Re: [CAD_CAM_EDM_DRO] First note-Help Mariss Help us with shielding???

Hi Tom and Tim,

I added G901 boards (PLL daughterboard, about $35) to my G201's to make
G210's. I'll bet that a G901 can be added to the G320's to make them
G340's. Mariss can confirm or correct this (I haven't seen them yet)!

I haven't worked through encoder mountings, and I'd like to examine some
pix. I saw Dan's, but I'm not sure what I'm looking at!

good comments on the shielding experiments, and quite curious results!
I take it that one has to "do it all at once" to get a servo system up.
Can't just add the motors and drivers, then worry about the more
difficult encoder mounting problems later!

Alan KM6VV


Tom Eldredge wrote:

>
> Dear Brave Soul,
>
> Tim Goldstein is correct about the 320's and 340's and although I am a penny
> pincher, I always seem to find some way to do something different with
> whatever I buy, sometime in its lifetime. So, for me, the $30.00 extra per
> drive gives me some added flexibility that I am buying. It also allows me
> to choose many different encoders. Sometimes I want to try some other
> machine, and with the built in multiplier, I can experiment on
> configurations. Of course, that is 30 * 3 or 90 bucks. It would not hurt
> to try one 340 and 2 320's, just so that you had one around. I will not
> drag this point out.
>
> As far as the encoder noise is concerned, what a puzzling thing. We used a
> foil shielded cable for the servo motor drive voltage, and a separate foil
> shielded cable for the encoder signals, and kept them separate all the way.
> We also put a .1 uf cap at the encoder end of the cable between +5 and gnd.
> Cables around 10 feet from drives. We grounded the encoder cable (no
> twisted pairs inside) at the drive end, and left the motor shield
> disconnected. The drives faulted constantly. We cut the ground wire
> connecting to the shield on the encoder cable, and it ran with only an
> occasional fault. We grounded the servo motor drive cable and the faults
> stopped. Never could see much on the scope in the way of noise. Before we
> found success, we also built a little amplifier and put it right in the
> cavity of the servo motor with the encoder. The amplifier was made with a
> 74HC04 (per Marris's advice). We paralleled three of the inverters for A
> and three for encoder B signal. It still faulted every time until we
> shielded the servo motor power cable. Jon Elson has pointed out to us that
> this foil shielding will not last the life of the cable if the cable flexes
> all the time. So, keep that in mind when you select a cable. If I have
> dragged this out too long to keep up, the bottom line is that the only
> configuration that works at this time is to have the servo motor drive cable
> shielded, and leave the encoder cable unshielded. Don't ask me why. I
> don't know. I would have thought it better to shield the encoder cable. If
> we try to ground the encoder cable sheild, it faults out all the time.
>
> Electrical noise has been a real pain for me in many projects I have worked
> on.
>
> ----- Original Message -----
> From: Tim Goldstein <timg@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Friday, June 29, 2001 10:51 AM
> Subject: RE: [CAD_CAM_EDM_DRO] First note-Help
>
> > I will second the recommendation of going with Gecko G3X0 step and
> direction
> > servo drives if you have not purchased anything for steppers yet. While
> Tom
> > is suggesting G340's my preference is to go with G320 and select the
> > encoders to give 6,000 - 10,000 steps per inch. The only difference
> between
> > the G320 and the G340 is the latter has an additional plug in board that
> > allows you to "multiply" you incoming pulses to drive servo setups that
> > require very high steps per second. Helps to take the stress off the
> > computer, but you can accomplish the same thing by selecting appropriate
> > encoder counts. The G320 is US$30.00 cheaper per axis that a G340. I have
> > G320's on my Shoptask and am in the process of setting up Bridgett (a
> > Bridgeport series II) with G320's. I love them and feel there is no
> > comparison to a stepper.
> >
> > I would also give an endorsement for US Digital ( www.usdigital.com ).
> Nice
> > products, reasonable prices and super to deal with. For motors I have been
> > very successful picking them up on E-bay.
> >
> >
> > Tom,
> > How did you avoid electrical noise interfering with the encoder? I seem to
> > be having some problem with that and just got some National DS9638 &
> DS9637
> > differential driver and receivers to eliminate the problem. Regarding the
> > 9638/9637 can any of you electronic gurus help me with a circuit diagram
> to
> > interface them with the encoders, the G320's, and an external power
> supply?
> > Don't want to tap the power off the G320 encoder power taps as I am sure
> the
> > current draw is beyond the Gecko spec.
> >
> > Tim
> > [Denver, CO]
> >
> > > -----Original Message-----
> > > I'll throw in my recommendation that you get some Gecko 340s
> > > and find some
> > > servo motors and skip the steppers, if you haven't already
> > > started down that
> > > road. The Geckos really only have two adjustments to make, Gain and
> > > Damping, and you can tinker with them and get them running
> > > pretty well. The
> > > limit pot adjustment is no big deal. I think CNC pro is
> > > very popular on
> > > this list, and many others will suggest their favorite cad
> > > /cam software.
> > > Yesterday, I just finished retrofitting a series I Bridgeport
> > > mill with the
> > > Geckos, and I love them for their simplicity. US digital has
> > > cheap encoders
> > > too. Just watch out for electrical noise interfering with the encoder
> > > wiring. Tim is also in the process of retrofitting a big
> > > Bridgeport mill.
> > > Get a catalog from US Digital on their encoder products.
> > > Their encoders
> > > will fit many shaft sizes.
> > >
> > > Others may suggest servo motor sources.
> > >
> > > Tom Eldredge
> > > >
> > > > Addresses:
> > > > FAQ: http://www.ktmarketing.com/faq.html
> > > > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> >
> > Addresses:
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> >
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