openclaw-wiki/sources/2890/canjectors.md

title, tags, type, owner, status, sources

title	tags	type	owner	status	sources
Canjectors — Chris's Custom CAN Bus Interconnect System	hardware electrical can-bus 2890 custom	hardware-spec	2890	active	https://swyftrobotics.com/products/swyft-cannect-wiring-system https://store.ctr-electronics.com/products/cancoder

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 five Canjector variants. Names are printed on the physical PCBs — Endz, Major, Minor are the actual designations.

All variants support configurable termination via a shunt jumper — populate the shunt to activate 120Ω termination anywhere in the chain.

PCB Name	CAN ports	12V outs	Primary role
Start	1	1	Bus origin at PDH side
Minor	3	1	Single wheel module — CANcoder + 2 motors
Middle	3	2	Mid-chain node + power distribution
Major	6	2	Heavy distribution — end of main runs
Endz	1	1	USB diagnostic tap — serves as first OR last device in chain

Minor — single wheel module design:

• 1 CANcoder (CTR Electronics CAN FD magnetic encoder for steering feedback)
• 2 motors (typically drive motor + steering motor, or drive + mechanism)
• 1 12V output for accessories

Minor was designed for MK4i swerve modules — one Minor per wheel handles the CAN bus connections for the encoder and both motors. Clean single-point connection for each corner of the robot.

Note on overlap:

• Start and Endz both serve end-of-chain positions (first or last device)
• Minor and Middle both have 3 CAN ports — Middle adds a second 12V output for power distribution

All Canjectors use the same shunt-activation scheme for 120Ω termination. This means any variant can terminate the bus when needed.

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-minor-render.png	Minor variant — 3D render, blue PCB
canjector-major-render.png	Major variant — 3D render, blue PCB, 6 CAN ports
canjector-endz-render.png	Endz variant — USB-to-CAN diagnostic interface
canjectors.md	This documentation file
canjector-gerbers/	Major variant manufacturing files
canjector-minor-gerbers/	Minor variant manufacturing files
canjector-endz-gerbers/	Endz variant manufacturing files