# Unconvential use of Brushless motor....



## grmanrocks (Jan 27, 2010)

so...i need help....

i need to power a tiny (17mm 2.6A Brushless Motor) using AC (from a wall outlet) for a little project of mine, and im having a terrible time trying to understand everything. 

I am well versed in electronics, having built hundreds of LED arrays, but when it comes to the "ESC", "LiPo", "BEC", "KV" (edited) you talk about i know (edited)...

all im trying to do is spin a 2gram neodymium magnet at a relatively fast speed but need the unit to be powerable via a wallwart type Dc power supply.

so heres what i came up with on my own....

from what i understand, brushless motors, like other DC motors, dont so much care about the voltage they recieve? as in, whether its 6V or 12V theyre gonna still turn, just slower at the lower voltages?

what i dont understand is:

1. Can i power a brushless motor with the following specs:

- Dimention(DxL): 17.3*17.8mm
- Weight: 8.4g
- Shaft diameter: 2mm
- Speed constant(rpm/v): 2290KV
- Operating Current(A): 1.8~2.6A
- Recommended ESC: >10A
- Battery: 2～3 Li-Po or 6~9 Ni-Mh

on a 6v 3A power supply? (keep in mind i dont need it to run at full bore, im using it to turn a tiny 2gram magnet).... if not, what sort of voltage/amperage should i supply via my power supply from the AV wall socket?

2. what a "10A esc" means, does that mean i should supply 10A of 6v DC to the ESC? or that it can drive UP TO 10A? 

3. From what i understand ESC's "Speak" PMW, and so do servo testers, so can i use an esky servo tester to act as a speed controller to turn the motors rotation speed up and down? this servo tester can be run off the same 6v power supply as the ESC/Motor correct? i need to be able to adjust the speed as i dont know exactly how fast i need the magnet to spin....

4. how much load is "too much" for these motors? as far as weight or resistance?


hope im not too far off....im just trying to understand a tad and have hit a few roadblocks in my research that im hoping can be cleared up by the experts....


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## grmanrocks (Jan 27, 2010)

nobody wants to help little old me?


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## Dale Goodchild (Jan 23, 2010)

Why dont you just use a standard 540 brushed motor??

A brushless motor works on a different principle to a brushed motor.
The magnet is in the middle (on the armature) of a brushless motor so the magnetic field to rotate the armature has to rotate itself (around the inside of the motor can), the armature just follows it. So, Im afraid to say, that applying a DC current to a brushless motor will just heat up the windings.


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## 420 Tech R/C (Sep 15, 2006)

Dale Goodchild said:


> Why dont you just use a standard 540 brushed motor??
> 
> A brushless motor works on a different principle to a brushed motor.
> The magnet is in the middle (on the armature) of a brushless motor so the magnetic field to rotate the armature has to rotate itself (around the inside of the motor can), the armature just follows it. So, Im afraid to say, that applying a DC current to a brushless motor will just heat up the windings.


Yep. Brushless motors are essentially built like a 3 phase ac motor.To operate them on DC takes a controller to "time" the sequence in which the windings fire to make it work.For a cheap DC speed controll look at nitrorcx.com . you can get one of their 1/18 scale controllers for around 20.00


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## RPM (Dec 20, 2004)

420 Tech R/C said:


> Yep. Brushless motors are essentially built like a 3 phase ac motor.To operate them on DC takes a controller to "time" the sequence in which the windings fire to make it work.For a cheap DC speed controll look at nitrorcx.com . you can get one of their 1/18 scale controllers for around 20.00


RIGHT! +1:thumbsup:


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## grmanrocks (Jan 27, 2010)

Dale Goodchild said:


> Why dont you just use a standard 540 brushed motor??
> 
> A brushless motor works on a different principle to a brushed motor.
> The magnet is in the middle (on the armature) of a brushless motor so the magnetic field to rotate the armature has to rotate itself (around the inside of the motor can), the armature just follows it. So, Im afraid to say, that applying a DC current to a brushless motor will just heat up the windings.


I know how a brushless motor operates, at least i belive so. 

The lipo batteries supply dc power to the ESC, which recives a PMW signal from the controller, that then tells the ESC to fire pulses of electricity to the motor. correct? 

that being said, i plan on doing the same thing, just without batteries, using a ac/dc wall adapter?



420 Tech R/C said:


> Yep. Brushless motors are essentially built like a 3 phase ac motor.To operate them on DC takes a controller to "time" the sequence in which the windings fire to make it work.For a cheap DC speed controll look at nitrorcx.com . you can get one of their 1/18 scale controllers for around 20.00





RPM said:


> RIGHT! +1:thumbsup:


i know this...i was planning on using the ESC and a servo tester...i thought i made that clear...

i cant use a brushed motor beceause the motor is going to be running 12 hours a day, and the "brushed" motor would burn out after a few days. 

if you could please reread the first post and try to understand what i intend to do...if anything this clarification, id be glad to try....


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## Watchman (May 19, 2009)

DC is DC whether from a battery of power supply...HOWEVER there may be an issue using an inexpensive power source (wall adapter) because the AC ripple component is too high..and damage the electronics

The power supplies used by racers to charge usually have built in filters to decrease the ripple...

just a thought


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## 420 Tech R/C (Sep 15, 2006)

Watchman said:


> DC is DC whether from a battery of power supply...HOWEVER there may be an issue using an inexpensive power source (wall adapter) because the AC ripple component is too high..and damage the electronics
> 
> The power supplies used by racers to charge usually have built in filters to decrease the ripple...
> 
> just a thought


x2. It would be best to use one with the least ripple.


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## 420 Tech R/C (Sep 15, 2006)

You seem to have all the info, so crunch the #'s and get your answers.


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## Dale Goodchild (Jan 23, 2010)

To reduce ripple put some caps across the input wires (from your wall power supply) say a couple of electrolytics and a couple of small ceramics...............sorry about the confusion.


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## Mike Clark (Apr 28, 2007)

Watchman said:


> DC is DC whether from a battery of power supply...HOWEVER there may be an issue using an inexpensive power source (wall adapter) because the AC ripple component is too high..and damage the electronics
> 
> The power supplies used by racers to charge usually have built in filters to decrease the ripple...
> 
> just a thought


Sorry but we will need to agree to disagree on this statement. The only true DC current comes from either a battery or a DC generator set, The rest is rectified DC which will be a pulsed source.


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## Mike Clark (Apr 28, 2007)

Dale Goodchild said:


> To reduce ripple put some caps across the input wires (from your wall power supply) say a couple of electrolytics and a couple of small ceramics...............sorry about the confusion.



I am still confused! Are you meaning to place caps across the A/C line before the power supply to quail the ripple? That is what I get from your post.


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## shintastrife (Apr 26, 2009)

i say buy a cheap esc and motor to start and try it out, and it if work then go and get something better. i know what he is saying it like me and wanying to put a power supply in my bump box so i dont need a battery when im at the house.

it sound like it will work .


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## ta_man (Apr 10, 2005)

Mike Clark said:


> Sorry but we will need to agree to disagree on this statement. The only true DC current comes from either a battery or a DC generator set, The rest is rectified DC which will be a pulsed source.


And I'll disagree with that.

A switching power supply does not rectify AC current, it creates a series of DC pulses from an inductor. In a properly designed switching power supply (meaning appropriate for the application), the capacitance of the power supply will be sufficient that there is no meaningful ripple as far as the application circuits go. You really think Intel could build processors that run a 3GHz on 3V and put up with ripple current? Nah.

But that is totally beside the point of the guy's original question.


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