Compact Wearable Fitness Band PCB Design

About the project

PROJECT TITLE: WEAR IT V1 – Compact Wearable PCB & Schematic Design PROJECT OVERVIEW: We are developing WEAR IT, a compact screen-free wearable health and fitness band. The functional proof-of-concept (POC) is already working. We now need an experienced PCB and electronics engineer to convert the existing engineering architecture into a professional, manufacturing-ready custom PCB. This is NOT a concept-stage project. The electronics architecture and major components have already been selected. The engineer's responsibility is to create the professional schematic, PCB layout, routing, libraries, verification and complete manufacturing documentation. MECHANICAL TARGET: Maximum PCB size: 33.5 mm × 23.0 mm Maximum complete wearable device envelope: 34.7 mm × 24.0 mm × 10.6 mm The PCB must be designed specifically for a compact wrist wearable and must leave space for: - Li-Po battery - Optical window - Skin-contact area - Haptic motor - Magnetic/pogo charging - Wearable enclosure - Strap/mechanical mounting CORE COMPONENTS: - ESP32-C3-WROOM-02-N4 – MCU + BLE - Bosch BMA400 – accelerometer/motion - Bosch BME280 – ambient temperature/humidity/pressure - MAX30102 – EVT optical reference - MAX86141 – optical sensor evaluation / production candidate - MAX30205 – skin/body temperature - MAX17048 – battery fuel gauge - BQ25185DLHR – battery charger/power path - W25Q64JV – external SPI flash - DRV2605L – haptic driver - LRA vibration motor - Li-Po battery - Battery NTC - Magnetic/pogo charging contacts - Status LED - Factory programming/debug/test points MAIN REQUIREMENTS: 1. CREATE COMPLETE NATIVE KICAD SCHEMATIC Use KiCad 10.x. Create a complete professional schematic with appropriate functional sections: - Power input + protection - Battery + charging - 3.3 V power rail - Optional 1.8 V rail where required - ESP32-C3 + reset/boot/programming - I2C sensor bus - SPI flash - Optical/PPG subsystem - Skin temperature - Haptic driver + motor - Status LED - Factory test/programming - RF/antenna section 2. EXACT COMPONENT VERIFICATION Use the exact manufacturer part numbers supplied by us. Do not substitute components without written approval. Verify: - exact MPN - package - pinout - symbol - footprint - manufacturer recommended land pattern - reference circuit 3. ESP32-C3 REQUIREMENTS Use ESP32-C3-WROOM-02-N4. Verify: - power - EN/reset - boot/strapping pins - GPIO assignment - I2C - SPI - interrupts - programming/debug - antenna layout - RF keep-out Do not use GPIOs in a way that interferes with boot or RF operation. 4. I2C BUS Integrate: - BMA400 - BME280 - MAX30205 - MAX17048 - other approved I2C devices Use a controlled pull-up network. Verify all I2C addresses and ensure there are no address conflicts. 5. OPTICAL / PPG DESIGN This is a critical part of the project. Provide an engineering-ready optical section for: - MAX30102 - MAX86141 evaluation For MAX86141, design the appropriate: - red LED - IR LED - photodiode - LED current path - optical signal path - supply rails - decoupling - interrupt - optical window / mechanical keep-out The optical section must be isolated from: - charger switching - regulator noise - haptic motor - high-current paths The final MAX30102 vs MAX86141 production decision will be made after on-wrist validation. 6. POWER DESIGN Use: - BQ25185DLHR - MAX17048 - approved 3.3 V regulator - approved 1.8 V regulator where required - battery NTC Design: - charging input - battery path - SYS rail - 3.3 V rail - optional 1.8 V rail - battery monitoring - protection - decoupling - current paths - test points Follow the exact manufacturer reference circuits. 7. PCB DESIGN Design a compact 4-layer PCB. Target: 33.5 mm × 23.0 mm maximum The PCB must be optimized for: - low power - BLE/RF performance - PPG signal quality - thermal performance - manufacturability - compact wearable mechanical integration 8. PCB PLACEMENT Use separate functional zones: - RF / ESP32 - Optical / skin sensors - Motion - Ambient sensor - Digital/MCU - Power/charging - Flash - Haptic - Factory test Critical placement rules: - Optical section close to skin - Optical section isolated from power switching and haptic - BMA400 mechanically stable - BME280 exposed to ambient air and away from heat - MAX30205 close to skin-contact area and thermally isolated - Power loops compact - Flash close to MCU - ESP32 antenna at board edge - Correct RF keep-out 9. PCB ROUTING Route carefully: - power - RF - optical - I2C - SPI - GPIO Provide: - continuous ground reference - appropriate power widths - short sensitive traces - controlled RF path - clean return paths - proper decoupling placement 10. MANUFACTURING / DFM Design for professional SMT assembly. Provide: - correct footprints - polarity indicators - reference designators - component clearances - assembly clearances - fiducials where appropriate - test pads - board edge considerations - manufacturing-friendly layout 11. VERIFICATION Before delivery, perform and provide evidence for: - schematic ERC - PCB DRC - footprint verification - pin verification - RF/antenna review - optical placement review - mechanical clearance review - PCB dimension verification - BOM/PCB consistency review 12. REQUIRED FINAL DELIVERABLES We require the complete editable source files, not only screenshots or PDFs. Deliver: - Native KiCad 10 project - .kicad_pro - .kicad_sch - .kicad_pcb - custom symbol libraries if required - custom footprint libraries if required - complete BOM with manufacturer part numbers - netlist - Gerber files - NC drill files - Pick-and-Place / centroid file - assembly drawing - fabrication drawing - schematic PDF - PCB PDF - 3D PCB view / model - test-point map - design-rule report - ERC report - DRC report - manufacturing README - revision-controlled source files 13. OWNERSHIP / SOURCE FILE REQUIREMENT All source CAD files created for this project must be delivered to us. We do not want a locked/cloud-only design. We need the complete editable KiCad project so another engineer/manufacturer can open and continue the design. 14. COMPONENT CHANGE CONTROL Do not change: - MCU - sensors - charger - fuel gauge - flash - haptic driver - critical power architecture without written approval. If a component must be changed because of availability, footprint, electrical or mechanical reasons, explain the reason and obtain approval before changing it. 15. EXPERIENCE REQUIRED Please apply only if you have practical experience with: - KiCad - BLE PCB design - ESP32 - wearable electronics - low-power battery products - PPG / optical sensor layouts - compact 4-layer PCB design - RF/antenna layout - DFM/SMT manufacturing - PCB bring-up/debug Experience with fitness trackers, smart bands, medical/wellness wearables or similar products is strongly preferred. 16. WHAT WE WILL PROVIDE We will provide: - existing WEAR IT engineering documentation - component/BOM information - current architecture - POC information - mechanical size target - relevant purchased component list - existing schematic/engineering reference documents 17. PROJECT SUCCESS CRITERIA The project will be considered complete only when: - schematic is complete - exact parts and footprints are verified - PCB is fully routed - PCB fits within 33.5 × 23.0 mm - RF requirements are respected - optical layout is properly designed - ERC is reviewed - DRC is reviewed - BOM matches schematic and PCB - manufacturing files are generated - all editable source files are delivered Please include in your proposal: 1. Similar wearable/ESP32/PPG PCB projects 2. KiCad experience 3. Experience with MAX30102/MAX86141 or similar optical systems 4. Experience with RF/BLE PCB layouts 5. Fixed project cost 6. Estimated completion time 7. Number of revisions included 8. Whether ERC/DRC and manufacturing files are included 9. Confirmation that all native KiCad source files will be delivered

Skills required