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

# 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 | Mid-chain node |
| **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 |

**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 |