Better timing for PID loop

kiln/manager.py

@@ -143,8 +143,8 @@ class Profile(threading.Thread):
 		self.running = False
 
 	def run(self):
+		_next = time.time()+self.interval
 		while not self.completed and self.running:
-			now = time.time()
 			ts = self.elapsed
 			#find epoch
 			for i in range(len(self.schedule)-1):
@@ -154,18 +154,19 @@ class Profile(threading.Thread):
 					frac = (ts - time0) / (time1 - time0)
 					setpoint = frac * (temp1 - temp0) + temp0
 					self.pid.setPoint(setpoint)
-					
-					pid_out = -1
+
 					temp = self.therm.temperature.temp
 					if temp == -1:
 						continue #skip invalid temperature readings
-					elif temp - setpoint > 20:
+					elif temp - setpoint > 10:
 						self.regulator.off()
 						self.duty_cycle = True
+						pid_out = -1
 					elif self.duty_cycle:
-						if temp - setpoint < -10:
+						if temp - setpoint < -5:
 							self.regulator.ignite()
 							self.duty_cycle = False
+						pid_out = -1
 					else:
 						pid_out = self.pid.update(temp)
 						if pid_out < 0: pid_out = 0
@@ -175,4 +176,7 @@ class Profile(threading.Thread):
 					if self.callback is not None:
 						self.callback(temp, setpoint, pid_out)
 
-			time.sleep(self.interval - (time.time()-now))
+			sleep = _next - time.time()
+			if (sleep > 0)
+				time.sleep(sleep)
+			_next += self.interval