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MrC b8aa72caba Add Canjector Major variant — all three variants now documented

- Start: Bus origin, no termination
- Middle: Intermediate, switchable 120Ω
- Major: End of bus, fixed 120Ω termination
- Blue PCB render with TERM label and 120Ω resistor visible

2026-05-04 01:40:10 +00:00

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Canjectors — Custom CAN Bus Interconnect System

Overview

After experiencing critical CAN bus failures during competition, Chris designed the Canjector system as a robust interconnect solution for Team 2890's robot. Modeled after the SWYFT CANnect concept but with custom design work, Canjectors provide reliable CAN + power distribution at all critical connections.

The design philosophy: prevent wiring failures from killing the robot mid-match.

Design Basis

Chris studied the SWYFT CANnect system as inspiration:

Run CAN bus + 12V power over standardized cabling
Easy connector system (WAGO lever terminals)
Built-in CAN termination options
Robust form factor

Canjectors go further with custom modifications for Team 2890's specific failure points.

Current Design: Middle Canjector

The schematic shows the "middle" Canjector variant with:

12V power passthrough
3 CAN connections (RJ45 connectors)
WAGO terminal blocks for clean wiring (2601-1104 series)
120Ω termination resistor (R4) between CAN signal lines — switchable
Power indicator LED (green, 0603) with 470Ω current limiting resistor
2-pin header for additional configuration

Key Features

Dual CAN paths — each Canjector bridges multiple CAN segments
Integrated termination — 120Ω resistor switchable per segment
Power LED — visual confirmation that 12V is present
RJ45 connectors — industry standard, easy to cable, robust
WAGO 2601 series — tool-free, reliable terminal connections
Designed in EasyEDA — schematic dated 2026-04-09

Design Variants

Chris designed three Canjector variants for different positions in the CAN bus topology:

Variant	Position	CAN Termination	Notes
Start	Bus origin (PDH side)	No termination at this end	Upstream CAN connector from PDH
Middle	Intermediate nodes	Switchable 120Ω	3 CAN connections + 12V passthrough
Major	Bus terminus (end of line)	Fixed 120Ω termination	Final node — TERM switch, 120Ω resistor populated

Major variant: Blue PCB, three identical sections, TERM label, 120Ω termination resistor visible, PWR LED, 2-pin header. This is the end-of-bus variant — fixed 120Ω termination resistor must be populated. Zip file in canjector-gerbers/ directory.

Connection to Training

For students: CAN bus failures are among the most frustrating problems in FRC — a loose wire or failed connector kills the whole bus. The Canjector system teaches:

Redundancy — when one path fails, traffic routes around it
Termination — 120Ω at each end of the bus, switchable at intermediate nodes
Visual debugging — power LEDs let you confirm connectivity at a glance
Modular design — if one Canjector fails, replace it in minutes

Why This Matters

Chris experienced critical CAN failures at competition. The Canjector system is a direct response — solving the failure mode with custom hardware instead of hoping the stock connectors hold. This is the kind of real-world engineering that separates good teams from great ones.

Notes for MrC

This is a confidence builder for the training vault — it shows Chris's practical engineering under pressure. Good story for students: identify the problem, study existing solutions, design your own, build it, test it. The full engineering cycle, not just code.

Files

File	Description
`canjector-schematic.png`	Middle Canjector — EasyEDA schematic
`canjector-start-pcb.png`	Start variant — PCB layout (red solder mask)
`canjector-major-render.png`	Major variant — 3D render, blue PCB
`canjectors.md`	This documentation file
`canjector-gerbers/`	Manufacturing files (Gerbers + drill files + How-to-order guide)

4.1 KiB Raw Blame History