Battery & Sensor Test Fixture

Objective: Design a Raspberry Pi controlled test fixture to verify the quality of temperature sensors and batteries. The system should:

  1. test up to 16 temperature sensors or 32 batteries at once.
  2. measure temperature accuracy and battery discharge performance.
  3. automate test result uploads to the cloud for easy access.

Electrical Design

Process:    

  • Collaborated on drafting the Pi-interface schematic and PCB, which incorporates six protocol-routing multiplexers, a 12-bit I²C ADC for battery monitoring, a latching mux for drain-enable control, and a 5 V buck converter for the ADCs and Raspberry Pi.
  • Drafted and routed the resistor-load drain board schematic and PCB.
  • Managed prototype build, ordering all parts, then soldering components and wiring up the assemblies

* Electrical design was collaborated on with Omar Abuabah.

Firmware Design

Process:    

  • Extended firmware support, coordinating with the firmware team to develop new Python libraries and control code on the Raspberry Pi for sensors originally supplied with only C drivers.
  • Initialized GPIO and pigpio interfaces for multiplexer control and 1-Wire bus setup in Pigpio_initializations.py
  • Implemented dedicated Python drivers for DS18B20, MCP3221, SHT35, and TMP107 sensors—handling bit-banged serial and I²C communications for seamless integration on the Pi
  • Built a telemetry pipeline using mttqPublish.py to timestamp sensor payloads and publish JSON-formatted telemetry to ThingsBoard via MQTT
  • Developed the main application flow in main.py to detect connected sensors, select communication protocols, schedule periodic sampling, log CSV outputs, and gracefully handle cleanup on exit

* Firmware was collaborated on within the firmware team with a significant contribution from Omar Abuabah.

 

Finished Product


Results, Testing & Validation

  • Temperature‑sensor validation — 16 temperature sensors were oven‑cycled from -30 °C to +50 °C in 10 °C steps. A maximum sensor‑to‑sensor error of 0.4 °C was calculated, meeting the ±0.5 °C spec across the full range.
  • Tracked the steady voltage drop of 32 batteries at once, with clean, even curves that confirm it reads discharge correctly.
  • Ready for production QC — the validated fixture has been adopted on the line and now screens every outgoing sensor and battery pack.