120A Main Circuit Breaker
The main breaker can be found mounted on the robot, typically on the outside of the frame perimeter in an accessible location. It must be easily reachable and operable by a referee or field staff at all times during competition.
What is this?
The Eaton Bussmann CB285-120 is the FRC-legal 120-amp main circuit breaker required on every FRC robot. It serves as the master power switch and overcurrent protection device for the entire robot. It connects in-line between the battery and the Power Distribution Hub (PDH), and can be used to manually cut all robot power in an emergency. It is a Type III (switchable/manual reset) thermally responsive breaker — it can trip automatically under sustained overcurrent, or be manually switched off.
Per the FRC Game Manual, this specific breaker (CB285-120) is the only legal main breaker for FRC competition robots.
Ports / Connections
| Port | Wire Type | Current Draw | Required | Where is it? | Additional Info |
|---|---|---|---|---|---|
| Battery-side stud (input) | 6 AWG copper, red (positive) | Up to 120A continuous | ✓ | One of two M6 terminal studs | Connects from the Anderson SB50 robot-side connector; ring terminal required |
| PDH-side stud (output) | 6 AWG copper, red (positive) | Up to 120A continuous | ✓ | Second M6 terminal stud | Connects to the PDH positive input terminal; ring terminal required |
Note: Only the positive (red) wire passes through the main breaker. The negative (black/blue) wire runs directly from the battery cable to the PDH negative terminal, unbroken.
Status Lights
The CB285-120 does not have a status LED. Instead, it has a visible yellow reset lever that shows the open (tripped) condition. When the breaker is tripped:
- The yellow lever will be in the raised/protruding position.
- Push the lever back in to reset the breaker (only after resolving the cause of the trip).
The breaker also has a red push-to-trip button that can be used to manually cut power.
Extra Information
- Manufacturer: Eaton Bussmann
- Part Number: CB285-120
- Rating: 120A, 6–48V DC
- Interrupt rating: 3 kAIC
- Type: Type III — switchable, manual reset, trip-free
- Terminal: M6 stud (accepts 1/4“ ring terminals)
- Operating temperature: -40°C to 85°C
- Size: 2.9“ × 1.9“ × 1.5“ (73.7 × 48.3 × 38.1 mm)
- Weight: 0.24 lbs
- IP Rating: IP67 (weather resistant / waterproof housing)
- The breaker is “trip-free” — it cannot be held closed after it trips. Do not attempt to force it closed during a trip.
- The breaker must be easily accessible on the robot; FRC rules require that a referee can cut robot power quickly.
- Do not substitute with any other breaker — only the CB285-120 is FRC-legal as the main breaker.