * self.v(adc) / (VCC - self.v(adc)) # resistance of thermistor lnr = log(r) Tinv = self.c1 + (self.c2*lnr) + (self.c3*pow(lnr,3)) - return (1/Tinv) - 273.15 # temperature + return (1/Tinv) - ZERO # temperature - def adc(self,temp): + 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) + x = (self.c1 - (1.0 / (temp+ZERO))) / (2*self.c3) + y = sqrt(pow(self.c2 / (3*self.c3),3) + pow(x,2)) + r = exp(pow(y-x,1.0/3) - pow(y+x,1.0/3)) # resistance of thermistor + return (r / (self.rp + r)) * ARES def main(argv): "Default values"