Advanced Search

You could get rid of the short and try adding an isolated 24v power supply (Meanwell hdr-15-24) that is connected to the plasma inputs on the thcad. When cutting, nothing will get damaged. The hypersensing component can see full torch voltage when you are cutting  and it does not care... so this should give you the confidence to do it

You might need to and2 the probe signal so it will only turn on when actually probing.

Here is a quick test where I jumped the shield to the nozzle and then feed voltage from my ohmic into it and then ground the nozzle and the voltage drops like a stone. My thcad-10 is using opto22 and relays to isolate everything so that’s why I have to trigger the ohmic button to send voltage to the nozzle.



youtube.com/shorts/fuJnQ76LXl8?si=pr583jeB8bvqNj0g

Yes, that was one of the original reasons the ohmic test was included. It was intended to check if there was a short like yours before starting a job. It does not happen very often. I only ever experienced it once and I found a bit of rubbish inside the tip,  much like you did. I have thought of setting it up to use one thcad. I'm sure it could be done fairly easily.

Oh ok so you’re not waiting for the voltage to go to zero to trigger the contact. Your looking at any voltage drop and once it does it’s triggering contact. That make perfect sense to use a thcad and watch the frequency output. Then you could set the trip frequency on the encoder input on your mesa board. I wonder if there is a way to double duty a single thcad-10.

You know I stumbled upon something the other day by accident that could work. I was using my fine cut consumables. And I was testing my retraction to make sure my actual retraction was what the display was stating it was. I held the ohmic button down and moved z down till it stopped from the ohmic trip. But I noticed when it touched I seen a +10v on the cut voltage. I did it agian and it was still there. So I started looking around and found a tiny slag bead stuck up in the nozzle bridging the nozzle to the shield. This was back feeding the ohmic voltage into the nozzle and it was showing up on the cut voltage.

Would there be a way to use this to sense ohmic. I don't know the ramifications to running the nozzle bridged to shield but it had been like that for awhile as I had just been cutting.

Stahlwerk
www.stahlwerk-schweissgeraete.de/Plasmaschneider-CUT
Good quality and cheaper than china, vertical machine torch is 40E in Germany, with 5 meter cable is 90E, bought both.
Mind the pilot arc, there are some without it so do not get those, it is easy just look for a red knob on the bottom front and usually it is written in spec info.

rodw and tommylight thanks for your answers. Although I have to admit I am stil confused.

I bought a cheap pilot arc plasma to play arround. It has an explicit connection between the tip and the workpiece. Ohmic sensing can't be done. Right?

Anyhow, I build a CNC Plasma and I am looking for a suitable frontend (plasma and torch) my wishlist includes:

1 plasma cutter (hopefully < $1000) with a european distributor
2 Ohmic or hypersensing (willing and able to build homemade electronics if I know what)
3 THC with a THCAD-x (best case with an avaibale THCAD-300)

Can someone propose a setup ?