Viper servo drive overview

[Larken]

Have you tested your drives with the Geckodrive G100 motion controller? I would love to use mach3 + the G100 + Viper drives.

Should work fine.
One question, why do you need the G100, if you have Mach2 that outputs step/direction ?

[turmite]

The G100 produces a much smoother pluse train at a lot higher frequency than the the engine used by Mach.

Mike

[sbalder]

I took the plunge and ordered 3 Viper 200 Servo drives this morning. I plan to use them on 140Volt-11AMP dc servo motors on a Milltronics Partner Mill that I am trying to bring back to life. My only hesitation is that the product is new so there isn't a lot of feedback I have been able to find.

[JerryFlyGuy]

I'm also interested in these [the 80v /20a] drives and would use them w/ a G100. The other concern I have is how fast a pulse train the drive can accept. The G100 can output up to 4Mhz step and direction pulse streams. Can your drive accept these? Also does your drive accept differential encoder signal's?
What encoder count speed has it been tested to?

[Larken]

I'm also interested in these [the 80v /20a] drives and would use them w/ a G100. The other concern I have is how fast a pulse train the drive can accept. The G100 can output up to 4Mhz step and direction pulse streams. Can your drive accept these?

Its easy for a counter based board (like Grex) to output 4mhz or 100 mhz, but it doesn't mean its useful.
If you even ran 100Khz, your machine would be flying faster than you could use.

Also does your drive accept differential encoder signal's?

Yes.

What encoder count speed has it been tested to?

2 Mhz

[JerryFlyGuy]

Larken thats true to a point. However I'd planned to use a 1800 line encoder. My servo can hit 3000rpm so that ends up being 360,000Hz on the encoder line. And the drive would have to handle that pulse speed to make it all work. Now, am I going to run it up there all the time.. no, but if I ever get things tuned out so that it gets close I don't want to have to worry about the drive missing steps or faulting out because of it.. these are just question's I ask before I buy.. they're kinda useless to ask afterwards

So if the drive will accept up to 2Mhz on the encoder side, does that mean they'll take 2Mhz on the step/dir side?

[Mariss Freimanis]

Let's see here: 100kHz or abve isn't useful. Your drive accepts 2MHz so it is useful.

It's not useful, it's useful. It's not useful, it's useful. My brain vibrates dangerously. Cognitave dissonance warning! Arggg!!!

Why as a circuit designer would you expose a port to 2MHz and its attendant 150nS noise pass-band if the intended resonse is limited to sub 100kHz step pulse rates?

About step pulse rates: Say you have a 6,000RPM motor equipped with a 2,000-line encoder; it's not an entirely unreasonsable proposition. The encoder results in 8,000 counts per revolution and there are 100 of them per second. This requires an 800kHz step pulse frequency and that's just a tad above the stated 100kHz to "make it fly".

At 100kHz that motor would reach 750RPM and only deliver 12.5% of the power it has available. It would take an 800kHz step rate to have it deliver 100% of the power the client paid for in buying the motor.

Mariss

[Larken]

Say you have a 6,000RPM motor equipped with a 2,000-line encoder; it's not an entirely unreasonsable proposition.

Thats a bit of a mismatch for most applications. Maybe in a space shuttle guidance system or semiconductor wafer fab, but i doubt they would be using a drive that costs under $200.

Why as a circuit designer would you expose a port to 2MHz and its attendant 150nS noise pass-band if the intended resonse is limited to sub 100kHz step pulse rates?

Two words > Step multipler

For now the viper has a step input of about 100,000 steps/second which is about 2x what Mach2 can output and satisfys about 99% of applications. (Encoder pulse rate can be up to 2Mhz.)

Probably in a year or so, I will have a drive that can take a 1-2mhz step-rate using newer DSP technology.

[routerman]

My servo can hit 3000rpm so that ends up being 360,000Hz on the encoder line.

So with a 4X step multiplier the step pulse would need to be 90,000 steps/sec. So it still has some head room to make your servo run 3000 rpm.

[JerryFlyGuy]

And why would I want to decrease my resolution when I've gone to the extra effort to buy a 1800 line encoder? Thats kinda defeating the purpose don't you think? It's obvious that the drive is up to the standards of the parrallel port [ I think] but it's got a few Hz to go before it will work smoothly w/ the G100. Maybe some day..

[Mariss Freimanis]

Step Multiplier = Lower resolution encoder.
Why bother with a step multiplier when you can just use a lower res encoder?

Mariss

[Xerxes]

Higher the better. High encoder resolution greatly helps operation of D controller and makes motor quieter. Today some machine tool encoders have millions of counts per revolution. Axis resoluton becomes nanometers which is unpractical but operation is much smoother.