Universal Cable Tester

Problem

Production cable verification had become a repetitive pin-by-pin task. A simple continuity beep was not enough: some harnesses included intentional opens, branches, Ethernet mappings, or specialized generator and stator connections.

Description

What I built or investigated

I built a profile-driven test fixture around an Arduino Uno, four CD74HC4067 multiplexers, an OLED, and purpose-built connectors. The tester drives one conductor at a time, senses the far side, compares the measured map with the selected profile, and reports opens, crosses, unexpected connections, or a pass.

Iterations

The work did not happen in one jump.

1. 01

   Started with direct one-to-one DB9 testing and a minimal menu.

2. 02

   Expanded the channel plan to cover DB9, RJ45, generator sense points, spring terminals, and stator posts.

3. 03

   Added profiles for intentional opens and branched Y-cables instead of treating every unconnected pin as a fault.

4. 04

   Removed duplicate Ethernet profiles after confirming that continuity sees pin numbers, not T568A/T568B colors.

5. 05

   Reworked physical channel mappings after real fixture wiring exposed assumptions that were correct in code but wrong at the connector.

6. 06

   Reduced flash use on the ATmega328P and simplified navigation so the full feature set fit on an Uno.

Result

Where the project landed

A working production-floor prototype that guides connector setup, tests the selected cable profile, and reports specific opens, wrong destinations, and shorts instead of reducing every defect to a continuity beep.

Lessons

What carried forward

• The fixture, connector labeling, and operator flow matter as much as the scan algorithm.
• Expected opens must be modeled explicitly or a correct cable looks defective.
• A profile database is more scalable than writing separate test logic for every cable.
• Public documentation should show the architecture without exposing employer pinouts or proprietary harness names.
• Specific fault reporting is what turns a tester into a useful production tool.

Images & evidence

Work in context