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Controlling a Brushless Motor without a Radio System? - 12/15/2012 7:47 AM   
Matt_M


 

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Status: offline 		I have a project I am working on for a company, and you could call it a form of integrated robotics, long story short, I have decided that brushless R/C 380-400 size motors are going to work best for what the prototype consists of, for the duty the motor is performing.

I will be powering different brushless motors off a Sky R/C EFuel 1200W AC->DC 15-24V, 60 amp power inverter.

This is a bench setup and although I have R/C TXs, in the final prototype I must: be able to modulate, setup, and run, all through the MOTOR/ESC system. So I need some sort of throttle signal generator. The cost does not matter. We just need a way to manipulate brushless motors on a benchtop, and control their I/O in something like 5-10% throttle increments. We basically need a lot of power in a narrow place, and this is where R/C motors shine, they are high output for their size, and very little to wear under clean room conditions besides bearings.

I know the power supply gives a second level of voltage modulation, but this project requires user hand input to turn on the motor(s) without actually producing any radio waves or ever requiring a TX to emit a starting signal. The end goal is to have a hand control where quick speed-up/slow-down can be set and locked, and the motor spins until an /off/ button is flipped or pushed to kill the motor.

Can you guys guide me here? It is much appreciated. Thank you

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 8:15 AM   
perttime



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Status: online 		Google "Servo tester"

That should find you information about circuits that can drive a servo or ESC.

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 9:12 AM   
SBOT


 

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Status: offline 		The servo testers I am familar with just put out a pulsed signal I don't think that is what you need. It could be easily done with a microcontroller; an embeded system. I play around with Parallax's "Basic Stamp" , but the "Propeller" ,"Adrino"(sp), or any of the others could be easily set up to do what you want with a very simple circuit. The work would be in writing the program. Not difficult or hard; in fact most people involved with these chips do it for fun, and there are many pages and forums to help on line. Try a search for one of these and you will see how powerfull they are.

O

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 2:12 PM   
guver


 

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Status: offline 		I just use one of those real cheap manual servo testers too. It works nice for "bench testing" Have to use the ESC too of course. HK sells them , but the digital ones might be jittery. I like the manual knob one (without display)

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 6:03 PM   
SBOT


 

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Status: offline 		A servo tester will run a brushless motor? I thought a brushless needs a three tired timed current. Never knew a servo tester was capable of that.

O

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 7:14 PM   
guver


 

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Status: offline 		Have to use the esc too.

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 7:47 PM   
perttime



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quote:

ORIGINAL: SBOT

A servo tester will run a brushless motor? I thought a brushless needs a three tired timed current. Never knew a servo tester was capable of that.

O
No.
If a servo tester can run a servo, what is stopping it from running an ESC?


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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 10:56 PM   
SBOT


 

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Status: offline 		Different requirments. The sevro just needs a single pulsed current. While a brushless motor needs three separate currents timed to keep the rotor, or can revolving around the stator. If you are using the ESC I don't see where you would need the servo tester also. Besides I'm not sure a servo tester would meet the needs of the ESC.

O

Excuse me all! I stand corrected, just tried it, and my servo tester does in fact run a brushless motor. My servo tester has a manual, netrual, and auto function,and as you would assume manuel runs the motor from zero to "more" rpms as you twist the dial. Netrual runs at a steady rate, and auto runs foward,stop,and backwards. So If this will fill the OP needs there you go. And my apologies for doubting the posters who advised the use of a servo tester.

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 11:16 PM   
opjose



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Status: online 		Matt.

Head over to the control line section.

Those guys face this problem all the time and have numerous solutions for NON-RC control of an brushless motor requiring an ESC.



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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 11:21 PM   
SBOT


 

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Status: offline 		Now on another note. The battery supplies the power and the servo tester is just acting as a switch. The ESC is running the motor. There are much better switches available than servo testers

O

That's it that is all you need motor,esc,battery, and a switch to control it. The fancyier the switch the more control you will have.

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RE: Controlling a Brushless Motor without a Radio System? - 12/15/2012 11:48 PM   
JeffinTD


 

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Status: offline 		I don't think the ESC is going to respond to a switch. It is looking for a pwm throttle signal.

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RE: Controlling a Brushless Motor without a Radio System? - 12/16/2012 4:33 AM   
OliverJacob


 

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Status: offline 		The servo tester would be the cheapest and easiest choice.
You can use y-cables to multiply the signal, if you want to run different esc.
You got to keep in mind that most speed controllers want to see a 0 reference upon startup (means you have to put the throttle stick to idle to initiate the esc).

As mentioned, HK has a good selection and they are inexpensive and functional:

http://www.hobbyking.com/hobbyking/store/__470__189__Servos_and_parts-Servo_Tester.html

With this setup you can easily add a plc to this, using an analog output and replace it with the tester's potentiometer.



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RE: Controlling a Brushless Motor without a Radio System? - 12/16/2012 4:39 AM   
mlj3



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Status: offline 		Vintage High Sky on -off controller. Anyone used one of these back in the day,Would it work ?? I have a few...

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RE: Controlling a Brushless Motor without a Radio System? - 12/16/2012 6:15 AM   
fredscz


 

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Status: offline 		I have actualy used one of the $5.99 servo testers shown in the above hobby king link to run a brushless moter using the esc and it worked fine.
Fred

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RE: Controlling a Brushless Motor without a Radio System? - 12/16/2012 8:01 AM   
SBOT


 

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Status: offline 		Once again the servo tester is not running the motor the ESC is. The servo tester is just turning the current on and off. @ JeffinTD
Quote "I don't think the ESC is going to respond to a switch. It is looking for a pwm throttle signal" It is not responding to the switch it is responding to the ESC. If the servo tester was running the motor you would not need the ESC.

O

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RE: Controlling a Brushless Motor without a Radio System? - 12/16/2012 8:15 AM   
OliverJacob


 

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Status: offline 		...the ESC is looking for a pwm signal, no switch works here. The op also stated that he wants to be able to control the motor speed. The speed controller with a simulated receiver signal (servo tester) will do this.



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RE: Controlling a Brushless Motor without a Radio System? - 12/16/2012 9:11 AM   
perttime



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Status: online 		This thread has been getting a bit complicated. Let's see if I can sum it up?

You need:

Brushless motor
Brushless ESC to run the motor
Servo tester, or something similar to run the ESC
Suitable power source

The brushless motor needs the brushless ESC. The motor is too dumb to work without the smart controller.
The Brushless ESC needs a signal, before it will do anything. The servo tester will do that, in absence of a R/C receiver.

Of course, all the components will need to be in proportion to whatever power requirements there are.

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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 1:29 AM   
Rob2160



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As perttime posted... that is all you need...

These items will power virtually any hobby sized brushless motor...

ESC http://www.hobbyking.com/hobbyking/store/__2166__TURNIGY_Plush_60amp_Speed_Controller.html

2 wires (black and red) to your DC source.. Polarity is critical or you will blow your ESC.. Red wire  to +ve

3 wires (all red as above or sometimes, Red Blue Black) to the Brushless motor.. if your motor runs backwards, reverse any two of the wires.

SERVO Tester..   I have this one and it works perfectly. I use it to test all my heli brushless motors before installation

http://www.hobbyking.com/hobbyking/store/__8296__Turnigy_Servo_Tester.html

A power source...  Noted you are using a 1200W inverter... that should be plenty... the ESC "should" will automatically sense the voltage..

I say should because I don't know enough about the actually workings of the ESC but when you use Lipo Batteries the ESC sense how many volts IE how many cells (S) and beeps accordingly..

IE.. a 3S battery will make the ESC beep 3 times during initialisation...   4S will beep 4 times etc.. this is just an aural confirmation so you know it is sensing the battery correctly..

How it will respond to a 15-24V DC input is unknown to me.. but I assume it will figure something out..

If using this power source I would turn off the low voltage protection in the ESC.. (most are easily programmed)

The low voltage sensing is a function of how many cells it detects and the input voltage.. IE  a 3S battery, dropping to 9 Volts etc will shut off the ESC..

Again, not sure how it will respond to the DC inverter.. but turning off the low voltage sensing should help..

Hope that all makes sense and helps..



< Message edited by Rob2160 -- 12/17/2012 2:41 AM >

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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 2:56 AM   
JeffinTD


 

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quote:

ORIGINAL: SBOT

Once again the servo tester is not running the motor the ESC is. The servo tester is just turning the current on and off. @ JeffinTD
Quote ''I don't think the ESC is going to respond to a switch. It is looking for a pwm throttle signal'' It is not responding to the switch it is responding to the ESC. If the servo tester was running the motor you would not need the ESC.

O


You totally missed my point.

The ESC runs the motor, but it needs a pulse width modulated throttle signal or the ESC will not arm and will not start the motor.

A switch hooked to the ESC, a motor and battery will not run, because a switch does not produce a pwm signal.

Normally the reciever generates the pwm signal in proportion to throttle stick position, and the ESC reads that signal and sends power to the motor in proportion.

With no receiver, something needs to provide a pulse width signal to the servo lead on the ESC, and that is why the servo tester is needed.


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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 3:21 AM   
OliverJacob


 

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Status: offline 		I think everybody except of one guy agrees with this.
This is RCU and one will always disagree, no matter what the subject is. So this is a pretty good discussion.

And I'd say that the op's question has been answered in the first response, so he probably works on his project already.

I'd just like to add that the ESCs and motors were designed to run a few minutes at max load, heat can become a problem with continous run times.
Also I'd make sure I don't run the components near their limits.




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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 6:31 AM   
JeffinTD


 

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Status: offline 		Another consideration is that airplane ESC's and brushless motors are designed to be cooled by airflow. Perhaps a car ESC, which often include a cooling fan, might be worth considering.

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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 5:44 PM   
Matt_M


 

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Status: offline 		First, thank you guys for answering and debating over this.

I sort of pointed it out if you read my post;

quote:

ORIGINAL: Matt_M



"This is a bench setup and although I have R/C TXs, in the final prototype I must: be able to modulate, setup, and run, all through the MOTOR/ESC system. So I need some sort of throttle signal generator."

"We just need a way to manipulate brushless motors on a benchtop, and control their I/O in something like 5-10% throttle increments. We basically need a lot of power in a narrow place, and this is where R/C motors shine, they are high output for their size, and very little to wear under clean room conditions besides bearings.

I know the power supply gives a second level of voltage modulation, but this project requires user hand input to turn on the motor(s) without actually producing any radio waves or ever requiring a TX to emit a starting signal. The end goal is to have a hand control where quick speed-up/slow-down can be set and locked, and the motor spins until an /off/ button is flipped or pushed to kill the motor."



I knew there had to be something that emits a specific pulse value to control servos and ESCs, I just had no clue what, on an R/C website, I would be searching for as a term. The link to hobbyking was perfect. We are purchasing 3 different modelswith analog knobsjust in case any do not work with our speed control as well as we want it to.

Now about the cooling. First off, I appreciate you looking out for me with that because I understand heat buildup is a condition of motor efficiency, voltage x amps (watts) running through the motor, load/friction of the motor, and it's ability to evacuate heatbut I am not sure about it getting hot, as loads are low. So I took that into consideration. I have bought 3 motors...well they are in the cart anyways as I type. I'm ordering an Inrunner that's 2000Kv(400W), A short Heli outrunner (250W), and a boat motor with liquid cooling (600W). The problem I'm having is I need very low Kv, like 500-750KV would be spectacular, if it would work in a maximum motor can OD of around 28mm. That's nearly non-existent from what I've seen.




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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 6:23 PM   
JeffinTD


 

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Status: offline 		Can you use a gear reduction? With brushless motors and ESC the more load you put on the motor at a given voltage the more current it will pull.

You might consider purchasing a power meter. These plug temporarily between the battery and ESC and let you see volts, amps, watts. As long as you are under the specs of the motor, ESC and battery...

With less cooling airflow, it is best to have a wider safety margin.

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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 7:16 PM   
opjose



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Status: online 		Control Line guys face this stuff all the time....

See: Click me!

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RE: Controlling a Brushless Motor without a Radio System? - 12/17/2012 10:48 PM   
kenh3497



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Status: offline 		There are a few cordless tools (chain saws, string trimmers, blowers) out there now that run brushless motors. I know the Stihl line, for sure, uses brushless. They are 36 volts though. As a thought could their speed control be adapted for use. All you would need is the battery and speed control. I don't know about Oregon or the other brands.

OK never mind..... I just did a quick search of the Stihl parts catalog. I found a P/N for the control module but there is no price. I'm guessing it is a call for warranty replacement only. I work at a Stihl dealer and so far have no experience with the cordless parducts.

Now on the other hand if one of the electronics gurus could maybe figure out the proper parts and pieces this could be fabricated.........

Ken

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