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X13 Bricks Board
IMAGE OF PCB, potentially including its place on the relevant ROV
| PCB Summary | |
|---|---|
| Vehicle | X13, ROV Triton |
| Contributors | Erin Park |
| Predecessors | X12-Bricks |
| Success? | Yes, with minor flaws |
Architecture Link
SID Link
REPO Link
- Primary function: receives 48v from distribution board and gives 12v back
- Passes through IO functions to distribution board
- Distribution board
- Heatsunk via thermal paste to the bottom of the power box
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)
- Provide capacity (board aera & connectors) for 48V and 12V lines (15A and 45A respectively, though polygons are short, so the optimal width isn't necessary)
- Added a trim-up resistor to make output voltage 13.2v instead of 12
- Added more robust IO passthrough to distribution for communication
- Address resistor for differentiation when communicating to it
- IO side may collide if placed close together on dist. Board - had to shrink the horizontal (longer) length of the board and place the IO pins close to the edge of the bricks board
- Vertical length (shorter side) could be larger without much issue
- No point in making board smaller than the brick
- Sam (Distribution person)
- Distribution goes on top of brick board + brick so there's often lots of space underneath it depending on how the bricks board to distribution connectors are placed
- Clearance between bricks and powerbox
- Tldr can be as big as u want as long as it doesn't collide with anything else, communicate with electrical lead and distribution
- Bricks Datasheet (link below)
- Max output: 12v 50 Amps per board (100A total)
- Shouldn't expect all 100A with 2 bricks in parallel, manufacturer says derate to 90% when parallelizing
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)
- Big capacitors for smoothing input line
- Find current per pin and multiply by how many
- Mounting holes - Tyler wanted 200 mil radius clearance from hole for screws
- Shifted connectors for hole clearance
- Trimmed board area on IO side to make it clear
- We must have Owo faces on the silkscreen
- Output voltages were slightly off even with 0.1% variance trim resistors - maybe we want to buy like 20 5% tolerance resistors and rotate until equal outputs
- Have another pad set to add like whatever resistance to make up difference (can do 0 ohm etc)
- Add silkscreen label for 12v, 12v gnd, 48v, 48v gnd
- Accidentally powered them on backwards once but it didn't break lmao
- IO pins from bricks are very close to the IO part of the connector, which made it hard to solder
- For this question and the previous one, go back to the board/schematic in eagle and either change them if it can be done quickly enough, or make a note for the future
- Plugging distribution into 2 bricks while its in power box is very hard because there's a lot of connectors - move to fewer big connectors and setting pins properly
Voltage Connector Current We want a certain mated height, also look at this link for the power draw per pin for connectors Remember: 50 amps per 12v thingy on 12v side, and 15 amps on 48v side - divide amps by number of pins and increase number of pins until current would be supported Current rating depends on temperature and how many adjacent pins So for the 2x5 array, current capacity is around 6A per pin at 40c And the other one we treat as 4A per pin at 40c because there's more of them adjacent so the 2x25 graph was used
(picture) This one is for a 2x25 array which is a worse case scenario than our bricks, for a 2x4 see datasheet (the line is just shifted up signifying more current capacity per pin). (picture)
Bricks Datasheet
Powerbox Connector Sheet
- Any fun side details
Search keywords.
The primary purpose of the Bricks Board is to serve as a shield for our power bricks, which convert 48v to 12v for our ROV. It interfaces with the Distribution board to achieve this, passing through 48v to the bricks and receiving and handing off 12v to the dist. Board. There are several changes made to this year's version compared to the previous year. The output voltage has been increased to 13.2v to help deliver more power to the thrusters, and we've implemented a more robust IO system with address resistors for direct communication from the solenoid board.
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