plasma control panel

Phill if you are into hacking hardware and want to pimp your Hypertherm 30 amp machine, I have a 50 amp ACS758 DIN rail mount current sensor module here and an LM358 low signal amplifier module I'd be more than happy to donate to the plasmac cause.

The ACS758 would need to be placed in series with the electrodes in your plasma cutter and will output a 0-5 volt analog output representing 0-50 amps. The LM358 will allow connecting 24 volts to it and step the 5v up to a few percent less than 24v.

So then you could connect the amplified signal and be able to read the arc current via one of the 7i76e analog inputs. This could open up a whole new world as you can synthesise your own arcOK signal based on a current threshold and do precision centre punch marks by turning off the arc at a low current threshold. If you are interested, send me a message here as the forum emails are pretty unreliable
www.vehiclemods.net.au/contact-us

Now I have a 120 amp machine, I need a bigger ACS758 module so this is of no use to me. I was put onto this by a guy in Melbourne who calls himself Beefy on some other plasma forums. He wanted to build his own external THC module using UCCNC. He is very knowledgeable about all things plasma.

Thanks for the hints guys.

John, did you go with the raw arc voltage interface or the simple series resistor network that seems to be common here.

Rod, you are a bit over my head with your idea, I will contact you off list later.

Cheers, Phill

I think John has built his own divider but the simple THCAD resistor works fine. I did try that on my Thermal Dynamics recently. Most machines with a CNC port add a 1k resistor on both sides of the raw arc voltage input and you need to count that as part of the THCAD's resistor divider network. PCW says you can overdrive the THCAD so you get more resolution in the 0-150 volt range and it will clip at full scale but you need some headroom to sense kerf crossing.

But I don't think you have an interface so just mount the THCAD in a metal jiffy box at the plasma cutter and power it with 5 volts from your control box. I think Hypertherm uses the same AMP connectors as Thermal Dynamics do so if you take care, you might be able to build this box with sockets on it so you can move it to your next machine.

Phill

The voltage divider I built (I up loaded the schematic earlier today) was originally met to work with any plasma box, blowback, HV,HV/HV and not cook the THCAD or other AtoD. You are using the THCAD with a well behaved HT box so a simple series resistor will work. If you are using a THCAD 10 then I would shoot for a full scale of about 180V. That is higher than any cutting voltage you will have. I removed all the caps from my original circuit when I was fighting the OE branch. I later found that any delay in the arc voltage sensing can play hell with the thc working. I think that using the F divide by 32 as PCW recommends should work well and provide good enough noise protection. Fast forward to now and more black ops on how the pros do it. It seems that most mechanics are way faster response than the constant current loop in the plasma box. The big boys seem to be limiting the both the Z speed and Z acceleration according to material thickness and desired response. Sorry for the long winded response. I put my voltage divider inside my plasma box and wired the output to the appropriate CPC sockets. Your HT does use the same connectors as the TD for the CNC interface, it is a standard AMP CPC series connector and you should be able to get pins and sockets from an online stockist ( no idea about where to buy this in Oz). My THCAD lives in a small box under my plasma power supply and connects to the main control box through a piece of shielded stranded cat 5 cable. I will up load a photo later when I am in the house. I send 24vdc over the connecting cable and then use a small ebay made in China buck converter to get 5v (don't like sending my logic supply all over the noisy shop). I do have a several LEDs on the box to indicate power, torch on and arcok.

John

PCW has shared the THCAD rise time delay here and its super quick. Z axis Acceleration is an important tuning parameter for THC I found. and the AMP connectors are available from RS Components in Oz. You are going to smash this Phill!

I have come up with this wiring diagram, all comments welcome.
I haven't forgotten limit switches, I don't really want to use them as I haven't on any of my other machines and not had too many dramas..
Actually this is the first time I will use home switches, I usually just eyeball matchmarks which has served well in the past.



Cheers, Phill.