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Sensor vs non-sensored BL motors
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offroader
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Sensor vs non-sensored BL motors - 11.15.2007, 09:38 PM

What is the difference between the Brushless sonsored and non sensored motors? Is one better then the other?
   
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jnev
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11.15.2007, 10:18 PM

I asked BrianG this question a little while ago, and this was his response:

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Sensored motors have Hall-Effect sensors on the motor which provide feedback to the ESC so it knows where the rotor is. These sensors work well at very low rpms, which is where a sensorless has the most trouble.

A sensorless motor is built the same way as a sensored motor except it doesn't have the sensors. The ESC has to rely on the back-EMF pulses generated by the motor coils to determine rotor position. However, the rotor has to be actually turning to generate these pulses. Really, the only time a sensorless ESC has trouble is during startup or very low speeds (<1mph), but the advanced programming in todays ESCs generally address this very well.

IIRC, there are a couple sensored ESCs that start in sensored mode (using the motor sensors), but once they get up to speed, they then use the back-EMF pulses like a sensorless ESC.


   
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jokerjustin
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11.15.2007, 10:20 PM

The search button is your friend..........sensored motors have sensors which tell the esc what position the rotor is in.this helps with smoother starts and most of the time it gives you the ability to move at a crawling speed with no cogging...
i personally like non sensored, with a good esc a non sensored motor will performe similar to a sensored
   
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offroader
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11.15.2007, 11:43 PM

Quote:
Originally Posted by jokerjustin View Post
The search button is your friend..........sensored motors have sensors which tell the esc what position the rotor is in.this helps with smoother starts and most of the time it gives you the ability to move at a crawling speed with no cogging...
i personally like non sensored, with a good esc a non sensored motor will performe similar to a sensored
Ok, understood now what is cogging and how do you prevent this or minimize this?
   
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zeropointbug
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11.16.2007, 02:28 AM

There aren't any really good (REALLY good) brushless motors out there that are sensored, all the good ones (and high powered) are sensorless.


“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens
   
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jokerjustin
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11.16.2007, 08:01 AM

cogging is were the esc cannot start the rotor....this can be caused by high current draw...or that your batteries cannot supply the needed current. a sensorless motor has a minimum rpm it can turn at so anything lower than this will appear to cogg
   
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offroader
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11.16.2007, 10:17 AM

Quote:
Originally Posted by jokerjustin View Post
cogging is were the esc cannot start the rotor....this can be caused by high current draw...or that your batteries cannot supply the needed current. a sensorless motor has a minimum rpm it can turn at so anything lower than this will appear to cogg
I'm using a MM esc and know there are software adjustments we can make can the throttle curves be adjusted to reduce the cogging? Just thought I would ask since I know quite a few guys here use the MM.
   
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zeropointbug
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11.16.2007, 01:19 PM

Quote:
Originally Posted by jokerjustin View Post
cogging is were the esc cannot start the rotor....this can be caused by high current draw...or that your batteries cannot supply the needed current. a sensorless motor has a minimum rpm it can turn at so anything lower than this will appear to cogg
I think it's more the esc's software/hardware to detecting rpm/rotor position which causes cogging... because, even if the motor is spinning at say 60rpm, there will be a voltage generated, albeit, small potential. It's just up to the tech of the controller to be able to 'see' this potential, past all the other electrical noise, w/e.


“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens
   
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11.16.2007, 02:04 PM

The mamba maxx for example simple has a minimum RPM it starts the motor at,my guess is that it's easier that way to read/measure the back EMF with less faults.
   
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11.16.2007, 02:06 PM

Quote:
There aren't any really good (REALLY good) brushless motors out there that are sensored
That has got nothing to do with sensorless or sensored, I think it would be easier to make an ultra high power esc/motor combo sensored. it's more a matter of costs.
   
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lincpimp
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11.16.2007, 02:51 PM

Lack of high end sensored motors most likely stems from the lack of high end sensored speed controllers. Griffinru made a feigao work with a novak hv using the hv motor as a sensor and putting the leads to the feigao. Neither are high end, but I bet it had great low speed driveability! The novak esc is supposed to be quite good, just the motors are a little small for heavier applications.
   
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11.16.2007, 03:36 PM

Well, with the new sintered rotors, their motors preform pretty well.

But griffinru finally succeeded in using a sensored Feigao motor instead of using the two motors.
   
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zeropointbug
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11.16.2007, 05:35 PM

I think the only way for high powered sensored systems to get going is for companies like Neu/Lehner and others to make their motors with built in sensors... after all, the Neu's have decent gap in the front of the motors inside, this space is perfect to throw in a hall sensor...

I guess there is little incentive for them to do this, seeing as they made there motors for a certain crowd... aircrafts.


“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens
   
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johnrobholmes
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11.16.2007, 10:16 PM

The startup is pretty dang good on sensorless, I just don't see anybody wanting to put effort into sensored motors for hobby use (unless they like to hold on to old tech as the only way worth pursuing).
   
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zeropointbug
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11.16.2007, 10:35 PM

I wouldn't call it 'old tech'... whats so old about a sensor? The motor would still be the very same.


“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens
   
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