1. The jack and the socket
The Matrix makes a fetish of the interface between mind and machine. The lesson is crude but valid: a connection is not just physical; it is the gateway for everything that follows. For the desktop, the electrical path across the attachment interface is the gateway for power.
This entry is about how power gets from the rack to the cell.
2. The power requirements
A compute cell may need 100 to 300 watts at low voltage, which means several amps. A power distribution cell or a high-power compute cell may need more. The connector must carry this current without excessive heating, voltage drop, or contact degradation.
The requirements include:
- Current capacity: enough conductors for the expected load with margin.
- Voltage drop: low enough that the cell receives stable power.
- Contact resistance: stable over thermal cycling and mate-demate cycles.
- Isolation: power and signal pins must not short, even under misalignment.
- Hot-swap capability: the cell may need to be powered while mating, or the rack may need to control power sequencing.
3. The connector choice
The connector is likely a blind-mate type with multiple power pins, signal pins, and possibly shielding. Key choices:
- Pin count and size: larger pins for power, smaller pins for signals and sensing.
- Mating sequence: longer ground pins that mate first and break last for safety.
- Keying: mechanical features that prevent a cell from being inserted into the wrong bay.
- Latch integration: the connector should not unmate under vibration or launch loads.
4. What the first test should measure
The ground experiment should measure:
- Contact resistance: initial and after cycles.
- Voltage drop: under representative load current.
- Temperature rise: of the connector under load.
- Mating force: to confirm the robot can seat the connector.
- Unmating behavior: whether power sequencing works and whether contacts are damaged.
5. What could go wrong
- Arcing: if hot-swap is attempted without proper sequencing.
- Fretting corrosion: micro-motion between contacts increases resistance.
- Overheating: a single high-resistance contact can become a hot spot.
- Backshell loosening: vibration can loosen the connector housing.
These are standard connector concerns, but they become critical when the robot cannot easily inspect or repair them.
6. What this changes
- The attachment interface is an electrical power interface as well as a mechanical one.
- Connector choice and pin assignment are part of the critical design.
- The first ground experiment must include electrical measurements under load.