Tmp118 sensor array module

TMP118-Sensor-Array-Module-Minitask

Overview

Compact TMP118-based I2C temperature sensor array module with custom PCB and enclosure concept.

The repository contains the KiCad PCB project, project-local TMP118 symbol/footprint libraries, FreeCAD enclosure model, STEP exports and preview images.

Repository Structure

hardware/kicad/        KiCad project, schematic, PCB layout and local libraries
mechanical/freecad/    FreeCAD enclosure source model
exports/step/          PCB and enclosure STEP exports
docs/images/           Preview images and screenshots

Task Scope

• 4x TMP118 sensors centered on the PCB
• minimized sensor-to-sensor distance
• I2C interface via slim Molex wire-to-board connector
• required passive components for sensor supply and I2C bus
• compact PCB with slim overall profile
• mechanical integration features for enclosure fitment
• custom enclosure with fully exposed and accessible connector
• STEP files for mechanical review

Main Design Decisions

PCB

The PCB is organized into a compact sensor area and a connector/interface area. The four TMP118 sensors are arranged as a centered 2x2 cluster, while the connector and pull-up resistors are kept outside the immediate sensor region.

A 2-layer routing approach is used to keep the dense sensor area routable while maintaining a compact layout. Local decoupling is placed close to the corresponding sensors, and the I2C lines are handled as shared bus nets.

A project-local TMP118 symbol and footprint are included to keep the KiCad project self-contained. The footprint uses the TMP118 package ball designators:

A1 = VDD
A2 = GND
B1 = SDA
B2 = SCL

Connector

A Molex PicoBlade 53261-0471 4-pin horizontal SMT connector is used as the external interface for:

VDD_3V3
GND
SDA
SCL

The horizontal connector supports a low-profile module concept and is placed at the PCB edge for direct enclosure access.

Enclosure

The enclosure consists of a bottom housing and a separate lid. The PCB STEP model was used as the mechanical reference for component clearance, connector position and internal fitment.

The connector remains fully exposed at the front opening. Since no sealed or IP-rated housing was specified, ventilation slots are included around the sensor area to support air exposure and reduce thermal lag.

Design Assumptions

• Supply voltage: 3.3 V
• Interface: I2C
• PCB thickness: 1.0 mm
• PCB material: standard FR4 assumed
• Enclosure type: non-sealed functional concept housing
• TMP118 sensors are treated as local/ambient temperature sensors
• Final thermal behavior would require physical validation

Verification

• KiCad schematic ERC: passed
• KiCad PCB DRC: passed
• TMP118 symbol-to-footprint mapping checked
• PCB STEP exported from KiCad
• PCB STEP imported into FreeCAD for enclosure design
• Connector access and internal component clearance checked visually in the assembly model

Known Limitations

• The custom TMP118 footprint does not include a dedicated 3D model.
• Thermal behavior was considered qualitatively but not experimentally validated.
• The enclosure is a functional concept model, not an IP-rated sealed housing.
• Snap/fit features may require tolerance tuning depending on manufacturing method and material.

Files

hardware/kicad/
  KiCad project, schematic, PCB layout and local TMP118 libraries

mechanical/freecad/
  FreeCAD enclosure source model

exports/step/
  PCB reference STEP
  bottom housing STEP
  lid STEP
  enclosure assembly STEP

docs/images/
  PCB and enclosure preview images