Set the current for the plasma generator from the Plasmac

tommylight wrote:

It sure seems to have exactly that : analogue control for current and some other stuff.
But it also has RS485, so a cheap USB to RS485 should do just fine, or might not as it does not seem to be a hypertherm so might have different comms.
Pins 10, 12, and 13 should do the trick with a Mesa 7i76, as they are GND, +12V and the analog IN.

Except RS485 is not real time.

PCW, I know Grotius replaced the pot on an ESAB with an ethercat controlled one and its based on the Thermal Dynamics machine.
Just looking at the circuit diagram the current control is definitely a pot on a seperate board connected via 40 pin connector. pin 1 is labelled -V_OUT_SIGNAL which I guess is the most likely candidate for the current control. I guess you could insert a piggyback 40 pin connector and intercept the pot. ONe day when I have time to dig....

Hmm, there is a test point TP7 called POT DEMAND so surely that must be the current signal pot output...

Hello together,

i have a other problem:

the hal command: plasmac_run.cut-amps-f
the connection does not seem to be available (see attachments)

Please can you help?

thanks

Place the code to your post gui hal file. I think the pin is a GUI pin so its not created when you are enabling it.

phillc54 wrote:

PlasmaC only uses the cut current if you have Powermax RS485 comms enabled.

You could use the associated HAL pin to do what you wanted, there are two pins available:

1. a float pin named plasmac_run.cut-current-f
2. a S32 pin named plasmac_run.cut-current-s

Aren't these user space pins so they are not real time?
Wouldn't the OP be better using the spindle speed to control this so its real time?
Will Plasmac allow that?

PlasmaC is a real time component so I would expect all of its pins
to at least be capable of real time response.

Ahh I see those pins dont come from plasmac proper but plasmac_run

They look like they would work for the current usage (presetting the current for a job?)

Dynamic current control is a whole different subject which would probably require
infrastructure in PlasmaC. Could this be used to vary the current based velocity
on corners and avoid THC corner lock?

I've tested it and it works so far.

postgui.hal:
net run_current plasmac_run.cut-amps-f => hm2_7i76e.0.7i76.0.0.spinout
(the spindle settings in the ini file isn´t necesarry because it makes no different if it´s in or out)

But the scaling is still wrong. If I set the ampere value to 0 - I measure -0.1 V. At 100A - I measure -0.2 V.
Second, the polarity is wrong.
How can I change this points?
One minor Point: the value in the material - amps i can only change with the up/down arrows. Its not possible to change the value with direkt entry.

My annotation:
for me it is advantageous if I can adjust the current setting from the material settings. I don't have to go back to the plasma generator every time to change the power setting on the device. And I can't forget to change the value!! For me it´s not
necessary in real time.

thanks

The 7I76e analog output is a potentiometer replacement device
It needs an external 10-12V DC power supply if the connected device
does not supply this power

I think there should be a small component with two input pins. One for the GUI and one for the Real time HALand one output pin which is the scaled value for the potentiometer. I'd need to think it a bit more but maybe HAL and the GUI could play well together this way.

One time stalled project I have is to read the arc radius (done) and calculate the centripetal velocity limit on holes and this would play nicely along with this as Hal could automagically control cut velocity, current and even offset the cutting path to account for the difference in kerf width at slower velocity.

I have some maths I am struggling with. Andy has helped a bit but I want to solve this puzzle

A tool on a CNC machine is travelling at 10.24 metres per minute (0.17067 metres per second) can accelerate at 5 metres per second.
What is the minimum arc radius it can follow at that velocity?

Its not as simple as it looks as there is a conversion between linear and radial velocities...