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Jun 17, 2009, 09:55 PM
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Murocflyer's Avatar

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:

Great Planes
Associated Reedy
HPI Racing
Super Tigre

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.


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Jun 17, 2009, 10:08 PM
MICKEL's Avatar
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.
Jun 17, 2009, 10:14 PM
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Murocflyer's Avatar
Smart or not on electronics, all I need is a link to a websites that describes its operation.


Jun 18, 2009, 05:39 AM
7000mw of raw power!
rich smith's Avatar
Google is your friend:

If you want very detailed info RCG is your friend:

In any case search is your friend.
Jun 18, 2009, 11:09 AM
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Murocflyer's Avatar
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.


Jun 18, 2009, 01:35 PM
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herk1's Avatar
Jun 18, 2009, 01:41 PM
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Murocflyer's Avatar
Originally Posted by herk1
Fantastic! That's exacltly what I was looking for.

Thanks Herk!

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Jun 18, 2009, 02:27 PM
Registered User
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.
Jun 18, 2009, 10:27 PM
Promoting Model Aviation...
Murocflyer's Avatar
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.

Jun 19, 2009, 06:18 AM
7000mw of raw power!
rich smith's Avatar
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.
Jun 19, 2009, 08:47 AM
100% electric since 1990
twest's Avatar
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).
Jun 19, 2009, 09:01 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Ignore the diodes.
The switches are the FETs.
Jun 19, 2009, 01:15 PM
Frequent Flyer
whitecrest's Avatar
This might provide some insight:

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 01:43 PM.

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