Wiring the Hypertherm interface cable

7i76e. I don’t have any of the hardware yet. I am trying to make sure I have absolutely everything right with my wiring and my configuration. Since this side of the machine doesn’t come naturally to me I don’t want to do what I’ve done in the past and wing it when I get the materials.

I’m trying to keep it just asking here, though I know I have a lot of annoying basic questions.

For Mesa 7i76E, pin 14 to +24V, pin 12 to input.
No need for resistor.

Okay, thank you. So is this correct?

 

as you previously mentioned it needs to be inverted in the hal file. Since we are using +v now does it not have to be inverted?

The use of a pullup resistor is discussed int he qtplasmac docs.
The current passing through the 7i76e (from an input to ground) is way below the minimum current of the internal Hypertherm relay so not using the resistor could see oxidisation build up on the relay contacts and result in intermittent operation over time which will prevent you from cutting.

The resistor allows some current to bypass the 7i76e to ensure that the minimum current of the relay is respected.

tommylight wrote:

No need for resistor.

This is bad advice. Read up on it in the qtplasmac docs and follow one of the recommendations

rodw wrote:

tommylight wrote:

No need for resistor.

This is bad advice. Read up on it in the qtplasmac docs and follow one of the recommendations

I really do not know how to reply to this, you are putting me in a very bad possition with this behaviour.
I have over 20 of CNC plasma machines on daily use that never needed a resistor or wetting or whatever, you have built 1.
You putting it in docs and insisting on it does not make it true, and it should not be there, but it does not break anuthing so i never insisted on removing it from the docs.
Not nice.

For what it’s worth, I don’t use the wetting resistor or capacitor either with no problems.

It is bad advice becasue it does not reference the documentation. There is a chapter about this issue.
linuxcnc.org/docs/devel/html/plasma/qtpl...html#qt-contact-load
Let the user make up his mind.

There have been enough people caught with this issue on the forum to add a component costing a few cents for a defensive circuit design.
Sure, he may never have an issue if its left out but its a very painful place to be if it bites.

snowgoer540 wrote:

For what it’s worth, I don’t use the wetting resistor or capacitor either with no problems.

I have built 2 machines so plus 2

The thing is plasma machines don't last forever so you might have several cutters on your table over the years. I've had 2 and will probably be running a third shortly. These machines might have different characteristics so for the sake of 10c, why not do the job properly? By the time you need it you will probably have forgotten the possible cause is the shortcut you took years ago..

Its nothing about the table you build or how many you've built. its the plasma cutter you use.