ArcOK when not built-in

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21 May 2021 21:35 - 21 May 2021 21:56 #209805 by Joco
ArcOK when not built-in was created by Joco
I have donevthe reading and understand the reed switch approach. I have even tested that setup to prove to myself it will work.

However it feels some what “hacky”. I was wondering if using a sensor such as this dc current sensor would not be an option?

When reading the items description please also refer to the photos. This is a DC sensor not an AC only as some of the text implies.

Thanks for your thoughts.

Cheers - J.
Last edit: 21 May 2021 21:56 by Joco.

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21 May 2021 22:42 #209808 by rodw
Replied by rodw on topic ArcOK when not built-in
Another not so "hacky" DIY approach you could try is to grab a ferrite ring large enough for the ground lead to pass through. Cut a slot in it and glue in a hall effect sensor like this
www.jaycar.com.au/ugn3503ua-hall-effect-sensor/p/ZD1902

You can grab some plastic rod and machine a housing for it to make it all neat.

I did make one of these but the plasma cutter died so I never used it.


Beefy has used an ACS758 current sensor which you can buy as a prebuilt module on ebay, Add to that a LM358 small signal amplifier (also available as a prebuilt module) to step up to say 24 volts and read it on a 7i76e analog input.
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22 May 2021 00:05 #209814 by tommylight
Replied by tommylight on topic ArcOK when not built-in
That should also work.
But lately i am starting to wonder why bother as i have been using two of my plasma tables for the last two months intentionally with the ARC_OK disabled in hal, with two different plasma sources and two different THCAD's while changing plasma supplies from time to time, using QTPlasmaC with debounce's at default, and i just do not have misfires or arc lost.
Take this as testing only, as the amount of use was pretty low, but the amount of experimenting was high, shamefully due to me skipping some steps in PncConf and then chasing gremlins .....
As for the reed switch, it never fails, must have over 10 plasma's using it daily on production machines.

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22 May 2021 22:20 - 22 May 2021 22:22 #209861 by Joco
Replied by Joco on topic ArcOK when not built-in
Thanks for the replies. I appreciate you sharing you experience.

When you guys refer to reed switches I assume you mean the reed side of these types of parts and not the little glass ones.
www.jaycar.co.nz/miniature-security-alarm-reed-switch/p/LA5074 Or
www.jaycar.co.nz/security-alarm-reed-switch/p/LA5072

The dc sensor looks like a potentially slick way of doing things but the more i look at this and reading your comments, just getting a spare earth lead i can dedicate to the table and do the reed swtch wrapped in lead. Its sounding like it will be the simplest, cheapest and probably robust option. I can bundle it all up in some plastic tube or a small plastic box to make it all tidy.

Essentially over engineering this isn’t going to gain you anything, at least that I can see.

Cheers. B)
Last edit: 22 May 2021 22:22 by Joco.

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22 May 2021 23:52 #209864 by phillc54
Replied by phillc54 on topic ArcOK when not built-in
I am pretty sure they the type that Clive used here:

linuxcnc.org/docs/devel/html/plasma/qtpl....html#qt_reed-arc-ok

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23 May 2021 00:33 #209869 by tommylight
Replied by tommylight on topic ArcOK when not built-in
I still have some glass ones and some plastic ones, they are the same thing.
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24 May 2021 14:08 #210062 by samforsey12345
You might find that the plasma cutter has a neat one internally. Picture shows tight coil of copper with a reed switch glued in on the ground side. Ideal really...

I didn't end up using it but expect would be highly reliable
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24 May 2021 15:39 #210067 by Clive S
Replied by Clive S on topic ArcOK when not built-in

I am pretty sure they the type that Clive used here:

linuxcnc.org/docs/devel/html/plasma/qtpl....html#qt_reed-arc-ok


Yes to confirm I used a glass one from an alarm contact fitted inside a bit of plastic tube with about 3 turns of the ground clamp cable as shown in the pic

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24 May 2021 19:02 #210091 by Joco
Replied by Joco on topic ArcOK when not built-in
Clive - so did you just use the alarm part as is or did you extract the reed switch from it?

I have a couple of bare glass reed switches that i will need to mount on some perf board to be useable. Easy to do and easy to add some screw terminals. But perhaps not as clean as just using pre built reed side of an alarm switch with screw terminals all ready to go.

Cheers.

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24 May 2021 20:43 #210100 by tommylight
Replied by tommylight on topic ArcOK when not built-in
-solder two wires to reed
-get a pen and cut a length a bit longer than reed body
-insert reed in
-wind 3 turns of the ground or the torch lead
-use zip ties to secure the windings in place.
The worst thing in all of that is the wire, it is thick and hard to wind, most times to short so lengthening is needed. Takes about 15 to 30 minutes of time.

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