131 lines
5.5 KiB
Python
131 lines
5.5 KiB
Python
# Temperature measurements with thermistors
|
|
#
|
|
# Copyright (C) 2016-2019 Kevin O'Connor <kevin@koconnor.net>
|
|
#
|
|
# This file may be distributed under the terms of the GNU GPLv3 license.
|
|
import math, logging
|
|
from . import adc_temperature
|
|
|
|
KELVIN_TO_CELSIUS = -273.15
|
|
|
|
# Analog voltage to temperature converter for thermistors
|
|
class Thermistor:
|
|
def __init__(self, pullup, inline_resistor):
|
|
self.pullup = pullup
|
|
self.inline_resistor = inline_resistor
|
|
self.c1 = self.c2 = self.c3 = 0.
|
|
def setup_coefficients(self, t1, r1, t2, r2, t3, r3, name=""):
|
|
# Calculate Steinhart-Hart coefficents from temp measurements.
|
|
# Arrange samples as 3 linear equations and solve for c1, c2, and c3.
|
|
inv_t1 = 1. / (t1 - KELVIN_TO_CELSIUS)
|
|
inv_t2 = 1. / (t2 - KELVIN_TO_CELSIUS)
|
|
inv_t3 = 1. / (t3 - KELVIN_TO_CELSIUS)
|
|
ln_r1 = math.log(r1)
|
|
ln_r2 = math.log(r2)
|
|
ln_r3 = math.log(r3)
|
|
ln3_r1, ln3_r2, ln3_r3 = ln_r1**3, ln_r2**3, ln_r3**3
|
|
|
|
inv_t12, inv_t13 = inv_t1 - inv_t2, inv_t1 - inv_t3
|
|
ln_r12, ln_r13 = ln_r1 - ln_r2, ln_r1 - ln_r3
|
|
ln3_r12, ln3_r13 = ln3_r1 - ln3_r2, ln3_r1 - ln3_r3
|
|
|
|
self.c3 = ((inv_t12 - inv_t13 * ln_r12 / ln_r13)
|
|
/ (ln3_r12 - ln3_r13 * ln_r12 / ln_r13))
|
|
if self.c3 <= 0.:
|
|
beta = ln_r13 / inv_t13
|
|
logging.warn("Using thermistor beta %.3f in heater %s", beta, name)
|
|
self.setup_coefficients_beta(t1, r1, beta)
|
|
return
|
|
self.c2 = (inv_t12 - self.c3 * ln3_r12) / ln_r12
|
|
self.c1 = inv_t1 - self.c2 * ln_r1 - self.c3 * ln3_r1
|
|
def setup_coefficients_beta(self, t1, r1, beta):
|
|
# Calculate equivalent Steinhart-Hart coefficents from beta
|
|
inv_t1 = 1. / (t1 - KELVIN_TO_CELSIUS)
|
|
ln_r1 = math.log(r1)
|
|
self.c3 = 0.
|
|
self.c2 = 1. / beta
|
|
self.c1 = inv_t1 - self.c2 * ln_r1
|
|
def calc_temp(self, adc):
|
|
# Calculate temperature from adc
|
|
adc = max(.00001, min(.99999, adc))
|
|
r = self.pullup * adc / (1.0 - adc)
|
|
ln_r = math.log(r - self.inline_resistor)
|
|
inv_t = self.c1 + self.c2 * ln_r + self.c3 * ln_r**3
|
|
return 1.0/inv_t + KELVIN_TO_CELSIUS
|
|
def calc_adc(self, temp):
|
|
# Calculate adc reading from a temperature
|
|
if temp <= KELVIN_TO_CELSIUS:
|
|
return 1.
|
|
inv_t = 1. / (temp - KELVIN_TO_CELSIUS)
|
|
if self.c3:
|
|
# Solve for ln_r using Cardano's formula
|
|
y = (self.c1 - inv_t) / (2. * self.c3)
|
|
x = math.sqrt((self.c2 / (3. * self.c3))**3 + y**2)
|
|
ln_r = math.pow(x - y, 1./3.) - math.pow(x + y, 1./3.)
|
|
else:
|
|
ln_r = (inv_t - self.c1) / self.c2
|
|
r = math.exp(ln_r) + self.inline_resistor
|
|
return r / (self.pullup + r)
|
|
|
|
# Create an ADC converter with a thermistor
|
|
def PrinterThermistor(config, params):
|
|
pullup = config.getfloat('pullup_resistor', 4700., above=0.)
|
|
inline_resistor = config.getfloat('inline_resistor', 0., minval=0.)
|
|
thermistor = Thermistor(pullup, inline_resistor)
|
|
if 'beta' in params:
|
|
thermistor.setup_coefficients_beta(
|
|
params['t1'], params['r1'], params['beta'])
|
|
else:
|
|
thermistor.setup_coefficients(
|
|
params['t1'], params['r1'], params['t2'], params['r2'],
|
|
params['t3'], params['r3'], name=config.get_name())
|
|
return adc_temperature.PrinterADCtoTemperature(config, thermistor)
|
|
|
|
# Custom defined thermistors from the config file
|
|
class CustomThermistor:
|
|
def __init__(self, config):
|
|
self.name = " ".join(config.get_name().split()[1:])
|
|
t1 = config.getfloat("temperature1", minval=KELVIN_TO_CELSIUS)
|
|
r1 = config.getfloat("resistance1", minval=0.)
|
|
beta = config.getfloat("beta", None, above=0.)
|
|
if beta is not None:
|
|
self.params = {'t1': t1, 'r1': r1, 'beta': beta}
|
|
return
|
|
t2 = config.getfloat("temperature2", minval=KELVIN_TO_CELSIUS)
|
|
r2 = config.getfloat("resistance2", minval=0.)
|
|
t3 = config.getfloat("temperature3", minval=KELVIN_TO_CELSIUS)
|
|
r3 = config.getfloat("resistance3", minval=0.)
|
|
(t1, r1), (t2, r2), (t3, r3) = sorted([(t1, r1), (t2, r2), (t3, r3)])
|
|
self.params = {'t1': t1, 'r1': r1, 't2': t2, 'r2': r2,
|
|
't3': t3, 'r3': r3}
|
|
def create(self, config):
|
|
return PrinterThermistor(config, self.params)
|
|
|
|
# Default sensors
|
|
Sensors = {
|
|
"EPCOS 100K B57560G104F": {
|
|
't1': 25., 'r1': 100000., 't2': 150., 'r2': 1641.9,
|
|
't3': 250., 'r3': 226.15 },
|
|
"ATC Semitec 104GT-2": {
|
|
't1': 20., 'r1': 126800., 't2': 150., 'r2': 1360.,
|
|
't3': 300., 'r3': 80.65 },
|
|
"SliceEngineering 450": {
|
|
't1': 25., 'r1': 500000., 't2': 200., 'r2': 3734.,
|
|
't3': 400., 'r3': 240. },
|
|
"NTC 100K beta 3950": { 't1': 25., 'r1': 100000., 'beta': 3950. },
|
|
"Honeywell 100K 135-104LAG-J01": { 't1': 25., 'r1': 100000., 'beta': 3974.},
|
|
"NTC 100K MGB18-104F39050L32": { 't1': 25., 'r1': 100000., 'beta': 4100. },
|
|
}
|
|
|
|
def load_config(config):
|
|
# Register default thermistor types
|
|
pheaters = config.get_printer().load_object(config, "heaters")
|
|
for sensor_type, params in Sensors.items():
|
|
func = (lambda config, params=params: PrinterThermistor(config, params))
|
|
pheaters.add_sensor_factory(sensor_type, func)
|
|
|
|
def load_config_prefix(config):
|
|
thermistor = CustomThermistor(config)
|
|
pheaters = config.get_printer().load_object(config, "heaters")
|
|
pheaters.add_sensor_factory(thermistor.name, thermistor.create)
|