Mesa 7i33 8i20 AC Servo configuration

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27 Jul 2013 00:27 #37073 by buster142
Have anyone a sample hal configuration for a mesa 8i20 with encoder/resolver feedback?

Thanks
Michael

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27 Jul 2013 08:24 #37082 by andypugh

Have anyone a sample hal configuration for a mesa 8i20 with encoder/resolver feedback?


I am using 8i20 + 5i23 + 7i49

I can give you my config if you want?

However, it is slightly complicated by also having a pair of 7i39 bldc drives and running those in different ways in different configs.
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27 Jul 2013 10:36 - 27 Jul 2013 10:37 #37086 by PCW
freeby.mesanet.com/5i20green.ini
freeby.mesanet.com/hm2-servogreen.hal

Is a hacked version of the hm2-servo demo hal file using the 8I20
and a BLDC motor (a big one painted green for some reason)
Last edit: 27 Jul 2013 10:37 by PCW.
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28 Jul 2013 23:18 #37171 by buster142
Thanks!
maybe little bit PID tuning but everything is working fine now

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29 Jul 2013 03:01 #37181 by andypugh

Thanks!
maybe little bit PID tuning but everything is working fine now


You might want to fiddle with the bldc.N.encoder-offset if you are using resolvers. My motors seem to need -950000 in that parameter to give the same current/velocity relationship

If you are using the pid-fb-deriv pin, and have it connected to the resolver-velocity pin then be aware that you may need to set the resolver.N.velocity-scale negative to make the Dgain term work properly.
(It was only today that I realised why I had to use a negative Dgain, now I have negated the scale and Dgain is positive again)

This is the machine working (hot off the camera)

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29 Aug 2013 17:49 #38212 by chimeno
hello.
I have a question, I am restoring a cnc machine that lleba 1000w AC servomotors but no driver, my question would be, which is better, buying a new set of servo + driver or ultilizar these old servomotors with the 8I20 + 150v transformer for these servos?
that would make me missing transformer for 3 motors?

thanks
Albert

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30 Aug 2013 03:10 #38228 by andypugh

buying a new set of servo + driver or ultilizar these old servomotors with the 8I20 + 150v transformer for these servos?

I would decide by price. If you can find a matching set of 1kW servo motors and drives then that is probably a good and reliable solution.
The 8i20 is only cheap in the context of servo drives, it still costs quite a lot of money.

that would make me missing transformer for 3 motors?

You might not even need a transformer. I am running on rectified mains (300VDC) with no transformer.
Things are a little safer with a transformer.

A good solution in a 240V country and require 150VDC would be to rectify the output of a site isolation transformer.
www.ebay.co.uk/itm/3-3KVA-SITE-TRANSFORM...ND-NEW-/390646842449
Or similar, you would need a good-sized rectifier bridge and some very large low-ESR capacitors too.

Be aware that the combination of large capacitors and high voltage is very dangerous. I made a circuit to discharge the capacitors.

However, if I was doing the same thing again I would use the fact that the 8i20 has voltage feedback to HAL to control the power supply.
I would make it impossible to turn on the machine and power supply if the voltage is >10V. I would also initially power the PSU through a ballast resistor, until the 8i20 said that the voltage was > 100V. Then I would switch out the ballast resistor and enable the machine. I would do all this in HAL.

You need big, high-current capacitors, for example:
www.ebay.co.uk/itm/EVOX-RIFA-PEH200-CAPA...&hash=item5640b68b16

Are you sure that your machine does not still have a Power supply?

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31 Aug 2013 00:53 #38261 by chimeno

hello,

No transformer leads because only I have the machine, the control unit is there and what I'm trying to do again, I will continue your advice be if I find a set of servo + driver and if it proves to the 8I20.


thanks
Albert

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