Re: [CAD_CAM_EDM_DRO] Re: Brushless motors from models and such

After re-reading my discription of the standard R/C receiver output signal I
realize I did not describe it well enough. My bad.

Most modern R/C systems use PPM Pulse Position Modulation. Big name for
something that very simple.

_--_--_---_----______________________--_--_---_--________________________--

Bad ASCII art but this represents the pulse train of a 4 channel (control)
from a transmitter to a receiver.

The starts of three frames are shown The start pulse is the first rise after
the long low level signal. The frame is the length of time between the start
pulses. This is ususally 16 to 20 milliseconds in length.

The sync pause is the time the signal remains low after a group of pauses,
it allows the decoder in the receiver to reset and know that the next pulse
it receives will be the start of another frame. This is in the area of 6 to
10 milliseconds.

Note that the high pulse level varies in width, this is the data the servos
or speed controls use for control position.
The receiver decodes the above signal and sends the first pulse to the
ailrons, the second to the elevator, the third to the rudder and the fourth
to the throttle. These control signals (positive 5 volt) vary in width
controled by the transmitter sticks from 1 to 2 milliseconds with 1.5
milliseconds being neutral (controls centered)

In the second group of pulses the 4th channel throttle has changed so the
throttle servo or electronic speed control will alter the carb positin or
change the power level to the motor.

All you need to control a R/C servo or speed controller is a one chip pulse
generator that outputs a 5 volt positive pulse of 1 to 2 milliseconds every
15 to 20 milliseconds.

Loss of signal stops the pulses to the servos and they simply stay where
they were. Usually full throttle with down elevator, buying the farm at
100MPH <GRIN>

Google "servo stimulator" and you should find several circiuts that can be
built with $5.00 worth of parts from Radio Shack etc. Your local hobby shop
can probablyget you one for under $30.00.

They are so simple that most repair shops just build their own, some simple,
some fancy with digital readouts etc.

I have some circut boards from a servo tester design that I did in the '80
that I could build up just the servo pulser if that would help. Requires 5
volts DC and a 10 K pot for pulse with control.

Most electronic speed controllers have a 5 volt output circut that is used
to run the receiver and other servos so you would not need a seperate power
supply for the servo stimulator.

Hope this helps
Hugh

----- Original Message -----
From: "turbulatordude" <dave_mucha@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, September 04, 2005 3:34 AM
Subject: [CAD_CAM_EDM_DRO] Re: Brushless motors from models and such


> Thanks Hugh,
>
> It application would be for a high speed spindle.
>
> seems the current unit of choice is a dremel or similar.
>
> there is a desire to get away from brushed motors for the maintenance
> problem, even if the brushless is less powerful.
>
> I am still not sure about the ESC (electronic speed control) it seems
> that there is a radio receiver in the model and that will output
> something to the (throttle) motor.
>
> For servo's like flaps or alerions or even steering, the servo is a
> motor with gear box that moves about 90 degrees. it receives a steady
> 1,500 hz signal to remain at center, or 1,000 hz to move fully one
> way, or 2,000 hz to move fully the other way, or anything inbetween.
>
> What I have not been able to find is what siganl would be needed for
> the throttle.
>
> I do understand the motor needs 7 to 12 volts for POWER, but the
> SIGNAL is something different.
>
> the 15-20mS instruction time makes sense, with a 1-2mS command,
> possibly 20mS for full speed ? I would expect a 'not zero' signal to
> indicate zero speed.
>
> industrially, we use 4-20mA and have 4 to show we are connected, but
> have a zero value. a real zero means the wire is cut or there is no
> power.
>
> From the looks of things, the motor run in the $80 range and a 20 amp
> or more ESC runs close to $100.00
>
> It sounds a little pricey for a 35,000 RPM motor, but it appears there
> are not a lot of options for high speed motors.
>
> Dave
>
>
>
> Dave
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Hugh Prescott" <hugh345@a...>
> wrote:
> > I think the OP is looking to use a propulsion motor for a spindle drive.
> >
> > The hobby industry is presently experiencing rapid growth in
> brushless DC
> > motors and controlers.
> >
> > Basically they are a VFD and 3phase motor. DC input 7.2 to ??? volts
> input
> > and require a 15 - 20 MS repeating 1 - 2 MS positive pulse from the
> radio
> > system throttle channel.
> >
> > No reason they would not make a good spindle drive motor for a small
> > drilling or milling system as in PCB work.
> >
> > As far as using the motor and speed controller for positioning I
> think not.
> > No feedback capability and way to course control.
> >
> > Hugh
> > Hobby shop owner/ hobby electronics electroinc tech.
> > Always willing to answer questions
> >
> >
> > ----- Original Message -----
> > From: <r@...>
> > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > Sent: Saturday, September 03, 2005 5:10 PM
> > Subject: RE: [CAD_CAM_EDM_DRO] Brushless motors from models and such
> >
> >
> > > Try googling for "hacking servos". It's a fairly popular activity for
> > > the robotics folks to remove the travel stops on RC servos and use
> them
> > > as motors.
> > >
> > > -----Original Message-----
> > > From: CAD_CAM_EDM_DRO@yahoogroups.com
> > > [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of turbulatordude
> > > Sent: Saturday, September 03, 2005 12:29 PM
> > > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > > Subject: [CAD_CAM_EDM_DRO] Brushless motors from models and such
> > >
> > > Hi all,
> > >
> > > I have been trying to find information on these small hobby motors and
> > > have come up pretty empty.
> > >
> > > It seems there is not listing or charts that show what sizes are
> > > available, surprizing that I didn't find manufacturers with such data.
> > >
> > > Also, I have not found the electronical link between the
> controllers and
> > > the R/C receiver. One guy at tech suppport said he thought it was
> > > 0-5 volts, but was not sure.
> > >
> > > Does anyone know of any hobby lists or other sources of
> information were
> > > the guys would actually know how the parts work ? it seems the whole
> > > hobby is orienteated towards using the toys and not engineering them.
> > > (just opposite of this list)
> > >
> > > Dave
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Addresses:
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> > > http://groups.yahoo.com/group/jobshophomeshop I consider this to
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> > sister site to the CCED group, as many of the same members are
> there, for OT
> > subjects, that are not allowed on the CCED list.
> > >
> > > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING
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timg@...
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[Moderators]
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>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
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>
> Yahoo! Groups Links
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