Plasma CNC-Table questions

[MaikTheBike2]

Hi,

currently Im building a CNC-Table that uses a Hypertherm 1000 plasma cutter with a SL60 hand-torch from ThermalDynamics.
Maybe someone can answer me some questions about the build.

1. How would you rate the cut-quality of the attached SL60- Hand-Torch ? How good is it compared to other Torches or hypertherms FineCut ?
Is it good for CNC-cutting ?

2. I made a little CNC cutting test with a small water-pan under the sheet-metal. While cutting water was spraying up to the torch. Does the water harm the torch or is this no problem ?

3. Which CNC-Software and Controller is the most professional and/or most user-friendly ?
Ive read that there is PlasmaC with Mesa-Cards, but then I would have to use Linux ?

Most users are familiar with windows. Is there a good ethernet-system that can be used on windows ? And which software do you recommend ? I tried Mach 3, but sometimes there seems to be some bugs ?
Which software and Controller are mostly used in industrial plasma cutting machines ?

4. Does it make sense to build the water-pan out of stainless steel and the slats out of mild steel ? Or should the water-pan also be made of stainless steel ?

Thanks a lot,
Maik

[beefy]

Hi Maik,

I've never had a problem with the torch and water. The main thing I'd do as a preventive measure is make sure the very LAST post cut air flow is done without any splashing in the water table, just so the air pressure within the torch "dries out" the nozzle, etc.

I started with Mach3, then moved to UCCNC, and have just ripped out all my fully functioning UCCNC equipment to have a go at moving over to Linuxcnc. I do have to say it's a bit more of an exhausting journey going the Linuxcnc route, but I feel it will be worth it once I get there. UCCNC is windows based and works pretty good but there hasn't been an upgrade for at least an entire year, so I'm worried something is happening to development. Many others are expressing the same concerns. For me, what's worse is I reported a very small but significant bug in their wireless pendant programming, yet one and a half years later this is still not fixed (I've pestered them about is several times). They told me the fix will come with the next major release (whenever that will be) but why I'll have to wait possibly 2 years or more for a very simply bug fix..............well all I can say is that sets alarm bells going off for me. It's almost as though the major programmer in the company is not there any more.

Having said that, quite a few users are very happy with a UCCNC ethernet controller board running together with the Neuron THC (a bit pricey). I did use that setup and it worked OK but due to my nerdy nature and not being happy with a "normal" system I wanted more control but the custom screen and the Neuron plugin prevented me from doing certain things. So I designed my own THC and plugin software, and then I found Linuxcnc LOL..........

I think a stainless water pan would be great, while keeping the sacrificial slats mild steel. If you use some sort of rust preventing plasma quench you'd be OK regardless but I personally would like a stainless pan. I made my pan out of 3mm mild steel because it was cheaper.

[acourtjester]

I agree with Beefy, and I have followed a similar path with software being used on my tables. You are correct in PlasmaC with Mesa cars requires Linux and it is a somewhat large shift in learning. With that being said I think the overall picture it is the cheapest route, as the package for the 7I76E and THCAD-5 and THCAD-10 is near $300, software is free. This covers table control and Ohmic sensing and THC from one supplier.
If you can justify the coat a stainless tank would be nice, one thing is the clean-up is no different as the melted metal is still in the bottom of the tank. One thing with the SL-60 torch is the selection of nozzles for different amps and kerf width, unless thing have changed their nozzles are only for blasting through metal.

[MaikTheBike2]

Thanks for your valuable replies.


I've taken a closer look at LinuxCNC with Mesa-controllers and it really seems to be a very good and reliable system.

At the moment there are no 7I76E- cards in stock (Germany). The seller told me, that there are 7I76ED in stock. Can sb. tell me, what the difference between both cards is ? What is "sinking" and "sourcing" ? Is the wiring or function of the 7i76ED different to the 7i76E ?

On youtube I've found some plasma-videos from people using the 7i96-Card. Would this card also be sufficient for a CNC- Plasma with THCAD ?
The 7i96 seems to cost much less than the 7i76e ( ~140€ vs 240€). Are there any drawbacks in functionality for plasma-cutting ?

Which THCAD would be suitable for the Hypertherm 1000 G3 ? I think there is a voltage-divider with ratio 1:50 build in.
In the THCAD-product-description it says:

"The THCAD has a frequency output range of approximately 100 KHz to 1 MHz. T his can be counted directly by our FPGA cards for conversion to voltage value".
But the 7i96 doesn't seem to have FPGA ?


And one more question about the water table: Would it also make sense to use 1-2mm Aluminium for the water table ? Or will it corrode after some time and not look good anymore ?

Thanks a lot,
Maik

[robertspark]

I will try to answer all of your questions, it may take a few goes.

the 7i76ed has sinking outputs. this means that when you send a signal to the output they will send that output to zero volts. you basically wire 24v to all devices, such as valves and relays, and the second wire you bring back to the 7i76ed board so that when you trigger the output it sends it to zero volts and the current flows and activates the output device.

the 7i76e has sourcing outputs..... you wire a zero volt connection to each device, and the second wire / connection you wire back to the 7i76e. when you trigger an output, the 7i76e will provide 24v to that device, current will flow and the device is activated.

the input pins of the 7i76e and 7i76ed are the same and require a 24v signal on them to be seen as the input being active (high)

the choice of board is really a personal preference, but some consider the 7i76e to be a safer board in its operation. because an output will only be triggered if you feed 24v to it. however with the 7i76ed if maybe I cut through a cable or a cable was chaffed or worn through it may be possible that the output could be triggered because you are feeding 24v to all devices and all it takes is that other wire to connect to zero volts and that output will be activated.

______________________________________
consider
https://eusurplus.com/
in Portugal, very quick delivery
also the manufacturer in the us
http://store.mesanet.com/index.php?route=common/home
and another us supplier (very quick too)
https://mesaus.com/

and there are other agents / suppliers too
http://store.mesanet.com/international-dealers
_______________________________________

the 7i96 has less outputs and inputs. the outputs are also isolated from each other (i.e they are NOT sourcing or sinking, and can be wired either way)
the board performs the same as the others (it has the same FPGA chip), but it has fewer inputs and outputs, it also does not have an analog output control (think digital potentiometer) usually used for spindle speed control on a mill or router

___________________________

I would suggest getting a spreadsheet and listing out all of your connection requirements and list next to them if they require an input or output so that you can get a pin / Io count
torch fire output
floating head input
plasma transfer / arc ok input

also consider if you want limit switches of the axis (they can be shared through 1 input or an axis or each end of an axis, they can also be set up as shared homing switches too or they could be individual). if you wish to square the gantry via a homing sequence then each axis will need to be on its own input. my configuration is as follows, but I have specific requirements for this and it may be different to your needs as I share a single 7i76e (using both expansion ports too) between a 4 axis (5xdrive) plasma cutter, 4 axis mill (4xdrive) and a 3 axis (4xdrive) router all using the same stepper drives, as their stepper motors are the same amperage at 4.2A each.

X++/X-- & home input
Y++/Y-- & home input
Y'++/Y'-- & home input
Z++ & home input

I also have each drives enable signals wired to individual inputs so I can enable the correct drives for the correct machine configuration, and I have fault signals from each drive so motion will stop if anything errors out
X drive enable input
Y drive enable input
Y' drive enable input
Z drive enable input
A drive enable input

X drive fault output
Y drive fault output
Y' drive fault output
Z drive fault output
A drive fault output
VFD drive fault output

but my setup is VERY complicated because I share one controls cabinet and PC between plasma mill router and lathe ( lathe via different controller + 2x drives + servo spindle). I also require 5v outputs and 5v inputs too (for a laser diode PWM control, and a SuperPID + other things such as MPG encoders)

__________________________________

I have a 50:1 powermax 45 (non XP) and use a THCAD5, as it provides a range of zero to 255v range. (the voltage divider is 50:1 the voltage divider ratio is 51.... 5v X 51 = 255v)hence I would use a THCAD5.

if you had a 20:1 voltage divider output instead then I would use a THCAD10 as it would provide a range of zero to 210V (10v X 21 = 210v)

___________________________________

the 7i96 does have an fpga (black square, LHS of board near ethernet connection)
http://store.mesanet.com/index.php?rout ... earch=7i96

the 7i96 has an encoder input so it can read 1 or 2 thcad cards should you wish to use ohmic sensing via a thcad. I do not but I already had / have an ohmic probe. it allows a bit of potential flexibility if you have a requirement for ohmic sensing. it depends on your ohmic sensor whether you can use it with a water table, and it can be adjusted for the electrical conductivity of the water in the water table (my ohmic sensor can via manual adjustment, but I don't use a water table).
___________________________________

you can use aluminium or mild (carbon) steel or stainless steel for the water trough.... they just normally add an inhibitor within it to prevent corrosion. (washing powder soda seems to work well and is cheap)... never used it, cannot comment from experience.

plasma cutting is a dirty process and a very hot cutting process. so items generally don't stay clean if you are using the plasma cutter because the effect of heat and swarf had to go somewhere.... and that would be your water trough, sacrificial slats etc....

my sacrificial slats are 15x3mm mild steel flat bar.... they worked fine when I was using a 30A plasma cutter, but the power of a 45A plasma cutter cutting thin 2mm mild steel ..... the slats take a hammering.... solution .... use fine cut consumables.... turn the amperage down appropriate to the material being cut 45A cutting current against 2mm mild steel is using a sledge hammer to crack a nut!

I think I've answered everything you have asked

feel free to ask something else

[robertspark]

it's worth saying that I too have followed the similar path to Keith / beefy and gone mach3 / mach4 / uccnc

uccnc is great, very simple to use and install. macros simple to write in c# (c sharp) or VB .

if you have a simple 3 axis or 4 axis machine then it's great out of the box.

there are a few issues that probably won't affect most users and not new users.

but when you get to know a bit more about CNC and maybe want to do something a little custom or different then in my opinion it fails because some of the functionality is locked into the firmware and beyond your control. also upgrading versions if you use a custom screenset means you may not be able to get the benefit of some of those features.... or your machine may fail to work because the updated software is looking for a parameter on the screenset that does not exist on your customised one or you have a tab numbering clash or possibly a screenset element numbering clash that the new software does not like.

if you are going to use it out of the box, great. you can be up and running very fast much faster than linuxcnc imo, and the learning curve is a lot less.

it does not do lathe or turning. but it does do / have a lot of synchronous miscellaneous (M) codes that you can use with plasma or laser and anything digital. it can have analog inputs and output control or PWM, but these are largely non-synchronous (except for M10 / M11 )

in the early days when there seemed to be few users or at least far fewer, cncdrive were keen to engage with various users and have a discussion about features and improvements, that were not always included or does as there was a healthy discussion and debate. but as the users rose they tended (imo) to just either ignore points raised or give a bs answer that it had been discussed previous and did not have the time to engage. I understand if you have 100,000, 500,000, whatever devices in use, what is the point of adding or changing something for 1 user... as the development cost can be enormous compared to the benefit (cash is already in the bank for 100k or 500k or whatever products and software licences sold)

covid hit and as they are based in Hungary, they have been hit bad with covid ~2600 deaths per 1million population (like most places with poor government guidance and let's face it all of us worried about jobs, money and how we are going to pay the bills if we cannot work + really governments that want "normal" to remain or get back to it asap).... hence it appears that software development has stopped (there have been NO development releases for over a year now, and they use to come out every 2 months or so) and are just spinning plates and answering the usual setup queries on the forum solved by RTM! twice!! three times!!!

uccnc does not do conditional parametric programming / gcode. it does parametric just not conditional, which was something I was now more and more in need of..... and because few (hobbyist? / small scale) CNC users need parametric programming there was zero interest in adding that to uccnc and I could not see it ever being added

I have removed my 2x uccnc controllers and my neuron thc from my control cabinet and am slowly switching everything to linuxcnc. not because it is better faster or provides a better finished part (given CNC is all about the bit in your hand at the end of the job and not which route you took to get there). but because it is more open to what would be with a windows environment firmware changes and integration, and it supports lathe and seems to have a very advanced wizard to adding groups of simple operations avoiding the use of cam for mundane tasks (facing, turning, parting, simple shapes etc)


linuxcnc also has a lot of components that allow for integration of other stuff without me having to write / create a plugin or component. both have modbus, both integrate some and different pendants, but uccnc does not have ethercat (not that I have a need) or rs232 (which I do have a need for now with a CNC keypad).

linuxcnc is not the best, it's just a solution to my complex needs, it is however the cheapest in capital cost (it's free!) but that will be offset by learning time.... but I have a little knowledge already about CNC, and a bit of programming experience, but if I were green to CNC and programming and computers and electronics and electrical wiring and was just an artisan welder / fabricator looking to add a CNC plasma cutter to my collection of tools, then I would probably NOT jump into linuxcnc directly but buy a package or prebuilt machine with some operator training package .....

the learning curve and time required to invest in linuxcnc can be costly if your time truly is money.... if your time is "free" then you don't value your time correctly imo.

[acourtjester]

I found this a small help in the setup of the THCAD-10 for THC, just plug in your info and it calculates things.
https://jscalc.io/calc/NTr5QDX6WgMThBVb

[MaikTheBike2]

Thanks a lot for your replies and all the valuable information.

I've contacted the eusurplus-shop, and they told me that the mesa-card(s) are out of stock because of corona.
Maybe uccnc also seems to be an alternative to linuxcnc because it runs on windows.

Robert, can tell me more about your uccnc-setup or post a picture of it ?
Which controller do you recommend and how did you connect it to the thc ?
The UC- ... -ETH controllers seem to tranfer data to the an LPT-output via ethernet and then another LPT-controller is needed ?

Would it also be possible to control the machine with such a smoothstepper - board

https://www.ebay.com/itm/271242258619?h ... SwQiRUl4sH

and a simple/cheap breakout board like that:

https://www.ebay.de/itm/283850844908?ha ... SwFAtemegw

using uccnc and a THC ?

Thanks

[djreiswig]

Pretty sure the SmoothStepper boards are Mach only.

[robertspark]

uccnc will only work with CNC drive boards
uc100 (check it's a genuine one as there are ones called uc100 that are not cncdrive ones)
uc300eth
uc400eth
axbbe

https://cncdrive.com/products.html

smoothstepper is a motion controller developed by warp9, and is not compatible with uccnc it will only run mach3 and mach4.
https://warp9td.com/

you can use cheap bobs with the uc100, uc300eth and uc400eth. on the uc300eth there are a few ports with are lpt ports and ethere are a couple of ecp printer ports (pins 2-9 are inputs )

please note you can use a Mesa 7i92 which is the same functionality as the uc400eth (or 2 ports).... but much more flexible as you can use standard bobs or even other Mesa boards 7i76.
http://store.mesanet.com/index.php?rout ... uct_id=302

and also the 7i80 which is similar to the uc300eth (but much more flexible)

http://store.mesanet.com/index.php?rout ... duct_id=60

[acourtjester]

To give you some additional info on the UCCNC setup, I use the UC400eth and their software for about $210. not much more than Mach software alone. This come with the either cable and one interface connection cable for a parallel printer port BOB board, there is a second printer port on the UC400eth if you want more input/output pins. I use one BOB for 3 axis with combined home/limit switch input, ohmic sensor input, and 3 THC inputs. Much smoother that Mach with normal Parallel printer BOB. Setup is similar to Mach but the screen set appears different with more info showing on the operational page.
https://www.automationtechnologiesinc.c ... controller $156.75
https://www.automationtechnologiesinc.c ... l-software $60.00

[robertspark]

UC motion controllers + uccnc is also available in the US via cnc4pc
https://www.cnc4pc.com/motion-control/m ... ucx00.html
cnc4pc also sell them (in the US) via amazon too.

The price variance is the options of buying it with or without software etc.

Please note: UCCNC is locked to the device...... each device has a unique serial number and when you buy the hardware, you register the hardware and they give you a unique license file for your hardware. One UCCNC license (~$60) will only work with one specific UCCNC device..... I have 2 x UCCNC motion controllers (UC300ETH + UC400ETH) and have 2 x UCCNC licenses. you can sell your license with your hardware should you sell it on. If you don't give it to your hardware purchaser they will need to buy another license from CNCDrive.

keep your UCCNC licence file safe as you will need it if you swap PC's (same with sheetcam etc).

You can install UCCNC in Demo mode and it will give you a feel for the software. It will not however output any motion without a UCCNC licence file corresponding to the hardware hard-coded serial number.

If your device ever failed the normal procedure is to buy another UC motion controller and drill a hole through the chip + issue a photo to CNCDrive and they will give you another free licence of uccnc for your new replacement hardware should you unfortunately kill it.

CNCRoom (Thailand) also offer compatible BoBs for the UC300eth (I have a UB1 and UD1-U).
https://www.cncroom.com/interface-cards ... boa4fijnm2
They are 24V and have a lot of IO's, and are another option to at least be aware of / worth considering.
They use DHL and arrive very quickly (pre-covid).

[MaikTheBike2]

Thanks,

I've installed LinuxCNC on my Laptop to play with it a little bit and it looks good.
Next week mesa-cards will be availibe again in Europe and then I will buy a card.

I still haven't found out, which THCAD-version I need. In the Hypertherm 1000-G3-manual I haven't found the answer ?

The seller of the plasmacutter wired something inside the Hypertherm 1000. There is a cable with 1/50 and 1/20 divided voltage comming out of the machine. Should I get THCAD 5 or 10 in this case ?


Thanks,
Maik

[robertspark]

if you use the 50:1, get a THCAD5

for 20:1, get a THCAD10

[MaikTheBike2]

Thanks Robert,
Is it safe to test the voltage divider the seller added by measuring the divided voltage using a multimeter when the pilot arc is firing ? Or do i neet to actually cut with the machine to see if the voltage divider works ? And are the results shown on the multimeter correct ?

I already made a small test without thc and a very cheap usb-controller and there was some dross on a 2mm sheet. Is that normal or can i improve cut quality ? As mentioned the torch is a sl60 from TD.

Thanks,
Maik

[acourtjester]

Testing the should be done with cutting, the pilot arc is much higher voltage. Most THC unit use a delay so the arc voltage is not checked until the torch is at cut height and as the torch starts to move. The dross should be handled by tuning the table for cut speed and cutting specs a small amount of dross is normal. Air pressure can affect the dross also.

[robertspark]

Voltage dividers are a bit of a strange discussion, as the only way to really know what they are (ratio wise) is to actually measure them or inspect the bands on the resistors.

a 50:1 voltage divider is the RESISTOR RATIO, i.e. 100K and 2K, so you get 50:1.
However, the voltage measured is actually 51 times less than the actual voltage read.... (OHMS law).
This can be affected by the parallel resistance of the voltage sense circuit that you connect onto the voltage divider.

a 20:1 voltage divider i.e. 100K and 5K, will give you a measured voltage 21 times less than the actual voltage.

The approach that really gets taken is everyone uses the voltage in the book as a bit of a guide (a starting pointing), and then dials the voltage up or down as needed. Most guys who use a hypertherm SEEM to just use the book values (I've had 2 hypertherms, an old PMX350 and a PMX45 (non-XP) and the book values are fine for me)

[Rodw]

The seller of the plasmacutter wired something inside the Hypertherm 1000. There is a cable with 1/50 and 1/20 divided voltage comming out of the machine. Should I get THCAD 5 or 10 in this case ?


Thanks,
Maik

My recommendation would be to use the 20:1 divider with a THCAD-10. Without a scaling resistor, this will measure up to 200 volts full scale. That is enough for accurate THC operation. The THCAD-10 is still rated to 500V over voltage so you won't break it. Typically on a pierce, by the time you get an arcok signal, the voltage will be well below 200v so you don't need to care about voltages > about 150 volts.
If you do decide you want to see up to say 300 volts, you an simply add a resistor as per the THCAD manual. But in my view it won't be required.

Accurate torch voltage is not really a requirement if you let LCNC auto sample the torch voltage (which I always do) After it is sampled, the THC will track the correct height. Who cares if your screen display is a few volts out?

I run a stainless tray with mild steel slats and the pan is still near perfect after a few years.

The SL60 uses the same consumables as my SL100 machine torch so you have 30amp, 40 amp and 60 amp consumables available. Thermal Dynamics has cut charts.

The 7i76e is a good choice. The D version is only needed for retrofits. Don't use it for new builds. It has an onboard spindle relay that can be used to trigger the torch and also MPG inputs if you want to add them. The 7i96 is a more economical choice. All 7i96 outputs have relays builtin but if you configure it to use a MPG, you start running out of IO pins.

[MaikTheBike2]

Thanks,

I've made a small cut with the plasmacutter and was able to get a voltage of about 4,8 volts on the 1:20 divider. So I guess its a good idea to get the THCAD 10.

I've been waiting for the mesa 7i76e to be availible in europe since 3 weeks. The seller says that they are on the way from usa to europe at the moment . Because of corona it seems to be very hard to buy them at the moment (in europe, eu surplus).

Nonetheless I already watched some tutorials about configuring the card. At the moment I ask myself how the plasma cutter can be started via the mesa-card. There doesn't seem to be a relay on the 7i76e, but I've read, that Its possible to start the plasma cutter via the mesa-card.

When I put 2 wires together (wired by the previous owner of the plasma machine), the plasma cutter starts. Maybe someone knows how to start the plasma (= connect both wires) with the 7i76e ?

Thanks

[acourtjester]

You use an external relay to trigger the plasma on, the board has output pins that switch 24 volts. You can select a pin for torch on in the board setup. This is what I bought to use https://www.ebay.com/itm/184355337322?s ... 2749.l2649
You can also use a standard relay with a diode across the input to protect the Mesa output, Rod shows both in his video.

[Rodw]

Here is a plot of piercing on my Thermal Dynamics A120 with SL100 torch.
I use a THCAD10 AND 30:1 divider with no scaling resistance that gives it a 300 volt range to full scale

arcvoltageplot.png

You can see the voltage (white line) flatlines at full scale (300v) for a while as the arc establishes.
But It drops rapidly over 2.3 milliseconds.

The blue line is the ArcOK signal and you can see by the time it comes on, the voltage is stable at around 115-120 volts.
We don't ever use the arc voltage before we get an ArcOK signal so it does not matter about the scale running out becasue regardless of the scaling the THCAD can handle 500volts 100% of the time without failing. With a smaller plasma cutter, you don't get up to the 170 volts that is the max arc voltage for 120 amps in the cutting charts.

Its this behaviour that leads me to recommend 20 volt full scale and a THCAD-10 becasue 200 volts is more than enough for your machine.

[MaikTheBike2]

You use an external relay to trigger the plasma on, the board has output pins that switch 24 volts. You can select a pin for torch on in the board setup. This is what I bought to use https://www.ebay.com/itm/184355337322?s ... 2749.l2649
You can also use a standard relay with a diode across the input to protect the Mesa output, Rod shows both in his video.

Thanks,

Can the relais you posted be used without a diode or can it only be used with a diode ?

Some time ago I tried to use the cnc-machine with this cheap usb-controller:

https://www.ebay.com/itm/263352844928?h ... SwC45b~KuF

At the beginning the outputs worked perfectly, but soon they didn't work anymore. I connected a 24v relais to the output without a diode.
Is it possible that the output of the card was damaged because I didn't use a diode ?

Where can I find Rods video you mentioned ?
And does somebody know where I can find some good information about wiring the mesa 7i76e with the thcad, plasma cutter and power-supply ?
And is there some information on how to build a switch cabinet professionally ?


Thanks,
Maik

[Rodw]

My video mentioned earlier


Your output could have been damaged becasue a flyback voltage fried it. I did not have a flyback diode on my torch trigger relay for a long time and must have been lucky!
or the current you are switching is less than the minimum current spec of the relay and oxide has built up on the contacts resulting in intermittent or failed operation. The solution to this is to add a pull up or pull down resistor (depending on your circuit design) that ensures the current flow through the contacts are within spec.

Assuming a Mesa card and 24 volt field power, I recommend using a 100 ohm 10 watt resistor as a pull down on the arcOK input as I have had oxidisation problems on the plasma cutters internal arcok relay in the past.

[MaikTheBike2]

Thanks Rod,

Thats a very good and informative video.

### THCAD
It seems that you are using a thcad 10 for voltage sensing and a THCAD5 for ohmic sensing ?
Maybe you can describe how the ohmic sensing works with the THCAD and would ohmic sensing also work with a THCAD 10 ?
Now I ask myself if the voltage-sensing would be sufficient for my plasma-cutter or if I should also go for ohmic sensing.

Did I understand it correctly, that a thcad 10 and thcad 5 can be used/wired simulaniously to a 7i96 without an additional mesa-card ?

Robert, you've written, that you want to switch to ohmic sensing. Is a floating switch too runreliable when it comes to thin sheets of metal ?

### Latency test

I've installed LinuxCNC and have run the Latency test.

The results are attached. Can this Laptop be used for LinuxCNC ? The values seem to be very high ?
1 result is with glxgears running and moving windows around and the other is the result without load.

Its a Lenovo-Laptop from 2012 with an i3-2330m -processor.

### Diode
On ebay I've searched for Diodes to save the outputs on the card. Which specifications should a diode have to protect the output ? Can a 1N4001 50V be used ? Or does the diode have to lock at a little over 24V voltage ?

[Rodw]

Laptops make poor choices for Linuxcnc becasue there are too many power saving features cause high latency. By the second image, that PC is unusable.

Mesa has additional firmware that can be downloaded that allows up to 3 THCAD cards to be installed on the product page on their web site. File name required ends in pl.bit

A THCAD 10 can be used for ohmic sensing with different scaling resistors but there are a few gotchas as its not well documented.
The THCAD in conjunction with the ohmic.comp component I wrote allows us to create a very robust ohmic sensing circuit. With an different component and some changes to the circuit, we can use ohmic sensing quite effectively on a water table as it can still sense a voltage drop when the torch is shorted out internally by water splash.

The IN4001 diode is probably OK but the IN4007 is what I try and use as it can handle 1000 volts