2 layers101.5 × 54.9 mm Iot crockpot, the printed circuit board in 3D

Iot crockpot

Repo for internet enabled crockpot

Size: 101.5 × 54.9 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 23
Nets: 49
Pads: 101
Tracks, vias: 0, 0
Routed: Not yet
KiCad: KiCad 9.0 (file 20241229)
Created: 25 Jan 2026
Updated: 4 Mar 2026

Overview

Iot crockpot is an open-source printed circuit board by AverageJoel, from the AverageJoel/iot_crockpot repository on GitHub, published under the MIT licence. It is a 2-layer board of 101.5 × 54.9 mm with 23 parts on 49 nets.

It is built around the HLK-5M05, MAX31855KASA+T and 1N4148W. Its parts include 6 connectors, 3 resistors, 2 capacitors, 2 ICs and 2 diodes. It belongs with the home automation and IoT boards and the STM32 boards of this library.

Main components

README

hardware/README.md

IoT Crockpot Power Board

Custom PCB for the IoT Crockpot controller. Single-board design — the ESP32-S3 handles WiFi, display, thermocouple, relay, and USB directly with no secondary MCU.

Architecture

text

AC Mains ──► Fuse ──► MOV ──► HLK-5M05 ──► P-FET ──► 5V Rail
                                           (AO3401)      │
                                         Gate: 100K→GND  │
                                         G-S: 100nF cap  │
                                                         │
                              ┌──────────────────────────┘
                              │
                              ├──► AP2112K-3.3 LDO ──► 3.3V Rail
                              │                           │
                              │              ┌────────────┘
                              │              │
                              │         ESP32-S3-WROOM-1-N4R2
                              │              │
                              │              ├──► ST7796 Display (SPI)
                              │              ├──► FT6336U Touch (I2C)
                              │              ├──► MAX31855 TC (SPI)
                              │              ├──► Relay driver (GPIO → 2N7002)
                              │              └──► USB-C (GPIO19/20, native)
                              │
                              └──► Relay coil supply (5V)

AC Mains ──► Relay NO contact ──► Crockpot heating element

Project Files

iot_crockpot.kicad_pro — KiCad project file
iot_crockpot.kicad_sch — Top-level schematic (hierarchical sheets)
MCU.kicad_sch — ESP32-S3 MCU sheet
power_relays_tempsens.kicad_sch — Power supply, relay, thermocouple sheet
iot_crockpot.kicad_pcb — PCB layout

Schematic Status

Section	Status
AC input (fuse, MOV, HLK-5M05)	Done
5V backfeed protection (P-FET AO3401)	Pending
AP2112K-3.3 LDO	Pending
ESP32-S3-WROOM-1-N4R2	In progress
USB-C connector (GCT USB4085 / HRO TYPE-C-31-M-12)	Pending
14-pin display header (ST7796 + FT6336U)	Pending
MAX31855 thermocouple	Pending
Relay driver (2N7002 MOSFET)	Done
Relay (G5LE-1)	Done
Connectors (AC screw terminals, thermocouple)	Done

See docs/schematic_rework_plan.md for the step-by-step schematic rework guide.

Components

MCU

Part	Value	Package	LCSC #
ESP32-S3-WROOM-1-N4R2	4MB flash, 2MB PSRAM	Module	C2913203

Display Interface

Part	Value	Notes
J_DISPLAY	14-pin 2.54mm header	ST7796 SPI display + FT6336U touch

Display modules (all electrically equivalent, 14-pin 2.54mm interface):

Hosyond (Amazon B0CMD7Y55M) ~$15
Waveshare 3.5" Capacitive Touch LCD ~$19
Elecrow 3.5" IPS SPI LCD ~$17

Note: Use ST7796 controller only. Avoid ILI9488 — no 16-bit SPI color and broken MISO tristate cause SPI bus conflicts.

3.3V LDO

Part	Value	Package	LCSC #
AP2112K-3.3TRG1	3.3V 600mA	SOT-23-5	(search)

Power Supply

Part	Value	Notes
HLK-5M05	5V 5W	AC-DC isolated PSU module

USB

Part	Value	LCSC #	Notes
USB-C receptacle	GCT USB4085 or HRO TYPE-C-31-M-12	C2765186 / C165948	USB 2.0 only
R_D-	22Ω 0402	—	GPIO19 to D-
R_D+	22Ω 0402	—	GPIO20 to D+
R_CC1	5.1K 0402	—	CC1 to GND
R_CC2	5.1K 0402	—	CC2 to GND

AC Input Protection

Part	Value	LCSC #	Notes
Fuse holder	5x20mm clips	C3130	Xucheng pair
Fuse	0.5A 250V slow-blow	C142839	Littelfuse 0215.500MXP
MOV	10D561K	(search)	Per HLK datasheet

Temperature Sensing

Part	Value	Notes
MAX31855KASA	K-type interface	SPI, cold junction compensated
Thermocouple	K-type probe	High temp

Relay

Part	Value	Notes
Omron G5LE-1	SPDT 10A	5V coil
2N7002	N-ch MOSFET	Relay driver (x2)
1N4148WQ-13-F	Flyback diode	SOD-123
10K resistor	Gate pull-down	Keeps relay off when GPIO floating

Protection

Part	Value	Notes
P-FET (AO3401)	SOT-23	Blocks USB-C VBUS backfeed into HLK-5M05
100K resistor	Gate to GND	P-FET gate bias
100nF cap	Gate-source	Miller coupling suppression

Connectors

Part	Value	LCSC #	Notes
Screw terminal (x2)	Phoenix 1935161	(search)	AC mains in, relay out

GPIO Assignments

Signal	GPIO	Notes
SPI SCK	12	Shared: display, MAX31855
SPI MOSI	11
SPI MISO	13
LCD CS	10
LCD DC	9
LCD RST	8
LCD BL	47	PWM backlight
SD CS	14	SD card on display module
Touch SDA	5	I2C
Touch SCL	4	I2C
Touch RST	6
Touch INT	7
MAX31855 CS	16
Relay	17	Via 2N7002 driver
USB D-	19	Fixed, native USB
USB D+	20	Fixed, native USB

ESP32-S3 Strapping Pins

Pin	Default	Action
GPIO0	Pull-up to 3V3	Ensures SPI Boot (normal) on power-up
GPIO46	Float (internal pull-down)	Leave unconnected
EN	10K to 3V3 + 1µF to GND	RC filter for clean power-on reset

BOOT jumper: 2-pin 2.54mm header (GPIO0 to GND). Install to enter download mode on next reset. Remove for normal boot. Not needed for routine flashing — native USB handles auto-reset via esptool.py.

Safety Notes

Mains Isolation: HLK-5M05 provides isolation; maintain clearance on PCB
Creepage/Clearance: Follow IPC-2221 for mains voltage traces
Fuse: Must be rated for AC mains (250VAC)
Relay Wiring: Use NO contact for fail-safe (de-energized = OFF)

Fabrication Notes

Generate Gerbers to production/gerbers/
2-layer board, 1.6mm thickness
HASL or ENIG finish
Minimum 2oz copper for mains traces

References

Hardware Decisions — Component selection rationale
Schematic Rework Plan — Step-by-step rework guide
ESP32-S3 Hardware Design Guidelines
ST7796 Display Module
Omron G5LE-1 Datasheet

Parts

Qty	Value	Footprint	References
3	10k	Resistor_SMD:R_0603_1608Metric	R1, R2, R3
3	Screw_Terminal_01x02	TerminalBlock_Phoenix:TerminalBlock_Phoenix_MKDS-1,5-2_1x02_P5.00mm_Horizontal	J1, J2, J3
2	0.1uF	Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder	C3, C5
2	1N4148W	Diode_SMD:D_SOD-123	D1, D2
2	2N7002	Package_TO_SOT_SMD:SOT-23	Q1, Q2
2	Conn_01x04_Pin	Connector_JST:JST_GH_SM04B-GHS-TB_1x04-1MP_P1.25mm_Horizontal	J4, J5
2	G5LE-14 5VDC	Relay_THT:Relay_SPDT_Omron-G5LE-1	K1, K2
1	1.5A	Fuse:Fuse_1206_3216Metric_Pad1.42x1.75mm_HandSolder	F3
1	Conn_ARM_SWD_TagConnect_TC2030	Connector:Tag-Connect_TC2030-IDC-FP_2x03_P1.27mm_Vertical	J6
1	Fuse	Fuses:Fuseholder_Clip-5x20mm_Littelfuse_111_Inline_P20.00x5.00mm_D1.05mm_Horizontal_with_3D_body	F1
1	HLK-5M05	Converter_ACDC:Converter_ACDC_Hi-Link_HLK-5Mxx	PS1
1	MAX31855KASA	Package_SO:SOIC-8_3.9x4.9mm_P1.27mm	U3
1	STM32G031F6Px	Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm	U1
1	Varistor	Varistor:RV_Rect_V25S440P_L26.5mm_W8.2mm_P12.7mm	RV1

Questions

How big is the Iot crockpot PCB?

It measures 101.5 × 54.9 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Iot crockpot use?

23 parts, built around the HLK-5M05, MAX31855KASA+T and 1N4148W. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Iot crockpot KiCad files?

From the AverageJoel/iot_crockpot repository on GitHub, at the commit this page was made from: the board is hardware/iot_crockpot.kicad_pcb and its schematic hardware/MCU.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Iot crockpot design in my own project?

Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

Category and platform

Home automation and IoT STM32

Project files

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Source

Repository: AverageJoel/iot_crockpot
Board file: hardware/iot_crockpot.kicad_pcb
Commit: 06dafc0
Licence: MIT

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