On Sun, 19 May 2019, Davide wrote:
Date: Sun, 19 May 2019 19:33:51 +0200
From: Davide <[email protected]>
Reply-To: "Enhanced Machine Controller (EMC)"
<[email protected]>
To: [email protected]
Subject: [Emc-users] Unusual help request.
Hi, and thanks for your suggestions.
The driver does support multiple ethernet cards (up to 4) so you could use a
7i92 (for example) for each motor. Though even then 150m would be
optimistic,
I suspect.
why? isn't it a standard ethernet? I can plug pc eth to a good gigabit switch
and run 4 lines to the winches, or put 2 other switches around and amplify
the signal.
Standard Ethernet maximum length is 100M
I also have in mind to use just one 7i92 near the pc, and build a ttl ->
fiber
optic converter using SN75451 (two channel Logic + LED drivers) to drive some
HFBR1414 plugs, which claim to transmit up to 1500 mt (minimum 500mt)
Fiber optics is not needed unless you have MHz step rates, RS-422 differential
should be fine up to a few hundred KHz step rates, and may not even need any
added hardware other than chosing a BOB with differential outputs and possible
reverse polarity protection if you are using low end drives
I have a tech question about 7i92. I have only run Lcnc using software step
gen, but I understand that a 7i92 does step generation on its own, freeing
the pc from doing the hard work. But what messages are sent from the pc? are
they just POS/SPEED? and, since I have my untrivial kinematics, are they
always done by the pc, right?
Yes, speed sent, current position returned, all position/velocity calculations
done in LinuxCNC, but if you can get the desired step rates from your parallel
port, you may not need a 7I92 and just need differential drivers at the BOB
end for the paralle port generated step/dir signals
when I run a latency test I have good results, something like Servo t. 2-3000
and Base t. 5-7000. Is the 7i92 driver linked to the Servo, or Base Thread?
what Latency time is it needed? and for 4*7i92?
The 7I92 uses a servo thread only and requires a Preempt-RT kernel (the
Stretch test ISO is the easiet way to do this)
I'm sorry for all these questions, but unfortunately I don't have a lot o f
time to experiment, so I need to clarify my mind, before buying a lot of
things..
Thanks, Davide.
Peter Wallace
Mesa Electronics
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