Re: Plasma Controller
I might be a bit biased becasue I have had a lot of input into Linuxcnc's Plasmac configuration becasue I tackled the plasma puzzle before it was conceived.
There are too many people migrating from Mach and UCCNC to ignore it. Whilst you can run it via a parallel port BOB, you will get much better results if you grab a $119 Mesa 7i96 ethernet board and a $69 Mesa THCAD-10.
To adopt a Windows solution today is much like buying a VHS video camera instead of one that records to SD cards.
With Linuxcnc, you don't actually need a THC, all you need is a way to read the torch voltage (via a THCAD-10) and then Linuxcnc's motion controller with sophisticated PID based algorithms can control the torch height. With Plasmac, you get a complete plasma controller, not just a tacked on THC unit. It includes RS485 communications to Hypertherm plasmas, statistics collection and a whole conversational module so you can walk up to the machine and cut simple shapes for flanges and brackets etc.
I started with an Everlast and if you select the 16:1 divider, then you need to set the THCAD up to read 24:1 (with no scaling resistors) becasue the THCAD sees the Everlast's resistors as being part of its scaling resistance (which is not an issue with hypertherm or thermal dynamics).
The other thing is that he ArcOK relay inside the everlast has a minimum current requirement of 100 mA. The Mesa card has a high impedance to ground so my recommendation is to add a 90 Ohm, 10 watt pull down resistor from the Mesa input to 0 volts (assuming 24 volt field power). This will ensure 267 mA passes through the ArcOK relay. A cheap way to do this from off the shelf components is to uses 3 x 270 ohm resistors in parallel to give 15 W of power dissipation (it needs to handle 6-7 Watts).
Finally, the new evolving QTPlasmac touch screen interface is purpose built for plasma control and is very exciting and easy to use.
Good luck!
Rod Webster
www.vehiclemods.net.au