Merge f7f63a00f9 into 165a8b16dd

config.py

@@ -30,6 +30,14 @@ currency_type   = "$"   # Currency Symbol to show when calculating cost to run j
 
 ### Outputs
 gpio_heat = 23  # Switches zero-cross solid-state-relay
+gpio_e_relay = 27 # pin 13; emergency cutoff relay
+
+#   Note: `gpio_e_relay` is used to and a redundant mechanical relay in series with
+#   the SSR. Because SSRs normally fail closed (i.e. energized), this provides a 
+#   way for the controller to shut off the kiln in the event that the SSR fails.
+#   It is designed to be used with the SSR input connected to the safety relay's
+#   Normally Open (NC) output; thus, the kiln can only heat when the RPi has
+#   energized the safety relay. 
 
 ### Thermocouple Adapter selection:
 #   max31855 - bitbang SPI interface

lib/oven.py

@@ -20,6 +20,7 @@ class Output(object):
             GPIO.setmode(GPIO.BCM)
             GPIO.setwarnings(False)
             GPIO.setup(config.gpio_heat, GPIO.OUT)
+            GPIO.setup(config.gpio_e_relay, GPIO.OUT)
             self.active = True
             self.GPIO = GPIO
         except:
@@ -27,6 +28,14 @@ class Output(object):
             log.warning(msg)
             self.active = False
 
+    def safety_off(self):
+        '''Energizes the safety relay'''
+        self.GPIO.output(config.gpio_e_relay, self.GPIO.HIGH)
+
+    def safety_on(self):
+        '''Deenergizes the safety relay'''
+        self.GPIO.output(config.gpio_e_relay, self.GPIO.LOW)
+
     def heat(self,sleepfor):
         self.GPIO.output(config.gpio_heat, self.GPIO.HIGH)
         time.sleep(sleepfor)
@@ -390,12 +399,14 @@ class RealOven(Oven):
 
         # call parent init
         Oven.__init__(self)
+        self.output.safety_off()
 
         # start thread
         self.start()
 
     def reset(self):
         super().reset()
+        self.output.safety_on()
         self.output.cool(0)
 
     def heat_then_cool(self):