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X13 Quad ESC Adapter
IMAGE OF PCB, potentially including its place on the relevant ROV
| PCB Summary | |
|---|---|
| Vehicle | X13, ROV Triton, with link |
| Contributors | Grant Geyer |
| Predecessors | X12 Quad-ESC |
| Success? | Yes, with flaws |
Architecture Link
SID Link
REPO Link
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)
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)
The quad esc adapter serves primarily as a pass through board to connect the new Lumenier 45A 4 in 1 ESC to the rest of the power system, namely the backplane from which it receives power and the thrusters which it drives. It is part of the split (along with the Quad ESC Controller) to separate the ESCs from the microcontrollers driving them. The adapter board connects to the controller via a JST 1mm pitch 8 pin connector that is part of the Lumenier ESC which passes through a slot in the backplane. The switch to the Lumenier ESC provides several advantages from the teams prior use of now discontinued Afro ESCs. The ESCs run newer 32 bit microcontrollers allowing for newer 32 bit BLHeli firmware to be flashed. The new firmware provides more customizable settings such as ramping, minimum voltage, etc. The ESCs also provide a telemetry (TLM) pin to send data about operation over UART. This data includes the temperatures, voltage, current, power consumption, and electrical RPM and can be read about in the KISS Telemetry manual. An analogue out pin also provides current maybe(?).
The 4 in 1 configuration allows for a dramatically smaller profile that was achieved with previous ESCs. The connection of ESCs to the board was also changed. Previous ESCs were connected via wires to the board. This changed to pads and vias for direct soldering of the ESC to the board. While the ESC is no longer removable, the complexity is minimal and the board is potentially reusable in the future, so the loss of removing an ESC was deemed acceptable. Resistance of the wires is now eliminated too. The lumenier is connected by two pads soldered to the castellated ESC vias for input power and ground and two columns of 3.5mm drill / 4.8 mm diameter octagonal plated through holes soldered to the ESCs motor phase pads. A bevel (also known as hoof) tip was most effective in soldering the PCBs together. In order to fit the ESC into the adapter, a large cutout profile needed to be made for components to not intersect the PCB. The width of the board was 4 inches to be wider than the backplane for plugging in thruster connectors. It has a length of ____ so that 3 can fit in beneath the backplane. The length was the shortest distance that could fit the lumenier and connector. The adapter board connects to the backplane via a 2x12 block of male headers, specifically chosen for a mating height with the backplane of ___. The connect to thrusters via TE Connectivity 3.5mm pitch screw terminal blocks plugs and headers. These provide a smaller profile than the 5mm pitch headers used in prior years, while still meeting the current requirement per phase (12A).
Each board contains 4 150uF tantalum capacitors for providing startup energy to the ESC as it begins driving a motor. The adapter board was moved beneath the backplane to put the thruster connections on the same plane as their panel jacks. The previous generation of electronics had them situated above the panel jacks they connected to, making accessing many connectors and electronics difficult. The split of ESC and controller also allows for the ESCs to be reprogrammed via their JST connection to an arduino programmer through an FPC 1mm breakout stick. The previous pcb designs did not add any ability to reprogram ESCs.
- Capacitors rated too low - As back emf from the motor did kill a capacitor, aluminum capacitors could be purchased to a higher rated voltage. The addition of a clamping zener diode could also remedy the solution. The soldering of power +/- input was rather difficult so a larger pad to which to solder would help.
- A polygon connecting one motor phase to the connector only had 1 connection, where it should've had 3 (with thermals).
Were this board to be redone, several small things could be improved. The outline for the cutouts was mismeasured slightly on what appears to be the ESC’s sense resistors, so some filing of the PCB was needed (fixed on github). While soldering a single 2x12 was easy, there is no prevention for misaligning the pins when plugging the board in. A 0.05" space between them would prevent this. The adapter board closest to distribution protruded under the Samtec MPPT connector slightly, preventing the backplane and boards above/below it from being pulled up cleanly. Had more height been available, the Samtec IPS1/IPT1 connectors provide nice shrouding for pins and generally prevent bending of pins when mating and unmating connectors. Labels for which side is 12V and which is ground would have been helpful (fixed in github). If in the future, the electronics are rearranged for more space, the capacitors could be switched to higher capacity, lower ESR, and cheaper aluminum capacitors.
The Quad ESC adapter board connects the all new Lumenier 4 in 1 ESCs to the backplane for input power and the thrusters they drive. The new ESCs allow for a more compact design, while providing new data for their operation, namely current. Bulk capacitors are placed on the board to provide current during startup for the ESCs.
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