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Unfortunately it would be pretty awkward with those breakouts as the inputs
are slow 12V signals. Even with level shifting I don't know if they could deal
with the ~8KHz signals from the THCAD using the highest divider ratio (128)

The breakout board inputs are activated by grounding so you could try adding
a NPN transistor/small MOSFET to do the level translation from the THCADs ~5V signals
to the 12V required but no guarantees...

A better solution might be to drive the appropriate 7I92 line directly (with maybe a 100 ohm
series resistor for safety)

If you are going to do this (I wouldn't) Make sure your divider resistors are rated for the voltage
and the power. This is difficult as 25KV times 5 mA = 125 W! (this is assuming a THCAD2 jumpered for
5V input and an external 5M resistor)

You can get away with a smaller watt rating because of the "peaky" nature of the HF signal
and it's short duration, but I would not skimp on the voltage rating. I would use  (5x) of
something like this as a minimum:

www.digikey.com/en/products/detail/visha...0001004FAC00/1994729

Because the voltage spikes are mainly in the negative lead,, I would put 4 resistors in the negative lead
and 1 in the positive lead. This combination will (with THCAD2 set for 5V) give a full scale voltage of 255V
 

The proper way would be to wire it to the rectifier output, and use 2 of 1.5Mohm resistors on each wire.
To answer your question, yes HF start can kill the THCAD, but... i have a THCAD10 wired through 2 of 1Mohm resistors at the plasma plugs, plasma is China made Kzubr 60A, it is HF start, it is in use for over 6 months i think, it did not die, yet.
Do this at your own risk, it is not recommended but it works.
Use 2 resistors, 1 on each wire, this is very important, short wires from plasma to resistors, no more than 20-30cm, keep those wires and resistors at least 10cm appart or mount the THCAD close to the source.
And, torch is not positive on plasma, it is negative, the clamp is positive.

Hello!
I just bought a THCAD2 board.
As the manual says i have to connect a 2.9M resistor in series between INPUT+ and thorch. That's clear.
I have a parkside ppsk 40 a1 plasma cutter.

My question is where do I have to connect the Analog IN terminals, is it OK to connect to the cutter's output(torch and clamp terminals) or I have to search on the PCB for the rectifiers and solder wire after them?
I'm asking that becouse the cutter have HF ignition and i don't know does the board survive 25kV ignition voltage(I read that value somewhere on the forum).
Thank you!
 

Hi all,

i have a similar question, as above. I want to connect a THCAD to my 7i92.
On the 7i92 i run 2 breakoutboards (see below) however i can't figure out what pins  i need to connect the thcad to.
How can i find where the encoder pins are connected to?


www.amazon.nl/DollaTek-5-assige-CNC-brea...rivers/dp/B07PNDXZQK

Thanks!

Do you have the HT200 plasma?
It should have a divider, so try to find the service manual for it, Hypertherm had those always available on their website, but not anymore, now they want money for documents, but still not much, so at least they are not greedy.
Have you looked inside the HT200?
Get the THCAD5 if available, with added resistors it works with any divider or raw voltage.

Hey Tom good day to you, my names Tom as well BTW
(theres never enough Toms on the job! haha)
So THCAD5 would be for a divider board with a 0-5v range and thc10 would be for a divider board with a 0-10v range correct? So I will need to see what the voltage output of the divider board on my hypertherm is if there is one or purchase a divider board and wire it up to the raw arc voltage correct? I apologize for bugging you guys with so many questions but I really don't want to order the wrong components so it is very much appreciated.

The mode can be automatically selected based on voltage sensed. You know at startup its not cutting, start in hypersensing mode but if the voltage exceeds 24 volts, calibrate to THC range and stay there until it falls to say < 5 volts, go back to hypersensing mode.

Yes will need 2 factors one for the arc voltage and one for the Hypersensing, also the QtplasmaC need to change from THC to Hypersensing Mode.
 

I don't think the contractor is required as the hypersensing circuit is impervious to high voltage.
Currently when the voltage exceeds 24 volts, the component is seeing an arc voltage and it never breaks now. The thcad always sees a bit past the full scale and the 390k resistor sets full scale to 23.5 volts anyway.

So what if you mux the  THCAD calibration instead? once it is > 24 volts, recalibrate it to be fullscale 200 or 300 volts?

PhillC54.
This is an interesting aproach, basically we are muxing the THCAD input, may be some processing power can be saved using only one encoder.
I re-draw your schematic just to make it more readable, I think this will require some changes to PlasmaC componet.
 

What resistor value would you use between positive of the isolated power supply and the positive input of the THCAD ?

Get the Mesa 7i85, without the S.
And THCAD5 or 10 and 2 of 1MOhm/2W resistors, it is most probably a HF/HV pilot start plasma, and 300 is not recomended for those, although i am sure it works, i have several of those in daily use.
For power supplies, 5V and 24V, both at 5A should do just fine, MeanWell or Delta preferably.

Okay so im putting together a parts list to get started with this build. I put power to the driver box, tripped the contactor with a screw driver and a green light comes on the power board and fan runs. im not sure what else I could do to test it besides connecting the burny 10 back up.
So far in my parts list I have

7I83 Analog output/ analog servo interface
7I85S 4 Channel encoder, 8 differential output 1 channel Serial RS-422 interface
THCAD-300 High isolation A-D accessory (Go to replacement: THCAD2)
7I96S STEP/IO Step & dir plus I/O card

I am going to assume that I can hook straight up to the raw arc voltage of the hypertherm ht2000 with the thcad-300. Is there any advantage to a voltage divider board other then the potential risk of electrical shock? Will I need a power supply to go along with these boards? do you have any recommendations for a reliable one on my previous build I used a cheapo china one and the fan stopped working a while ago.

Hey everyone.

I'm documenting my journey to control a CHC-200F (Capacitive Height Controller) as a Torch Height Controller.

CHC-200F is superior to CHC-200E as the "F" has faster processing and also provides a probe output signal.

These systems are made for use with a DC motor in the torch : which LCNC doesnt.

They communicate to the motor with a PWM signal, which overrides the controller's PWM to provide a height correction.

 

The PWM signal provided is 10V with 9 to 18 KHZ frequency. Which can be read by either the Mesa Encoder input with the proper voltage scaling.

Unlike the arc voltage, which the THCAD converts into an encoder signal, the PWM signal will have a polarity so it will have scaled and offsetted..
It will also have a different "meaning" as the encoder in the THCAD, so it will have to be 'read' in a different way.

Has anyone used mesa systems to read PWM?

Is it more suitable to read it with a THCAD?

PS: Im guessing I could also use the polarity of PWM signal to generate two inputs: Move Torch Up & Move Torch Down, and use QTPLASMAC in Mode 2 (Up/down signals). But this wouldn't provide such a fast thc response as the "arc voltage" does.

This post will be advanced as more progress is made.