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Merge pull request #27 from adq/noisecouple

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Thermocouple improvements
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Jason Bruce 2021-06-07 10:20:10 -04:00 committed by GitHub
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4 changed files with 149 additions and 40 deletions
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13
config.py
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@ -117,3 +117,16 @@ kiln_must_catch_up_max_error = 10 #degrees
# set set this offset to -4 to compensate. This probably means you have a
# cheap thermocouple. Invest in a better thermocouple.
thermocouple_offset=0
# some kilns/thermocouples start erroneously reporting "short" errors at higher temperatures
# due to plasma forming in the kiln.
# Set this to False to ignore these errors and assume the temperature reading was correct anyway
honour_theromocouple_short_errors = True
# number of samples of temperature to average.
# If you suffer from the high temperature kiln issue and have set honour_theromocouple_short_errors to False,
# you will likely need to increase this (eg I use 40)
temperature_average_samples = 5
# Thermocouple AC frequency filtering - set to True if in a 50Hz locale, else leave at False for 60Hz locale
ac_freq_50hz = False

24
lib/max31855.py
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@ -13,7 +13,7 @@ class MAX31855(object):
'''Initialize Soft (Bitbang) SPI bus
Parameters:
- cs_pin: Chip Select (CS) / Slave Select (SS) pin (Any GPIO)
- cs_pin: Chip Select (CS) / Slave Select (SS) pin (Any GPIO)
- clock_pin: Clock (SCLK / SCK) pin (Any GPIO)
- data_pin: Data input (SO / MOSI) pin (Any GPIO)
- units: (optional) unit of measurement to return. ("c" (default) | "k" | "f")
@ -26,6 +26,7 @@ class MAX31855(object):
self.units = units
self.data = None
self.board = board
self.noConnection = self.shortToGround = self.shortToVCC = self.unknownError = False
# Initialize needed GPIO
GPIO.setmode(self.board)
@ -70,20 +71,13 @@ class MAX31855(object):
if data_32 is None:
data_32 = self.data
anyErrors = (data_32 & 0x10000) != 0 # Fault bit, D16
noConnection = (data_32 & 0x00000001) != 0 # OC bit, D0
shortToGround = (data_32 & 0x00000002) != 0 # SCG bit, D1
shortToVCC = (data_32 & 0x00000004) != 0 # SCV bit, D2
if anyErrors:
if noConnection:
raise MAX31855Error("No Connection")
elif shortToGround:
raise MAX31855Error("Thermocouple short to ground")
elif shortToVCC:
raise MAX31855Error("Thermocouple short to VCC")
else:
# Perhaps another SPI device is trying to send data?
# Did you remember to initialize all other SPI devices?
raise MAX31855Error("Unknown Error")
self.noConnection = (data_32 & 0x00000001) != 0 # OC bit, D0
self.shortToGround = (data_32 & 0x00000002) != 0 # SCG bit, D1
self.shortToVCC = (data_32 & 0x00000004) != 0 # SCV bit, D2
self.unknownError = not (self.noConnection | self.shortToGround | self.shortToVCC) # Errk!
else:
self.noConnection = self.shortToGround = self.shortToVCC = self.unknownError = False
def data_to_tc_temperature(self, data_32 = None):
'''Takes an integer and returns a thermocouple temperature in celsius.'''
@ -138,7 +132,7 @@ class MAX31855(object):
GPIO.setup(self.clock_pin, GPIO.IN)
def data_to_LinearizedTempC(self, data_32 = None):
'''Return the NIST-linearized thermocouple temperature value in degrees
'''Return the NIST-linearized thermocouple temperature value in degrees
celsius. See https://learn.adafruit.com/calibrating-sensors/maxim-31855-linearization for more infoo.
This code came from https://github.com/nightmechanic/FuzzypicoReflow/blob/master/lib/max31855.py
'''

45
lib/max31856.py
View File

@ -89,7 +89,7 @@ class MAX31856(object):
MAX31856_S_TYPE = 0x6 # Read S Type Thermocouple
MAX31856_T_TYPE = 0x7 # Read T Type Thermocouple
def __init__(self, tc_type=MAX31856_S_TYPE, units="c", avgsel=0x0, software_spi=None, hardware_spi=None, gpio=None):
def __init__(self, tc_type=MAX31856_S_TYPE, units="c", avgsel=0x0, ac_freq_50hz=False, ocdetect=0x1, software_spi=None, hardware_spi=None, gpio=None):
"""
Initialize MAX31856 device with software SPI on the specified CLK,
CS, and DO pins. Alternatively can specify hardware SPI by sending an
@ -100,6 +100,8 @@ class MAX31856(object):
MAX31856.MAX31856_X_TYPE.
avgsel (1-byte Hex): Type of Averaging. Choose from values in CR0 table of datasheet.
Default is single sample.
ac_freq_50hz: Set to True if your AC frequency is 50Hz, Set to False for 60Hz,
ocdetect: Detect open circuit errors (ie broken thermocouple). Choose from values in CR1 table of datasheet
software_spi (dict): Contains the pin assignments for software SPI, as defined below:
clk (integer): Pin number for software SPI clk
cs (integer): Pin number for software SPI cs
@ -112,6 +114,8 @@ class MAX31856(object):
self.tc_type = tc_type
self.avgsel = avgsel
self.units = units
self.noConnection = self.shortToGround = self.shortToVCC = self.unknownError = False
# Handle hardware SPI
if hardware_spi is not None:
self._logger.debug('Using hardware SPI')
@ -132,11 +136,13 @@ class MAX31856(object):
self._spi.set_mode(1)
self._spi.set_bit_order(SPI.MSBFIRST)
self.cr1 = ((self.avgsel << 4) + self.tc_type)
self.cr0 = self.MAX31856_CR0_READ_CONT | ((ocdetect & 3) << 4) | (1 if ac_freq_50hz else 0)
self.cr1 = (((self.avgsel & 7) << 4) + (self.tc_type & 0x0f))
# Setup for reading continuously with T-Type thermocouple
self._write_register(self.MAX31856_REG_WRITE_CR0, self.MAX31856_CR0_READ_CONT)
self._write_register(self.MAX31856_REG_WRITE_CR0, 0)
self._write_register(self.MAX31856_REG_WRITE_CR1, self.cr1)
self._write_register(self.MAX31856_REG_WRITE_CR0, self.cr0)
@staticmethod
def _cj_temp_from_bytes(msb, lsb):
@ -297,8 +303,39 @@ class MAX31856(object):
'''Convert celsius to fahrenheit.'''
return celsius * 9.0/5.0 + 32
def checkErrors(self):
data = self.read_fault_register()
self.noConnection = (data & 0x00000001) != 0
self.unknownError = (data & 0xfe) != 0
def get(self):
self.checkErrors()
celcius = self.read_temp_c()
return getattr(self, "to_" + self.units)(celcius)
if __name__ == "__main__":
# Multi-chip example
import time
cs_pins = [6]
clock_pin = 13
data_pin = 5
di_pin = 26
units = "c"
thermocouples = []
for cs_pin in cs_pins:
thermocouples.append(MAX31856(avgsel=0, ac_freq_50hz=True, tc_type=MAX31856.MAX31856_K_TYPE, software_spi={'clk': clock_pin, 'cs': cs_pin, 'do': data_pin, 'di': di_pin}, units=units))
running = True
while(running):
try:
for thermocouple in thermocouples:
rj = thermocouple.read_internal_temp_c()
tc = thermocouple.get()
print("tc: {} and rj: {}, NC:{} ??:{}".format(tc, rj, thermocouple.noConnection, thermocouple.unknownError))
time.sleep(1)
except KeyboardInterrupt:
running = False
for thermocouple in thermocouples:
thermocouple.cleanup()

107
lib/oven.py
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@ -8,6 +8,7 @@ import config
log = logging.getLogger(__name__)
class Output(object):
def __init__(self):
self.active = False
@ -29,10 +30,10 @@ class Output(object):
def heat(self,sleepfor):
self.GPIO.output(config.gpio_heat, self.GPIO.HIGH)
time.sleep(sleepfor)
self.GPIO.output(config.gpio_heat, self.GPIO.LOW)
def cool(self,sleepfor):
'''no active cooling, so sleep'''
self.GPIO.output(config.gpio_heat, self.GPIO.LOW)
time.sleep(sleepfor)
# FIX - Board class needs to be completely removed
@ -82,7 +83,9 @@ class TempSensor(threading.Thread):
threading.Thread.__init__(self)
self.daemon = True
self.temperature = 0
self.bad_percent = 0
self.time_step = config.sensor_time_wait
self.noConnection = self.shortToGround = self.shortToVCC = self.unknownError = False
class TempSensorSimulated(TempSensor):
'''not much here, just need to be able to set the temperature'''
@ -94,6 +97,11 @@ class TempSensorReal(TempSensor):
during the time_step'''
def __init__(self):
TempSensor.__init__(self)
self.sleeptime = self.time_step / float(config.temperature_average_samples)
self.bad_count = 0
self.ok_count = 0
self.bad_stamp = 0
if config.max31855:
log.info("init MAX31855")
from max31855 import MAX31855, MAX31855Error
@ -110,26 +118,48 @@ class TempSensorReal(TempSensor):
'do': config.gpio_sensor_data,
'di': config.gpio_sensor_di }
self.thermocouple = MAX31856(tc_type=config.thermocouple_type,
software_spi = sofware_spi,
units = config.temp_scale
software_spi = software_spi,
units = config.temp_scale,
ac_freq_50hz = config.ac_freq_50hz,
)
def run(self):
'''take 5 measurements over each time period and return the
average'''
'''use a moving average of config.temperature_average_samples across the time_step'''
temps = []
while True:
maxtries = 5
sleeptime = self.time_step / float(maxtries)
temps = []
for x in range(0,maxtries):
try:
temp = self.thermocouple.get()
temps.append(temp)
except Exception:
log.exception("problem reading temp")
time.sleep(sleeptime)
if len(temps) > 0:
self.temperature = sum(temps)/len(temps)
# reset error counter if time is up
if (time.time() - self.bad_stamp) > (self.time_step * 2):
if self.bad_count + self.ok_count:
self.bad_percent = (self.bad_count / (self.bad_count + self.ok_count)) * 100
else:
self.bad_percent = 0
self.bad_count = 0
self.ok_count = 0
self.bad_stamp = time.time()
temp = self.thermocouple.get()
self.noConnection = self.thermocouple.noConnection
self.shortToGround = self.thermocouple.shortToGround
self.shortToVCC = self.thermocouple.shortToVCC
self.unknownError = self.thermocouple.unknownError
is_bad_value = self.noConnection | self.unknownError
if config.honour_theromocouple_short_errors:
is_bad_value |= self.shortToGround | self.shortToVCC
if not is_bad_value:
temps.append(temp)
if len(temps) > config.temperature_average_samples:
del temps[0]
self.ok_count += 1
else:
log.error(f"Problem reading temp N/C:{self.noConnection} GND:{self.shortToGround} VCC:{self.shortToVCC} ???:{self.unknownError}")
self.bad_count += 1
if len(temps):
self.temperature = sum(temps) / len(temps)
time.sleep(self.sleeptime)
class Oven(threading.Thread):
'''parent oven class. this has all the common code
@ -152,8 +182,22 @@ class Oven(threading.Thread):
self.pid = PID(ki=config.pid_ki, kd=config.pid_kd, kp=config.pid_kp)
def run_profile(self, profile, startat=0):
log.info("Running schedule %s" % profile.name)
self.reset()
if self.board.temp_sensor.noConnection:
log.info("Refusing to start profile - thermocouple not connected")
return
if self.board.temp_sensor.shortToGround:
log.info("Refusing to start profile - thermocouple short to ground")
return
if self.board.temp_sensor.shortToVCC:
log.info("Refusing to start profile - thermocouple short to VCC")
return
if self.board.temp_sensor.unknownError:
log.info("Refusing to start profile - thermocouple unknown error")
return
log.info("Running schedule %s" % profile.name)
self.profile = profile
self.totaltime = profile.get_duration()
self.state = "RUNNING"
@ -183,6 +227,9 @@ class Oven(threading.Thread):
def update_runtime(self):
runtime_delta = datetime.datetime.now() - self.start_time
if runtime_delta.total_seconds() < 0:
runtime_delta = datetime.timedelta(0)
if self.startat > 0:
self.runtime = self.startat + runtime_delta.total_seconds()
else:
@ -192,12 +239,24 @@ class Oven(threading.Thread):
self.target = self.profile.get_target_temperature(self.runtime)
def reset_if_emergency(self):
'''reset if the temperature is way TOO HOT'''
'''reset if the temperature is way TOO HOT, or other critical errors detected'''
if (self.board.temp_sensor.temperature + config.thermocouple_offset >=
config.emergency_shutoff_temp):
log.info("emergency!!! temperature too high, shutting down")
self.reset()
if self.board.temp_sensor.noConnection:
log.info("emergency!!! lost connection to thermocouple, shutting down")
self.reset()
if self.board.temp_sensor.unknownError:
log.info("emergency!!! unknown thermocouple error, shutting down")
self.reset()
if self.board.temp_sensor.bad_percent > 30:
log.info("emergency!!! too many errors in a short period, shutting down")
self.reset()
def reset_if_schedule_ended(self):
if self.runtime > self.totaltime:
log.info("schedule ended, shutting down")
@ -326,6 +385,10 @@ class RealOven(Oven):
# start thread
self.start()
def reset(self):
super().reset()
self.output.cool(0)
def heat_then_cool(self):
pid = self.pid.compute(self.target,
self.board.temp_sensor.temperature +
@ -338,8 +401,10 @@ class RealOven(Oven):
if heat_on > 0:
self.heat = 1.0
self.output.heat(heat_on)
self.output.cool(heat_off)
if heat_on:
self.output.heat(heat_on)
if heat_off:
self.output.cool(heat_off)
time_left = self.totaltime - self.runtime
log.info("temp=%.2f, target=%.2f, pid=%.3f, heat_on=%.2f, heat_off=%.2f, run_time=%d, total_time=%d, time_left=%d" %
(self.board.temp_sensor.temperature + config.thermocouple_offset,