Is there any reason you don't purchase an in-stock BLDC motor driver
such as:
https://www.mouser.com/ProductDetail/Texas-Instruments/DRV10983SQPWPRQ1?qs=%2Fha2pyFadujPwfH%2FXzivpU8AHrIO6U7ALudxKfjNJze3U2dD%2F68jly3tmYweXSYm
Mouser shows 66 in stock, and at $4.61 each.
I'm only showing the one device rated to 2 amps that I filtered from all
the parts currently available and am not endorsing.
Hope this helps.
Rick
On 10/7/2021 2:32 AM, Mike Lisanke via TriEmbed wrote:
Charlie,
You can commutate the motor phase from a rotary encoder. No need for
Hall effect sensors. Just phase lock to a zero point and know
(measure) the 120 degree phase angles.
I did much open loop motor control at IBM. It wasn't difficult and we
did it with very simple controllers. It does pay to have a watchdog
timer power-off all op amps in-case your SW debug locks up or runs
away. I had our HW tech eventually create a socketed linear amp. Our
HW engineer was an audiophile and said my SW brought tears to his eyes
(not in a good way).
BTW, linear motes and steppers with microstepping can all be
encoder-commutated and driven off 1 sinusoid table at 3 offsets.
On Wed, Oct 6, 2021 at 9:44 PM Charles West via TriEmbed
<[email protected] <mailto:[email protected]>> wrote:
@Pete:
When you were working on it, did the motor you were using have
hall effect sensors in it? That's about all that makes me willing
to try this. In the worse case, I should be able to fall back to
trapezoidal control based off of the hall effect sensors without
any sort of fancy estimation. I hope I can do better than that
though.
@Carl&Rodney:
I've been actively looking through motor control gate drivers
trying to find something that is simple enough I can work with it,
available and capable enough. So far, the best I've found is the
STDRIVE101
(https://www.mouser.com/ProductDetail/STMicroelectronics/STDRIVE101?qs=xZ%2FP%252Ba9zWqYdY88AYx%252Blxg%3D%3D
<https://www.mouser.com/ProductDetail/STMicroelectronics/STDRIVE101?qs=xZ%2FP%252Ba9zWqYdY88AYx%252Blxg%3D%3D>).
I'm bumbling my way through designing a test circuit for it now,
but I would be the first to admit that I am rather terrible at
analog electronics.
Thanks,
Charlie
On Tue, Oct 5, 2021 at 3:35 PM Carl Nobile via TriEmbed
<[email protected] <mailto:[email protected]>> wrote:
So my bad, I read Charlie's email and missed the brushless
part. I must have brushes in my mind.
So brushless DC motors are actually 3 phase synchronous AC
motors, So three different PWM modulators are needed for each
motor. Each PWM is 120 degrees out of sync with the others.
and there can be absolutely no overlay on the others. There
are special MCUs that are made for these motors. See the link
below, it's for an older 8 bit MCU, but will give you an idea
as to what needs to be done.
http://ww1.microchip.com/downloads/en/devicedoc/atmel-7710-8-bit-microcontroller-at90pwm216-316_datasheet-summary.pdf
<http://ww1.microchip.com/downloads/en/devicedoc/atmel-7710-8-bit-microcontroller-at90pwm216-316_datasheet-summary.pdf>
~Carl
On Tue, Oct 5, 2021 at 12:55 PM Pete Soper via TriEmbed
<[email protected] <mailto:[email protected]>> wrote:
I once got the idea I could control a brushless motor by
being "clever" controlling set of drivers. I was mistaken.
Without some means of sensing the behavior of the motor,
whether it be back EMF or some other feedback it's about
99% of hopeless. Which is to say I was too stubborn to
give up and managed to see the motor (from a server disk
drive) spin, but if I squinted at it there was
misbehavior. A truly silly waste of time.
-Pete
On 10/5/21 12:45, R Radford via TriEmbed wrote:
Carl, Charles is looking for a brushless controller, not
just a DC motor driver. Brushless motors are closer to a
stepper motor than a regular DC motor, but the 'steps'
are controlled by sensing hall effect sensors to know
when to step to keep the motor running smoothly.
They are great as they have less mechanical issues over
time (no brushes to replace) and also produce less
electrical noise.
The circuit you show is a nice DC to PWM circuit that is
similar to one I did many years ago, but now most (all?)
microprocessors have built in hardware assist PWM so that
part is already handled. The first time I used a similar
circuit was controlling a robot from a 286 PC based robot
where I used the parallel port to drive an R2R D/A
circuit comparing against a triangle wave similar to your
circuit. It worked great at the time, but now would not
be needed. I still have that old hardware somewhere -
perhaps I should pull it out and upgrade it.
On Tue, Oct 5, 2021 at 12:02 PM Carl Nobile via TriEmbed
<[email protected] <mailto:[email protected]>> wrote:
Charly,
There are a few solutions to the controller problem.
I designed an analog PWM circuit using op-amps and
comparators that works great. You would also need an
H-Bridge you would then need just one MCU board to
control the PWM circuits then then control the
H-Bridge circuits.
My design is at:
https://github.com/cnobile2012/VoltageControlledPWM
<https://github.com/cnobile2012/VoltageControlledPWM>
My motors are fairly low current and voltage so the
H-Bridges I'm using won't work for you, however
MPJA.com has one in the link below, that will handle
higher currents.
https://www.mpja.com/Dual-H-Bridge-DC-Motor-Driver/productinfo/35567+MP/
<https://www.mpja.com/Dual-H-Bridge-DC-Motor-Driver/productinfo/35567+MP/>
It will handle two motors and is only $22.95 ea. They
give full docs on their site.
My PWM board shou interface with it fine.
~Carl
On Sun, Oct 3, 2021 at 11:16 PM Charles West via
TriEmbed <[email protected]
<mailto:[email protected]>> wrote:
Hello all!
For the past 5 years or so, I've been working on
a open source low cost sidewalk delivery robot.
The current draft (prototype picture:
http://goodbot.ai/lib/exe/fetch.php?media=mk3draft1.jpg
<http://goodbot.ai/lib/exe/fetch.php?media=mk3draft1.jpg>)
has 4 hoverboard style motors in a skid steer
arrangement. Each robot will need 4 motor
controllers, which is one the big cost drivers
right now (even prior to the covid shortage, the
controller cost more than the motors).
My last stab at designing a brushless motor
controller failed spectacularly and the covid
parts shortage has also made the central parts of
that design completely unavailable. In addition,
the bulk price for the motor controllers I've
been using jumped from $56 per to ~$100 per.
Given that, I thought it might be time to get
back to the drawing board. However, I am not an
expert at this sort of thing, so I thought it
might be good to post what I am thinking and see
if I am completely off the reservation.
I'm currently using off-brand VESC motor
controllers (schematic for normal ones here:
https://vesc-project.com/sites/default/files/Benjamin%20Posts/VESC_6.pdf
<https://vesc-project.com/sites/default/files/Benjamin%20Posts/VESC_6.pdf>).
They are great but do way more than I need. They
can handle sensored and sensorless motors and be
reconfigured with MANY different options using a
desktop application. I don't need to make
something that is easy to make work for lots of
different motors and I don't need to support
sensorless operation. I just need to make
something that works for my motors.
The approach that the VESC takes is a central
microcontroller which talks with a (not currently
available) DRV8301 chip. This chip in turn
senses voltage/current across each motor coil and
drives 6 N-channel mosfets to control the motor
(3 high side, 3 low side). It does FOC control,
which I believe is state of the art in terms of
smooth motor control. It also integrates the 3
halls sensors that sensored motors have if they
are available.
I'm having trouble finding any of these 6 mosfet
motor controller optimized gate drivers, so I am
thinking that I will just get some high side/low
side mosfet drivers (like maybe these:
https://www.mouser.com/ProductDetail/STMicroelectronics/SRK2000A?qs=WHlX%252B%252B9%2FRwCG%2FkukabfLqA%3D%3D
<https://www.mouser.com/ProductDetail/STMicroelectronics/SRK2000A?qs=WHlX%252B%252B9%2FRwCG%2FkukabfLqA%3D%3D>)
and some nice mosfets. Particularly without
dedicated chips being available, I'm not going to
try to do current or voltage sensing. I am
thinking that I would just PWM the 3 half bridges
and try to do sinusoidal motor control using a
STM32 microcontroller to drive it and the hall
sensors in the motors to estimate position
relative to the coils.
If I may ask, does this sound reasonable or am I
totally off base?
Thanks,
Charlie
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