created KilnController class which sets the kiln temperature according to a schedule using

PID temperature control

kiln/manager.py

@@ -1,3 +1,134 @@
-from Adafruit_alphanumeric import AlphaScroller
-from stepper import Regulator
+import stepper
+import datetime
+import numpy as np
+import warnings
 
+class KilnController(object):
+	""" schedule is of the format:
+	[(time1, temp1), (time2, temp2), .... (timen, tempn)]
+	where time is in seconds from start of firing and temp is in C"""
+
+	def __init__(self, schedule, monitor, interval=None):
+		self.schedule = schedule
+		if interval is not None: # interpolate schedule at specified interval size
+			temp = np.array(self.schedule)
+			temp2 = []
+			for i in range(len(self.schedule)-1):
+				times = np.arange(self.schedule[i][0], self.schedule[i+1][0], interval)
+				temps = np.arange(self.schedule[i][1], self.schedule[i+1][1], interval)
+				temp2.extend([(times[j], temps[j]) for j in range(len(times))])
+			self.schedule = temp2
+		self.start_time = datetime.datetime.now()
+		self.setpoint = schedule.pop(0)
+		self.monitor = monitor
+		self.pid = PID(3.0,0.4,1.2)
+		self.regulator = stepper.Regulator()
+		self.regulator.start()
+
+	@property
+	def elapsed(self):
+		''' Returns the elapsed time from start in seconds'''
+		return datetime.datetime.now() - self.start_time
+
+	def run(self):
+		self.pid.setPoint(self.setpoint[1])
+		while self.elapsed<self.setpoint[0]:
+			pid_out = self.pid.update(self.monitor.temperature)
+			if pid_out<0 or pid_out>1:
+				warnings.warn('PID output out of range at ' + str(pid_out) + '!')
+			if pid_out < 0: pid_out = 0
+			if pid_out > 1: pid_out = 1
+			self.regulator.set(pid_out)
+		self.setpoint = self.schedule.pop(0)
+		if len(schedule)>0:
+			self.run()
+
+class PID(object):
+	"""
+	Discrete PID control
+	#The recipe gives simple implementation of a Discrete Proportional-Integral-Derivative (PID) controller. PID controller gives output value for error between desired reference input and measurement feedback to minimize error value.
+	#More information: http://en.wikipedia.org/wiki/PID_controller
+	#
+	#cnr437@gmail.com
+	#
+	#######	Example	#########
+	#
+	#p=PID(3.0,0.4,1.2)
+	#p.setPoint(5.0)
+	#while True:
+	#     pid = p.update(measurement_value)
+	#
+	#
+	"""
+
+	def __init__(self, P=2.0, I=0.0, D=1.0, Derivator=0, Integrator=0, Integrator_max=500, Integrator_min=-500):
+
+		self.Kp=P
+		self.Ki=I
+		self.Kd=D
+		self.Derivator=Derivator
+		self.Integrator=Integrator
+		self.Integrator_max=Integrator_max
+		self.Integrator_min=Integrator_min
+
+		self.set_point=0.0
+		self.error=0.0
+
+	def update(self,current_value):
+		"""
+		Calculate PID output value for given reference input and feedback
+		"""
+
+		self.error = self.set_point - current_value
+
+		self.P_value = self.Kp * self.error
+		self.D_value = self.Kd * ( self.error - self.Derivator)
+		self.Derivator = self.error
+
+		self.Integrator = self.Integrator + self.error
+
+		if self.Integrator > self.Integrator_max:
+			self.Integrator = self.Integrator_max
+		elif self.Integrator < self.Integrator_min:
+			self.Integrator = self.Integrator_min
+
+		self.I_value = self.Integrator * self.Ki
+
+		PID = self.P_value + self.I_value + self.D_value
+
+		return PID
+
+	def setPoint(self,set_point):
+		"""
+		Initilize the setpoint of PID
+		"""
+		self.set_point = set_point
+		self.Integrator=0
+		self.Derivator=0
+
+	def setIntegrator(self, Integrator):
+		self.Integrator = Integrator
+
+	def setDerivator(self, Derivator):
+		self.Derivator = Derivator
+
+	def setKp(self,P):
+		self.Kp=P
+
+	def setKi(self,I):
+		self.Ki=I
+
+	def setKd(self,D):
+		self.Kd=D
+
+	def getPoint(self):
+		return self.set_point
+
+	def getError(self):
+		return self.error
+
+	def getIntegrator(self):
+		return self.Integrator
+
+	def getDerivator(self):
+		return self.Derivator