X13 Backplane

IMAGE OF PCB, potentially including its place on the relevant ROV

	PCB Summary
Vehicle	X13, ROV Triton
Contributors	Kaitlyn Yu
Predecessors	X12-Backplane
Success?	Yes, with minor room for improvements

Architecture Link
SID Link
REPO Link

What purpose does this board serve?

The purpose of the Backplane is to assist in routing signals throughout the ROV.

To what boards (or enclosures etc) does it connect?

The Backplane connects to many boards:
- Power Distribution
  - Power (12V, 3.3V, 5V), SMBUS
- Solenoid Board
  - CAN, Programming, Power, Solenoids
- Quad ESCs ( Power, CAN, Programming, ESC ID
- Quad ESC Adapter
  - For Power & Thruster connections
- 3 Cameras (on first draft architecture)

What priorities did you have in your design? What design considerations did you have? What methodologies did you follow? (routing a differential pair, keeping something separate for isolation, etc)

What changes were made to your board from the previous year(s)?

Power Distributions connection was distributed across two separate connectors which split connection differently (Androgenous power connector exclusively for 12V& GND) - More user-friendly connection.
Solenoid board was moved from the solenoid enclosure to being directly mounted to the board - cuts out the need for a separate 12-3.3V conversion and directly links backplane to manage solenoid connections.
Added connection to power the the secondary cameras
MUX was changed from 2, 2x1 MUXs to 1 4:1 MUX - Decrease footprint on board
ESC Connection became split across two connectors to minimize the footprint & adapt for the Lumenier 4-in-1 to separate the ESCs from their microcontrollers.
6 Gauge wire soldered directly to the board for 12V and 12V GND.

What factors affected your board outline?

Cutout in the bottom to increase accessibility to ethernet switch and cables
Because the Backplane connects to so many boards, the layout of the other boards affected connector positioning.
Cutouts in the center of the board were required to accommodate a connector for the ESC's

What reference materials did you use for circuits? (Provide links to these)

MUX Wiring

What is the throughput of your board (power, data/speeds, etc)?

Distribution:
- Input: 90A at 12V
- Receives & Returns 3A at 5V, 1A at 3.3V, DATA, ALERT, CLK, C2
Solenoid Board:
- Receives and/or returns 3.3V, Solenoid Signals, 3.3V, SWCLK, SWDIO, ALERT, DATA, CLK, CAN, 12V
Programming:
- GND, PROG (1-3), 3.3V, NRST, SWCLK, SWDIO

Why did you pick certain components for your board? (If you don't know the answer/were told, now is a great time to ask)

Androgenous power connector: Connector between distribution board & backplane chosen due to ergonomic design- easier to plug in compared to previous years. This connector exclusively carries 12V & 12V GND.
2X6 logic wire connector (https://www.samtec.com/products/ipl1-106-01-l-d-k): to connect from Distribution to carry 5V, 3.3V, GND, DATA, Alert signals, CLK, and C2 signal from each brick.

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What issues did you have with your board (in both design and assembly)

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How did you go about integrating with mechanical? What changes did you make?

Narrowed board to access ESC connections on the ESC adapters
Added indent at end for switch accessibility
Spaced out boards to fit everything

What errors/mistakes were made?

The stop layer was not set around the samtec TMM connector to the ESC board so the soldermask there needed to be scraped off
Simply making a box on the dimension layer didn’t make a hole, so Scott ended up drilling out holes for the wire connectors between the ESC controller board and the ESCs
The ESC adapter closest to distribution stuck out into the connector. This wasn’t a problem with fitting everything, just with putting the boards into place.
Labels on connectors would’ve been helpful
Many of the connectors stuck out over the edge of the board which was awkward at times.

If you had to do it over again, what might you change?

Measure the ESC continuous and burst current to know how much current actually needs to be supported on the 12V line

Calculations

90-100A on 12V -> 6 AWG

Keywords

Search keywords.

Tech Report Paragraph

The Backplane exists with the purpose of assisting to route signals throughout the ROV. The board works through receiving 12V, 5V, and 3.3V from Distribution. It then sends 12V, 3.3V and the CAN bus to the Solenoid board, 12V to the ESC Adaptors, 3.3V and the CAN bus to the ESC controllers, 5V to the Raspberry PI & Pi Shield, and 5V to the additional cameras. The Power Distribution connection was split across two separate connecters to make routing and connecting more user friendly. To ensure enough current for the ESC adaptors, 6 Gauge wire was soldered directly to the board for 12V.