PIDKiln - PID Temperature Controller to Ceramic/Glass/Metal Kiln

This is "yet another" PID temperature controller. I've made this one, because bought one was crappy and I needed something solid. There are two or three other DIY controllers "on the market" but this one, at least I see it this way :), is much more robust and has all features I needed.

Key features:

  • interface accessible both from LCD screen and WWW webpage
  • unlimited (only by storage) kiln programs number,
  • program file size limited to 10KiB (but this is artificial limit - can be extended)
  • internal ESP storage for programs, data, logs (perhaps later SD - but I'm not sure yet)
  • local preferences on disk, editable with Web interface
  • online monitoring, program management, editing, graphs and kiln controll
  • build in clock synchronised with NTP servers (if Internet connected)
  • safety features build in (temperature run out protection, probe failure, SSR failure, kiln insulation failure)
  • simply cool and cheap (comparing to commercially available products) all in one solution

Supplies:

  • ESP32-Wrover board
  • MAX31855 breakout board (or two)
  • K-type thermocouple
  • DC->AC solid state relay

Kind of optional, but recommended:

  • 128x65 dot matrix LCD 12864B v2
  • Rotary encoder with button

Optional:

  • DC/AC secondary relay - like SLA-05VDC-SL-C (240V/30A) mechanical relay
  • Additional MAX31855 board with K-type thermocouple for housing temperature measuring
  • Perhaps a kiln :)

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Step 1: Wiring

LCD


Connected to one of three SPI on ESP32 - called VSPI (MOSI-23, MISO-19, CLK-18, CS-5)

ESP32   | LCD
--------|---------
+3.3V   | BLA (this can be also +5V if you wish)
GND     | BLK
4       | RST
GND     | PSB
+5V     | VCC (This should be - for ESP sake - 3,3V, but my LCD doesn't work with lower voltage. Try first with 3,3V)
GND     | GND
5       | RS
18      | E
23      | R/W

Encoder

ESP32   | Encoder
--------|---------
+3.3V   | 5V/VCC
GND     | GND
32      | Key
34      | S2
35      | S1

MAX31855


Connected to one of three SPI on ESP32 - called HSPI (MOSI-13, MISO-12, CLK-14) CS-15/27

EPS32   | MAX31855 A
--------|---------
+3.3V   | VCC
GND     | GND
12      | SO/DO (slave output/data output)
14      | SCK (clock)
15      | CS (chip select)
EPS32   | MAX31855 B
--------|---------
+3.3V   | VCC
GND     | GND
12      | SO/DO (slave output/data output)
14      | SCK (clock)
27      | CS (chip select)

Relays

ESP32   | SSR
--------|-------
GND     | GND
19      | IN
ESP32   | EMR (SLA-05VDC-SL-C)
--------|----------------
GND     | GND
21      | IN
5-48V*  | VCC

* Do not connect 5V from ESP - use external source. This can be any 5V-48V power supply with around 1W power.

Required source code is part of the Github: https://github.com/Saur0o0n/pidkiln

Some more information you can find on my webpage: https://adrian.siemieniak.net/portal/tag/PIDKiln/

3d printable case: https://www.thingiverse.com/thing:3907643

Step 2: Assembled Controller

This is fully assembled controller - on the left, and remote relay box (with power meter) - on the right. I've split those two elements because SSR relay can get quite hot and I wanted to have mains voltage away from logic boards.


PIDKiln is in 3d printed box, for relays I've used old 3,5'' aluminium disk enclosure and some 3d printed sides. I wanted this to be metal as an additional heatsink for SSR.

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