For Real Pilot Arc Conversion of Plasma Torch!

[@peeteebee123]

I think you're correct that this is the only correct implementation of a pilot arc on KZbin. I learned a lot from your video. Many thanks. I started planning to implement a switched pilot lead approach using an Arduino and a hall sensor (so that I could additionally drive a display and also derive arc voltage for THC at some time later), until I read your comment that you tried doing this electronically and it all got fried. That seems obvious. Now. So I've emulated your approach. One difference, though, is that I 3D printed a 30mm diameter bobbin that takes 2 turns of the "ground" lead on my plasma cutter (8mm O.D.). This bobbin has a hole through it for a standard 2.4mm x 16mm reed switch to be inserted. The resulting "current relay" switches at around 7 amps. About perfect. The only downside is that I lose about 180mm of the length of my ground lead. But that's acceptable for me - I haven't chopped or modified any of the standard parts of my cutter. Also different to your design - I _have_ decided to go down the automotive relay route.. I chose an 80 amp relay (my plasma cutter is only 40 amps) si it _should_ be OK, and I'm happy to treat it as a consumable. (Unless it fries *really* often. Hopefully not.) Huge thanks again.

[@JakevonSlatt]

That’s awesome and I’d love to see a picture of the bobbin and reed switch assembly!

[@peeteebee123]

@@JakevonSlatt - aarrgh!!!! My replies keep getting deleted. 😥 Presumably because there's a link to a (Google, which owns KZbin) photo album. How else can I send you these pictures? ❓

[@JakevonSlatt]

@@peeteebee123 put the text in without the “https” part and I’ll type that by hand.

[@joelshopefullyhelpfulvideo3010]

Awesome video, nice fairly simple modification for non pilot arc machines. Thanks

[@JakevonSlatt]

Glad you liked it!

[@onomatopoeidia]

Great idea nicely done. I contemplated this then donated the HF machine to my dad instead who will put it to great use chopping up stuff freestyle. They are godsend for removing old exhausts etc

[@JakevonSlatt]

They are indeed!

[@karljolley8346]

If I understand this correctly: modifying a non-pilot arc machine is going to reduce cutting ability, and be sketchy, and mostly unnecessary. Unless one takes the time and expense to add all the extra components. So if I feel I need a pilot arc I just buy one in the first place which allows the mfg to be the one to add the electronics inside the case.... Jake has presented the best explanation of what and why that I have seen.....

[@JakevonSlatt]

You are correct sir! There are now relatively inexpensive pilot arc units on the market, not so the case when I bought mine several years ago.

[@wgenerotzky]

Nice, simple and robust, cool. 👍

[@digitizer101]

I like the idea behind this. What would happen if the arc is lost do to a gap in the metal being cut. would the pilot arc re-engage until the arc is re-established once over metal again?

[@JakevonSlatt]

Yes, if the cutting current drops out the pilot arc will kick back in.

[@xt1200z1]

Super video and solution. I am fighting a multi function machine with HF for my just built DIY JDsGarage cnc plasma table. I will check your other videos for help with the problem as I refuse to purchase another CNC friendly machine just to get my CNC table to work. Gotta be a way to make the HF work I'm thinking.

[@JakevonSlatt]

Thank you and best of luck getting your machine working!

[@yngndrw.]

I wonder if this could also be used for a marking mode now that you can control it electronically, just using the pilot arc for the marking?

[@JakevonSlatt]

Oh! That is interesting! I'll have to run some tests to see if the consumables hold up.

[@plb53apr06]

Interesting idea. I think the reason you went with a reed switch was for durability. My inclination would be to use a hall effect sensor and a 24V driver for the contactor (or 2 step, relay to contactor) though the EMI environment might make that challenging. I'm part of a group working on a torch height controller set up for grblHAL and have several questions about your approach - How does the EMI profile of your set up compare to a built in Pilot Arc set up. There is a lot of folklore around PA vs HF. Also, could your design be modified to produce Arc Good and Arc Voltage (proportional to the torch height) for the THC input. Basically, what's missing from the cheaper/HF start cutters out there. Would love to get your thoughts on this.

[@JakevonSlatt]

I actually started with a hall effect based current sensing relay but the RFI blew up the semiconductors after about five minutes. Next I tried a current shunt with op amps, but had the same problems. When I first built the CNC table, I had terrible RFI problems that would crash the controller, If you look at two or three videos back, you’ll see what I had to do to get the cheap CNC controller Stable. When I was researching how to protect Hall effect sensors from RFI I came across a webpage that talked about replacing reed switches with Hall effect sensors, and I remembered that I had a bunch from a job I worked about 20 years ago, and I thought I’d give it a try. The whole device came together within a couple hours after that.

[@JakevonSlatt]

I think an Arc Good signal could just be taken from the relay. Arc voltage is something I haven’t dived into yet, though THC is something I’d like to add in the future.

[@DaveEtchells]

To get arc voltage you’d have to use semiconductors somewhere, so you’ll have to deal with the RFI and collage spikes somehow. My quick thoughts are to use an analog-out (linear) optoisolator to get the signal out of the box while protecting your controller circuitry. - use a transformer to get a floating power supply for the voltage-sense circuitry. (You might want a separate one from what runs the relay, I think the wires coming from the reed switch would couple-in a lot of nasty noise.) Filter the heck out of the power, series choke, maybe out the analog circuits in a small grounded metal box(?) - Use an op-amp with appropriate input divider to measure the voltage between the arc positive and ground. (A differential-input or “instrumentation” amp might be useful or necessary to help cut noise, but I don’t know if that would be necessary.) Use an RC network between the voltage divider and the amp input (or just bridge the low-side resistor in the voltage divider with a cap) to cut the higher-frequency noise. (I’m guessing that you wouldn’t need more than ~3-10 Hz bandwidth for your THC control output, so get rid of any higher-frequency stuff as early in the process as you can.) - Have the output of your voltage-sense amp drive the input of the linear optocoupler. - Run the output of the optocoupler to an external interface board that’ll use another op amp circuit to produce the level of voltage the controller needs to see. Use well-shielded cable to carry the signal, with the shield of the cable grounded at the controller side only. That’s just an outline, there’ll be a lot of calculating and tinkering to get to the final circuit. The basic idea though is to use a linear optocoupler to isolate the arc voltage measurement from the controller, to use a floating power supply for the arc measurement circuit, and to connect the shield of the cable running to the controller side to the ground of the controller. (Do *not* connect the other end of the shield to anything on the plasma cutter side or you’ll create a ground loop and possibly fry your controller.) I hope this helps, good luck! (It’d be fantastic to have an open-source solution for THC!)

[@dumdidumdumification]

Thanks for the video Jake!

[@JakevonSlatt]

You bet!

[@peeteebee123]

As per my other comment, I'm building a pilot arc setup along the lines you've described. (Did you get the photos yet?) It's just occurred to me that the _normally open_ contact of the relay, which is unused at present, could be used as the +ve supply to a voltage divider (pair of resistors) as a means of determining the arc voltage, in order to implement Torch Height Control (THC). The advantage of using the relay in this way is that it's open circuit _until the arc is established_ and therefore *after* the high voltage arc start has been cut. So this would prevent the high voltage (10's of thousands of volts, I believe) from frying the arc voltage reading circuit. Does that sound viable?

[@JakevonSlatt]

I did get the photos, thanks! This sounds viable, but it will take some trial and error to get proper isolation. Do a search for “DIY TIG HF start” projects, there will be some good information on how to keep the hf from blowing up semiconductors in welders.

[@Keith12001]

Very good and instructional video, thanks for sharing knowledge

[@JakevonSlatt]

Thanks for watching!

[@patrickm.8425]

So what if I already have a machine that is a pilot arc? Do I just use it as is or do I need to get a different machine?

[@JakevonSlatt]

Yes, most CNC tables assume pilot arc.

[@alexchliwnyj5941]

Brilliant rock solid design, no sensitive electronic components. Is the biggest difference between an expensive plasma cutter and a cheap one? Why are some plasma cutters so expensive?

[@gonzaloromero2705]

la verdad es lo mas completo y razonable que vi .pero tengo una pregunta para hacer el tororide prodia usar un caño de hierro en vez de una ferrita. Estoy en argentina y es dificil conseguir casi cualquier cosa. desde ya muchas gracias por el video se gano un suscriptor!!!

[@JakevonSlatt]

I think that a piece of iron pipe probably will work! Thanks for the kind words!

[@gonzaloromero2705]

gracias a usted por su respuesta . hace poco termine mi mesa cnc pero la verdad que la alta frecuencia fue y es un problema que no pude superar ,pero ya cambie cables puse ferritas hice una jaula para la electonica asique estoy por probar . ya estoy consiguiendo lo necesario para hacer este implemento .

[@JakevonSlatt]

Have you seen this video? kzbin.info/www/bejne/n5Wuk2Vqa9ahd80si=Xtlj1xQHlzvq0DS6 it’s the shield cable and the capacitors that I think solved my RF problems. Also I recently heard from another view that they made a bobbin with a reed switch in the center of a couple of turns of wire and it worked without ferrite or an iron pipe ring.

[@stokestack]

Very informative, not just about this application but also some basic electronics. Not familiar with plasma cutters, but what about the inexpensive "non-contact" ones? Is there something bogus about the ones that claim: "This plasma cutter has the pilot arc function. It is a high frequency non-touch arc starting mode." And if those suck, how expensive are "legit" pilot-arc ones? Do either of those continue to leak current as you've described? It's hard to evaluate the cost savings vs. time expenditure of what you've done here without that knowledge. Regardless, cool solution!

[@JakevonSlatt]

I think the cheap pilot arc units are probably just fine, with the possible exception of RFI. I've only ever use my cheap "contact" unit which was indeed a nightmare with respect to RFI! This video documents what I need to do to keep the CNC controller from crashing whenever I lit the torch: kzbin.info/www/bejne/n5Wuk2Vqa9ahd80

[@stokestack]

@@JakevonSlatt Thanks! I wouldn't be surprised if they're noisy too. I'll check out that video.

[@keithjurena9319]

All high frequency will have issues with electronics. I fried a motor controller with my Miller Dynasty DX as I welded too close to the circuit board

[@jeremygray9782]

Great video. You saved me from the automotive relay path I was going to take and I'm going to emulate your approach. I'm looking at replacing my PT-31 cutting torch (roughly same as your high frequency start one i think) with a straight handle plasma for the CNC I'm building. I haven't purchased it yet, but it's significantly more expensive than the one I currently have. I don't understand the difference aside from the internally routed pilot lead and the tip/consumables which are clearly of a different configuration. At roughly $150USD more expensive what is that cost attributed to?

[@JakevonSlatt]

Hmm, I used a generic torch like this: www.ebay.com/itm/265701724204?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=-ueydqfvR6O&sssrc=4429486&ssuid=SIF5RPlxTlO&var=&widget_ver=artemis&media=MORE it was about $35

[@Docv400]

So if I'm understanding this correctly, if you start Cutting with your HF Start Torch, then lift the Tip a few mm off the Workpiece, it would continue to cut?

[@JakevonSlatt]

Once the arc is established it will continue to cut, regardless. With an hf start torch contact is required to start the arc. With a pilot arc torch you can start the arc without contact. This is advantageous on a CNC table because it helps prevent molten metal being blown up into the torch ruining the tip.

[@Docv400]

@@JakevonSlatt Thanks for the swift reply Jake. Another quick question if I may; Could you not just have a simple Momentary Switch to initiate the Pilot Arc, which you could just release once cutting is started? You'd hold it 'on' to start the Arc (along with the main Switch), then release it to open the Pilot Arc Circuit.

[@JakevonSlatt]

@@Docv400 you could do that, but if you were making a complex part on a CNC table you have to stand over it pushing the button

[@Docv400]

@@JakevonSlatt Understood. I'm only doing manual cutting at the moment, but am planning a CNC build also. I suppose you could wire a relay into the circuit, which could be controlled by a CNC Controller output.

[@navneetpandit7299]

How does this differ from the TIG plasma?

[@JakevonSlatt]

I not sure I understand the question, can you rephrase?

[@vonnorman6737]

He may be referring to multi-function combo machines, like the Vevor CT520D machines I've seen that claim to have Stick, TIG and plasma cutter functions in 1 machine.

[@JakevonSlatt]

@@vonnorman6737 ah! This is the only machine I have any experience with so I don’t think I can be helpful here

[@VinokDesign]

The voltage is way higher around 90-110 volts in order to break the air into plasma. Tig is 20 ish volt breaks down argon easily. You want to plasma cut with a tig. Change the torch and use high pressure argon. It will cost you some argon😅

[@gonzaloromero2705]

lo volvi a ver y creo que ahora entiendo la placa de los condensadores . Me costo un poco !! voy a ver volver a comentar cuando tenga resultados gracias

[@AserraderosMikuman]

Te salio?

[@gonzaloromero2705]

@@AserraderosMikuman todavia no hice la plaqueta con los capasitores y no encontre el lugar para poner la maquina con todas sus conecciones por lo pronto tiene una fresadora puesta , pero sigue en pie el proyecto no falta mucho, el aparato que muestra en este video ya esta hecho y funciona muy bien

[@ls87gbody]

Would you be willing to build another one to sell? I dont have much electrcal experience and i need a setup like this.

[@JakevonSlatt]

There are good cheap pilot arc torches out there now that would cost less than a custom build, this sort of thing only really makes sense as a DIY project build with parts already on hand.

[@ls87gbody]

Totally understandable.

[@Z-Ack]

Brilliant.. thumbs up..

[@MNB_Construction]

Hello, can you help me, my plasma cutter has a problem with the pilot arc. exactly the same, well, I have Pris 1000 kzbin.info/www/bejne/foKQlaWGj9t2ocU It works hard at 2 bar. and this is a problem when cutting metal. I want to send you the whole picture to make it clear. I will be grateful to you for this