Arc OK intermitent issues on torch fire

txtrone wrote:

snowgoer540 wrote:

This schematic is very similiar to the schematic in the the primer, to which I was referring. However, this one has a bit more detail and also an additional resistor. My original question could have been worded better. I was asking how exactly to wire the 390K resistor into the circuit, ie: do I simply solder a wire onto each end and attach them to +IN on THCAD5 and +24V on isolated power supply?

Your drawing clarifies the power rating of the 390k resistor at 1w, which was another question I had, so that is great!

It also has another resistor in the circuit, unlike the schematic in the manual, the 24k 5w. Is this a newer/updated schematic which has not yet been incorporated into the manual?

thx

forum.linuxcnc.org/plasmac/38848-hypersensing-questions?start=0

^—— This thread has everything you could ever want to know about the evolution thus far of ohmic sensing using a thcad, at least as it pertains to that diagram.

I can understand your confusion/frustration with the plasma primer. It is definitely out dated in some areas. But that said, none of this is etched in stone. You should be doing your best to understand the process, experiment, and see what works best for you. You will find conflicting advice sometimes because what works on one person’s table, doesn’t work on another. Not everyone here has the same power sources, stepper motors, stepper drivers, servos, etc. about the only commonality we all share is the Mesa hardware (mostly, some still use parallel ports), and Linuxcnc be it with PlasmaC or QtPlasmaC.

There are a lot of good reads in the PlasmaC section alone, I would encourage you to take time to read through the treads and understand how things came to be... A lot of the questions we’ve all had in the beginning have been answered several times over.

That said, the 24k resistor was added as a method to reduce sensitivity of the sensing circuit, especially when used around water tables.

As for how to insert the wires into the connectors, that’s up to you. Some people crimp the ends on them, some people “tin” the ends with solder, etc. I’d do what seems safest and most reliable given your scenario... keep in mind that you are dealing with lethal voltages. Most of the circuits ive seen here totally negate fuses, breakers, etc. So I would consider everything “use at your own risk, your mileage may vary, etc.” Whatever you do, please make sure you do it safely.