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heater: Add support for a generic "NTC 100K beta 3950" thermistor 

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2017-08-17 14:34:25 -04:00
parent 1f4c6443ef
commit 4b5f3bec4b
2 changed files with 21 additions and 4 deletions
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3
config/example.cfg
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@ -176,7 +176,8 @@ heater_pin: ar10
# periods) to the heater. The default is 1.0.
sensor_type: EPCOS 100K B57560G104F
# Type of sensor - this may be "EPCOS 100K B57560G104F", "ATC
# Semitec 104GT-2", or "AD595". This parameter must be provided.
# Semitec 104GT-2", "NTC 100K beta 3950", or "AD595". This parameter
# must be provided.
sensor_pin: analog13
# Analog input pin connected to the sensor. This parameter must be
# provided.

22
klippy/heater.py
View File

@ -41,11 +41,25 @@ class Thermistor:
def calc_adc(self, temp):
temp -= KELVIN_TO_CELCIUS
temp_inv = 1./temp
y = (self.c1 - temp_inv) / (2. * self.c3)
x = math.sqrt(math.pow(self.c2 / (3.*self.c3), 3.) + math.pow(y, 2.))
r = math.exp(math.pow(x-y, 1./3.) - math.pow(x+y, 1./3.))
if self.c3:
y = (self.c1 - temp_inv) / (2. * self.c3)
x = math.sqrt(math.pow(self.c2 / (3.*self.c3), 3.) + math.pow(y, 2.))
r = math.exp(math.pow(x-y, 1./3.) - math.pow(x+y, 1./3.))
else:
r = math.exp((temp_inv - self.c1) / self.c2)
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):
@ -66,6 +80,8 @@ Sensors = {
"ATC Semitec 104GT-2": {
'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. },
"AD595": { 'class': Linear, 't1': 25., 'v1': .25, 't2': 300., 'v2': 3.022 },
}