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Maybe the EL5101 can say when it doesn't have a good reading, or something along those lines. Obviously check cabling.
It seems you get zero Hz as frequency, that's a unique signal, THCAD always give some hundred/thousand of Hz.
Maybe some hal trickery to hold the last good value while frequency is zero. An own component perhaps.

Hmm, can you advise how long it drops to zero for? I did a component once that does a moving average of the torch voltage. You might be able to use it to bridge the outage...

Also you could try just using a 0-10 volt Ethercat analog input instead of the encoder input and thcad..

1. check wiring, literally remove each wire and re-seat it properly on the THCAD side and BeckHoff side
2. use a DVM with memory min/max and measure the 5V supply for the THCAD, if it goes under 4.75V change the power supply or add a 100-220Ufarad capacitor at the THCAD terminals and test again
3. set the divider higher or lower depending on how you look at it, if it is 1/32 set it to 1/64 and plot again.

Hello everyone,

I am currently setting up my plasma cutter and encountering some initial issues that need resolution. One of these issues is the intermittent loss of my THC encoder signal, which occurs briefly at irregular intervals. Aside from this, the signal quality appears to be satisfactory in terms of noise. When the signal is lost for a few milliseconds, the torch attempts to compensate by raising itself before leveling again. I have attached a photograph (apologies for the quality) that illustrates the signal drop, followed by a voltage increase caused by the raised torch before it levels again.

I am utilizing a Beckhoff EL5101 incremental encoder interface in conjunction with a Mesa THCAD2. I have also tested with a THCAD300 I had available, and the issue persists. Additionally, I am employing hypersensing with a second THCAD2 and another Beckhoff EL5101, exhibiting the same behavior. Given that I previously used the THCAD300 with a 7i76e without issues, I suspect that the Beckhoff modules might be the cause.

Attached are three screenshots: one showing arc voltage at 0V, another displaying encoder frequency initially at 0V and then at 12V for testing purposes, and finally, the problematic screenshot showing encoder frequency during cutting. What options do I have to filter these signal drops effectively?

Thank you in advance for any advice or recommendations.

I was asking as I was wondering what is the practical resolution. Everyone talks about better resolution, but do we practically need this "better" resolution? From mesa website: "10 bits at a 1 KHz sample rate and 12 bits at a 250 Hz sample rate"
is 250 Hz update slow? is 10-bits @ 1 kHz not enough? Heard somewhere that 0.01" THC control accuracy today is pretty good and pairing it with other info that 1 V arc voltage change relates to ca 0.004" (varies but can be used as rule) gives 2.5V arc voltage change. 300 V range @ 10-bit gives 300mV resolution. If 250 Hz is enough then 12-bit gives 73 mV.

I know 0.1 nV is better, but do we need it?
It's just because i have two plasma sources: Powermax 45XP and CUT 70P from Stahlwerk. I'm not going to buy CPC kit for 45XP so THCAD-300 will be more universal. I don't know if my 45XP has any divider installed inside. I don't know if CUT 70P has divider as well. I'm away so have no access to machines to open them and check internals. But I have now option to buy THCAD cheaper (shipping to US instead of to europe to avoid unnecessary and significant costs).

BrysonW wrote:

Hello, this is a reply to beauxnez post from few days ago."hello, is it possible to make an nvem card work with qtplasmac?" The answer is yes, another friend and myself are right at the end of a plasma machine build, were using a ec500 as the controller and it works fantastic with qtplasmac. I will say the THC is the only thing that we don't have working at the moment. On ours the plasma output is just on output 1, torch is either on or off. It goes from the board and turns a relay on and off which is the actual switch. For ours we have a Everlast 82i for the plasma cutter which has a 50:1 voltage divider, that gives us a 0 - 5v output for the torch voltage but from my understanding there aren't any analog inputs on these boards. A analog to digital converter may be a option. I'm not sure what the output of the mesa THCAD boards looks like, there may be a way to use one of those. I'm just getting started on trying to setup a arduino to take the analog voltage, work some magic on it, and send the info to linuxcnc that way using modbus.  The downside I'm seeing to this approach is effectively I'm setting up a second controller to take just one analog input, and I'll have to put a switch inline on the ethernet cables.  The upside is another controller and analog input, so now I can dream up more features to add to this machine (During our build process it started as a basic machine, we now have individual limit switches for every axis, probing, etc. , touchscreen interface, and so on..) I saw that you managed to make a card work under remora with qtplasmacmy card now works with the 3 axes under axisI would now like to pass it under qtplasmac, you can help me because I have an error message 

I saw that you managed to make a card work under remora with qtplasmac
my card now works with the 3 axes under axis
I would now like to pass it under qtplasmac, I need help because I have an error message?

 
 
 
 

There was nothing wrong with my THCAD-300, I just switched to a divided voltage source from the new plasma cutter instead of the raw voltage from the older plasma source. By changing the input voltage for the THCAD I would get better resolution with my divided voltage source signal.

tommylight wrote:

CandCNC ?

I was to polite to say anything but a lot of users have bought a THCAD and converted to QTplasmac.

May I know what was wrong with THCAD-300 so you decided to convert it? Just curious.

Thanks, Rod for your input. I guess i'll buy THCAD. CPC is hard to swallow. Simply expensive. Any options to get usable signals from machine internals in other way?
ArcOk should be easile obtainable from PCB, controls from Linux via relays to start plasma should be easy. THCAD-300 straight from the torch connector should be fine as well, isn't it?

I really think becasue your budget is blown already you should buy the 45XP and purchase a CPC CNC interface for it from Hypertherm. I'd also buy the Connector cable they  have although you can just buy the plug and make yor own cable. Then If you get that far. you might as well buy the THCAD2 from Mesa. (If you are in Australia, I might have a THCAD-10 here I could part with.)

PLasma is not an entry level sport in my experience

Gents!

Starting new topic as I don't want to do off topics somewhere else. The time has come to make some metal parts using tools I already have. During annual review of my "weird boxes" (as my wife use to called them) I found some Mesa cards, old Dell Optiplex PC, some servos, Stahlwerk CUT 70P plasma cutter. I think it is enough to say that probably a new CNC plasma cutting machine will emerge from it after 9 months.

Initial assumptions:
- 150 cm x 100 cm work area
- light construction
- belt drive (HTD-3M 20 mm or 25 mm wide)
- Linunxcnc on board
- THC internally in Linuxcnc

My biggest interest is cutting light gauge mild steel and stainless: 0.6 mm (GA 24) to 3.0 (GA 11). Occasionally chunks like 20 mm. 
My understanding is that the lower amperage setting of plasma cutter will force me to increase cutting speed the thinner sheet i will cut. Thus machine gantry and Z-axis assembly weight must be as weight efficient as possible yet still. For drive side - i have a bunch of AC servos - some are chinese 180W integrated AC servos (reguire 48 VDC PSU), some are chinese AC servopacks (230 VAC power) 400W, 600W and 750W. I found some Electrocraft E240 DC permanent magnets servos as well, together with UHU drives (some grandpas probably still remember what UHU servo is:D:D).
Not to waste resources (those servos will be assigned to various projects) i plan to use one drive for Y axis (gantry) - mechanically coupling both sides of the gantry and use HTD 3M 20 (25) mm belts for drive. There is pros and cons - i'm aware of it. Wanna try. After all - it is home shop fun project.
There is two main concers here:
1) THC (i'm not smoking)
2) plasma source
3) Mesa cards

1) I have no Mesa THCAD among my Mesa boards, so the question here is: is there other way or I have to find a way how to finance it (my budget is already gone). How accurate voltage measurement must be for Linuxcnc to perform THC well? I know some of you will say "not worth to reinvent the circle". At some places 1 USD means waaay more then in other places. In my place i need to add sadistic taxes, import fees, customs, freight and VAT on top of every oversea purchase. And i like thinkering:) 

2) My plasma source - Stahlwerk CUT 70P is, unfortunately, HF/HV arc start type. After reading here and there this is the easiest way to get frustrated during first trial and error cutting. I have a change to ruin my budget even more by buying almost new Hypertherm Powermax 45 XP. Unfortunately with no CPC port and with handheld torch. Machine torch price is more than my Stahlwerk CUT 70P brand new with 7 years warranty! (Are they crazy in Hypertherm?!). Anyway I can get 45XP for USD 1000. The rest of the machine I will make out of logs and branches from nearby forest - no problem:)

What you think about plasma source choice? If i go with 45XP I'll have to stick to handheld torch and do some mods due to the lack of CPC port. Is it doable to mod 45XP? Where to get ArcOK signal from? 

3) I have the following Mesa cards: 7i85S, 7i76D (i think two pieces) sinking, 7i96S (i think still two pieces) and 7i92TF (i think still two pieces). What would be the best pick for my machine? Keep in mind I'm planning to make CNC router and CNC conversion on lathe and milling machine out of those cards...

Thank you for your inputs and constructive criticism:)

PCW wrote:

No, 7I96 TB2 pin 12 is the correct 5V source.

What are the scaling factors that you used?
(there must be a missing hal file  where plasma voltage scaling/offset is done)

QTplasmac stores the THCAD scaling settings in the GUI as per the previous screen dump the OP shared.

Here is my latest EtherCAT card, the EaserCAT 6000, with 12 digital inputs, 4 digital outputs, and one frequency counter input for THCAD output.
 
It's the one down in the corner. There are three RTelligent ECT60 EtherCAT stepper motor drivers as well.
The inputs are limit switches for X, Y, Z, e-stop, floating, break-away and arc-OK.
Plasma-on is controlled by output 1.
There is one frequency counter input. Come to think of it it wouldn't be difficult to add another frequency counter for ohmic sensing, but I don't think my plasma cutter supports that, a Herocut 55X.
More details are here, including all schematics and source code.
github.com/MetalMusings/MyOwnEtherCATDevice
I haven't been cutting a whole lot with it yet. The worry has been the frequency counter that had some interference, seems to have been due to poor cable choice. With that sorted, voltage reading is now stable and THC works just fine.

thanks tommylight for your quick reply. Well, I'm not sure about that in Arc Pilot, that's why I wrote likely. I relied on the information I was able to find on the Internet. However, I have no doubt that you are right and cutter is not an Arc Pilot. Does it change anything? I think I saw somewhere that you have implemented projects with HF plasma and THCAD300. Could you tell me where exactly those wires should be connected? anyway, if it is necessary to make this cutter work with CNC, I also have PROMA THC 150,