Newbie Questions for servo setup, ports and pins e

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16 Jan 2011 15:27 #6731 by johnn1
Hi all

I am just returning to EMC2 after quite some time with Mach3

My reason for now wanting to use emc2 is its ability to be closed loop with servos

I have been sending myself gogle eyed trying to get started

I need some basic help with initial setup. I am not sure how to set up the parallel ports and specific pins.

I am going to be using analog drives, ie +/- 10v control, for 4 axis. pluss a spindle control. Usual home switches etc.

Encoders on each axis.

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16 Jan 2011 18:55 #6734 by PCW
The etch-servo config (2 axis servo using a parallel port) might be a good start on a configuration close
to your requirements.
Note that if you have +-10V drives you have some missing hardware (to convert the PWM outputs to +-10V)

Also note the parallel port only system will have limited performance capabilities due to
1. Low PWM resolution (this depends on your base thread frequency)
2. Low maximum encoder count rate (also dependent on your base thread frequency)

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16 Jan 2011 21:37 #6735 by BigJohnT
Hi John,

When I converted my Hardinge CHNC lathe to EMC I used Mesa 5i20, 7i33, 7i37's to complete the hardware loop. Pico also makes hardware that is supported in EMC but I'm not familiar with it to say what does what. When using something like the 5i20 the latency of your computer is less important as you don't need a base thread (the fast one for generating step pulses). Like Peter suggested picking one of the sample configurations is the best way to start with a servo setup till 2.5 comes out then there is a configuration wizard for servos.

Welcome aboard...

John

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17 Jan 2011 18:10 #6751 by johnn1
Thanks for the replys

Could I use the mesa 7i33 to test my servo drives if i connect step pulses to the input pins of the card and supply external power. This would be just to check that i get motor power from my drives as they are used and not been tested at all.

Thamks John

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17 Jan 2011 18:16 #6752 by BigJohnT
John,

If you have +- 10vdc velocity inputs on your drive simply use a battery (I used a 1.5v) to test your drives. I rigged up a simple circuit with a momentary push button for velocity and one for enable.

John

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18 Jan 2011 00:31 #6761 by johnn1
thanks

I had thought of similar but didnt think it would be so simple so didnt try it !!

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24 Jan 2011 13:43 #6821 by andypugh
johnn1 wrote:

I had thought of similar but didnt think it would be so simple so didnt try it !!


Can the drives work with 0-5V and direction input? +/-10V needs extra hardware, but 0-5V + direction can be done with a parport using nothing more technical than software PWM, a resistor and a capacitor.

However, it is probably worth yourself some time, a mesa 7i43 is pretty cheap ($80) and converts your P-port into a 48-pin IO port with fast PWM generators into which you can plug the Mesa +/-10V conversion daughterboard.

There seems to be no real performance difference between the P-port and PCI cards in an EMC2 installation, though you get an extra header with the 5i20 (72 total pins)

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28 Jan 2011 22:11 #6858 by johnn1
Just +/- 10v i'm afraid, decided to go the mesa route as funds allow.

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