Peter,
I have a question about the the 7i33. The machine we are discussing
has three 25 HP spindle motors operating on 3 separate VFD's. We have a
Italian control that was fitted onto a machine and it has a 100ma limit on
its analog output. Each VFD requires a minimum of 70ma to run. We had to put
a small phoenix contact amp on it to boost the analog signal to run all
three drives on that machine. The problem comes when you turn one spindle
off and only run on two. The RPM runs higher than it should due the
decreased load on the circuit. In other words the analog VREF increases and
the two drives have to be retuned. We get around this by putting a blank
tool in the spindle and running all 3 wether they are cutting or not. Not
only is this a waste of energy it also puts unnecessary wear on the unused
spindles bearings. What is the limit of the analog out on the 7i33 channels?
I can always use one out per spindle and that would completely solve the
issue. What is your take on this? One output or three? Anyone else feel free
to jump in!
Paul
----- Original Message -----
From: "Peter C. Wallace" <p...@mesanet.com>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Sent: Sunday, March 21, 2010 12:36 AM
Subject: Re: [Emc-users] G52 and Fanuc conversion to EMC
> On Sat, 20 Mar 2010, cogoman wrote:
>
>> Date: Sat, 20 Mar 2010 16:02:39 -0400
>> From: cogoman <cogo...@verizon.net>
>> Reply-To: "Enhanced Machine Controller (EMC)"
>> <emc-users@lists.sourceforge.net>
>> To: emc-users@lists.sourceforge.net
>> Subject: Re: [Emc-users] G52 and Fanuc conversion to EMC
>>
>> That price seems overkill to me too. I have been thinking about
>> trying to develop a product for just this kind of situation. The
>> solution seems simple, and inexpensive. Take an AVR microcontroller and
>> have it monitor the Q-encoder signals. The program would start out
>> counting the time between changes of the signals. When the RPMs get
>> high enough it could switch to counting encoder events for a certain
>> small amount of time. The RPM that is found would be converted to a DC
>> voltage by a PWM signal from one of the counters. The PWM would always
>> be clocked at a few MHz, so the RC filter would have a high corner
>> frequency, and the DC voltage would be able to change faster than most
>> (if not all) servo systems. For older servo motors that top out at
>> about 2500 RPM this should be overkill.
>
> Actually theres a better way than changing counting modes at different
> speeds
> (from 1/T_Encoder to DeltaN/T_Sample): always timestamp encoder edges,
> that
> way, at T_Sample you have both encoder counts (N) and the time it took to
> get
> those counts (TsubN) from the timestamps. The velocity can now be
> calculated
> as KDeltaN/TsubN. This is what the HostMot2 hardware/driver does to
> calculate
> its velocity estimate (glossing over some nastiness that the driver fixes
> at
> reversals and stops)
>
> Dont know if the AVR has the hardware to do this, We've implemented this
> on a
> DSPIC (using DMA) but it wasn't pretty...
>
> Peter Wallace
> Mesa Electronics
>
> (\__/)
> (='.'=) This is Bunny. Copy and paste bunny into your
> (")_(") signature to help him gain world domination.
>
>
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