Inputs & outputs & relays ohmic

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11 May 2019 05:46 #133425 by JTknives
I think I got it solved.
I just went into machine.hal and changed
net plasmac-ohmic-probe    <= hm2_7i76e.0.7i76.0.0.input-11

To this
net plasmac-ohmic-probe    <= hm2_7i76e.0.7i76.0.0.input-11-not

This has seamed to invert the input pin and all is well in the world.

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11 May 2019 06:04 #133427 by rodw

JTknives wrote: So how are you using an IDC24 opto22 as the ohmic signal generator? From all my research the IDC24 is a negitive logic opto22. This means the logic output pin is allways high till it’s triggured. I can’t quite wrap my head around it. Only way I can see it working is if you removed the pull up resistors from the G4PB4 board and did not connect the ground to it either. What’s up?


Just use the pin ending in -not on your 7i76e board for that input. Each input has a matching -not pin which is the inverse of the actual state. Just look in halshow. Hope I read right and you are referring to the output from the opt22 which is wired to a 7i76e input

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11 May 2019 06:05 #133428 by rodw
don't you hate that when the next response is on the next page. You worked it out without help. You will conquer the world now!

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14 May 2019 21:44 #133790 by JTknives
The new relay module arrived today. The 8 channel I ordered had all the commons tied together on the output. So returned that and ordered this.

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The following user(s) said Thank You: rodw

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23 May 2019 07:50 #134669 by JTknives
So I had a thought today while at work. I was thinking about the ohmic sensing and the fine cut consumables I want to use. Befor work I tossed a set of fine cut consumables in and realized the nozzle extends past its shield. This removes any ohmic function as the nozzle will touch first. But then I was thinking why not just tap into the THCAD line coming from the plasma. I have dule 1meg resistors in-line right where I taped into the board. You would need to be running the same polarity as the plasma (nozzle negitive and table positive). You would just run it through a DPDT that’s triggered by the ohmic enable pin. When not enabled it would be switched to alow voltage to the THCAD. One issue I could see is the in-line resistors dropping the amperage. At 2megs you would only have 6ua (micro amps). If you dropped to 1meg by just tying into the table for the other leg you at 12ua. I’m not sure what an opto 22 needs to trigger.

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23 May 2019 13:17 #134693 by islander261
I use Finecuts on a daily basis. Get the correct shield for them and you will be fine. You actually don't want to use the non ohmic one unless you have access problems.

John

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23 May 2019 14:28 #134701 by JTknives
Thy only list a non ohmic for the 30XP. But I was wondering if the one for the 45xp would fit. I know the 30XP consumables will fit in the 45xp.

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24 May 2019 01:15 #134762 by tommylight
@JTK
That will most probably not work as the nozzle is only wired to the arc start wire inside the plasma ( usually red wire ), thus the risk of arcing inside the relay used for sensing.
The wires used for THC go to the electrode ( negative ) and to the table ( positive ).
Still, you might want to check where that wires goes inside the plasma as in some cases it is floating and connected by relay only when firing. That would make it usable.

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24 May 2019 01:53 - 24 May 2019 01:56 #134767 by Grotius
Finecut option's for HP :

When you have TD, your ohmic sense signal is provided at cpc port.

XP30 is not fertig for mechanical or cnc machines, see attached table of content,
machine torch and ohmic sensing not provided so far for xp30.
TD can also mark at the 60i level.
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Last edit: 24 May 2019 01:56 by Grotius.

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24 May 2019 06:28 #134781 by JTknives

tommylight wrote: @JTK
That will most probably not work as the nozzle is only wired to the arc start wire inside the plasma ( usually red wire ), thus the risk of arcing inside the relay used for sensing.
The wires used for THC go to the electrode ( negative ) and to the table ( positive ).
Still, you might want to check where that wires goes inside the plasma as in some cases it is floating and connected by relay only when firing. That would make it usable.


I just gave the circuit a look over. I had not thought about the actual nozzle. But it would be perfect actually for touch off as it would give you a true zero. As long as touching off does not damage it. But that part aside it looks like the “relay” is just a NPN transistor. It had freewheeling diode parallel to the collector and emitter to prevent voltage spikes from cutting the power. So according to the schematic you could easily tie into that and get sensing right off the nozzle. You would have high voltage to contend with but if you stuffed a diode in line you could nip the reverse voltage off and not have any of the start/run arc voltage head down the wire. And the freewheeling diode will prevent spikes. Here is the schematic, not to complicated.
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