Re: Single Servo circuit / computer&touch panel combo

[Doug Fortune <pentam-at-home.com>]

Jon Elson wrote:

> > >From what I have read on CAD_CAM_EDM_DRO list, Jon Elson
> > is very close to having this done.
>
> Yes, the hardware IS done!  I'm just waiting for the PC boards to come
> back from the fabricator.  I also need to design a motherboard for the
> individual boards to plug into and get that made.

Good work Jon!

> Now, this only goes from encoders to a +/- 10 V servo velocity command.
> I think what the originator of this thread was interested in was a
> complete digital PWM servo drive, which would get rid of all that nasty analog
> circuitry.  I'm not sure that is practical at low cost.  You will need
> to have an ADC reading motor current at a pretty high rate, and something
> to do servo loop calculations and set the desired pulse width.
> I do this 100,000 times a second (in other words, on every pulse).
> It obviously isn't practical to have the main CPU handle it at this rate.

<Jon, see the reference to an embedded PWM in the computer below>

I'd like to mention I've been looking for a combination industrial
color touch sensitive screen and IBM PC motherboard, obviously to
use EMC as a replacement for an original toasted CNC controller.

I have come across a really REALLY nice unit at:
http://www.zflinux.com/netdisplay.html

which has a host of features to drool over:

The ZF netDisplay  5MX OEM Flat-Panel Computer is a complete,
ready-to-run, 180MHz Pentium-class PC  (also a 486/100 version)
with a color LCD and touch-screen in a compact form factor,
ideal for a wide range of OEM applications. The netDisplay
offers 100% desktop computer functionality in a rugged,  easily
integrated package just over 2 inches deep and weighing only 2 pounds.

The ZF netDisplay is available with a 12.1" or 15.1"  active matrix
color LCD. A high reliability, advanced technology 4K x 4K matrix
touchscreen is included.

The netDisplay boots into DOS straight out of the box.   The net-Display
is certified to run many other popular operating systems including
Linux,  Microsoft® Windows® 3.1, 9x, NT, CE, Phar Lap's TNT
Embedded ToolSuite®,  Microware OS-9, and Sun Embedded Java.
Specifically, there is a Linux development kit!

It has 6 serial ports (one can be RS485),  1 parallel port,  2 USB ports,
10/100 ethernet, PCI or PC104 expansion slots, a CompactFlash socket,
IDE/floppy, KB, and soundblaster (for that all-important drown-out-the-noisy-machine  rock
music).

It also has an additional 12 TTL I/O bits which will be very handy.

I know this sounds expensive, but they claim "When your design calls
for a flat-panel PC, turn to netDisplay, the industry's fastest, most
cost-effective  path to embedded touch-screen computing."

 - - -

It is interesting that Jon mentions the need for PWM, and that if the
above computer is based on the MachZ (their base chip) then it would
seem to include (at least one)  onboard programmable 100 Khz PWM.
http://www.zflinux.com/machz_specs.html

Maybe it might not be programmable fast enough for motion servo
motors, but it might be good enough to use to control the spindle
motor (for constant surface speed machining in a cnc Lathe application).

At the current time, it looks like I will like to try Mariss' Geckodrive G340
modules (parallel port step and direction to DC servo) http://www.geckodrive.com
for the X, Z, and turret motors,  but I have to find a solution to drive
the big 30 HP  spindle motor (ie a single one of Jon's drivers), and just
maybe the embedded PWM is good enough for that (ie maintaining an
exact constant speed for threading, and varying the spindle speed for
CSS machining).  Hope this explanation makes sense!

Doug Fortune