Mesa 7i96 and Hypertherm 45xp

Hi Folks and happy New Year to all.

I am building a control box based on the following diagram from Kyle:
 
My build is almost identical except I'm using different drivers and 48V to power them.  My question is regarding the 45xp hookup and the fuse inline with pin 3 of the cpc port.  Is this necessary and why?  I have no problem putting it in, just trying to understand.
There is a similar build on a different forum where the builder says this is wrong and the fuse should be inline with pin 12. Can someone elaborate on this.  Thanks in advance.

I don't think there is any need for fuses anywhere in either the arc ok or start signals.
Think about it. To start the arc, you are merely closing a switch and the specs of that circuit are advised by  Hypertherm docs.
The ArcOK/transfer circuit is powered by the 7i96. How can it exceed a safe current?
But I would use a pull down resistor to ensure the minimum current exceeds the transfer relay.
Its always best to do your own resaearch and devise your own circuits.
Pretty documentation does not imply best practice in operation!

Topic moved to Plasma & Laser

Ok Rod Thanks for the reply. No fuses are necessary. But can you please tell me exactly where to put the resistor and what value should I use? Thanks again.

Blackslacks wrote:

Ok Rod Thanks for the reply. No fuses are necessary. But can you please tell me exactly where to put the resistor and what value should I use? Thanks again.

I don't think he said no fuses are necessary. He said they're not necessary for the arc ok or start circuits, and to do your own research to design a proper schematic. That said, one place to consider one is on the main +24v leg of the power supply.

It's impossible for any of us to tell you the proper resistor (or capacitor) value for your circuit(s) without knowing what components you are using, here's a good read with a schematic: linuxcnc.org/docs/devel/html/plasma/qtpl...html#qt-contact-load