Preparing the FlexSEA-Execute 0.x board (Hardware)

List of parts:

  • 1x FlexSEA-Execute 0.x assembled PCB
  • 1x aluminum mounting plate
  • 1x thermal pad
  • 5x M2x4 screws
  • AWG16 wire in red, black and white (McMaster 6659T48)
  • PowerPole housings and crimps

Estimated time: 1h00 (1h15 if Step 0 is required).

Step 0A) FlexSEA-Execute 0.1 only

If you are using the first batch of PCBs, the pull-ups I selected for the on-board I2C bus are too resistive for speeds above 100kHz (we are using 400kHz). R45 and R46 are currently 4.7k and they should be 1.8k. You can de-solder the 4.7k and solder 1.8k resistors (recommended) or add a 3k resistor in parallel to the 4.7k one. Failure to change these resistors will lead to inconsistent behavior as the code will sometimes hang in the I2C routines.

Step 0B) FlexSEA-Execute 0.2 only

The first production batch of FlexSEA-Execute 0.2 uses an MCP1700T-3302E/MB as the 3V3 voltage regulator. I used the wrong pad numbers, therefore we need to change the IC for a RT9064-33GX. Make sure that the board you have has the RT9064, or swap it
How to swap the IC: Soldering on this PCB is harder than usual, because of the numerous power planes. The best solution I found is to heat the top of the IC with my 160W iron for 20-25s, then apply hot air (Hakko FR-801: max temperature, 22/25 airflow) for ~10s while holding the chip with tweezers.

Step 1)

Cut 3 pieces of wire, 4″ long, one piece per color. Cut 2 pieces of wire, 3″ long, black and red. Remove 3mm of insulation from one end and 5mm from the other end.

Step 2)

Crimp the terminals to the 5 wires, on the end with 5mm of exposed copper. Make sure to crimp on the sleeve and not just on the copper. Insert the crimped wires in their housings.

Step 3)

Solder the wires to the PCB. +VB = Red, GND = Black, A = White, B = Black, C = Red. There is copper planes on all 6 layers: a regular (60-80W) soldering iron will have a hard time melting solder. Use a high power soldering iron (such as a Weller WD 1 M 160W) or pre-heat the PCB with a hot air gun (careful, you can easily de-solder components with that!). On the picture below you can see the solder joints on the white and black wires. The red solder joint was cut close to the PCB with cutters. When all 5 wires are soldered clean the flux with alcohol (I use 91%) and a toothbrush.

Step 4)

Link the PowerPole connectors together, and wist the cable assemblies. The color coding and order is up to you (it depends on the motor you use, and on the way you connect the Hall effect sensors (if you use Hall)).

Step 5)

I’m using a phase-change thermal transfer pad made by Laird, TPCM 585 (Digikey 926-1155-ND). It comes in sheets of 9×9 in. I laser cut 16 pads per sheet. Epilog settings: 90% speed, 80% power, 2500Hz. You can also use a blade or scissors, cut a square and make little openings for th 5 screws.
Remove the plastic protection, stick the thermal pad to the PCB and screw it to the aluminum plate. If you are using v0.1, make sure that the two FFC programming ports are in the unlocked position first.

Step 6) (optional)

It’s easy to rip the USB connector from the PCB if you often plug & un-plug it, or if you can’t provide stress-relieving in your application. You can use Epoxy glue over the backing of the connector for extra strength (make sure not to glue the contacts!)

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