Re: Stepper program w/Encoders?

On 2 Dec, CAD_CAM_EDM_DRO@onelist.com wrote:

> Message: 6
> Date: Wed, 1 Dec 1999 10:58:52 -0700
> From: "Tim Goldstein" <timg@...>
> Subject: Stepper program w/Encoders?
>
> I seem to remember someone mentioning a stepper controller program that
> would support encoder feedback for a closed loop, but don't remember what
> the program was. Does anyone remember which program supports this
> functionality and the URL for it?
>
> Thanks,
> Tim

Tim;

I'm attempting to do this in hardware.

This counter that I'm sending to you ( this weekend, all going well )
is actually the first rev of a project to close the loop in hardware.

Being too cheap to spend the money on ballscrews and being an
electronics kinda guy and NOT a machinist, I've trying to produce an
electronic solution.

Here's what my gizmo will do.

It accepts input from a positioning device. Currently I'm struggling
with getting zero-lash rotary devices. ( I'm about to have some 1000
line linear films made up and give up on the rotary idea ) The device
happens to display the current position; that is, the gizmo is a DRO.

However, it also accepts step and direction inputs AND OUTPUTS step and
direction signals. It has one other output I call "pause".

The gizmo normally acts as a conventional DRO, while at the same time
looks for step signals. When it sees a step input, it outputs a step
AND THEN WATCHES THE DRO TO SEE IF SOMETHING ACTUALLY HAPPENED. If no
movement occurred ( i.e., backlash ), PAUSE is asserted, stopping the
CNC software and additional step commands are issued by the gizmo until
movement DOES occur. Pause is then released and normal CNC operation
continues.

( CNCPro now accepts this "pause" input, although I haven't actually
purchased a copy yet, as I'm not quite ready to use it. I certainly
will once all IS ready to go, though )

This device is somewhere between breadboard and installation. As I
said, I'm still twiddling with the DRO, still twiddling with my stepper
controller ( adding microstepping to the current half/full step ) and
still finishing the new shop that the machines live in ( if a 7x11 room
can be called a shop .. cave is a bit more appropriate ).

It's taking a while longer than planned, as I have a small electronics
design business as well as my normal 9-5 and people just won't leave me
alone ! Normally, this is good cuz the business pays for my toys, but
now I want some time to PLAY with my toys, darnit !

Also, there is likely to be some finetuning of the software in the
microcontroller, specifically to do with timing. ( How long should we
wait after a step before deciding that more steps are required and how
quickly should we issue those steps and at what rate. Smoothness as
it affects surface finish is less of an issue here, thankfully, as the
cutter isn't actually moving as a result of these extra steps. )

Anyway, your counter-tach is soon on the way.

Alan

--

Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta