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heater: Merge ThermistorBeta class into Thermistor class 

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2018-04-04 13:38:28 -04:00
parent aed958eb5c
commit 7e78b2665e
1 changed files with 15 additions and 13 deletions
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28
klippy/heater.py
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@ -12,10 +12,16 @@ import math, logging, threading
KELVIN_TO_CELCIUS = -273.15
# Thermistor calibrated with three temp measurements
# Analog voltage to temperature converter for thermistors
class Thermistor:
def __init__(self, config, params):
self.pullup = config.getfloat('pullup_resistor', 4700., above=0.)
self.c1 = self.c2 = self.c3 = 0.
if 'beta' in params:
self.calc_coefficients_beta(params)
else:
self.calc_coefficients(params)
def calc_coefficients(self, params):
# Calculate Steinhart-Hart coefficents from temp measurements.
# Arrange samples as 3 linear equations and solve for c1, c2, and c3.
inv_t1 = 1. / (params['t1'] - KELVIN_TO_CELCIUS)
@ -34,6 +40,13 @@ class Thermistor:
/ (ln3_r12 - ln3_r13 * ln_r12 / ln_r13))
self.c2 = (inv_t12 - self.c3 * ln3_r12) / ln_r12
self.c1 = inv_t1 - self.c2 * ln_r1 - self.c3 * ln3_r1
def calc_coefficients_beta(self, params):
# Calculate equivalent Steinhart-Hart coefficents from beta
inv_t1 = 1. / (params['t1'] - KELVIN_TO_CELCIUS)
ln_r1 = math.log(params['r1'])
self.c3 = 0.
self.c2 = 1. / params['beta']
self.c1 = inv_t1 - self.c2 * ln_r1
def calc_temp(self, adc):
adc = max(.00001, min(.99999, adc))
r = self.pullup * adc / (1.0 - adc)
@ -52,17 +65,6 @@ class Thermistor:
r = math.exp(ln_r)
return r / (self.pullup + r)
# Thermistor calibrated from one temp measurement and its beta
class ThermistorBeta(Thermistor):
def __init__(self, config, params):
self.pullup = config.getfloat('pullup_resistor', 4700., above=0.)
# Calculate Steinhart-Hart coefficents from beta
inv_t1 = 1. / (params['t1'] - KELVIN_TO_CELCIUS)
ln_r1 = math.log(params['r1'])
self.c3 = 0.
self.c2 = 1. / params['beta']
self.c1 = inv_t1 - self.c2 * ln_r1
# Linear style conversion chips calibrated with two temp measurements
class Linear:
def __init__(self, config, params):
@ -84,7 +86,7 @@ Sensors = {
'class': Thermistor, 't1': 20., 'r1': 126800.,
't2': 150., 'r2': 1360., 't3': 300., 'r3': 80.65 },
"NTC 100K beta 3950": {
'class': ThermistorBeta, 't1': 25., 'r1': 100000., 'beta': 3950. },
'class': Thermistor, 't1': 25., 'r1': 100000., 'beta': 3950. },
"AD595": { 'class': Linear, 't1': 25., 'v1': .25, 't2': 300., 'v2': 3.022 },
}