add emergency relais support, inspired by pr60

config.py

@@ -79,17 +79,21 @@
 #######################################
 # Output to control the relay
 #######################################
-# A single GPIO pin is used to control a relay which controls the kiln.
+# One GPIO pin is used to control a relay which controls the kiln.
 # I use GPIO pin 23.
+#
+# A second GPIO pin is used to control an emergency cutoff relay which 
+# stops the kiln even if the SSRs short out.
 
 try:
     import board
-    spi_sclk  = board.D17    #spi clock
-    spi_miso  = board.D27    #spi Microcomputer In Serial Out
-    spi_cs    = board.D22    #spi Chip Select
-    spi_mosi  = board.D10    #spi Microcomputer Out Serial In (not connected) 
-    gpio_heat = board.D23    #output that controls relay
-    gpio_heat_invert = False #invert the output state
+    spi_sclk  = board.D17      #spi clock
+    spi_miso  = board.D27      #spi Microcomputer In Serial Out
+    spi_cs    = board.D22      #spi Chip Select
+    spi_mosi  = board.D10      #spi Microcomputer Out Serial In (not connected) 
+    gpio_heat = board.D23      #output that controls relay
+    gpio_heat_invert = False   #invert the output state
+    gpio_emergency = board.D26 #output that controls emergency relay
 except (NotImplementedError,AttributeError):
     print("not running on blinka recognized board, probably a simulation")
 

emergency-off.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+import config
+import digitalio
+import time
+import datetime
+
+try:
+    import board
+except NotImplementedError:
+    print("not running a recognized blinka board, exiting...")
+    import sys
+    sys.exit()
+
+########################################################################
+#
+# shut down the mergency relais
+
+# Edit config.py and set the following in that file to match your
+# hardware setup: gpio_emergency
+########################################################################
+
+emergency = digitalio.DigitalInOut(config.gpio_emergency)
+emergency.direction = digitalio.Direction.OUTPUT
+
+print("\nboard: %s" % (board.board_id))
+print("emergency configured as config.gpio_emergency = %s BCM pin\n" % (config.gpio_emergency))
+
+print("\nsetting emergency IO low")
+emergency.value = False

lib/init/kiln-controller.service

@@ -3,6 +3,7 @@ Description=kiln-controller
 
 [Service]
 ExecStart=/home/pi/kiln-controller/venv/bin/python /home/pi/kiln-controller/kiln-controller.py
+ExecStopPost=/home/pi/kiln-controller/venv/bin/python /home/pi/kiln-controller/emergency-off.py
 
 [Install]
 WantedBy=multi-user.target

lib/oven.py

@@ -37,14 +37,21 @@ class Output(object):
     inputs
         config.gpio_heat
         config.gpio_heat_invert
+        config.gpio_emergency
     '''
     def __init__(self):
         self.active = False
         self.heater = digitalio.DigitalInOut(config.gpio_heat) 
         self.heater.direction = digitalio.Direction.OUTPUT 
+        self.emergency = digitalio.DigitalInOut(config.gpio_emergency) 
+        self.emergency.direction = digitalio.Direction.OUTPUT
         self.off = config.gpio_heat_invert
         self.on = not self.off
 
+    def emergency_set(self,state):
+        log.info("emergency relais = %s" %(state))
+        self.emergency.value = state
+
     def heat(self,sleepfor):
         self.heater.value = self.on
         time.sleep(sleepfor)
@@ -346,6 +353,7 @@ def reset(self):
         self.heat_rate_temps = []
         self.pid = PID(ki=config.pid_ki, kd=config.pid_kd, kp=config.pid_kp)
         self.catching_up = False
+        self.emergency_trigger()
 
     @staticmethod
     def get_start_from_temperature(profile, temp):
@@ -392,11 +400,13 @@ def run_profile(self, profile, startat=0, allow_seek=True):
         self.totaltime = profile.get_duration()
         self.state = "RUNNING"
         log.info("Running schedule %s starting at %d minutes" % (profile.name,startat))
+        self.emergency_release()
         log.info("Starting")
 
     def abort_run(self):
         self.reset()
         self.save_automatic_restart_state()
+        self.emergency_trigger()
 
     def get_start_time(self):
         return datetime.datetime.now() - datetime.timedelta(milliseconds = self.runtime * 1000)
@@ -676,6 +686,11 @@ def heat_then_cool(self):
         # a simulation, so sleep.
         time.sleep(self.time_step / self.speedup_factor)
 
+    def emergency_trigger(self):
+        log.info("emergency triggered -> heating disabled.")
+
+    def emergency_release(self):
+        log.info("emergency released -> heating enabled.")
 
 class RealOven(Oven):
 
@@ -729,6 +744,14 @@ def heat_then_cool(self):
         except KeyError:
             pass
 
+    def emergency_trigger(self):
+        log.info("emergency triggered -> heating disabled.")
+        self.output.emergency_set(0)
+
+    def emergency_release(self):
+        log.info("emergency released -> heating enabled.")
+        self.output.emergency_set(1)
+
 class Profile():
     def __init__(self, json_data):
         obj = json.loads(json_data)