Some help with a circuit I'm working on...hopefully

[mark_s]

Hi,

If its for controlling a plasma torch z axis. See pages 4, 5 and 6

http://www.eaziform.co.uk/files/THC.pdf

[kevlar129bp]

Hey Mark,
Thanks for the link. Cool info to stash in my file of goodies. The circuit they are referring to in the pages you pointed out, is for an "arc ok" or "ok to move" signal. My Thermal Dynamics machine has a built-in "ok to move" dry contact to signify arc transfer. What my machine does lack, as I'm sure you have gathered is the voltage divider circuit. In my travels, I cam across a cool thread on the Parallax forum...check it out:
http://forums.parallax.com/showthrea...Height-Control
Head to post #17 and take a look at the schematics. They have been my wealthiest resource to date.
Look forward to all of your input,
Chris

[kevlar129bp]

Hey Mark,
After reading the pages that you pointed out more in depth, I digress. They do seem to be using a current transformer to sense voltage...Which is very weird, in and of itself because plasma machines are constant current devices. I would love for one of the circuit gurus on this board educate me further on this scheme. It sure has me scratching my head All of the other THC's out there do it with a scaler (divider)... Oh boy, I'm baffled now!
Thanks Mark,
Chris

[mark_s]

Hey Mark,
After reading the pages that you pointed out more in depth, I digress. They do seem to be using a current transformer to sense voltage...Which is very weird, in and of itself because plasma machines are constant current devices. I would love for one of the circuit gurus on this board educate me further on this scheme. It sure has me scratching my head All of the other THC's out there do it with a scaler (divider)... Oh boy, I'm baffled now!
Thanks Mark,
Chris

It's beyond my knowledge. You may want to ask over on the cnczone forum. Someone can probably tell you if this method works?

[mark_s]

Thanks for the link!

I am working a new cnc machine now. In the future, when time allows I want to build a plasma cutter,
so I will be interested in your progress.

[kevlar129bp]

No problem Mark, and thanks for yours. I actually have had a THC on my radar for about 6 years now, but a friend of mine just got his table set up and asked me if I would go back to the drawing board for him. What a guy won't do for his friends huh! I do have to admit, it is self-serving too. Heck, I'll get a THC out of it too. Here's some progress of the PCB's ready to go to OSHPark. RS232 and 20x4 lcd display through the RJ-45 jacks up top. All menus and settings will be controlled through a 24 detent encoder with a built-in push switch. The scaler and gpio boards are set up as daughter boards to the main board as well. I guess I should breadboard the project, now that I have the PCB's done
Any input on this thread is still more than appreciated.
Thanks guys,
Chris