HAL Question

phillc54 wrote:

I think that is all part of the ohmic component.

This line:

net plasmac:ohmic-enable plasmac.ohmic-enable => ohmicsense.is-probing

connects the plasmac.ohmic-enable output pin to the ohmic component. This pin should go True when you do an ohmic test. From there the ohmic component handles everything.

rodw wrote:

phillc54 wrote:

OK, it looks like you will need Rod to help you.

Sorry but I have my machine in pieces for another few days so I can't help much. Ohmic2 is still a work in progress and it not 100% reliable.

There should be some thresholds set via a setp command and I'm not seeing that is included in your connections.hal

But before that, you need to make sure that you are seeing the encoder velocity change with hal show, then make sure you can see the voltage in halshow when the torch touches the material.

I'm also not sure how it handles Phill's new fast probing.

net ohmic:power => hm2_7i76e.0.7i76.0.0.output-11

rodw wrote:

There should be some thresholds set via a setp command and I'm not seeing that is included in your connections.hal

# ---OHMIC signals---
#0V = 139.8 KHz
#5v = 953.9 KHz
setp hm2_5i25.0.encoder.01.scale -1
setp hm2_5i25.0.encoder.01.counter-mode 1
setp hm2_5i25.0.encoder.01.filter 1

loadrt ohmic2 names=ohmicsense
addf ohmicsense servo-thread
 
setp ohmicsense.thcad-0-volt-freq    139800
setp ohmicsense.thcad-max-volt-freq  953900
setp ohmicsense.thcad-divide         32
setp ohmicsense.thcad-fullscale      5
setp ohmicsense.volt-divider         4.9
setp ohmicsense.ohmic-threshold      23.5
setp ohmicsense.ohmic-low            21.5
setp ohmicsense.mode                 1 
setp ohmicsense.num-readings         10
net ohmic-vel ohmicsense.velocity-in <= hm2_5i25.0.encoder.01.velocity
unlinkp debounce.0.2.in
net ohmic-true ohmicsense.ohmic-on => debounce.0.2.in
net plasmac:ohmic-enable plasmac.ohmic-enable => ohmicsense.is-probing
net ohmic:type  <= motion.motion-type
net ohmic:type  => ohmicsense.motion-type-in
net ohmic:power <= ohmicsense.power-on
net ohmic:power => hm2_5i25.0.7i76.0.0.output-01

rodw wrote:

What I was trying to do was to turn the ohmic sensing circuit on when the machine started to run a job and off at the end of it to prevent any corrosion of consumables inside the torch if the machine is left powered on. The trouble is I could not use the spindle on pin (which is normally how its done) because ohmic runs before the spindle turns on. So it got a bit messy.

Thats why I decided to use motion.motion-type and power on if it was not zero so I needed to add some code to output a bit pin type. See
linuxcnc.org/docs/2.8/html/man/man9/motion.9.html

I did this cos earlier sometimes the circuit was not powered when probing.

rodw wrote:

Supposedly. But Plasmac breaks so many NC rules....
The probe enable switch was designed to turn the relay based system off when not probing to avoid any chance of arc voltage doing bad things to the electronics. You could check for a shorted torch (generally from water) by pressing that button before running a job. If the ArcOK light came on, you had a problem.

Hypersensing makes the isolation relay redundant due to the overvoltage protection of the THCAD and also the isolation of the power supply.
Plus the added resistor suggested by PCW and revised sensing algorithm means there is no need to connect an isolation relay to test ArcOK. It will be visible anyway if its stuck on. This is one of the things I wanted to improve on.. I wanted it to be on while cutting becasue it can sense if an arc is on but I am not sure what it could be used for..