Electrical & CAN

The electrical system supplies power and carries device communication. Every other subsystem depends on it working under load.

Power is a system

Trace energy from the battery through protection and distribution to each actuator. Wire size, connector quality, mechanical strain relief, current limits, and battery condition all affect delivered voltage.

CAN is shared communication

Every CAN device shares the bus. Keep the topology valid, terminations secure, identifiers unique, status rates reasonable, and documentation matched to the physical robot.

Diagnose with evidence

Inspect voltage, current, resistance, device presence, fault history, and physical connections before assuming a software defect.

Follow both paths

Every controlled device has a power path and a communication path. Trace them separately.

Power:         battery → main breaker → distribution → branch protection → device
Communication: roboRIO → CAN segment → device → next device → termination

A device may appear in software while lacking enough voltage to do useful work. It may also have full power but no valid command because communication is broken.

Build a device inventory

Maintain one source of truth for CAN identifiers, bus names, breaker sizes, wire gauges, and expected firmware. Check it against the physical robot after rewiring.

public final class CanIds {
  public static final int FRONT_LEFT_DRIVE = 1;
  public static final int FRONT_LEFT_STEER = 2;
  public static final int FRONT_LEFT_ENCODER = 3;

  private CanIds() {}
}

The exact structure can vary, but duplicate IDs should be difficult to introduce and easy to review.

Read faults in context

Log battery voltage, total current, CAN utilization, receive errors, device resets, and brownout state together. A timestamped group of signals is more useful than a photo of one dashboard value.

Symptom	Check first
Several devices reset together	Battery, main connections, and voltage under load
One device disappears intermittently	Connectors, strain relief, branch wiring, and termination path
Commands lag while devices remain present	CAN utilization and status-frame rates
Motor reports output but does not move	Branch power, breaker, controller output voltage, and mechanical load
Fault appears only during hard acceleration	Voltage sag, current limits, and connection resistance

Before enabling after service

1. Inspect polarity and exposed conductors.
2. Tug-test changed connections.
3. Confirm breaker and wire sizing.
4. Check the device inventory and CAN topology.
5. Power on with mechanisms in a safe position.
6. Confirm device presence before commanding motion.

De-energize before service

Follow team lockout and verification procedures before changing power wiring or working near stored mechanical energy.