7i76E + THCad 10V

The velocity estimation is a counts/time estimator but the time is not the sample period but rather the time between the first and last counts, which means the resolution can be much better than counts/servo period.

Note that this is not specific to the 7I76 or 7I76e, the encoder counter and velocity estimation code is common across all Hostmot2 based hardware

If you only need 25 Hz servo bandwidth, this is all rather academic anyway as you can increase the integration time to even 5 or 10 ms. Just depends on what your Z mechanics can do and how fast and how bumpy a surface you want to track

Thank you, I assume from your answer that this explanation is not available in a public document.

I don't know if a 25hz servo rate is good enough for my mechanics, that is just a magic number a Hypertherm guru quoted one time. I am still building my new Z axis mechanics. Based on the performance of my X &Y axis I see no reason the actual Z maximum velocity and accelerations will be lower, same drive, same stepper, nearly same reduction, 1/4 the mass. My X and Y axis run reliably at 225ipm so if my Z can move that fast I should be able to cut some pretty wavy sheet, I will not be trying to cut corrugated sheet steel like some of the THC ads show. Some day I will shell out for 5 new Gecko drivers and power supply to boost my top end.

To increase the integration time do I need to instantiate a new thread running at the desired integration period? I assume that this is the thread that will call the THC component? I have not gotten to creating ini and HAL files yet, I only know that the communication between my PC and the 7i76E works!

John

islander261 wrote: Thank you, I assume from your answer that this explanation is not available in a public document.

It is, to an extent. The source-code is here:
git.linuxcnc.org/gitweb?p=linuxcnc.git;a...cab5bd11fe3f2ed#l862

And the FPGA code is here
git.linuxcnc.org/gitweb?p=hostmot2-firmw...f8568c80b728818b9a8b

I also has same problem at the moment: trying to attach THCAD-10 to 7i76E. Unfortunatelly I have created the topic under HAL configuration questions before I've met this thread. My initial intention was to attach THCAD to the hardware encoder counter on 7i76E board and configure thc component by providing the right pins. But on the first attempt my setup didn't work. Here my config files. Physically I connected feedback from plasma to analog input on THCAD board, and verified that it shows some meaningfull value while arc is on. Then I've connected pins FO+ FO- to 7i76e enc A+ A- inputs according to the documentation. Then I've running 'thc' component on servo thread and connected encoder frequency out signal to thc in signal:

# Set up the Encoder for the THC
setp hm2_[HOSTMOT2](BOARD).0.encoder.00.counter-mode 1
net thc-vel-in hm2_[HOSTMOT2](BOARD).0.encoder.00.velocity => thc.encoder-vel
setp thc.scale-offset 119000
setp thc.vel-scale 0.00037866834

# this might need to be increased
setp thc.correction-vel 0.0001

As the result I don't see it working yet: the voltage indicator shows 0 and not changing while arc is on.
What's wrong with my config?

I also have 2 further questions:

1. Is 'thc' component built-in or it requires explicit halcomp 'install'?
2. Am I right that 'thc' also can move Z axis without 'thcud' component, or both components shold be configured?

Thank you in advance!
Oleg

I would trace the encoder velocity signal with halmeter
if its always 0 you likely have a connection issue on the encoder inputs
Note that you may have to set the B input to the proper state or the velocity will be negative

Finally get it working. My issue were connected to wrong switch on THCAD board - it's been set to unipolar encoder signal but on 7i76e were set to bipolar. Now seems it work but I have weird behavior of THCAD.

Initially I've used battery cell 3V to calibrate the velocity scale and set correct values for 'thc' module parameters. Also to see how the system works against the stable voltage source. The problems start appear right from the beginning: when using 1:1 default divider halmeter showed me that the signal from ecoder.velocity pin is jamping like a random in range from 0 to about 200000+ HZ. It looked like the encoder on mesa board is out of time to count the frequency in correct way (which I don't beleave because it's hardware encoder). Then I've switched of the reference voltage to measure frequency for 0V, and it given me 0Hz??? (according to sticker should be 120000 Hz). Really strange...

Next: I've used 1:32 divider to see if encoder interface will cope with the divided value and find that the frequency counted more or less stable. But it still jamping between 23785 and 23809 Hz. Another surprise was to see the frequency of 0V input, which was not 120000 / 32 = 3750Hz but 16000+??? another surprise

So my general impression the THCAD board seems to work but totally different way that it explained in documentation, and I have feeling that the board of mine is probably either misconfigured or broken. Guys do you have any similar issues with it and suggestions how to get it work? Could you recommend me contact from MESA to fix the issues I have?