Building a brushless motor controller

brushless_motor_controller

Brushless motors and the way in which they are controlled can be a bit of an enigma to those just starting out in hobby electronics. [Andrew] from spingarage thought it would be helpful to put together a quick tutorial showing how he built a simple brushless motor controller in about a day’s time. He constructs everything on protoboard from components he acquired at RadioShack in order to demonstrate the ease of sourcing parts and building a brushless motor driver.

While he skips most of the theory behind brushless motor control itself, he does touch on the signaling these motors require for movement as well as how motor position is determined. Specifically, he expands on how half-bridges can be used to create the sine wave signaling required by a single motor input, as well as how three of these can be combined to drive a brushless motor.

The post is the first in a series of posts about brushless motors, so we should see some code examples and some practical applications in the near future.

Comments

  1. andrew says:

    Not a bad intro, kudos for the good writeup, decent wiring and photos.

    One thingI noticed though is that the design of the high side and the design of the low side of the half bridges is not symmetrical. It will take longer to turn on the high side than the low side and any asymmetry is nasty. The low-side should be designed to use two transistors as well (even though technically unnecessary) in order to get the deadband calculations cleaner.

    Ideally, though, he should be using simple FETs. Much easier to drive, higher current in the same package, way faster, and none of the nasty bipolar transistor gotchas (although there are some nasty FET gotchas).

    Looking forward to seeing more installments of this project!

  2. ino says:

    You definitely should use MOSFET (as andrew mentioned) to drive brusless motors.
    The RDSon parameter is the key for not wasting power.

  3. I was looking for information on making an ESC for brushless motors the other day, and I found out that Microchip has posted two Application Note documents on the subject with schematics and source.

    I can’t find the links at the moment, but they’re AN847 and AN857, and it’s all very interesting.

  4. Buzz says:

    The OpenPilot UAV project is going about making their own brushless controler. There is already a working prototype. Check it out:
    http://forums.openpilot.org/forum/24-esc-development/

  5. Keith says:

    Nice work!

    Radio Shack … Booo!

  6. strider_mt2k says:

    Keep booing Rad Schmack.

    Pretty soon they’ll be gone and boos will turn to boo hoos.

    Get the good out of ‘em while you can.

    VERY nicely done project, and lo and behold accessible to all who are in range of a Rad Schmack that still carries parts.

    yay fot that

  7. Stew says:

    @Bakamoichigei

    AN847 – RC Model Aircraft Motor Control
    ww1.microchip.com/downloads/en/AppNotes/00847a.pdf

    AN857 – Brushless DC Motor Control Made Easy
    ww1.microchip.com/downloads/en/AppNotes/00857a.pdf

  8. chami says:

    It would be nice to have caps connected to the base of the driver transistors. Then the voltage will ramp up bit slowly and spikes will be less and corners of the square pulses will be slightly rounded. Same way, a few turns of wire on the output of the power transistors will provide a better drive. Extra: six 0.22 uF 50V ceramic caps and 5-20 turns of cu wire made into a solinoid.

    The mathematica example is apparently wrong. We need sin(x), sin(x+2*pi/3) and sin(x+4*pi/3). To see the graphs, we need mathematica installed (expensive!)

    This arrangement will not be able to see back EMF produced. No speed information will come from the motor or the driver.

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