Custom PCB Design for IoT Fire Safety Device — AC/DC Isolated, Enclosure-Ready, UL/CE Compliant

We're building HeatSinc, an IoT fire safety device that monitors electrical line resistance and current in real time to detect high resistance faults and thermal degradation before they cause fires. We've validated our Gen 2 prototype and are now moving to a proper MVP with a custom PCB replacing all off-the-shelf modules. We need an experienced PCB designer to design a single, fully integrated board that consolidates our current component stack into a manufacturable, enclosure-ready, safety-compliant design. What You'll Be Designing The board must integrate the following functions, currently implemented as discrete modules: Overview: Microcontroller: Waveshare ESP32-S3 Nano Voltage sensing: ZMPT101B transformer Current sensing: SCT-015 current transformer / ZMCT102 High-precision ADC: ADS1256 24-bit SPI interface AC-to-DC power supply: HLK-PM series (5V or 3.3V) Technical Requirements: Safety & Isolation: Full galvanic isolation between AC mains side and DC logic side (creepage/clearance per IPC-2221B and IEC 60950-1 / UL 62368-1) Isolated power rail for AC-side sensing circuitry Proper PCB zone separation — no shared ground planes across isolation barrier Fusing and TVS protection on AC input Pass-Through Architecture: Board and enclosure must support a live AC pass-through — mains inlet and outlet both land on the PCB via rated screw terminals (minimum 20A, 300V rated) SCT-015 current transformer must be positioned to clamp around the pass-through line conductor — CT placement and the conductor routing path through the enclosure must be coordinated in the layout Pass-through conductors must maintain full IEC 60950-1 creepage/clearance from all sensing and logic circuitry Connector positions for AC inlet and outlet must align with enclosure cutouts on opposite faces of the housing Signal Integrity: Differential routing for ADS1256 analog inputs from both sensors ADC analog and digital ground planes separated and star-joined at single point Keep sensor signal traces away from switching power supply traces and ESP32 RF antenna keep-out zone Shielding provisions (copper pour or physical shield can footprint) around analog front end Component Placement: ESP32-S3 with antenna positioned at board edge with clear RF keep-out (no copper, no planes within antenna zone) ADS1256 analog supply decoupled per datasheet (1µF + 0.1µF per supply pin, placed within 2mm) ZMPT101B and SCT-015/ZMCT102 primary side on isolated AC zone; secondary outputs cross isolation barrier via differential pair HLK module on isolated input side, output crosses to logic domain cleanly Test points on all critical nets: VLOGIC, AGND, DGND, ADC inputs, SPI bus Enclosure & Assembly: Form factor to fit a standard 2-gang electrical wall box or similar enclosure (approx. 80mm × 60mm or to be confirmed with us) All connectors oriented toward enclosure cutouts (terminal blocks for AC in, JST or screw terminal for sensors) 4× M3 mounting holes at corners with copper keepouts All SMD components on top side only; through-hole limited to connectors and transformers Clearly labeled silkscreen for AC live/neutral, sensor polarity, programming header Design Rules & Deliverables: Minimum trace width for power: 1.0mm (AC), 0.5mm (DC logic) Minimum clearance AC-to-DC: ≥ 6mm (adjust to clearance calculator output for 250VAC working voltage) Design rule check (DRC) must pass with zero errors Gerber files (RS-274X), BOM with MPN/distributor links, pick-and-place CSV, and assembly drawing (PDF) Schematic in PDF and source file (KiCad preferred; Altium acceptable) STEP or IGES 3D model of populated board for enclosure fit-check What We'll Provide: Current schematic block diagram and signal flow Datasheet links for all components Enclosure dimensions and mounting constraints Prototype photos showing Gen 2 layout (for context, not reference) Review availability throughout the project Ideal Candidate: Proven experience with mixed-signal PCB design (analog + digital + power on one board) Demonstrated work with mains-voltage isolated designs (share examples) Familiar with IEC 60950-1 / UL 62368-1 creepage/clearance rules KiCad proficiency preferred Can deliver DRC-clean Gerbers ready for JLCPCB or PCBWay fabrication Bonus: experience with ESP32 RF layout rules or ADC front-end design Scope & Timeline: Budget: Fixed price, open to bids — please break down schematic capture vs. layout vs. review Timeline: First draft layout within 2 weeks; final files within 4 weeks Revisions: Up to 2 revision rounds included To apply please include: 2–3 examples of past PCB designs involving AC/DC isolation or mixed-signal layouts Brief note on your approach to AC-DC creepage compliance Your preferred EDA tool Your fixed-price quote and timeline estimate HeatSinc is an early-stage hardware startup. We move fast and communicate directly. We're looking for a designer who takes ownership and flags problems early.