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sharp_reaper wrote:

When I turn on QTPlasmaC the value of Arc Voltage is 145.
The encoder velocity pin seems to be working fine on halshow.
 

Sounds like you have not correctly calibrated qtplasmac for your THCAD settings
The THCAD 0 volt frequency should be what you observe on the encoder velocity pin give or take some bouncing around.
This offset needs to be entered in qtplasmac.

If you read the QTplasmac docs, there is a link to a calculator to determine your settings.

One 2.4M resistor in series to the negative lead will give you a 250V full scale range
which should be OK

Would the resistor I have listed work for the THCAD to read the voltage?

So I was able to double check for short/faulty cables on P1. I've disconnect the encoder connector from 7i96s and no contact to GND.
Made the change of the location of the THCAD board to the outside of the plasma source in a plastic box.
Connected the shield only on the 7i96s side in the pin TB2.9 with the GND cable.
When I turn on QTPlasmaC the value of Arc Voltage is 145.
The encoder velocity pin seems to be working fine on halshow.

What you recommend to do?

Thanks in advance, really don't understand what's happening.

Thank you for your advice!

The THCAD is mounted inside of the plasma source near the control board.

I'm making the recommended change for a plastic box outside of the plasma source.

This is the first Thermal Dynamics equipment that I work.
I've worked with several Hyperthem plasma cutting systems. All of those got an THCAD inside working well.

The THCAD boards seems to be fine. I have to check the encoder inputs from 7i96s but appears to be usable.

I am making that change to the future plasma systems to guarantee the best care for the boards.

When I have the chance I will make the changes and update you.
Thanks

rodw wrote:

But as PCW says, seeing 0 volt and 45 volts indicates it is working.
 

As i understood, he had 0V before firing the torch, and after the first firing it drops to -45, that absolutely points to THCAD working prior to firing and fails miserably after the firing as be it THACD output or 7i96S inputs are gone from the huge amount of EMI the actual torch firing causes and THCAD being enclosed inside a metal case where the source of all that EMI is.
-
The THCAD should be wired at the rectifier, not at the plasma output.
And yes, i have a THACD10 wired directly at the output lugs on an inverter plasma, but i would never advise that.
-
Just to be clear, yes you can mount the THCAD inside the plasma source, but absolutely should be avoided by inexperienced members of the human race.
The plasma source has a plethora of warnings plastered all over it, and the manuals spend several pages describing just how dangerous those things are.

The 200XT may be a HF start device. hyperthem machines that size are. This might mean you need to connect the thcad upstream of the HF generator. If not, It's likely to have damaged the THCAD or the 7l96 encoder. Tommy is the expert in this area.

But as PCW says, seeing 0 volt and 45 volts indicates it is working.

Rather than look at the reported voltage, check the encoder velocity pin in halshow. When not cutting, it should hover at or near the 0 volt frequency. Also it should be bouncing around. If it isn't and just a fixed value either there is an error on your encoder config in HAL or there is an issue on the high voltage side.

Using the plasma bit file, you have 3 encoders so damaging one encoder might have an easy  work around.

 

sharp_reaper wrote:

I have an error with the reading of arc voltage (-45 V) after one piercing.
Before piercing I was reading 0 V.

The THCAD-300 is mounted inside of the plasma source connected directly to raw Arc Voltage.
The output from THCAD-300 is connected to the encoder from 7i96s (TB2.7 and TB2.8).

Already switch the THCAD-300 and 7i96s to brand new ones and at start the readings of arc voltage seems to be ok.
But when I put Torch On the Arc Voltage goes to -45 V, after that the value doesn't change. No matter if plasma is on or off.

Should have asked before doing all that...
And do not mount THCAD's inside plasma sources, mount it on the back of it, in a plastic box.
Using new equipment after a failed test, also not good.

Both the 7I96S and the THCAD(if damaged) are likely repairable with a
single chip/card

Thank you for your reply.

The cable is shielded and twisted pair.

Sorry, what you mean by digital side of THCAD (IN+ IN-) ?

It sounds like a large voltage spike (>25V) is being coupled into the encoder input.
I guess this could be a wiring error. I would disconnect the encoder connector at the 7I96S
and verify that there is no connection from any THCAD digital side pin to the
plasma source GND

Is the cable shielded? If so the shield should be terminated at 7I96S TB2 pin 9 (GND)

 

Hi PCW,

My connections are in twisted pair cables and are connected as follows:
 

From TB4 (200XT plasma system) to THCAD-300 to TB2 (7i96s)

Edit:
 
 

I would expect the THCAD300 to connect to the 7I96S TB2 pins:

7  A+
8  A-
9 GND
12 +5V
A+ and A- should be a twisted pair

Its also very important that none of those pins connect to _anything_
inside the plasma source.

Hello everyone.
I have an error with the reading of arc voltage (-45 V) after one piercing.
Before piercing I was reading 0 V.

My plasma source is AutoCut 200XT from Thermal Dynamics.
I am using a 7i96s mesa card with THCAD-300 also from mesa.
The interface I am using is QTPlasmaC.

The THCAD-300 is mounted inside of the plasma source connected directly to raw Arc Voltage.
The output from THCAD-300 is connected to the encoder from 7i96s (TB2.7 and TB2.8).

Already switch the THCAD-300 and 7i96s to brand new ones and at start the readings of arc voltage seems to be ok.
But when I put Torch On the Arc Voltage goes to -45 V, after that the value doesn't change. No matter if plasma is on or off.
If I look to halshow I get no readings at all in encoder counts signal.

Looks like for some reason that I cannot understand I am damaging the encoder input on the 7i96s board.
I've made the exactly same connections on Hypertherm Plasma Systems and works fine.


   

I wouldn't use the 50:1 voltage divider. a THCAD5 with a 5 volt full scale would be more suited to use with it. Instead just calibrate the THCAD to read 200 to 300 volts full scale with a resistor.