Ceramic Kiln/Controller
From Makers Local 256
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Creator: |
Overview
I'm building an arduino based kiln controller for driving our Kiln. The Arduino code is here. The libraries that I'm using are:
Goals/Features
- Add mode button for Candling. (raise temp to 190F and maintain temp for 12 hours.)
- Add mode buttons for Timed Firing (not sure how this might be useful, but then I know nothing of ceramic arts either. maybe glazing?)
- Add mode button for Gradual Heating (slowly heat the kiln as opposed to full electric on.)
Materials/Links
- Arduino Uno
- 2x Thermocouple Amplifier MAX31855 breakout board (~$40)
- Type K High Temp Thermocouple ($28)
- DC-AC Solid State Relay SSR-40DA 40A 3-32VDC 24-380VAC w Heat Sink ($24)
- DigiSpark Relay Shield (because I had spares and am a little afraid of hooking the SSR directly to the arduino without a transistor circuit; also I'm lazy)
- Seeed SD Shield ($10 + $12 sd card)
Technical Details
- Current Status: We tested the Thermocouple board and determined that for the thermocouple that we are using (adafruit's is only rated to 900F, the kiln fires to 2307F) is passing heat through the wires to the cold end; to the tune of 700F! Our solution: Get another MAX31855 chip, attach it to the cold end, and sum the two temps! I'll be changing the pin map the reflect the new reality and using this method for the buttons. (its a good thing I hadn't soldered the ends to the pins yet...)
- prior comments: reading temp and displaying it on LCD display; The high fire Type K thermocouple arrived and is installed. All SolidStateRelays are in from China. Initial Draft of code is written for governing firing schedule segments. I added a SD Card shield to the design. I am now out of pins on the Arduino. If I want it to do more, I'll have to go to the Mega 2560. ^__^ I need to add more debugging info to the SD log.
PIN MAP - currently the code and the pin map do not agree with each other. The code will be changing.
| Pin | Group | Use |
|---|---|---|
| D13 | SD Card Shield | SCK |
| D12 | SD Card Shield | MISO |
| D11 | SD Card Shield | MOSI |
| D10 | SD Card Shield | CS |
| D09 | LCD | RS |
| D08 | LCD | Enable |
| D07 | LCD | d0 |
| D06 | LCD | d1 |
| D05 | LCD | d2 |
| D04 | LCD | d3 |
| D03 | MAX31855 Thermocouple board | CLK |
| D02 | MAX31855 Thermocouple board | CS |
| D01 | TX | pin |
| D00 | RX | pin |
| A5 | MAX31855 Thermocouple board | CLK |
| A4 | MAX31855 Thermocouple board | CS |
| A3 | MAX31855 Thermocouple board | d0 |
| A2 | MAX31855 Thermocouple board | d0 |
| A1 | Kiln Relay | pin |
| A0 | Buttons |
Usecases
1.Turn On / Clear
- Press Init Button
2.Select Cone
- Starts at 022 and goes to 8
3.Select Hold Time (mutually exclusive with the physical cone switch)
- 0 to 9 hrs
4.Select Kiln Mode - default is Fast speed
- Press Mode Button to switch between Slow, Medium, Fast, Slow w/ controlled cooling, Medium w/ C.C. (back to slow)
| Mode | Time Segments | Description |
|---|---|---|
| Fast | 1 | Balls to the wall/As hot as the elements can get |
| Medium | 4 | 1(0F-250F@200F/hr), 2(250F-1000F@400F/hr), 3(1000F-1200F@180F/hr), 4(1200F-1700F@300F/hr), Further heating at 200F/hr |
| Slow | 4 | 1(0F-250F@80/hr), 2(250F-1000F@250/hr), 3(1000F-1200F@150/hr), 4(1200F-1700F@180/hr), Further heating at 80F/hr |
| Slow w/Controlled Cooling | 8/9 | Heating cycle as Slow. Cooling is a reverse of Segments. |
| Medium w/Controlled Cooling | 8/9 | Heating cycle as Medium. Cooling is a reverse of Segments. |
5.Start Button
- Verifies all selections are valid and begins Firing Cycle.
