Author Topic: Running a brushless motor w/o RC  (Read 7213 times)

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Offline gamefreakTopic starter

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Running a brushless motor w/o RC
« on: April 25, 2010, 07:28:09 PM »
For my current project I need to run a brushless motor at full speed and have no idea how to do this.
A little research shows that the motor controllers take PWM to control the motor and from my understanding of that simply holding the input high should by 100% but that does not work, any ideas?
« Last Edit: April 25, 2010, 07:34:18 PM by gamefreak »
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Offline corrado33

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Re: Running a brushless motor w/o RC
« Reply #1 on: April 25, 2010, 07:54:34 PM »
Do PWM signals with a duty cycle less than 100% work?  If not, I'd think it's something wrong with the controller, or with your signal.

Offline gamefreakTopic starter

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Re: Running a brushless motor w/o RC
« Reply #2 on: April 25, 2010, 09:15:21 PM »
If I hook it up to a standard radio receiver I can run it just fine. I notice that it makes a beep when I hook it up to the RC receiver and then turn on the transmitter so I am guessing there is something else going on.
« Last Edit: April 25, 2010, 09:27:26 PM by gamefreak »
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Offline Razor Concepts

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Re: Running a brushless motor w/o RC
« Reply #3 on: April 25, 2010, 09:37:52 PM »
It is not PWM in the sense of 100% is on and 0% is off:
« Last Edit: April 25, 2010, 09:39:09 PM by Razor Concepts »

Offline Soeren

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Re: Running a brushless motor w/o RC
« Reply #4 on: April 25, 2010, 09:51:11 PM »
Hi,

If I hook it up to a standard radio receiver I can run it just fine. I notice that it makes a beep when I hook it up to the RC receiver and then turn on the transmitter so I am guessing there is something else going on.
Sounds like you have an ESC on it. Which is it (make and model)?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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Offline corrado33

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Re: Running a brushless motor w/o RC
« Reply #5 on: April 25, 2010, 10:01:54 PM »
Hi,
Sounds like you have an ESC on it. Which is it (make and model)?

Electronic speed controller?  I'm just making sure. 

Offline Soeren

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Re: Running a brushless motor w/o RC
« Reply #6 on: April 25, 2010, 10:15:35 PM »
Hi,

Electronic speed controller?  I'm just making sure. 
Yes.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline dunk

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Re: Running a brushless motor w/o RC
« Reply #7 on: April 26, 2010, 04:01:24 AM »
as Razor says,
RC pulses are not simple PWM signals. you still need to generate a pulse every 20ms or so.

use a pair of ne555 to generate a 2ms pulse every 20ms.


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Offline gamefreakTopic starter

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Re: Running a brushless motor w/o RC
« Reply #8 on: April 26, 2010, 05:45:48 AM »
It is a Power Up 20A ESC with a 2A BEC, meant for Lipo 2-3 cells or NiMh 5-10 cells, there is no more info written on it.

I guessed I would have to use a 555 timer but I was hoping for an easier solution, in any case i'll hunt through my stuff for a couple 555 timers and see if I can get it to work.
All hail Rodney, the holy 555 timer
And Steve said: "Let there be lead!"

Offline Soeren

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Re: Running a brushless motor w/o RC
« Reply #9 on: April 26, 2010, 06:04:42 AM »
Hi,

use a pair of ne555 to generate a 2ms pulse every 20ms.
A single 555 should do.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline gamefreakTopic starter

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Re: Running a brushless motor w/o RC
« Reply #10 on: April 26, 2010, 07:13:00 AM »
Alright now the other question I had is: Does the Battery Elimination Circuit(BEC) regulate power and can I use it to power the 555 and control the motor?

I am guessing that it would since too much power would blow those expensive RC rigs and a quick google search confirms but RC is not my friend and I can not test anything until at least 8 hours from now(curse you school, always preventing me from learning....).

The schematic floating around my head is basically the batteries hooked up to the ESC with the wire meant for the RC receiver heading towards a PCB with a 555 timer on it designed to output (as close as possible)a full on PWM signal.
Unfortunately I also have the vision of this thing suddenly jumping to life and tearing itself apart from the sudden jump in speed. Is there any way to make it start slow and after a few second reach top speed and sit there?
All hail Rodney, the holy 555 timer
And Steve said: "Let there be lead!"

Offline Razor Concepts

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Re: Running a brushless motor w/o RC
« Reply #11 on: April 26, 2010, 09:38:09 AM »
BEC output provides a regulated 5v at 1 to 2 amps

Offline dunk

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Re: Running a brushless motor w/o RC
« Reply #12 on: April 26, 2010, 10:35:00 AM »
I guessed I would have to use a 555 timer but I was hoping for an easier solution, in any case i'll hunt through my stuff for a couple 555 timers and see if I can get it to work.
if you want simpler than that have you considered ditching the brushless motor and using a DC motor instead?

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Offline gamefreakTopic starter

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Re: Running a brushless motor w/o RC
« Reply #13 on: April 26, 2010, 11:04:19 AM »
Well a plain old DC motor is electrically friendly, I never quite got the concept of couplers down. Couple that(hehe, its a pun) with low torque and 20k+ RPM +/- 12% I am not a fan. The BLDC motor has a threaded shaft and gets about 1000 RPM/V, it also has more torque and is more mechanically friendly then the ordinary motors. It is just a matter of getting the electronics to work...
« Last Edit: April 26, 2010, 11:34:20 AM by gamefreak »
All hail Rodney, the holy 555 timer
And Steve said: "Let there be lead!"

Offline Razor Concepts

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Re: Running a brushless motor w/o RC
« Reply #14 on: April 26, 2010, 03:06:29 PM »
This circuit works great, I've tried it:


Offline Soeren

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Re: Running a brushless motor w/o RC
« Reply #15 on: April 26, 2010, 03:57:13 PM »
Hi,

Alright now the other question I had is: Does the Battery Elimination Circuit(BEC) regulate power and can I use it to power the 555 and control the motor?
Yes to both counts.


The schematic floating around my head is basically the batteries hooked up to the ESC with the wire meant for the RC receiver heading towards a PCB with a 555 timer on it designed to output (as close as possible)a full on PWM signal.
Does the manual say anything on the length of a full signal (it varies a bit depending on manufacture).


Unfortunately I also have the vision of this thing suddenly jumping to life and tearing itself apart from the sudden jump in speed. Is there any way to make it start slow and after a few second reach top speed and sit there?
The easy way to do that would be to make the signal in a small controller, that way you can program any curve you want.
In a 555 it would need some extra work and just toying with the control voltage input would change both the pulse and the pause, so won't do, while in controller it's a piece of cake.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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