From 4d201abdc91c5eebeae0047ed2f1c1c12c2ef3ed Mon Sep 17 00:00:00 2001
From: Tanaes <jonsan@gmail.com>
Date: Sat, 8 Jan 2022 19:02:23 -0500
Subject: [PATCH 1/2] added e relay code

---
 config.py   |  1 +
 lib/oven.py | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/config.py b/config.py
index 1931eee..9d7da2d 100644
--- a/config.py
+++ b/config.py
@@ -30,6 +30,7 @@ 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
 
 ### Thermocouple Adapter selection:
 #   max31855 - bitbang SPI interface
diff --git a/lib/oven.py b/lib/oven.py
index af2b42f..e20d36a 100644
--- a/lib/oven.py
+++ b/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)
@@ -384,12 +393,14 @@ 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):

From f7f63a00f9ca7bc40abbe497cf62bb903cacaf4c Mon Sep 17 00:00:00 2001
From: Tanaes <jonsan@gmail.com>
Date: Sat, 8 Jan 2022 19:05:02 -0500
Subject: [PATCH 2/2] added comment

---
 config.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/config.py b/config.py
index 9d7da2d..4240f2f 100644
--- a/config.py
+++ b/config.py
@@ -32,6 +32,13 @@ currency_type   = "$"   # Currency Symbol to show when calculating cost to run j
 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
 #   max31856 - bitbang SPI interface. must specify thermocouple_type.