Re: [CAD_CAM_EDM_DRO] Re: DC motor controller

John,

See the "CW" for rotation on the motor tag? That means it's intended to spin only one direction. Possibly the brushes are mounted angular or offset to the shaft allowing only one direction of rotation. If thats the case it will not work, for long anyway.

For a while on Ebay, not sure if they are still available, "Silicon Salvage" had the Ametek type DC motors for like 20 a piece. They are 40 volt and about 10 or 12 amps peak if I remember correctly. Search for "DC motor" leave "servo" out of the search or they start adding zero's to the prices :-) They look exactly like the Ametek servos folks sell, they are probably the same thing.

Ron



John Hansford <kz1927@...> wrote:
Hi Jesse,

I hook it up to an 18v Dewalt battery..about 1/2 dead.
It turns probably 800 rpm. If I load it(with my hand) and with what
you say in mind, I can feel a pulsing. I wouldn't notice it if
I weren't looking for it.

As far as using them a servo motors...can this be "ironed-out" to
a degree with the timing belts? I would guess it could but I'm
in uncharted territory on this subject.

So I'd want to run if fast and gear it down.

It's not gonna break my heart too badly if they're not excellent
servos, I'd get some real ones later on, but how BAD could they
be as servos??? Mediocre? Practically unusable?

I have to be able to cut out basically simple shapes in MDF or
plastic on a homemade machine without losing steps and waiting
all day to use several passes to cut thru.

Even though it's kind of embarrassing (I know many of you use real
machines) I'll let you see what it looks like.

http://www.flickr.com/photos/26361144@N00/

Hey, it's a Test Machine! :)

John

--- In CAD_CAM_EDM_DRO@yahoogroups.com, jesse Brennan <jkbrennan@...>
wrote:

>
> A lot of people are using these-- The control system is an scr one
> not filtered .. It is not a pulse width modulation one.
>
> Nothing is wrong with it and it has been made by an excellent
> supplier.. Treadmill motors are a mixed bag . Some are fairly
> good others are not.
>
> They do have limitations as they are designed to be high speed
> units. If run at slower speeds you may (probably will ) see
> cogging.
>
> A cogging Or detenting motor is having problems with torque
> fluctuations. It acts like motor is running in a gear train where
> you can see the motor fluctuating from gear tooth to gear tooth..
> Detenting is another way of describing the same thing and may be a
> little easier to visualize. --the motor is driving a wheel with a
> spring loaded plunger against a mating wheel with a detent in it .
> when they engage the drive slows and the motor has to develop more
> torque to proceed. so it pulses. It ends up looking mechanical but
> is really electrical in origin. There are ways of designing this
> out and reducing the effect but the threadmill motors are not
> built this way.
>
> To learn a lot about motors go to the Bodine site and download
> their handbook. Bodine makes SUPERIOR small motors. www.bodine-
> electric.com/Handbook/
>
> I buy stuff from surplus center too.
> jesse

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