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Friday, February 14, 2020

S-Core SBBM v1.5

The original S-Core did its duty as a dev mule, but it's time for a "production" board for both me and other people to use.


Changes:

  • Delete the solenoid driver - It is decided. Steppers are NOT going anywhere.
    • Solenoid-driven magfed applications are going to get their own, smaller, simpler board. If a coil driver is needed at the same time as the DRV8825, that can be something plugged into the GPIO connector.
  • Switch pusher motor DC link cap and logic power supply filter cap to through hole 10mmOD electrolytics - No more SMD lytic hassle. Also, cheaper, and many options of lower ESR which matters for the former.
  • Fix inductor footprint near AOZ1282 for easier soldering
  • Fix MCU ceramic resonator footprint for easier soldering
  • Put all components on front side - Does it matter? Not really... There's through-hole leads sticking out the back for all the headers and such so you can't whack it against a flat surface anyway without some standoff but it felt right to do this. When I do the mini version, this likely won't be the case.
  • Add mounting holes
  • Replace cheesy little Bourns TC33 trimpot for tournament lock with a Bourns 3362
  • Replace DC bus wire pads with wire holes plus 2 pin 0.1" connector footprint for options and better wire management in-blaster
  • Add TVS diode footprint (SMA package) for DC bus transient overvoltage protection (opt.)
  • Change BOLT connector to 2 pin
  • Change GPIO connector to 4 pin (adding pin formerly eaten by the solenoid driver)
  • Add ISP header pinout legends (Not shown in the above render)
  • Add motor drive pinout legends (Not shown yet as well)
  • Improve MCU decoupling
  • Via stitch front and back ground planes generously and improve ground connectivity/impedance to everything
  • Circle VREF test points in the silkscreen, if they needed to be any more obvious
30x75mm. 2 layer, 7/7mil, 1oz. Minimum drill 20mil (I use large vias by habit) Should be easy stuff to get made by any vendor.

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