Re: Re: pic-servo & EMC

Thanks for the comments.

The Pic Servo is a 2" x 3" board with a custom programmed Pic chip running
the PID loop and another dedicated pic chip to read the encoders and feed
that info to the first chip. It talks only with a RS485 serial connection
using a simple binary protocol. It outputs a 20 Khz PWM pulse and a
direction signal line. There is a variant that I am trying to use that fools
a stepper into thinking it is a brushless DC motor. The board including a 5
amp amplifier is 170 bucks. Combine that with a stepper motor and encoder it
looks an effective way to run an axis if software were available to control
it.

At this point it sure looks more straightforward to use Dan Mauch's stepper
controller and potentially close the loop with the DRO board project.

----- Original Message -----
From: Fred Proctor <proctor@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Monday, July 19, 1999 3:05 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: pic-servo & EMC


> From: Fred Proctor <proctor@...>
>
> Andrew Werby and Andy Olney were discussing the PIC-Servo and using it
> in place of the Servo To Go board for the EMC. I have been referring to
> the STG board as a "dumb" IO card since it has no CPU or other chips
> that do any calculations. It's just a board with an ISA bus interface to
> digital-to-analog converters, encoder quadrature counters, and some
> digital IO. It doesn't do any PID calculations, trajectory planning,
> etc. like full-featured motion control boards (e.g., Delta Tau PMAC,
> Galil DMC-1000).
>
> The PIC-Servo sounds like it does what the STG board does, plus some
> servo calculations. Some boards are in this category, where they use a
> small chip for the PID calculations. This puts it in the "smarter"
> category, but it still lacks the full-blown motion control of the Delta
> Tau or Galil.
>
> One easy way to use the PIC-Servo is to simply read its encoder counter
> and write its DACs, bypassing any calculations. If the PIC-Servo only
> has a serial interface this can get messy. I haven't done any serial
> port programming in RT-Linux, but others have.
>
> --Fred
>
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