Re: RS 232 Output for DRO...closed-loop feedback?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "p0p0k0pf" <p0p0k0pf@a...>
wrote:

> I just ordered a CBX 3-axis DRO from Star Techno for my Shoptask
> Lathe/Mill. They offer an RS232 output for positioning feedback,
> and I bought it.
>
> I would like to know if anyone offers a CNC program that uses these
> outputs for absolute positioning info provided by the dro scales

for

> CNC.

I have the same unit on my fullsized Gorton mill. I did not buy the
RS232 otpion but I made sure that the encoders inside the sender
units were standard quadrature units. I got the RJ11 pinout from SS
and plan on tapping in to the basic encoder signal and feed it to the
encoder inputs on the servo controllers I bought from Rutex. I
already have my motors (1/2HP DC PWM motors) on X & Y and a gearhead
servo waiting for the Z. The project was started last year but I have
to take the table apart to install the zero backlash ballscrews
(essential for servo control) and the CNC plasma/router project has
superceded it. I have to have my mill and DRO to build all of the
special plates and brackets for my other CNC projects! There is a
circuit in the files section on how to share an encoder between two
sources. The RS232 thing sounds good but without compatible software
to read it and use it the value is less than sterling. MACH 2 from
www.artofcnc.ca is rumored to have encoder readouts but they are
not "closed loop". I doubt they will be anytime soon. The dynamics
of trying to use feedback off encoders or even the RS232 into a PC
based program without using additional external circuitry presents
some real loop tuning issues that will be difficult to overcome. The
Rutex and Gecko Servo designs close the encoder loop at the hardware
device. If you want more info just yell.