Dynomotion

Group: DynoMotion Message: 622 From: Marty Escarcega Date: 8/27/2010
Subject: Re: Kflop, SnapAmp & Back EMF

Thank you Tom, not so sure there will be a lot of mass decelerating on my lathe.  Sounds like you have built many tools into your hardware. I’m very anxious to get them.

Given my 2 Servo motor’s peak terminal voltage is 60VDC, would it be ok to buy an unregulated power supply of 63VDC (no load) or should I buy the 58 VDC power supply, 1.0kw?

 

I plan on using your schematic you posted in the files area for KFLOP & Snap Amp. Is it possible to wire in an MPG for each axis or put in a switch to switch between the two axis?

 

Thanks Tom for such great support, its this support that has convinced me to by the KFLOP/SNAPAMP combination for my Lathe Conversion.

 


Marty

 

From: DynoMotion@yahoogroups.com [mailto:DynoMotion@yahoogroups.com] On Behalf Of Tom Kerekes
Sent: Friday, August 27, 2010 3:28 PM
To: DynoMotion@yahoogroups.com
Subject: Re: [DynoMotion] Re: Kflop and Gecko 320X servo Amps

 




Marty,

 

Regarding Back EMF as a big system decelerates energy gets pumped back into the power supply which can cause the power supply voltage to rise up and potentially damage components.  SnapAmp has a programmable clamp voltage that you should set a few volts above your normal max power supply voltage.   The big power resistors on SnapAmp can absorb several KW of power momentarily.  Take care not to set the clamp voltage to a voltage lower than your power supply.  SnapAmp allows you to plot your supply voltage so it is easy to see exactly what is going on with your power supply.  What the initial voltage is, how much it drops under load, how much it spikes up during deceleration, how the clamping functions, etc...

 

Regarding encoder cables:  you should use shielded with twisted pairs if possible.  Each pair of differential signals should be twisted together.  We don't supply cables other than those that connect our boards together (small 16 pin ribbon between KFlop and SnapAmp) and a USB cable.

 

Yes one SnapAmp can drive 4 brush motors.

 

Regards

TK

 

From: Marty Escarcega <escarcega@...>
To: DynoMotion@yahoogroups.com
Cc: carlcnc <cebcnc@...>
Sent: Fri, August 27, 2010 6:42:24 AM
Subject: Re: [DynoMotion] Re: Kflop and Gecko 320X servo Amps

 

Carl, thanks I see Antek has a website. They have a 63VDC 1.0kw and 1.5kw power supply. Fairly reasonably priced. I don't think the 3V over the max rated voltage of 60V would make a huge difference as its no load? Otherwise they make a 56VDC power supply for the same money and gives a margin of protection. How about Back EMF? Not an issue with Snap Amp?

Sorry for all the questions. I would rather do this right the first time rather than spend MORE money by buying the correct items, or letting the magic smoke out of something.

I bought matched servo motors to hopefully make tuning them easier. Tom already confirmed the encoders were fine.

I do have another question, I have to lengthen or replace the encoder cables. Should I purchase shielded wire or would twisted pair work fine? I was considering CAT5 cable but that wire is solid and wondered with the motion of the lathe carriage if it would eventually fatigue.

I have settled on KFLOP and SNAPAMP. (Do I read the specs correctly on snap amp, it can drive 4 DC Brush Servos? I only need to drive 2 on my lathe) While I can make breakout boards, are cables supplied to be able to utilitze the connectors or are those up to the user?

Thanks
Marty
---- carlcnc <cebcnc@...> wrote:

> Marty
> sorry so late, I don't visit the forum often
>
> with only 2 motors I believe you can expect 20amp peak from the snap
amp[right Tom??]
> YOu should only need 1 supply but I would go for a 1kw
> using an undersized one and adding lots of capacitors will probably cost
more than a better supply
> have a look at Antek power. I think they have a 60v 1 or 1.5kw with
multiple taps,ready to go for around 160$ real bargain
> carl
>
> --- In DynoMotion@yahoogroups.com,
"Marty Escarcega" <escarcega@...> wrote:
> >
> > :-)
> > Hi Carl. Haven't bought them yet. Makes more sense to stick with
Kflop and
> > Snapamp.
> >
> > Given my motor specs and that they are a pair and going on a lathe,
how
> > would you size the power supply? A friend suggested get the voltage
as close
> > to the servo max voltage, and build the power supply to be able to
supply
> > the PEAK current, 22a. He suggested using several large capacitors.
> >
> > Looks like Peak current on Snap Amp is 15A.
> > Would this power supply suffice and be safe and efficient to run both
Servo
> > motors or would I need one for each motor?
> > http://cgi.ebay.com/56V-500W-Power-Supply-Gecko-Driver-CNC-Servo-Stepper-/37
> > 0420959369
> >
> > I like this one a little better as it has 5VDC, 12V/24VDC regulated
power as
> > well.
> >
> > Thanks in advance.
> > Marty
> >
> >
> >
Group: DynoMotion Message: 623 From: Tom Kerekes Date: 8/28/2010
Subject: Re: Kflop, SnapAmp & Back EMF
Hi Marty,
 
I'd say go with the 58V supply to stay within the ratings.  The difference would only be a slightly less top end speed.
 
Regarding the MPG: it has been done both ways.  A Kflop User program is used to count the MPG pulses so it can be written to monitor two encoders if you have them, or most MPGs have an XYZA switch which can be monitored by the program to tell it which axis to move. 
 
Thanks and good luck with your system.
TK