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Author Topic: Has anyone used Viper Servo drivers?  (Read 13651 times)

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Offline simpson36

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Has anyone used Viper Servo drivers?
« on: June 03, 2009, 03:24:54 PM »
Being unhappy with the Gecko 340, I did some reasearch and came up with this:

http://www.viperservo.com/Sales.htm

If it does all they claim, it will not have the limitations of the Gecko.

Just wondering if anyone is using this product and can render and opinion of it.

Re: Has anyone used Viper Servo drivers?
« Reply #1 on: June 04, 2009, 04:44:37 PM »
What don't you like about the Geckos ?
Re: Has anyone used Viper Servo drivers?
« Reply #2 on: June 04, 2009, 07:01:10 PM »
I have these drives in a couple of machines.They work great.
I have called Larry Kenny a few times with some minor issues and
he is great to deal with.If you have some specific questions post them.

Offline Chip

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Re: Has anyone used Viper Servo drivers?
« Reply #3 on: June 05, 2009, 12:57:27 AM »
Hi, JHChoppers

The only Issue with Gecko's is the 80 volt Max limit, Allot of older servo motor's could use the 170 volt max with these.

Chip.

Offline simpson36

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Re: Has anyone used Viper Servo drivers?
« Reply #4 on: June 05, 2009, 05:22:00 AM »
The 80V max is not a problem for me. Since I was buying new motors, I simply bought 72V. I read that anything over 80V is lethal, so I'd just assume stay under that anyway.

My issues with the Gecko Servo drive are several. Prior to buying the Gecko and the 1,800 line encoder, Gecko tech support assured me that their 340 would not limit my speed with an 1800 line encoder, and that drive's 250khz pulse rate "can easily handle anything Mach3 can throw at it".

Well, it turns out that the 250khz limit is not only on the input side, but also on the encoder side, so even though you can multiply the inputs by an order of magnitude, you still hit a wall on the motor side. With the 1,800 line encoder, the Gecko limits my speed to about 2,080 RPM. The motor is capable of over 4,000RPM. The Viper can read encoder pulses at 625khz, which is over 5,000 RPM with an 1,800 line encoder.

The Gecko faults at a fixed rate of 147 steps. On a 300 line encoder, that's plenty, but on an 1,800 line encoder used on a spindle, the Gecko faults constantly on harmless tiny following errors. And the Gecko has no 'soft fault' It just shuts down the motor and does not recover which is a huge PIA, and the Gecko is not configurable in any way, so it is not possible to correct these issues.  The Viper, by contrast, can have the fault steps programmed wherever you need them to be and it has a 'soft fault' where it will just issue a warning.

There are other annoying characteristics of the Gecko, but those are the two critical problems that make the Gecko unuseable in my application. The Viper has a lot of other very useful features, not the least of which is reporting back to a host via RS232 port. You can read the following erroe, and the mortor load in real time. With a VB macro or more likely a 'Brain' monitoring the servo, Mach3 could actually approach something like t a true closed loop system.

I've ordered the Viper, so we'll see how it goes. Incidentally, I have several of the Gecko 203V stepper drives and I am happy with those.





Re: Has anyone used Viper Servo drivers?
« Reply #5 on: June 05, 2009, 02:01:33 PM »
Agreed:

1) 80Volt Limit.  This alone makes it harder to find a transformer that is just less than 2:1 when making a DC Power Supply.

2) Fault limit of 147 (I thought it was 128) that is not scalable.  This is a real pain when you use the pulse multiplier feature because the fault limit does not scale with multiplier, to get things to move without faulting your acceleration / deceleration profiles have to be slow (ie: takes longer to reach the MAX IPM during rapids)

Thanks for the info



Offline Bloy

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Re: Has anyone used Viper Servo drivers?
« Reply #6 on: June 05, 2009, 05:52:47 PM »
Yup!  The 80VDC limit would be the first thing I would like changed in future servo upgrades from gecko.  I'm using the G320's on a slaved axis and the motors are 1000rpm/60Vdc-max 3000rpm, so basically the motors are 180VDC.    They work well with rack and pinion,  but fault if I try to move the gantry more than 323ipms(a little more at nightdue to slightly higher line votage).   Hey I got the motors with gear reductions cheap and experimented if they would work at all.   They did and the machine still does move fast enough...for now....but the gantry could easily handle more speed.  
   had I spent more for motors/gear reductions in the ideal range, I would be out in the doghouse.   :o

Those Vipers!....I might negotiate with the better half for those.....just for the two controlling the gantry motors..... ;)

The toroid transformer I use is huge and would accept extra turns without any problems....In fact, I took off windings to accomodate the 80VDC limit of the Gecko servo drives.

...included a dated(2006) pic for reference........just itching for those Vipers with more voltage.
« Last Edit: June 05, 2009, 06:16:07 PM by Bloy »

Offline simpson36

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Re: Has anyone used Viper Servo drivers?
« Reply #7 on: June 06, 2009, 03:35:43 AM »
I have these drives in a couple of machines.They work great.
I have called Larry Kenny a few times with some minor issues and
he is great to deal with.If you have some specific questions post them.

Good info,thanks. Calling Kenny might be what I need to do. You can't order from his web site and I sent him an e-mail order on Thursday morning asking for the paypal account he wants the payment sent to and I have not had a response back.

On the Viper questions: So far, I have read that there is no facility for connecting a scope, but one fellow has written a scrpit that reads the drive via RS232 and feed the data into Excell to create a chart that shows the 'waveform' that a scope would show. Very slick! Have you tried this?

In general, I'm interested in how you got along with the RS232 tuning/programming? Do you use more than one setup? Can the setups be swapped in real time? I am contemplating the possibility of having two setups; one optimised for indexing and one optimised for turning.

I have more Qs, but these are the ones I am most interested in at the moment.

THANKS!





Offline simpson36

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Re: Has anyone used Viper Servo drivers?
« Reply #8 on: June 06, 2009, 03:50:37 AM »
Agreed:

1) 80Volt Limit.  This alone makes it harder to find a transformer that is just less than 2:1 when making a DC Power Supply.

I'm at 'Electronics for Dummies' level. Can you elaborate on what 2:1 means relative to transformer design?

2) Fault limit of 147 (I thought it was 128) that is not scalable.  This is a real pain when you use the pulse multiplier feature because the fault limit does not scale with multiplier, to get things to move without faulting your acceleration / deceleration profiles have to be slow (ie: takes longer to reach the MAX IPM during rapids)
Thanks for the info

The Gecko manual says both 120 and 128. The 147 figure comes from forum discussions that I was reading. Whatever the number, it is far to tiny to be useful in my application, and as you pointed out it does not scale with the multipier. I had not thought of it in those terms, but that is the perfect way to describe it, methinks. The Viper I think can be programmed out to 2000. More important to me is the 'soft fault' and the motor load warnings. The Gecko would be useable if it didn't "hard fault" (if that's actually a real term :-\).

Mostly I am inrigued by the Viper's RS232 real time communications capbility. I know of a USB Oscilloscope/Signal generator that is programmable in real time also. The conbination could make for an interesting spindle control.
 

Offline simpson36

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Re: Has anyone used Viper Servo drivers?
« Reply #9 on: June 06, 2009, 03:59:28 AM »
  I'm using the G320's on a slaved axis and the motors are 1000rpm/60Vdc-max 3000rpm, so basically the motors are 180VDC.   

This is interesting. What is the proper way to interpret motor specs? From your example, it would seem that the relationship of voltage to RPM is linear? Which of the numbers you quoted are the published motor specs, and which are you extrapolating?

Increased voltage increases the RPM, so what property actually causes the real world limit on RPM?

Same question on voltage. What property dictates the practical limit?