Re: [CAD_CAM_EDM_DRO] Safety -- servo vs. stepper

Leslie M. Watts wrote:

>Hi Rayhex
>
>Yes, this is done by various companies using everything from PICS
>to Basic Stamps to dedicated motion control chips like the $30
>National LM 628/629.
>
>The idea with emc was to use perhaps the easiest control platform
>one could imagine...a commodity pc. Servo control is really not a
>very demanding application, so an old $25 clunker pc can easily
>run a machine tool...in fact it is capable of outperforming some $3000
>machine controllers!
>
>The only problem with this has been the interface. No one seems to
>have come up with a REALLY low cost interface that would be in the
>range hobbyists would be willing to spend to get the advantages of
>full servo control.
>
>My system is a good case in point: A $50 old pc with a $900 interface
>card installed!
>
>If someone came up with a $200 or less pc interface for full servo control
>with emc the program would really take off. Something like frequency
>modulation
>on a couple of cheap sound cards (they don't go to dc) and/or parport.
>Or USB 2.0.
>
>

I've got it! I have a new version of my Universal Stepper Controller
reprogrammed
to generate PWM waveforms. This controls up to 4 axes for $250. That
includes
4 encoder counters, 4 PWM generators, 16 digital inputs and place to
install 8
solid state relays. Add several of my $100 PWM-input servo amps (160V, 20A)
and that is just about it. $550 for a 3-axis system. Just add power
supply and
box. I don't think you'll find a cheaper true servo system than this.


Another way to go is with my USC board, Gecko 320 drives and my Gecko
interface.
This runs the encoders from the USC board, and repeats the encoder
signals to the
Gecko drives. On E-stop, the interface shuts off DC power to the Geckos and
connects a braking resistor. Since the encoders are connected directly
to the
USC, the computer gets continuous position feedback all the time, even in
E-stop.

See my web pages for these items : http://jelinux.pico-systems.com/

Jon