Gecko 540 and THCAD-10

Hi Gents,

We are getting a bit lost in all the info on the forum while trying to figure out how to configure our plasma cutter. Mind you, there is a lot of good info, just trying to find the bits that we need for our setup is a bit difficult and time consuming, also because some of the info is obsolete when software like PlasmaC is released.

The machine we are building to replace our old 2-axis machine is a XYYZ gantry table, with a floating switch for torch height probing. We have a Gecko 540 to drive the 4 motors and a THCAD-10 form Mesa to read Arc Voltage from the plasma cutting source, a Hypertherm Powermax 85. Home/limit switches will be built in on all axis. The table itself can hold a 3x1.8m sheet, has room for a rotary axis in the future and is setup so it can be loaded with a forklift. The machine is not a production machine, we are setting it up as a jobbing machine, to handle a large variety of parts in a as large of a range of thicknesses and materials as possible. We need this capability so we can quickly make 1 off or short run parts when we are repairing agricultural machines, often with very short lead times in high season.

Connecting the Gecko G540 and the switches to the motors and the parallel port is straightforward, where I get confused is connecting the THCAD-10 : the connector on the Hypertherm has a (+) and a (-) pin for the voltage divider, I assume they are connected to Analog in (+) and Analog (-) on the THCAD -10 ? On the output side, is only 1 wire needed to feed a signal from pin 2 FOUT (+) to an input on the Gecko 540 (and by extension to the parallel port ? (Aside from +5V power and GND to power the THCAD-10.) From what I have read using the reference frequency on the THCAD-10 is not necessary to obtain the resolution needed for a torch height controller ? And opinions abound, but where is the best place to mount the THCAD-10, right on the Hypertherm or in the control box ?

I see quite a few people using extra Mesa cards, like 7i96 and what not, what is the advantage of using them ? I thought everything could just as easily be controlled via the parallel port (as we do with our old machine) ? What am I missing ? It's been awhile since I have built the old machine, and it seems a lot has improved, but also has gotten more complicated, so I am seeking some solid advice on the way forward.

Cheers, Peter

The THCAD output is a frequency and its usually read with the encoder input on a Mesa card but some people have used the software encoder component to decode using a breakout board (eg your 540). Its a bit slower so you probably need to reduce the frequency jumper on the THCAD board. I think you will need 2 free pins.

Tommylight shared a machine built this way just recently.

There is a description of where to connect the THCAD board in the plasma primer in the 2.8/2.9 docs.

But yes, the divided arc voltage connects to one side and the other side has 4 wires for 5 volt power (2) and the encoder (2)

An issue with using a G540 with a THCAD is that the G540 inputs are slow and not compatible with the THCADs 5V signals. It may be possible to use the THCADs 1/128 mode
(~8 KHz max) and some kind of level shifting (a transistor or optocoupler) but it might be
easier to use a second parallel port.

The reference frequency is not needed and you do not lose resolution at lower THCAD frequencies.

oops sorry for duplicated post