Re: 20 Amp 80 V $99 DC Servodrive

> I have a couple questions here, and maybe they are of general

interest

> so I will post them to the list.
>
> First, exactly what are you offering here? a pc board 'kit' or a

fully

> populated module ready to run?

The G320 is a finished and tested motor drive just like you would get
from any major drive mfg. It is in a black-anodised aluminum package
(not open frame), has a 4-layer PCB and uses surface mount components
wherever possible. It is the same size and shape as our G201
microstep drive ( See www.geckodrive.com ).

> With this board what else do I need to move a servo motor-

Obviously I

> need a motor, of less current draw than the board spec. I assume the
> motor needs an encoder wheel of some kind? does it need a tach

winding?

> any kind of encoder board needed?

You need a DC brush servomotor with a quadrature encoder mounted on
the back of the motor. If the encoder supply spec. is +5VDC at less
than 100 mA, the G320 will power it. No tach is necessary, the G320
derives PID signals directly from the encoder. The quadrature inputs
are "X4" decoded inside the G320.

> If I hooked up a couple of these directly in place of the step and
> direction stepper board I have now would that be a fully functional
> system?

Yes it would. You would have to "tune" the servodrive to your motor
however.

> What do I loose in running a servo in step and dir mode? I recall a

note

> here a while back knocking the JR Kerr PicServo in that mode as

being to

> slow. Is that true here, or what magic does your board do to

prevent it?

You lose all the drawbacks of a step motor, the vibration, low
maximum speed, heat, low power, etc. I am not familiar with the Kerr
drive; it may have been slow because of low power, small motor or a
high encoder line-count requiring step frequencies beyond the ability
of the computer. We will shortly have out a "X10" step pulse
multiplier version of our microstep drive. The same circuit can be
used in the G320. What is exciting is if a 1000 line encoder is used
with the "times 10" pulse multiplier, the servomotor would look just
like a half-step driven step motor. All speeds and distances would be
identical. Otherwise it would be like a 20 microstep drive.

> For motor selection I see lots of DC motors that look about the

right

> size and current draw in surplus sources. How would I choose one of
> these to run with this board? What if I wanted a small motor, maybe

only

> 1-2 amps?

If it is a brush DC servomotor mounted with a quadrature encoder, the
G320 will run it. There is no minimum motor size.

> Sop far all my CNC tinkering has been done with steppers because I

know

> how to use them, Id like to try a servo ssytem but have always been
> turned off by the complexity of it all. I hope this board is an

answer.

>
> ron