Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Jun 17, 2009, 10:55 PM
Murocflyer is offline
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What Does an ESC Do and How Does It Do It? -Link Please


I often see that question asked and I always like to provide a reference link when I post answers to people's questions. This one has me stumped. I cannot find a good reference link for that question.

I checked the following manufacturer's websites:

Castle
Medusa
Great Planes
Novak
Aquacraft
Associated Reedy
Traxxas
Astroflight
FlightPower
Futaba
Global
Helimax
Hobbico
HPI Racing
Kontronik
Scorpion
Super Tigre
Venom

Did I miss any and has anyone seen a website that talks to the basic function and operation of a brushless ESC? Normally Amp Aviators has very good info, but they did not cover this topic.

Thanks,

Frank
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Old Jun 17, 2009, 11:08 PM
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I'm very lame electronically, but I think an esc could as well be described as an amplifier, like for your stereo.

I'm sure plenty of EE's and knowledgeable folks alike will join in. This is a fun topic.
Old Jun 17, 2009, 11:14 PM
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Smart or not on electronics, all I need is a link to a websites that describes its operation.

Thanks,

Frank
Old Jun 18, 2009, 06:39 AM
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Google is your friend:

http://radiocontrol.wikia.com/wiki/E..._speed_control

If you want very detailed info RCG is your friend:

https://www.rcgroups.com/forums/showthread.php?t=200567

In any case search is your friend.
Old Jun 18, 2009, 12:09 PM
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Well, I wanted basic, but that website is a little too general and basic on how and what an ESC does.

I know there must be something better out there.

Come on guys, help me out please.

Thanks,

Frank
Old Jun 18, 2009, 02:35 PM
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http://www.math.niu.edu/~behr/RC/pwm.html
Old Jun 18, 2009, 02:41 PM
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Quote:
Originally Posted by herk1
Fantastic! That's exacltly what I was looking for.

Thanks Herk!

Frank
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Old Jun 18, 2009, 03:27 PM
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That seems to only tell part of the story. The PWM of the ESC output stage is correct and complete for the brushed motor, but if you want a brushless setup, you do the same PWMing, but you have to rotate the fields of the three phase power output to actually get the motor to turn. You rotate it faster, the motor should spin faster, and you vary the PWM signal intensity to overcome what's known as Back-EMF, or the voltage produced by the motor's turning magnetic field. This is partial, but if you do a wikipedia lookup on Pulse Width Modulation and brushless motors, it will tell you the theory of operation and control.
have fun, it is a great topic.
Curtis
Old Jun 18, 2009, 11:27 PM
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Well shucks, so that was a link to a brushed motor ESC? I'll have to annotate that on my reference page. If so, we are back to square one.

Still looking for a website link that talks to what and how an ESC does what it does.

Frank
Old Jun 19, 2009, 07:18 AM
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Quote:
Originally Posted by Beau0090_99
You rotate it faster, the motor should spin faster, and you vary the PWM signal intensity to overcome what's known as Back-EMF, or the voltage produced by the motor's turning magnetic field.
Not so much "overcome" EMF as depend in it to know when to switch the next commutuation.
Old Jun 19, 2009, 09:47 AM
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First of all , esc's refer to two different things, so that might be confuisng (similar to "BEC" which may refer to switching or non-switching bec):

Brushed motor esc: Simple brushed motors will spin by themselves when you place voltage accross the two leads. Battery + motor = spin. A simple switch can turn them on or off. An electronic speed control simply gives you the function of a throttle. Some controller are more efficient than others at partial throttle (surprise- Steve Nue back in the early 2000's showed that many brushed motors/escs are actually more efficient at partial throttle than brushless).

Brushless motor esc: A brushless motor has three wires sticking out of it, and they will NOT spin if you simply hook a battery up to two of the wires. The motor will simply get hotter and hotter. In a brushless motor, a microprocessor inside the "electronic speed control" is actually sending positive and negative current to the various wires in a specific, timed progression that makes your motor spin. As an aside, the brushless ESC's can also give you a throttle function. The ealry, 1990's vintage controllers needed extra wires hooked up to small sensors inside the motor in order to work. By 2000, most controllers developed the ability to sense the magnet position by back emf, and only need the three power wires (these are called sensored and sensorless esc's, respectively, today everything is sensorless).
Old Jun 19, 2009, 10:01 AM
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Ignore the diodes.
The switches are the FETs.
Old Jun 19, 2009, 02:15 PM
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This might provide some insight:
http://ww1.microchip.com/downloads/e...tes/00885a.pdf
http://ww1.microchip.com/downloads/e...tes/00857a.pdf
http://www.microchip.com/stellent/id...GE&nodeId=1523

The controller chip and its software makes electronic commutation possible. There is a lot of detail here, but it is interesting to see how many dynamic problems must be solved to achieve practical control of a BLDC motor.
Last edited by whitecrest; Jun 19, 2009 at 02:43 PM.


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