codepad
[
create a new paste
]
login
|
about
Language:
C
C++
D
Haskell
Lua
OCaml
PHP
Perl
Plain Text
Python
Ruby
Scheme
Tcl
#!/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 --r0=... thermistor rating where # is the ohm rating of the thermistor at t0 (eg: 10K = 10000) --t0=... thermistor temp rating where # is the temperature in Celsuis to get r0 (from your datasheet) --beta=... thermistor beta rating. see http://reprap.org/bin/view/Main/MeasuringThermistorBeta --r1=... R1 rating where # is the ohm rating of R1 (eg: 10K = 10000) --r2=... R2 rating where # is the ohm rating of R2 (eg: 10K = 10000) --num-temps=... the number of temperature points to calculate (default: 20) --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 """ from math import * import sys import getopt class Thermistor: "Class to do the thermistor maths" def __init__(self, r0, t0, beta, r1, r2): self.r0 = r0 # stated resistance, e.g. 10K self.t0 = t0 + 273.15 # temperature at stated resistance, e.g. 25C self.beta = beta # stated beta, e.g. 3500 self.vadc = 5.0 # ADC reference self.vcc = 5.0 # supply voltage to potential divider self.k = r0 * exp(-beta / self.t0) # constant part of calculation if r1 > 0: self.vs = r1 * self.vcc / (r1 + r2) # effective bias voltage self.rs = r1 * r2 / (r1 + r2) # effective bias impedance else: self.vs = self.vcc # effective bias voltage self.rs = r2 # effective bias impedance def max_adc(self): "Find the maximum value of adc with a resistance greater than 0" return 1024 * self.vs / self.vadc - 1 def voltage(self,adc): "Convert ADC reading into a temperature in Celcius" return adc * self.vadc / 1024 # convert the 10 bit ADC value to a voltage def resistance(self,adc): "Convert ADC reading into a temperature in Celcius" v = self.voltage(adc) r = self.rs * v / (self.vs - v) return r # resistance of thermistor def temp(self,adc): "Convert ADC reading into a temperature in Celcius" return (self.beta / log(self.resistance(adc) / self.k)) - 273.15 # temperature def setting(self, t): "Convert a temperature into a ADC value" r = self.r0 * exp(self.beta * (1 / (t + 273.15) - 1 / self.t0)) # resistance of the thermistor v = self.vs * r / (self.rs + r) # the voltage at the potential divider return round(v / self.vadc * 1024) # the ADC reading def main(argv): r0 = 12120; t0 = 17.8; beta = 3796.577472; r1 = 0; r2 = 1465; num_temps = int(20); max_adc = int(1022); try: opts, args = getopt.getopt(argv, "h", ["help", "r0=", "t0=", "beta=", "r1=", "r2=", "max-adc="]) except getopt.GetoptError: usage() sys.exit(2) for opt, arg in opts: if opt in ("-h", "--help"): usage() sys.exit() elif opt == "--r0": r0 = int(arg) elif opt == "--t0": t0 = int(arg) elif opt == "--beta": beta = int(arg) elif opt == "--r1": r1 = int(arg) elif opt == "--r2": r2 = int(arg) elif opt == "--max-adc": max_adc = int(arg) t = Thermistor(r0, t0, beta, r1, r2) if t.max_adc() < max_adc: max_adc = int(t.max_adc()) increment = (max_adc - 2)/float(num_temps-1) adcs = [int(x * increment + 2) for x in range (0, num_temps)] first = 1 print "// Thermistor lookup table for RepRap Temperature Sensor Boards (http://make.rrrf.org/ts)" print "// Made with createTemperatureLookup.py (http://svn.reprap.org/trunk/reprap/firmware/Arduino/utilities/createTemperatureLookup.py)" print "// ./createTemperatureLookup.py --r0=%s --t0=%s --r1=%s --r2=%s --beta=%s --max-adc=%s" % (r0, t0, r1, r2, beta, max_adc) print "// r0: %s" % (r0) print "// t0: %s" % (t0) print "// r1: %s" % (r1) print "// r2: %s" % (r2) print "// beta: %s" % (beta) print "// max adc: %s" % (max_adc) print "#define NUMTEMPS %s" % (len(adcs)) print "short temptable[NUMTEMPS][2] = {" counter = 0 for adc in adcs: counter = counter +1 if counter == len(adcs): comma = " " else: comma = "," resistance = t.resistance(adc) voltage = t.voltage(adc) heat = 1000 * voltage * voltage / resistance t0 = t.temp(adc-1) t1 = t.temp(adc) t2 = t.temp(adc+1) dt = (t0 - t2) / 2 ddt = (t0 - t1) - (t1 - t2) print " {%4d, %4d}%s // %.2f V %.2f mW %.3f C/step %.5f C/(step^2)" % (adc, int(t1), comma, voltage, heat, dt, ddt) print "};" def usage(): print __doc__ if __name__ == "__main__": main(sys.argv[1:])
Private
[
?
]
Run code
Submit