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Hello!

I am doing a Biesse retrofit and I am replacing original servodrives because they are showing errors and I decided to go with Mesa 8i20.
I have attached one 8i20 and am trying to get it to move the motor (belt is removed, motor is not connected to machine) without any PID modules or anything.

Here is the part of HAL file that relates to BLDC component and 8i20 pins:
loadrt bldc cfg=qi

addf bldc.0        servo-thread

setp bldc.0.scale     4000
setp bldc.0.poles    4
setp bldc.0.initvalue     0.7
setp bldc.0.init     0

# setp bldc.0.rev        1

setp bldc.0.encoder-offset     1517


setp hm2_5i24.0.8i20.0.4.current-minlim        -10
setp hm2_5i24.0.8i20.0.4.current-maxlim        10

net motor.02.rawcounts    hm2_[HOSTMOT2](BOARD).0.encoder.02.rawcounts
net motor.02.rawcounts    bldc.0.rawcounts

net motor.02.index-ena    hm2_[HOSTMOT2](BOARD).0.encoder.02.index-enable
net motor.02.index-ena    bldc.0.index-enable

net motor.02.angle     bldc.0.rotor-angle
net motor.02.angle     hm2_5i24.0.8i20.0.4.angle

net motor.02.current     bldc.0.out
net motor.02.current     hm2_5i24.0.8i20.0.4.current

net test-vel        bldc.0.value


Encoder-offset was calculated following way:
1) connected motor U to 24V, V and W to 0V
2) started LinuxCNC, halshow encoder counts and rawcounts
3) removed 24V from motor
4) setp encoder.index-enable 1
5) turn motor by hand until counts reset to 0
6) difference between counts and rawcounts is 1517

For encoder-offset value I have tried 1517, -1517, 2483 and -2483 (because 4000 - 1517 = 2483 as per suggestion by PCW somewhere in these forums).
I have tried with bldc.0.rev set to 0 and 1
I have tried bldc.0.scale both 4000 and -4000.

Signal test-vel is getting its value from pyvcp slider in range from 0 to 20 with increments of 0.1
The result I am getting:
with setp bldc.0.init 1 it starts rotor homing. With uneven motion it will finish it (initdone pin is set "true") although it is really hard to turn motor by hand with current set at 0.7
Then with slider giving input to bldc.0.value motor will snap to another position with jerking at value of around 8-10 and snap back around at 5-6.
With bldc.0.scale -4000 motor would constantly jerk with bldc.0.value at 7.4 or higher and stop jerking with bldc.0.value lower than 5.3

It was suggested that motor should turn equally fast in both directions with low current as an indication that encoder-offset parameter is correct. I just do not understand what do I need in HAL file to command the motor spin at constant speed.

I have no idea what exactly am I missing or what should I try differently, so any hints will be appreciated.

yathish wrote:

Hi @tommylight, thankyou for your insight.
Now i want to expand my inputs and outputs in raspberry pi 5, can you suggest me how to expand my i/o and if there is any solution can you also tell me how to configure HAl

Refer to this post forum.linuxcnc.org/18-computer/53136-can...g-step-pulses#304365

tommylight wrote:

Sorry but i do not use RPI's at all,and that will not change untill their price drops back to under 50$.

Sorry, why not ? i like the RPI's, especially via SPI

Now i want to expand my inputs and outputs in raspberry pi 5, can you suggest me how to expand my i/o and if there is any solution can you also tell me how to configure HAl. I do not want to use MESA board as it is expensive, can someone suggest something cheaper?

Cant do this anymore bye all wrote:

No don't use a hub.

Linuxcnc-rio is awesome, with a single WT32-ETH0 and a direct cable connection and inexpensive FPGA you can do 4 axis easily and way more.

i think he will use ethernet for wiring like with ethercat.


 

Sorry but i do not use RPI's at all,and that will not change untill their price drops back to under 50$.

Hi @tommylight, thankyou for your insight.
Now i want to expand my inputs and outputs in raspberry pi 5, can you suggest me how to expand my i/o and if there is any solution can you also tell me how to configure HAl

No don't use a hub.

Linuxcnc-rio is awesome, with a single WT32-ETH0 and a direct cable connection and inexpensive FPGA you can do 4 axis easily and way more.

Awesome used all of elovalo bits to setup an Rpi5 with Pineberry NVME hat, works great.

Can you tell me how to configure HAl and ESP32 if I have to build it for just 1 axis?

Using ethernet hub or switch will add a lot to network latency, so it might not work at all, even if everything else works.
Never tried with a hub, but i do have a switch that works with Mesa boards for days without issues.
Still, i never use a switch on production machines, the risk is to big.
-
Network hub = old, any packet sent to any pc wired to it will be sent to all connected PC's.
Network switch = new, any packet sent will be sent only to the PC with the IP address contained in that packet.

At 1ms tick time round trip for the ECAT bus, you can theoretically achieve .001mm granularity of position. At that rate one could also have 60000mm/m velocity or 2362 ipm. Very few machines in the CNC world can even handle such speeds and the acc/dec inertial demands this velocity creates. Any attempt to advance the bus cycle time aka tick time is a waste of time and energy especially for a hobby/light industrial machine.

I would recommend doing some study of basic physics before walking down a road to nowhere. No matter how faster your motor, bus, etc... you are limited by the physical construction of your machine. Period. End of discussion. Or you have a $1 million machine for the likes of DMG or Chiron. Or simply a million bucks you like throwing away fixing the scrap heap that speed would create of your machine.

Millions of motion control systems utilizing ECAT run using the standard tick cycle of 1ms. I will default to a proven theory put to practice any day. A theory I have proven over years of practice myself.

Have a nice day.

Are the stepper motors 0.9 degree per step?
Should be written on the back of the motors.

in principle, yes,
but you would have to build the hal component in such a way that the ethernet packets are sent and received in parallel,
otherwise it takes too long.

EDIT:
but since udp is used, this can lead to collisions.
maybe send with minimal delay and then wait for the responses

Hi Linuxcnc community, 
I have installed OS in raspberry 5 and Instead of using IO expander I want to use individual ESP32+W5500 for every motor and generate step pulses. If this is possible please help me with the steps in achiving it.
Refer the image below and get what I want to achieve
https://drive.google.com/file/d/1JCuLksqd7dcpAcJ44GajRwzOFmay_xuQ/view?usp=sharing 
Thankyou