Re: Brushless Motor Spindle with CNC desktop machine

If Mach has a Modicon output, that is a serial output and could tell a
PIC what to do. then the PIC just sits there happily.

Dave


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Alan Marconett" <KM6VV@a...>
wrote:

> Hi Richard,
> Cc Dave,
>
> The RF format follows the "servo" format used in the R/C world. A PWM
> signal designed to control an R/C servo. The pulse width varies

around a

> center of 1.5 mS (.5 - 2mS), and the pulse is repeated at a 20 mS rate.
> There are PIC controllers to run R/C servos that can do this. The robot
> guys use 'em all the time.
>
> It would be difficult to control this R/C servo with Gcode, unless

it was

> the only thing the controller did! A special PWM signal (which

would have

> to run continuous) would be needed.
>
> A PIC controller could be devised to take step/dir signals and ramp

up/down

> a continuous PWM signal (1 "slot" in about 10). In this case, the CNC
> controller would generate an "up" direction and a few pulses to set the
> speed to the desired level.
>
> I like the idea of the high speed R/C spindle, just what I need for PCB
> work. I take it I can look for an "AXi 2826/10" motor at my local hobby
> store? How much?
>
> "continuous pulses" That's an oxymoron! The pulses are no doubt TTL

(.5V

> low, 4.5V hi) signals of sorts, it's the generation of them that is

a little

> more complex. And this stream of pulses doesn't start/stop like the

axis

> moves do. The "1 in 10" may be thought of as "time slots", if one were
> running 10 channels of servos (!), then the time allotted to one

servo would

> be similar to what's being described.
>
> Chuck, an old friend of mine from the "Homebrew Robotics club" (Silicon
> Valley, circa '86) has a good write up.
>
> http://www.mcmanis.com/chuck/robotics/projects/servo.html
>
> Humm... That's a good circuit for an H-bridge, if the FETs are big

enough,

> (or half an H-bridge) ...could drive your motor. And the PIC code

could

> be modified to take an occasional step/dir command to set the spindle
> speed. COOL!
>
> Alan KM6VV
>
>
> > Subject: [CAD_CAM_EDM_DRO] Brushless Motor Spindle with CNC desktop
> > machine
> >
> > hey everyone,
> > I am building a small desktop 3D milling machine and needed a
> > brushless motor for the main spindle. I got sick up and fed of
> > changing brushes on the prototype I built, and a brushless motor will
> > also be much quieter for indoor use and last a whole lot longer.
> > I purchased a model aeroplane motor - AXi 2826/10 motor (rotating
> > outer housing for better torque and the rotor doesn't throw off it's
> > windings) with an "easy 25" 25amp controller and I need to know how
> > the controller signals are sent from the RF module to the controler
> > and the type of pulses. In the "easy 25" instructions it lists
> > positive pulses at 1.5 ms with a period of 10 - 30 ms. What voltage
> > would these be. "3v - 5v"? and are they continuous pulses. If this is
> > the case then I think it would (maybe)be a case of programming the
> > software to use the 4th axis as the speed controller and inputing the
> > appropriate commands into the G-Code
> > These motors spin around the 10K-20K revs at 12V(and faster) and pull
> > up to 40 amps so the power is there for a small Miller but I am not
> > sure how they would react to a filtered DC power supply with the BEC
> > (Battery Economiser Circuit).
> > The best case scenario would be to just have a switch to turn the
> > thing on and off and if anyone out there has a way of doing this
> > (small circuit board with a pulse module?) then that would be great if
> > they could contact me about doing this or better still post here.
> > If anyone else has any ideas Idea about controlling a brushless motor
> > with a CNC spindle then I will be forever, eternally greatful if you
> > could let me know how you can do this.
> > I haven't found anyone else doing this sort of thing with radio
> > controlled stuff on CNC machines so maybe this will be a first and if
> > it works the we can tell all the other CNC people out there how to do
> > it and I know they will be greatful as brushed motors just aren't
> > cutting it when it comes to running a CNC/engraving job for 9 hours at
> > a time. The brushes wear out after a very short period of time and
> > usually halfway through a job and I know you can all sympathise

with this.

> > Please help.
> > Warm regards
> > Richard.
> >