Quote from: Bloy on June 05, 2009, 05:52:47 PM

  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?

Here's a pic of the actual motor specs:
The motors of the other axes are rated at 55VDC max and they fly during rapids under the 75VDC gecko320s(required for the "one fault all fault" setup), but when creating Gcodes, if the rapids are kept to a minimum, they never get more than warm....although the brushes take a hit during the short spurts of rapids.
When winding the toroidal transformer I originally installed a secondary tap for the 55VDC to run the other motors, but lost the "fault all" feature.

 This is getting slightly off track, but here are the figures for putting these "under votaged" motors in use:
http://www.cnczone.com/forums/showpost.php?p=79685&postcount=14
 I'm sure if they had more votage(more than the 80VDC geckos), that they would move much more above the 323IPMs without lagging and consequently causing the gecko320 to fault.
Heh, as you can see, I don't really understand the BEMF rating...but it worked.
....Anyway, all this extra posting stimulates activity...hopefully.
 

What don't you like about the Geckos ?

Gekos are fine even outstanding within their envelope. when you get into the larger dc servo motors they are just not big enough to do the job and geko (marriss) will not be making bigger (higher current and voltage drives)  us who have the larger, heavier machines have moved out of the range of machines that the geko's will support.
archie =) =) =)

jeep,

My issues have nothing to do with the size of the motor. The Gecko340 is 'big' enough, and it ran the same motor with a 300 line encoder just fine. But a 300 line encoder is not adequate in this application.

It does not seem like it would be a huge problem to have the fault steps scale with the multipier, or have it be separately settable via jumper, or be programmable.

If none of that is feasible, then a socketed eprom where a customer could swap to a chip with different parameters would be a solution. That would not be blazing new trails for Gecko as they already sell the multiplier board sparately and you remove a chip and plug in the daughter card in it's place.
 
I may well be severely underestimating what would be involved, but never the less, hopefully the Viper will do the trick in my application, if I can get the thing ordered.

Quote from: JHChoppers 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.

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

It’s easy to find a transformer with a 2:1 ratio, these are used in kinds of applications where an AC device, like a Heater or Vacuum Pump is used.  This allows the product design to support 110VAC or 220VAC using the transformer to change the input voltage to the internal AC devices. 

The problem is when this is rectified to DC, you get about 85VDC (just over the limit), so you have a find a transformer with multiple taps (1.8:1, 2:1, 2.2:1) and use the 2.2:1 ratio.  These are just a little harder to find and requires more research for the pinouts.
Here is one I built with a 2:1, the VDC is just over the limit

But .  what does the ratio refer too? Primary to secondary? So far the Torroids I have found are listed as to output voltage. The ratio spec is something new to me. 

I'll take a stab:

120V 2:1 nets 60V secondary multiplied by 1.4  yields  84V . . . . is that pretty much how it goes?

What it the purpose of the resistor across the CAP?

What it the purpose of the resistor across the CAP?

I believe that resistor is simply a "bleed-off" to discharge the cap after power is disconnected.  It isn't real quick at discharging, but allows you to work with the circuit after a shorter time.....a safety practice really.
 While powerd up, the resistor has little affect on the circuit's performance.

Don't get me wrong about the Geckos...I like them and have 9 320s and a couple of the multipliers.  All my motors/encoders (save the two pictured above) fall into their operating range.  A while back, I considered getting 250(1000ppr) encoders  instead of the existing 500(2000ppr) encoders for those two motors to increase the speed (I think), but lose resolution. I decided, for now, to keep it as is.
  For the toroid and voltages pictured by JHChoppers,  I would just remove several coils/rounds of wire to bring the voltage within the gecko's limits.  In fact when I did this to my toroid I removed too many loops and cut them off in bits before measuring.    Now, I didn't have any coated wire to replace, so I took regular #10 (or 12) house wire with the insulation still on and spliced it in to rewind it to get the maximum (72VDC) recommended for the gecko 320/340.  It works great and doesn't get more than a little warm...but it is an 8" diameter transformer.   ...granted, it is quite an operation to go through(sore fingers and all), but after taping up the tranny, it looked like the original.

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.

Which model drives you you have?

http://www.viperservo.com/V200.htm  Here is a link to the Viper 200.
This is the drive I'm using.Here are some machines running with the Viper drives.
http://www.viperservo.com/V200apps/V200_apps.htm

keithmech,

I had a feeling you were using the bigger drives.

On the Viper web site, when you click to download the manual for the Viper75/95 what you actually get is the manual for the 100/200. Combining similar products into a single manual is not an unusual practice so even though the Viper75/95 was not specificaly mentioned in the manual I was not concerned about it. From the manual, the drive looked impressive and influenced my buying decision, but the Viper95 that I actually received is nothing like the 100, so the manual was not representitve of the product, nor was it useful in installing or tuning the drive.