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X12 Solenoid board
Grant Geyer edited this page Sep 18, 2021
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1 revision
IMAGE OF PCB, potentially including its place on the relevant ROV
| PCB Summary | |
|---|---|
| Vehicle | X12, ROV Triton, with link |
| Contributors | Alex Wilson, Katherine Sandys |
| Predecessors | X11 Solenoid board, X6 something maybe? |
| Success? | Yes! |
Architecture Link
SID Link
REPO Link
- Toggles solenoids based on incoming CAN packets.
- Housed inside the solenoid enclosure
- Connect to the backplane in the power box via a binder cable
- Solenoids plug directly into the board
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)
- Make it small and make it fit
- Solenoids were changed to 12V solenoids from the 24V ones in X11, so the boost converter was removed
- Solenoids were driven by H-bridges then a transistor array instead of discrete mosfets or a shift register
- The tiny bit of space that mechanical gave for the board (and even less where connectors could be)
- ULN2003AD Datasheet
- Split CAN Termination
- Supports 500mA per solenoid (V2)
- CAN at whatever
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)
- H-bridges so they could drive the solenoids in either direction (see below for more info on why that was wrong)
- ULN2003AD transistor array since it could support 7 outputs and sink 500 mA each. It was able to be driven by the microcontroller and had flyback diodes for when the solenoids turned off.
- Phoenix Contact PTSM connectors because they are bae. The spring cages can be wired without a crimp and the wires can be disconnected. They are keyed too!
- Routing was real tight
- Soldering some things was a little tricky
- Trimmed programming headers to fit under the solenoids
- Added a second mounting hole in V2
- User an actual 6-32 clearance hole on V2
- When some X12 boards were reordered for ongoing maintenance of the X12 stack while the X13 stack was in development, the V2 board was sent out to test the transistor array that was going to be used and to use better connectors.
- It was annoying to add CAN termination to the powerbox when the solenoid board or enclosure wasn't ready. This is one of the benefits of moving the board to the powerbox in the X13 stack so that termination was on the backplane.
- The 12V->3.3V buck converter was flipped on V1 of the board
- Standard headers were used everywhere which proved difficult to connect to. In V2, phoenix contact PTSM connectors were which which are easy to wire up and a keyed.
- (Minor) the reset switch footprint had the pads rotated 90 degrees (fixed in V2)
- Would've tested the solenoids before designing the circuit. Initially it was thought they would allow air flow in one direction when powered one way and woudl allow airflow in the opposite direction when powered the other way. However, they simply had a unpowered state and a powered state (independent of which way the were powered). So the H-bridges weren't necessary on the high side and all functionality was consolidated to a single transistor array
- Transistor array worked very nicely
- PTSM connectors were great
Any addition links if relevant
- Any fun side details
Search keywords.
Summarize the first three questions above into a paragraph for our technical report
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