Looking for the cheapest plasma cutter that will work with Mesa THCAD

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23 Jan 2020 11:26 #155533 by BlueManRising
Yeah, just double checked the plasma that I bought, HeroCut 55i, clearly says signal out for arc OK, so I have to add my own relay, knew it was simple and I was over thinking it.. Thanks everyone!!

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23 Jan 2020 23:17 #155593 by BlueManRising
Ok I'm a idiot again, it say "dry contact closure when the arc transfers" so a dry fire might not be closing the arc ok, I'm going to be running some tests tonight, what's the worst case of running the machine without arc ok? Intermittent cutting out incase the torch didn't start? It's a blowback system and I have yet to see a non start from the machine even when try firing the arc... It also could be my machine, might break it open to see if the relay is damaged...

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23 Jan 2020 23:30 #155595 by BlueManRising
Ok relay inside the torch works for ARC ok, ONLY when in contact with the grounded metal, not when dry firing, soooo that means it should work, I'm putting it all back together and hooking it up to the 7i96. I'll report back later

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23 Jan 2020 23:31 - 23 Jan 2020 23:32 #155596 by rodw
Try something like this. Assumes sourcing inputs

High quality CAD file attached....

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The Mesa Card has very high impedance to GND so on a cheap plasma cutter, the current draw is probably below the minimum current spec of the Internal ArcOK relay so it may not be able to trigger the circuit or the contacts will oxidise and be intermittent in operation. (Ask me how I know this).

The resistor needs to be matched to your field power voltage to get over the minimum and be able to handle the current in the circuit but for 24 volts 1k 1W is fine for the Everlast I used to have
Attachments:
Last edit: 23 Jan 2020 23:32 by rodw.
The following user(s) said Thank You: AgentWD40, BlueManRising

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23 Jan 2020 23:34 #155597 by rodw

Ok relay inside the torch works for ARC ok, ONLY when in contact with the grounded metal, not when dry firing, soooo that means it should work, I'm putting it all back together and hooking it up to the 7i96. I'll report back later


Thats how it works, you can't possibly have a valid arc if you are not cutting something.

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23 Jan 2020 23:45 #155598 by BlueManRising
Ok so riddle me this, I hooked it all back up, and I'm still not getting the green light on ARC OK when I pulse the torch, I'm going to meter the pin and validate the computer is seeing that it is closing, if not then I'm assuming it's hooked up on the wrong pin, or there's something in the software that will only check ARC OK when it's running GCode..

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23 Jan 2020 23:47 #155599 by BlueManRising
That's some really high quality cad skills ;) ok I will have to pick up some resistors tomorrow, gonna probe the board in LinuxCNC
The following user(s) said Thank You: rodw

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24 Jan 2020 00:11 #155600 by BlueManRising
Wait a Sec... is the GPIO pins not set up to just go from the pin number to common? have i been setting this up wrong the entire time on the GPIO pins?! is it looking for voltage to the GPIO to trigger or just closing the contact? i thought the GPIO was just looking for a closed pin connection to ground? i hooked a switch to the GPIO pin and common and still not seeing anything.. i have a feeling i just been hooking up the GPIO pins wrong....

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24 Jan 2020 00:25 #155602 by BlueManRising
ok, yes im a idiot... its looking for voltage and per the Mesa 7i96 manual....

"11 isolated inputs provided for general control use including limit switch and control
panel inputs. Inputs operate with 4V to 36V DC and can have a positive or negative common for sourcing or sinking input applications. Six 36V 2A isolated outputs allow sinking, sourcing combinations of both"

ok lets try to mooch off of the 5 volt from the board...

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24 Jan 2020 00:54 #155606 by BlueManRising
ok my apologies for using this board to vent my issues, but hopefully it just makes someone learn my mistakes so they dont do the same. I went ahead and grabbed the 5v from the board. when it goes through the plasma it dropped down to 4 volts, no biggie. then on the I/O board it saw the 4 volts, and bingo, green light on the Torch ON. The plasma is officially hooked up the the Mesa Board....

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