Circle

slow_bldc

parts selection

microcontrollers

Goal: Fast Cortex-M with FPU (at least for now). HS USB would be nice for tons of datalogging, but not necessarily required.

• Selection: STM32F303CCT
• Other parts considered:
  • STM32F723ZET6: a bit spendy but is fast with HS USB, which is neat.
  • STM32F4
    • Access line: F401, F410, F411, F412, F413 only have one ADC
    • Fancier ones have multiple ADC's which would be nicer.
  • Atmel SAM E / V / S

motor driver

Goal: something completely-integrated with power capacity comfortable for 1A to 2A.

• Selection: TI DRV8312

encoder

Requirements: SPI interface, relatively high resolution

• Selection: AMS 5048A
  • 14 bit, SPI, 3.3v single-supply, 11 kHz
• Other parts considered:
  • AMS AS5047D and AS5047P are intended for high-speed BLDC and automatically compensate for encoder latency
    • super cool, but probably not necessary for super low-speed applications
  • Melexis MLX90316
    • 12 bit, SPI
    • 5V supply
    • 1 kHz
  • MPS MA700
    • 3v3 supply, only 7 mA
    • 11 bit
    • 500 kHz
    • can be mounted off-axis and calibrated for donut magnets
  • Allegro A1335
    • 12 bit, SPI
    • can be mounted off-axis
  • AK7451
    • 12 bit
• Analog output IC's are pretty difference since they output analog sine/cosine, which allows lots of flexibility would would require high-precision simultaneous-sampling ADC to be awesome
  • NXP KMZ60
  • KMT37
  • NVE AAT00x is super low power and tiny since it just provides the sine/cosine half bridges; you need to supply amps and ADC's
  • AS5115 has differential analog sine/cosine outputs

comms

• MCU has USB full-speed (12 mbps)
• Half-duplex RS-485 IC included for chaining these boards together: SN65HVD75

power supply

• assumes a regulated 12V supply to provide both the gate-drive and motor bus voltage
• onboard Recom DC-DC used to generate local 3.3v supply

current sense

• TI INA240 used for inline current measurement on flying series current-sense resistors to each phase lead