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heater: Add support for AD595 type sensors

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Add support for sensor chips that produce a voltage that linearly
scales with temperature.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2017-03-06 16:11:58 -05:00
parent ff6a96665a
commit f66b1ac450
2 changed files with 29 additions and 9 deletions
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28
klippy/heater.py
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@ -9,9 +9,13 @@ import math, logging, threading
Sensors = {
# Common thermistors and their Steinhart-Hart coefficients
"EPCOS 100K B57560G104F": (
"thermistor",
0.000722136308968056, 0.000216766566488498, 8.92935804531095e-08),
"ATC Semitec 104GT-2": (
"thermistor",
0.000809651054275124, 0.000211636030735685, 7.07420883993973e-08),
# Linear style conversion chips and their gain/offset
"AD595": ("linear", 300.0 / 3.022, 0.),
}
SAMPLE_TIME = 0.001
@ -30,8 +34,14 @@ class PrinterHeater:
error = error
def __init__(self, printer, config):
self.name = config.section
self.sensor_c = config.getchoice('sensor_type', Sensors)
self.pullup_r = config.getfloat('pullup_resistor', 4700.)
sensor_params = config.getchoice('sensor_type', Sensors)
self.is_linear_sensor = (sensor_params[0] == 'linear')
if self.is_linear_sensor:
adc_voltage = config.getfloat('adc_voltage', 5.)
self.sensor_coef = sensor_params[1] * adc_voltage, sensor_params[2]
else:
pullup = config.getfloat('pullup_resistor', 4700.)
self.sensor_coef = sensor_params[1:] + (pullup,)
self.min_extrude_temp = config.getfloat('min_extrude_temp', 170.)
self.min_temp = config.getfloat('min_temp')
self.max_temp = config.getfloat('max_temp')
@ -80,21 +90,27 @@ class PrinterHeater:
self.mcu_pwm.set_pwm(pwm_time, value)
# Temperature calculation
def calc_temp(self, adc):
r = self.pullup_r * adc / (1.0 - adc)
if self.is_linear_sensor:
gain, offset = self.sensor_coef
return adc * gain + offset
c1, c2, c3, pullup = self.sensor_coef
r = pullup * adc / (1.0 - adc)
ln_r = math.log(r)
c1, c2, c3 = self.sensor_c
temp_inv = c1 + c2*ln_r + c3*math.pow(ln_r, 3)
return 1.0/temp_inv + KELVIN_TO_CELCIUS
def calc_adc(self, temp):
if temp is None:
return None
c1, c2, c3 = self.sensor_c
if self.is_linear_sensor:
gain, offset = self.sensor_coef
return (temp - offset) / gain
c1, c2, c3, pullup = self.sensor_coef
temp -= KELVIN_TO_CELCIUS
temp_inv = 1./temp
y = (c1 - temp_inv) / (2*c3)
x = math.sqrt(math.pow(c2 / (3.*c3), 3.) + math.pow(y, 2.))
r = math.exp(math.pow(x-y, 1./3.) - math.pow(x+y, 1./3.))
return r / (self.pullup_r + r)
return r / (pullup + r)
def adc_callback(self, read_time, read_value):
temp = self.calc_temp(read_value)
with self.lock: