Wednesday, October 22, 2014

First Parts Came In!


My first order of parts came in today. I am starting with the basics for right now. My goal is to get a BLDC motor driver up and running for 1 motor with the same MCU that will be used on the GatorQuad, and then go from there. This will allow me to start to prove the concept while saving as much of my code and work moving forward.

Parts Ordered:

  • 6 x CSD18537NKCS - N Channel Power Mosfet - Texas Instruments (Digi-key, TI free samples)
  • 3 x FAN7842MX - High side, Low side, Mosfet driver - Fairchild Semiconductor (Digi-key)
  • 3 x US1881 - Hall effect latching sensor, Melexis (Sparkfun)
  • 3 x SOIC to DIP adapter 8-pin, Sparkfun (Sparkfun)
  • 1 x NTG Propdrive 28-30s 800kV BLDC motor, Turnigy (Hobby King)
  • 1 x 3.5mm 3 wire Bullet wire connectors, Hobby King (Hobby King)
  • Already on Hand:
  • 1 x XMOS startKIT multicore microcontroller, XMOS (XMOS)

The motor was ordered from Hobby King because it was inexpensive and widely used. I did not know what I was getting with it because It's Hong Kong manufacturer "Turnigy" does not have a lot of documentation online. This motor does not come with built in Hall effect Sensors for sensored control. I ordered a few bullet style connectors from HobbyKing so i can make and connect my own wire. Thus I ordered some from Sparkfun and hope they will fit my needs. I did not notice when I ordered the Hall effect sensors that they are a latching version, so I will find out if that will effect my control and ultimately may need to order non latching sensors. The TI Power mosfets are capable of sourcing 50A of drain current while the motor is only rated for 20A. Obviously I way over sized here, these will likely be scaled down in later designs, but for now I wanted to be on the safe side. Picking the gate drivers was a little tricky, the main things that I wanted was independent control of the High side and Low side of an H-bridge, as well as enough source current to switch the mosfets fast enough. I found scattered resources across the web to help with determining the source current for certain mosfet capacitance's and switching speeds. Right now I think I am okay, If my calculations were wrong we will revisit this. The gate drivers were a small SOIC package and I am doing my initial prototyping from a breadboard and desktop power supply. Additionally I will be using my Xmos StartKit development board, so no self designed PCB's yet.

Immediate To Dos:

  • Attach the hall effect sensors to the BLDC motor to allow for sensored control
  • Wire up initial motor driver circuit to startKIT xCore microcontroller
  • Get to coding



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