More features for createTemperatureLookup.py.
Contribution by DaveX, see http://forums.reprap.org/read.php?147,33082,165159#msg-165159
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Markus Hitter
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@ -8,6 +8,7 @@
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# temps are now in 14.2 fixed point notation (i.e. measured in quarter-degrees)
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# temps are not permitted to be negative (BUG:may result in numtemps fewer than requested)
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# bugfix: --num-temps command line option works.
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# 2012-11-08, DaveX: Modified to add --vcc=, --min_adc=, --mult and to print per-ADC comments
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"""Thermistor Value Lookup Table Generator
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@ -15,7 +16,7 @@ Generates lookup to temperature values for use in a microcontroller in C format
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http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
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The main use is for Arduino programs that read data from the circuit board described here:
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http://make.rrrf.org/ts-1.0
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http://make.rrrf.org/ts-1.0 or http://reprap.org/wiki/Temperature_Sensor_2_0
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Usage: python createTemperatureLookup.py [options]
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@ -28,6 +29,9 @@ Options:
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--r2=... R2 rating where # is the ohm rating of R2 (eg: 10K = 10000)
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--num-temps=... the number of temperature points to calculate (default: 20)
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--max-adc=... the max ADC reading to use. if you use R1, it limits the top value for the thermistor circuit, and thus the possible range of ADC values
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--min-adc=... the minimum ADC reading to use.
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--vadc=... ADC reference voltage (high leg of R2) same as Vcc
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--vcc=... Voltage divider supply (high leg of R2) Unused
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It is suggested to generate more values than you need, and delete some of the ones in the ranges
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that aren't interesting. This will improve accuracy in the temperature ranges that are important to you.
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@ -39,26 +43,34 @@ import getopt
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class Thermistor:
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"Class to do the thermistor maths"
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def __init__(self, r0, t0, beta, r1, r2):
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def __init__(self, r0, t0, beta, r1, r2,vcc,vadc):
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self.r0 = r0 # stated resistance, e.g. 10K
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self.t0 = t0 + 273.15 # temperature at stated resistance, e.g. 25C
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self.beta = beta # stated beta, e.g. 3500
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self.vadc = 5.0 # ADC reference
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self.vcc = 5.0 # supply voltage to potential divider
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self.vadc = vadc # ADC reference
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self.vcc = vcc # supply voltage to potential divider
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self.k = r0 * exp(-beta / self.t0) # constant part of calculation
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if r1 > 0:
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self.vs = r1 * self.vcc / (r1 + r2) # effective bias voltage
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self.vs = r1 * self.vadc / (r1 + r2) # effective bias voltage
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self.rs = r1 * r2 / (r1 + r2) # effective bias impedance
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else:
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self.vs = self.vcc # effective bias voltage
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self.vs = self.vadc # effective bias voltage
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self.rs = r2 # effective bias impedance
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def temp(self,adc):
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"Convert ADC reading into a temperature in Celcius"
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v = adc * self.vadc / 1024 # convert the 10 bit ADC value to a voltage
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r = self.rs * v / (self.vs - v) # resistance of thermistor
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try:
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return (self.beta / log(r / self.k)) - 273.15 # temperature
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except:
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print "// error for ADC={adc}, {v},{r}".format(adc=adc, v=v,r=r)
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return 0
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def resistance(self, t):
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"Convert a temperature into a thermistor resistance"
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return self.r0 * exp(self.beta * (1 / (t + 273.15) - 1 / self.t0)) # resistance of the thermistor
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def setting(self, t):
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"Convert a temperature into a ADC value"
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@ -75,9 +87,13 @@ def main(argv):
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r2 = 1600;
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num_temps = int(20);
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max_adc = int(1023);
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min_adc = int(1);
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vadc=5.0
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vcc=5.0
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mult=4
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try:
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opts, args = getopt.getopt(argv, "h", ["help", "r0=", "t0=", "beta=", "r1=", "r2=", "max-adc=", "num-temps="])
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opts, args = getopt.getopt(argv, "h", ["help", "r0=", "t0=", "beta=", "r1=", "r2=", "max-adc=", "min-adc=", "num-temps=", "vcc=","vadc=","multiplier="])
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except getopt.GetoptError:
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usage()
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sys.exit(2)
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@ -98,28 +114,41 @@ def main(argv):
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r2 = int(arg)
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elif opt == "--max-adc":
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max_adc = int(arg)
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elif opt == "--min-adc":
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min_adc = int(arg)
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elif opt == "--num-temps":
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num_temps = int(arg)
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elif opt == "--vadc":
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vadc = float(arg)
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elif opt == "--vcc":
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vcc = float(arg)
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elif opt == "--multiplier":
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mult = float(arg)
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if r1:
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max_adc = int(1023. * r1 / (r1 + r2))
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else:
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max_adc = 1023
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increment = int(max_adc/(num_temps-1));
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increment = int((max_adc-min_adc)/(num_temps-1));
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t = Thermistor(r0, t0, beta, r1, r2, vcc, vadc)
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t = Thermistor(r0, t0, beta, r1, r2)
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adcs = range(1, max_adc, increment);
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adcs = range(min_adc, max_adc, increment);
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adcs.append(max_adc)
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# adcs = [1, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 130, 150, 190, 220, 250, 300]
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first = 1
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#Chop of negative temperatures (as we're using a unsigned 16-bit value for temp)
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for i in range(0,len(adcs)):
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if int(t.temp(adcs[i])*4) < 0:
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if int(t.temp(adcs[i])*mult) < 0:
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adcs=adcs[0:i+1]
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#Replace this with the ADC reading for 0C
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adcs[i]=int(t.setting(0))
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#If the closes ADC reading to 0C is negative, convert to next highest ADC reading
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if int(t.temp(adcs[i])*4)<0:
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if int(t.temp(adcs[i])*mult)<0:
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adcs[i] -=1
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break
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print "// Thermistor lookup table"
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print "// Thermistor lookup table for RepRap Temperature Sensor Boards (http://reprap.org/wiki/Temperature_Sensor_2_0)"
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print "// Made with createTemperatureLookup.py (https://github.com/triffid/Teacup_Firmware/blob/master/createTemperatureLookup.py)"
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print "// (patched per https://github.com/drf5n/Teacup_Firmware/blob/Gen7/createTemperatureLookup.py)"
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print "// default thermistor lookup table"
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print "// You may be able to improve the accuracy of this table in various ways."
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print "// 1. Measure the actual resistance of the resistor. It's \"nominally\" 4.7K, but that's ± 5%."
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@ -129,24 +158,31 @@ def main(argv):
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print "// Since you'll have to do some testing to determine the correct temperature for your application anyway, you"
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print "// may decide that the effort isn't worth it. Who cares if it's reporting the \"right\" temperature as long as it's"
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print "// keeping the temperature steady enough to print, right?"
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print "// ./createTemperatureLookup.py --r0=%s --t0=%s --r1=%s --r2=%s --beta=%s --max-adc=%s" % (r0, t0, r1, r2, beta, max_adc)
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print "// Temp*%s table from https://github.com/triffid/Teacup_Firmware/blob/master/createTemperatureLookup.py" %mult
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print "// ./createTemperatureLookup.py --r0=%s --t0=%s --r1=%s --r2=%s --beta=%s --max-adc=%s --min_adc=%s --multiplier=%s --vadc=%s" % (
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r0, t0, r1, r2, beta, max_adc, min_adc, mult, vadc)
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print "// r0: %s" % (r0)
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print "// t0: %s" % (t0)
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print "// r1: %s" % (r1)
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print "// r2: %s" % (r2)
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print "// r1: %s (parallel with rTherm)" % (r1)
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print "// r2: %s (series with rTherm)" % (r2)
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print "// beta: %s" % (beta)
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print "// max adc: %s" % (max_adc)
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print "// min adc: %s at %s V" % (min_adc, min_adc*t.vadc/1024)
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print "// max adc: %s at %s V" % (max_adc, max_adc*t.vadc/1024)
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print "// ADC counts from {min} to {max} by {x}".format(min=min_adc, max=max_adc, x=increment)
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print "#define NUMTEMPS %s" % (len(adcs))
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print "// {ADC, temp*4 }, // temp"
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print "// {ADC, temp*%s }, // temp Rtherm Vtherm resolution power" % (mult)
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print "uint16_t temptable[NUMTEMPS][2] PROGMEM = {"
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counter = 0
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for adc in adcs:
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counter = counter +1
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if counter == len(adcs):
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print " {%s, %s} // %s C" % (adc, int(t.temp(adc)*4), t.temp(adc))
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else:
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print " {%s, %s}, // %s C" % (adc, int(t.temp(adc)*4), t.temp(adc))
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degC=t.temp(adc)
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resistance=t.resistance(t.temp(adc))
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vTherm= adc*t.vadc/1024
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ptherm= vTherm*vTherm/resistance
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resolution = ( t.temp(adc-1)-t.temp(adc) if adc>1 else t.temp(adc) -t.temp(adc+1))
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sep = (',' if counter != len(adcs) else ' ')
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print " {%4s, %6s}%s // %7.2f C, %7.0f Ohm, %0.3f V, %0.2f C/count, %0.2fmW" % (adc, int(t.temp(adc)*mult), sep,degC, resistance,vTherm,resolution,ptherm*1000)
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print "};"
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def usage():
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