Erik vd Zalm
12 years ago
2 changed files with 42 additions and 167 deletions
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#!/usr/bin/python |
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# |
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# Creates a C code lookup table for doing ADC to temperature conversion |
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# on a microcontroller |
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# based on: http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html |
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"""Thermistor Value Lookup Table Generator |
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Generates lookup to temperature values for use in a microcontroller in C format based on: |
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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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Usage: python createTemperatureLookup.py [options] |
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Options: |
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-h, --help show this help |
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--r0=... thermistor rating where # is the ohm rating of the thermistor at t0 (eg: 10K = 10000) |
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--t0=... thermistor temp rating where # is the temperature in Celsuis to get r0 (from your datasheet) |
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--beta=... thermistor beta rating. see http://reprap.org/bin/view/Main/MeasuringThermistorBeta |
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--r1=... R1 rating where # is the ohm rating of R1 (eg: 10K = 10000) |
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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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""" |
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from math import * |
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import sys |
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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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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.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.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.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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return (self.beta / log(r / self.k)) - 273.15 # temperature |
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def setting(self, t): |
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"Convert a temperature into a ADC value" |
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r = self.r0 * exp(self.beta * (1 / (t + 273.15) - 1 / self.t0)) # resistance of the thermistor |
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v = self.vs * r / (self.rs + r) # the voltage at the potential divider |
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return round(v / self.vadc * 1024) # the ADC reading |
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def main(argv): |
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r0 = 10000; |
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t0 = 25; |
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beta = 3947; |
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r1 = 680; |
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r2 = 1600; |
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num_temps = int(20); |
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try: |
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opts, args = getopt.getopt(argv, "h", ["help", "r0=", "t0=", "beta=", "r1=", "r2="]) |
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except getopt.GetoptError: |
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usage() |
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sys.exit(2) |
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for opt, arg in opts: |
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if opt in ("-h", "--help"): |
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usage() |
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sys.exit() |
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elif opt == "--r0": |
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r0 = int(arg) |
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elif opt == "--t0": |
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t0 = int(arg) |
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elif opt == "--beta": |
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beta = int(arg) |
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elif opt == "--r1": |
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r1 = int(arg) |
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elif opt == "--r2": |
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r2 = int(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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t = Thermistor(r0, t0, beta, r1, r2) |
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adcs = range(1, max_adc, increment); |
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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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print "// Thermistor lookup table for RepRap Temperature Sensor Boards (http://make.rrrf.org/ts)" |
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print "// Made with createTemperatureLookup.py (http://svn.reprap.org/trunk/reprap/firmware/Arduino/utilities/createTemperatureLookup.py)" |
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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 "// 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 "// beta: %s" % (beta) |
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print "// max adc: %s" % (max_adc) |
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print "#define NUMTEMPS %s" % (len(adcs)) |
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print "short temptable[NUMTEMPS][2] = {" |
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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}" % (adc, int(t.temp(adc))) |
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else: |
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print " {%s, %s}," % (adc, int(t.temp(adc))) |
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print "};" |
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def usage(): |
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print __doc__ |
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if __name__ == "__main__": |
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main(sys.argv[1:]) |
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