Hardware & Mechanical Engineer for Ultra-Compact IoT Hub
Budget: $200 – $750 USD
I am seeking a senior hardware engineer to design a highly dense, 4-layer PCB and a matching 3D-printable enclosure for a travel IoT device. The device acts as an IR blaster, audio-occupancy monitor, and environmental sensor. I need a fully turnkey design ready for automated PCBA manufacturing (no hand-soldering required on my end).
Dimensional & Enclosure Constraints:
PCB Size: 12mm wide x 25mm long.
Enclosure Size: Target external dimensions are approximately 14mm wide x 30mm long, with an overall thickness (height) of 7mm to 8mm.
Case Materials: CNC-milled silver aluminum body with an IR-transparent smoked polycarbonate/glass top. ( As shown in attached image)
Connectors: A mid-mount USB-C plug is required to keep the overall thickness as low as possible.
Core Hardware & Sensor Specifications:
MCU: ESP32-S3-PICO-1 (7x7mm SiP).
Storage: Molex 104031-0811 MicroSD socket (11.4mm wide, push-pull friction fit).
Sensors: Bosch BME690 (AQI/Temp) and 2x TDK MMICT5838-00-012 (Bottom-ported I2S Mics).
IR LEDs: 1x Top-firing SMD (Vishay VSMA1094750X02) and 1x Side-firing right-angle SMD (e.g., Kingbright).
Expansion: 1x JST-SH 1.0mm 4-pin port (for future I2C/Grove additions).
Antenna: Johanson 2450AT18A100 2.4GHz Ceramic Chip Antenna.
Physical Controls: 2x micro SMD tactile buttons for BOOT and RESET to ensure USB recovery without soldering.
Circuit Callouts & Engineer Responsibilities (Please define these in your design):
Power Regulation: Select an appropriate ultra-small LDO (e.g., Richtek RT9080) to safely step 5V USB power down to 3.3V.
IR Drivers: Design an N-Channel MOSFET driver circuit with appropriate current-limiting resistors to safely drive the high-power 940nm IR LEDs from the 5V line.
RF Matching: Design the required 50-ohm trace and Pi-matching network for the ceramic antenna, strictly adhering to the manufacturer's copper keep-out zones.
Decoupling & Pull-ups: Fill in all required passive components (capacitors, resistors) required for stable I2S, I2C, and ESP32-S3 operation.
Key Mechanical Challenges:
Thermal Isolation: The BME690 must be thermally isolated from the ESP32-S3 (via milled air gaps in the PCB) to ensure accurate room temperature readings.
Acoustic Routing: Proper unplated through-hole design (min 0.5mm) for the bottom-ported MEMS microphones.
Required Deliverables:
Native PCB CAD files (KiCad or Altium) including Schematics and 4-Layer Layout.
Standard manufacturing exports: Gerbers, NC Drill, and Pick & Place (Centroid) data.
Comprehensive BOM mapped to active LCSC or DigiKey part numbers for automated assembly.
3D Mechanical CAD files of the fully populated PCB and the designed aluminum/glass enclosure. Deliverables must include native 3D source files, .3ds format files, .STEP files (for CNC machining), and .STL files (for 3D printing).
All required information to order the PCB and Case from a common online provider like PCBWay.
The part must be validated as working after development before the project is considered complete.
Application Instructions:
To help me filter out generic, automated bids, please begin your proposal with the exact phrase: "Turnkey 12x25". Bids without this phrase will be ignored.
Dimensional & Enclosure Constraints:
PCB Size: 12mm wide x 25mm long.
Enclosure Size: Target external dimensions are approximately 14mm wide x 30mm long, with an overall thickness (height) of 7mm to 8mm.
Case Materials: CNC-milled silver aluminum body with an IR-transparent smoked polycarbonate/glass top. ( As shown in attached image)
Connectors: A mid-mount USB-C plug is required to keep the overall thickness as low as possible.
Core Hardware & Sensor Specifications:
MCU: ESP32-S3-PICO-1 (7x7mm SiP).
Storage: Molex 104031-0811 MicroSD socket (11.4mm wide, push-pull friction fit).
Sensors: Bosch BME690 (AQI/Temp) and 2x TDK MMICT5838-00-012 (Bottom-ported I2S Mics).
IR LEDs: 1x Top-firing SMD (Vishay VSMA1094750X02) and 1x Side-firing right-angle SMD (e.g., Kingbright).
Expansion: 1x JST-SH 1.0mm 4-pin port (for future I2C/Grove additions).
Antenna: Johanson 2450AT18A100 2.4GHz Ceramic Chip Antenna.
Physical Controls: 2x micro SMD tactile buttons for BOOT and RESET to ensure USB recovery without soldering.
Circuit Callouts & Engineer Responsibilities (Please define these in your design):
Power Regulation: Select an appropriate ultra-small LDO (e.g., Richtek RT9080) to safely step 5V USB power down to 3.3V.
IR Drivers: Design an N-Channel MOSFET driver circuit with appropriate current-limiting resistors to safely drive the high-power 940nm IR LEDs from the 5V line.
RF Matching: Design the required 50-ohm trace and Pi-matching network for the ceramic antenna, strictly adhering to the manufacturer's copper keep-out zones.
Decoupling & Pull-ups: Fill in all required passive components (capacitors, resistors) required for stable I2S, I2C, and ESP32-S3 operation.
Key Mechanical Challenges:
Thermal Isolation: The BME690 must be thermally isolated from the ESP32-S3 (via milled air gaps in the PCB) to ensure accurate room temperature readings.
Acoustic Routing: Proper unplated through-hole design (min 0.5mm) for the bottom-ported MEMS microphones.
Required Deliverables:
Native PCB CAD files (KiCad or Altium) including Schematics and 4-Layer Layout.
Standard manufacturing exports: Gerbers, NC Drill, and Pick & Place (Centroid) data.
Comprehensive BOM mapped to active LCSC or DigiKey part numbers for automated assembly.
3D Mechanical CAD files of the fully populated PCB and the designed aluminum/glass enclosure. Deliverables must include native 3D source files, .3ds format files, .STEP files (for CNC machining), and .STL files (for 3D printing).
All required information to order the PCB and Case from a common online provider like PCBWay.
The part must be validated as working after development before the project is considered complete.
Application Instructions:
To help me filter out generic, automated bids, please begin your proposal with the exact phrase: "Turnkey 12x25". Bids without this phrase will be ignored.