8i20 brushless servo drive output amps

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21 Apr 2014 20:22 #46172 by johns00056
When I turn the pulley on the motor, by hand, the halmeter 8i20.0.0.current increases gradually,but won't go

higher than 1 amp.

I am thinking that it should blow a fuse on the power supply,or at least go up to the default setting on 8i20

of 7.5 amp.

The motor is rated 22nm stall torque . I am thinking that I should not be able to turn it with my hands.

I am working on the tuning.

Other than this problem , the motor runs the axis fine except that one end of the travel is a little tight and I

would like to have more torque.

I have tried a bunch of different settings for output scale and max output.

If I set max_output to more than 1, it has no effect.

If I set max_output to less than 1 , it works as expected and limits the output.


File Attachment:

File Name: hm2-servogreen.hal
File Size:9 KB



File Attachment:

File Name: 5i25green.ini
File Size:5 KB
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21 Apr 2014 20:45 #46174 by PCW
The 8I20 driver uses 1 as full scale current (the current set by the 8i20 EEPROM maxcurrent parameter)
so an output current of 1 would be 7.5 A with the 8I20s maxcurrent set to 7.5A

Note that it may take substantially less than 1 A of DC bus current to generate
7.5A of 3 phase winding current when stalled (depending on the DC bus voltage)

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21 Apr 2014 22:15 - 21 Apr 2014 22:25 #46178 by johns00056
Thanks for the good explanation.

So the next question is how do I change the EEPROM setting.

Do I need a cable as described in the manual? I don't think my computer has aDE-9F connector.

I downloaded the 8i20 support software from the Mesa website, but It looks like a windows file or something

and I don't know what to do with it.
Last edit: 21 Apr 2014 22:25 by johns00056.

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21 Apr 2014 23:22 #46183 by PCW
possible ways to do this:

Upgrade to linuxcnc 2.6 and use setsserial
(this is doable through the existing interface, no funny cables required)

Use windows and the Mesa WPD utility
(this needs that funny cable described in the manual
and either a serial port on your computer or a USB-serial adapter)

(WPD does compile under linux, but I have not tried using it with serial (TTYN) ports)

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22 Apr 2014 06:06 #46201 by andypugh

The 8I20 driver uses 1 as full scale current (the current set by the 8i20 EEPROM maxcurrent parameter)


I think that in HAL the signal shows as amps, not 0-1. So he should be seeing 7.5 not 1.

I see that the PID maxoutput is set to 1 for axis.1 and axis.2, but 4.3 for axis.0 (In the HAL, from the INI)

Do you see more current on the X axis then Y or Z?

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22 Apr 2014 06:33 #46202 by andypugh

So the next question is how do I change the EEPROM setting.


It is easier in 2.6, but I think it is possible (with some inside knowledge) in 2.5.

In 2.6 you need to stop the serial port, put "magic" numbers into certain HAL pins then toggle a write command.

"man hostmot2" contains the following information:

$>halrun

halcmd: loadrt hostmot2
halcmd: loadrt hm2_pci config="firmware=hm2/5i23/svss8_44 sserial_port_0=x0xxxxxxx"
halcmd: loadrt threads
halcmd: addf hm2_5i23.0.read thread1
halcmd: addf hm2_5i23.0.write thread1
halcmd: start
halcmd: setp hm2_5i23.0.sserial.0.port-0.run 0
halcmd: setp hm2_5i23.0.sserial.0.port 0
halcmd: setp hm2_5i23.0.sserial.0.channel 1
halcmd: setp hm2_5i23.0.sserial.0.0.parameter 0x8e8
halcmd: setp hm2_5i23.0.sserial.0.0.read 1
halcmd: show pin hm2_5i23.0.sserial.0.0.value

"0x8e8" is the address to be read, and the command sequence above should read back the max current setting.

By setting the value pin and toggling the "write" pin it is possible to set a new value. However I recall it being necessary to put some magic numbers in the higher-order bytes of the value pin, and I can't now recall the details.
(Specifically you need the LBPNONVOL flag and the LBP_WRITE flag)
It should be possible to work it out by looking at the source code and docs (I worked it out when I wrote the code, but it was years ago, and it was always awkward, which is why setsserial was written.)
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24 Apr 2014 01:59 - 24 Apr 2014 02:03 #46265 by johns00056
I made up the special cable to use the Mesa utility.

On page15 of the 8i20 manual-- does XX mean that the wire is not used?

I connected a computer, equipped with windows 7, to 8i20 and tried to read a parameter in a command prompt window.

The result was-- COM167 open failed, and the red fault LED stayed on.

I have the w6 jumper down ( in setup position).

What does this line mean? Usage: rp parm [axis] [q] [h] [r] [a]

Do you see more current on the X axis then Y or Z?

I only have one axis hooked up now.


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File Name: driveparwind.txt
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Last edit: 24 Apr 2014 02:03 by johns00056.

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24 Apr 2014 04:25 #46269 by johns00056
I got it working now!

I entered--
SET COMPORT=COM1

enter

Then clicked and dragged the application into the command prompt window and added the word maxcurrent after it , then pressed enter.

C:\Users\John>C:\Users\John\Documents\8i20\8i20\UTILS\WINDOWS\rpd.exe maxcurrent

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24 Apr 2014 04:38 - 24 Apr 2014 04:38 #46270 by PCW
OK so to set the non-volatile maxcurrent to 3000 (30 Amps), you will want to type
wpd nvmaxcurrent 3000

(in a console window)
Last edit: 24 Apr 2014 04:38 by PCW.
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24 Apr 2014 09:21 #46276 by johns00056
I have it set to 15 amps and it made a huge difference. The motor has lots of torque and is practically unstoppable with my hands.

I am really happy with it now.

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