Author Topic: Brushless motors  (Read 3417 times)

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Offline CommanderbobTopic starter

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Brushless motors
« on: February 15, 2008, 12:27:21 AM »
Has anyone used a nice brushless motor and ESC? I need an ESC that can go forwards and backwards for a robot tank. Any ideas? I have seen the Mystery ESC 30A (available on e-bay) but I am not sure they go backwards as they are intended for planes. If you fine any well priced ESCs with reverse please tell me.

Thanks,
Justin

Offline Trumpkin

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Re: Brushless motors
« Reply #1 on: February 15, 2008, 07:57:41 AM »
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Offline hgordon

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Re: Brushless motors
« Reply #2 on: February 15, 2008, 10:26:52 AM »
You will pay a premium for an ESC that provides forward and reverse, but these folks seem to have some decent motors and controllers that are designed for R/C trucks such as E-Maxx that might be suitable for a tank -

    http://www.teamnovak.com/products/brushless/hvmaxx/index.html

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Offline CommanderbobTopic starter

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Re: Brushless motors
« Reply #3 on: February 15, 2008, 11:37:15 AM »
Thanks,
I did find http://www.horizonhobby.com/Products/Default.aspx?ProdID=LOSB9594 but at $50 each and I need two it is quite a lot. Why is it so hard to make the ESC reversible? For brushless all that needs to be done is change the way the pulses are sent. I can see why there are not very many brushed ESC that go in reverse as you need something like an h-bridge.

For the DIY ESC if I used a h-bridge on the motor output I could make it reversible right?

Justin

Offline Rebelgium

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Re: Brushless motors
« Reply #4 on: February 15, 2008, 12:36:51 PM »
Thanks,
I did find http://www.horizonhobby.com/Products/Default.aspx?ProdID=LOSB9594 but at $50 each and I need two it is quite a lot. Why is it so hard to make the ESC reversible? For brushless all that needs to be done is change the way the pulses are sent. I can see why there are not very many brushed ESC that go in reverse as you need something like an h-bridge.

For the DIY ESC if I used a h-bridge on the motor output I could make it reversible right?

Justin

It's not that easy, where would you connect the four inputs of a H-bridge?
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Offline CommanderbobTopic starter

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Re: Brushless motors
« Reply #5 on: February 15, 2008, 12:55:07 PM »
I could connect it where the servo motor was. As the servo can go both ways using a h-bridge (if the servo drives the motor with +5v) will just increase the voltage and amperage so it could drive a larger motor. You could then uses the potentiometer to set the neutral position.

Justin

Offline hgordon

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Re: Brushless motors
« Reply #6 on: February 15, 2008, 02:20:21 PM »
Unless a brushless ESC specifically states that it will drive the motor in forward and reverse, it probably won't.  The ESC you flagged does not appear to drive in reverse.

There are a LOT of brushless ESC's on the market, and very few support foward/reverse.  Technically, there's no reason why not, as the microcontroller programming just needs to be changed to reverse the order in which the coils are switched.  However, brushless motors are mostly used on aircraft where there's no value in having a reverse rotation.

You'll probably also notice that brushless gearmotors are almost non-existent, so probably you won't find a gearbox with 100:1 reduction for a brushless motor.   Again, this is because aircraft use them for direct drive without gear reduction.
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Offline CommanderbobTopic starter

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Re: Brushless motors
« Reply #7 on: February 15, 2008, 04:36:24 PM »
Thanks for the reply.

I made my own double brushed ESC. I consists of the insides of two servos and one H-bridge driver from http://www.sparkfun.com/. It drives two motors in forward and reverse and require few changes to the servos. I tested it and it seems to work.

Justin
« Last Edit: February 16, 2008, 09:48:01 AM by Commanderbob »

Offline CommanderbobTopic starter

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Re: Brushless motors
« Reply #8 on: February 15, 2008, 06:27:39 PM »
Unless a brushless ESC specifically states that it will drive the motor in forward and reverse, it probably won't.  The ESC you flagged does not appear to drive in reverse.
The http://www.horizonhobby.com/Products/Default.aspx?ProdID=LOSB9594 ESC does drive the motor in reverse. It says in the manual.

Justin

Offline hgordon

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Re: Brushless motors
« Reply #9 on: February 16, 2008, 09:07:13 AM »
You're right.  That's not a bad price for the controller and motor combo.
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Offline CommanderbobTopic starter

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Re: Brushless motors
« Reply #10 on: February 16, 2008, 07:09:15 PM »
Well my home made ESC did not work too well. I think I will go and buy a 1/18 Losi RTR car and go from there. Some are only $100 with all electronics, radio and receiver (not needed), battery, brushed motor, ESC with reverse, servo for steering, suspension, and all nicely built.
Thanks for you help,
Justin