Re: Basic Servo Motor Question...

Mariss,

Thanks for the reply. What is a "quadrature" type encoder? How can I
tell if the surplus motor has it? The line count (if you mean number
of slots in the wheel) is about 500 from memory... it has very fine
slots on about a 3" wheel (from memory). I will take a picture or
two
of the motor/encoder and post them. I looked at post 9342 and have a
few questions... You give the following formula:

W=(1 – T/S)N*T/1351.8

What is the best way to measure torque applied (T) and stall torque
(S)? Is there a device to help me do this? I imagine no-load RPM is
the RPM rating on the motor.

How many watts should I shoot for when considering the sherline mill?

Thanks
- Dan


--- In CAD_CAM_EDM_DRO@egroups.com, "Mariss Freimanis"
<geckohall@h...> wrote:

> Dan,
>
> If you are planning to use a STEP and DIRECTION input DC servodrive
> then a tachometer is not necessary. It will derive all PID
> information from the encoder.
>
> It sounds like you have a good motor there. Make sure the encoder

is

> a "quadrature" type. What is the line count?
>
> Regards to what you can get out of the motor; please refer to

message

> #9342. It goes into a little detail on that subject.
>
> Mariss
>
>
> --- In CAD_CAM_EDM_DRO@egroups.com, djr@n... wrote:
> > I want to jump in head first in a CNC servo sherline mill
> conversion,
> > but I am really ignorant when it comes to DC servo motors and
> > drivers.
> >
> > I see that some servos have slotted encoder wheels with optical
> > detectors and/or tachs and/or brakes. I can see what the slotted
> > wheels and brakes do... the tell position and stop the thing, but
> > what
> > is the need for tachs? Can't you tell position AND speed with

the

> > optical detectors? What motor stats are important for me if I am
> > going to use a servo motor with the sherline? Does stall current

x

> > volts (watts) tell me something? What RPM range is good?
> >
> > I was browsing a local surplus store this past weekend ran across

a

> > servo motor with one of those slotted wheels and an optical
> detector
> > circuit board attached still in the anti-static wrap. It was

made

> by
> > Japan Servo and it's rated at 24v 3000 RPM. It is about 3" in
> > diameter and 5" long. I don't have any other data on it. How

can

> I
> > determine if this motor is a good candidate for the sherline? At
> 12
> > volts it really seems to have a good bit or torque.
> >
> > Thanks in advance for any answers... Pointers to "servo CNC

motors

> > and drivers for dummies" websites would also be great!
> >
> > Thanks
> > - Dan