title	tags	version	updated	license
ProtoEtch	protoetch pcb etching hardware esp32 open-hardware	v0.3	2025-09-03	CERN-OHL-S v2

License Notice
This work is licensed under the CERN-OHL-S v2.
You may redistribute and modify this documentation under the terms of the CERN-OHL-S v2, as published by CERN.
This documentation is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY,
including of MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE.
Please see the CERN-OHL-S v2 for applicable conditions.

🧪 ProtoEtch

ProtoEtch is an open-hardware PCB etching station that makes etching simple, repeatable, and safe.
It automatically agitates and heats the etchant, uses a DS18B20 sensor for feedback, and shows live data on a local display. Remote monitoring and control (MQTT, OTA updates) are planned.
Designed for makers who want consistent results without babysitting their etching tank.

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✨ Features

• Automatic fluid agitation with a quiet 24 V BLDC pump (PWM controlled). (planned)
• Controlled heating of the etchant with a titanium immersion heater. ✅
• DS18B20 sensor feedback for temperature regulation. ✅
• Local UI with TFT display + rotary encoder + buttons. ✅
• Safety features: fuses, grounding, TVS, bulk caps, watchdog cut-offs. (partially implemented)
• OTA updates and MQTT integration for remote control/monitoring. (planned)
• Open hardware: CERN-OHL-S v2 for electronics & mechanics, software under permissive license.

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🛠 Hardware Overview

Electronics

• ESP32-WROOM-32E (8 MB) main controller.
• ST7789V SPI TFT (240×320).
• Rotary encoder + push, 2 momentary buttons, 1 toggle switch.
• Relay module (5 V) to switch 230 V heater.
• IRLZ44N MOSFET low-side driver for 24 V pump.

Mechatronics

• Pump: 24 V DC BLDC centrifugal, ~30 W, ~800 L/h, mag-drive.
• Heater: Titanium immersion heater (300–500 W).
• Sensor: DS18B20 waterproof probe.
• Tubing: Silicone ID10/OD14 with barbs + clamps, vibration mounts.

Power & Protection

• Mean Well LRS-75-24 PSU (24 V / 3.2 A).
• Buck converters: LM2596 (5 V & 3.3 V).
• Fuses:
  • AC: T3.15 A slow-blow (main & heater).
  • DC pump: T2.0 A slow-blow.
  • 5 V polyfuse (MF-R110), 3.3 V polyfuse (MF-R050).
• TVS P6KE33A + 3300 µF bulk elco + 0.1 µF ceramic near pump.

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📜 Bill of Materials (BOM)

Quick Purchase Checklist

• ESP32-WROOM-32E (8 MB)
• TFT ST7789V SPI (240×320)
• DS18B20 probe (waterproof)
• 24 V BLDC centrifugal pump (~30 W, ~800 L/h)
• IRLZ44N MOSFET + resistors + TVS + elco
• Titanium heater (300–500 W)
• Relay module 5 V (heater)
• Mean Well LRS-75-24 PSU
• LM2596 buck modules (5 V & 3.3 V)
• GX16 connectors (pump, heater, sensor)
• Silicone tubing ID10/OD14 + barbs + clamps
• Assorted fuses + fuse holders

Detailed BOM

👉 See hardware/electronics/bom/ProtoEtch_BOM_v2.0.md

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📡 ESP32 Pin Mapping

Function	GPIO	Notes
TFT SCK	18	SPI
TFT MOSI	23	SPI
TFT CS	5	SPI
TFT DC	16	SPI
TFT RST	17	SPI
Rotary A	32	Input
Rotary B	33	Input
Rotary SW	22	Input_pullup
Button1	14	Input_pullup
Button2	27	Input_pullup
DS18B20	21	+4.7 kΩ pull-up
Pump MOSFET	25	100 Ω gate + 100 kΩ pull-down
Heater Relay IN	26	Active-LOW

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⚠️ Safety

• ⚡ Mains (230 V AC): always fuse the heater line and earth bond the enclosure.
• ☣ Chemicals: Sodium persulfate etchant is corrosive. Use only silicone tubing & titanium heater.
• 🔥 Overheating: DS18B20 regulates heater; consider thermal cutoff.
• 🔌 Fuses: see Power & Protection section.

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🖥️ UI Overview (v0.3)

• Header “ProtoEtch” centered; 2 px margin to top and divider.
• Sections: Etch (Time), Heater (State, Temp), Agitation (State, Power).
• Fonts (TFT_eSPI FreeFonts):
  • Headers: FreeSansBold 9pt
  • Labels: FreeSans 9pt
  • Values: FreeMonoBold 9pt (monospaced, stable)
• Flicker-free updates: redraw only when values change.
• No inner panel; more usable space and better edge margins.

🚀 Roadmap

• Repo structure defined
• BOM finalized (v2.0)
• DS18B20 driver (non-blocking, CRC, calibration, stats)
• Heater HAL + Controller:
  • Relay switching
  • Bang-bang control with hysteresis
  • Min on/off hold
  • NVS persistence
  • Serial CLI for tuning
• Pump control module + MOSFET HAL
• Wi-Fi provisioning (captive portal)
• MQTT integration
• OTA updates
• UI firmware (TFT) – v0.3
• PCB layout → prototype board
• Enclosure CAD
• Full system assembly & test

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🤝 Contributing

Contributions welcome!

• Fork → branch → pull request.
• Follow CONTRIBUTING.md.
• Please respect CERN-OHL-S v2 for hardware & MIT/Apache for firmware (to be dual-licensed later).

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📜 License

• Hardware: CERN Open Hardware License v2 – Strongly Reciprocal (CERN-OHL-S v2)
• Firmware: MIT (planned; TBD)
• See LICENSE.