Updated made to be compatible with industrial modbus based industrial thermocouple input modules. This has been confirmed to solve problems assosicated with MAX31856 at temperatures above 900 C.

config.py

@@ -20,9 +20,9 @@ listening_port = 8081
 # This is used to calculate a cost estimate before a run. It's also used
 # to produce the actual cost during a run. My kiln has three
 # elements that when my switches are set to high, consume 9460 watts.
-kwh_rate        = 0.1319  # cost per kilowatt hour per currency_type to calculate cost to run job
-kw_elements     = 9.460 # if the kiln elements are on, the wattage in kilowatts
-currency_type   = "$"   # Currency Symbol to show when calculating cost to run job
+kwh_rate        = 1.6  # cost per kilowatt hour per currency_type to calculate cost to run job
+kw_elements     = 7.3 # if the kiln elements are on, the wattage in kilowatts
+currency_type   = "kr"   # Currency Symbol to show when calculating cost to run job
 
 ########################################################################
 #
@@ -99,8 +99,17 @@ except (NotImplementedError,AttributeError):
 # There are only two breakoutboards supported. 
 #   max31855 - only supports type K thermocouples
 #   max31856 - supports many thermocouples
-max31855 = 1
+max31855 = 0
 max31856 = 0
+modbus = 1
+
+modbus_port_name = "/dev/ttyUSB0"
+modbus_slave_address = 1
+modbus_baudrate = 38400
+modbus_registernumber = 12
+modbus_decimal = 1
+
+
 # uncomment these two lines if using MAX-31856
 import adafruit_max31856
 thermocouple_type = adafruit_max31856.ThermocoupleType.K
@@ -140,9 +149,9 @@ sensor_time_wait = 2
 # well with the simulated oven. You must tune them to work well with 
 # your specific kiln. Note that the integral pid_ki is
 # inverted so that a smaller number means more integral action.
-pid_kp = 10   # Proportional 25,200,200
-pid_ki = 80   # Integral
-pid_kd = 220.83497910261562 # Derivative
+pid_kp = 9.044738632122836   # Proportional 25,200,200
+pid_ki = 14.245288572837554   # Integral
+pid_kd = 291.3421380094641 # Derivative
 
 ########################################################################
 #
@@ -155,7 +164,7 @@ stop_integral_windup = True
 ########################################################################
 #
 #   Simulation parameters
-simulate = True
+simulate = False
 sim_t_env      = 65   # deg
 sim_c_heat     = 500.0  # J/K  heat capacity of heat element
 sim_c_oven     = 5000.0 # J/K  heat capacity of oven
@@ -176,7 +185,7 @@ sim_speedup_factor = 1
 #
 # If you change the temp_scale, all settings in this file are assumed to
 # be in that scale.
-temp_scale          = "f" # c = Celsius | f = Fahrenheit - Unit to display
+temp_scale          = "c" # c = Celsius | f = Fahrenheit - Unit to display
 time_scale_slope    = "h" # s = Seconds | m = Minutes | h = Hours - Slope displayed in temp_scale per time_scale_slope
 time_scale_profile  = "m" # s = Seconds | m = Minutes | h = Hours - Enter and view target time in time_scale_profile
 

lib/oven.py

@@ -83,6 +83,9 @@ class RealBoard(Board):
             return Max31855()
         if config.max31856:
             return Max31856()
+        if config.modbus:
+            return Modbus()
+
 
 class SimulatedBoard(Board):
     '''Simulated board used during simulations.
@@ -323,6 +326,40 @@ class Max31856(TempSensorReal):
                 raise Max31856_Error(k)
         return temp
 
+class Modbus(TempSensorReal):
+    '''each subclass expected to handle errors and get temperature'''
+    def __init__(self):
+        TempSensorReal.__init__(self)
+        log.info("thermocouple modbus")
+        import minimalmodbus
+
+        port = config.modbus_port_name
+        slave = config.modbus_slave_address
+        baudrate = config.modbus_baudrate
+        self.register = config.modbus_registernumber
+        self.decimal = config.modbus_decimal
+
+        self.instrument = minimalmodbus.Instrument(port, slave)
+        self.instrument.serial.baudrate = baudrate
+
+        """
+        if (config.ac_freq_50hz == True):
+            self.thermocouple.noise_rejection = 50
+        else:
+            self.thermocouple.noise_rejection = 60
+        """
+
+    def raw_temp(self):
+        # The underlying adafruit library does not throw exceptions
+        # for thermocouple errors. Instead, they are stored in
+        # dict named self.thermocouple.fault. Here we check that
+        # dict for errors and raise an exception.
+        # and raise Max31856_Error(message)
+
+        temp = self.instrument.read_register(self.register, self.decimal)
+
+        return temp
+
 class Oven(threading.Thread):
     '''parent oven class. this has all the common code
        for either a real or simulated oven'''

test-thermocouple.py

@@ -58,13 +58,30 @@ if(config.max31856):
     print("thermocouple: adafruit max31856")
     sensor = adafruit_max31856.MAX31856(spi, cs)
 
+
+
 print("Degrees displayed in %s\n" % (config.temp_scale))
 
 temp = 0
 while(True):
     time.sleep(1)
     try:
-        temp = sensor.temperature
+        if(config.modbus):
+            import minimalmodbus
+
+            port = config.modbus_port_name
+            slave = config.modbus_slave_address
+            baudrate = config.modbus_baudrate
+            register = config.modbus_registernumber
+            decimal = config.modbus_decimal
+
+            instrument = minimalmodbus.Instrument(port, slave)
+            instrument.serial.baudrate = baudrate
+
+            temp = instrument.read_register(register, decimal)
+        else:
+
+            temp = sensor.temperature
         scale = "C"
         if config.temp_scale == "f":
             temp = temp * (9/5) + 32