Powermax 45xp lost arc delay (Solved)

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16 Feb 2021 13:43 #199061 by robertspark

tommylight wrote: Seen plenty of :
Set it to 10A and stick the leads into a wall socket!
Always funny ....


well it does measure the current..... probably just not the way you want it to!

at one point I had a sideline as a housebashing spark, and my best time (funniest) for business was always after a bank (public) holiday weekend.... husbands got moaned at by wives to fit light fittings and use to take the cheap ceiling rose down and end up with a load of red and black wires (blue and brown).... they join all the reds and blacks (or blues and browns) together in two bundles and turn the mains back on.... only for it to trip.... they have forgotten to consider the switch wires...

never had any money but those were the days of having a chuckle.... 2-way or intermediate switching got even better when they decide to change fittings on a staircase....

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16 Feb 2021 13:53 #199063 by snowgoer540

PCW wrote: Note that a normal external SSR block type relay's would not be expected to work well
as these often need a minimum current and have significant voltage drop because they use
bipolar transistors and must get their base drive from the switched power side

A MOSFET type SSR would be superior to a mechanical relay


In the interest of trying to understand why a MOSFET type SSR wouldn't work in my case, attached is the data sheet for the exact MOSFET type SSR that I had issues with. Any insight into why it didn't work reliably would be appreciated, as I said, I like to learn new things :)

Here is a link to the product as well (it was not cheap): www.grainger.com/product/SCHNEIDER-ELECT...D26BD&searchBar=true

Also, here is a video I made when I was having the issue:


I thought I had made one of pulsing with mechanical relay... but just picture a torch pulse with pilot arc as it should :laugh:

It may be of importance to note: When this was all going on, with the SSR, I noticed that if i had the ground clamp near the torch I had a MUCH higher chance (but not always and the length of time the pilot arc was stable varied) of getting a reliable pilot arc. If I took the ground clamp off the table, it would never fire. With a mechanical relay, I could disconnect the ground clamp and it still reliably pilot arc's for the proper length of time. In fact, I discovered the problem was the SSR by simply touching the two wires together while the ground clamp was disconnected (after I confirmed that a manual torch didn't need to be near the ground clamp to fire reliably). It sure was a roller coaster for a few days, but it got sorted :)

One final test may be to hook the works up to the 7i76's spindle on SSR and see if I had similar results, but as mentioned, after I went to a mechanical relay, it's been 100% reliable, so I never really looked back.

I will still try to get torch on amperage from my powermax 65 when I get a few.
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16 Feb 2021 15:14 #199070 by robertspark
Load current 0.0025...6 A (i.e. 2.5mA minimum current? .... possible issue??)

I've just stuck my ammeter on the PMX45 and this time I got the current rising to about 15.1mA in a little over a minute.

I will try again in the evening, and try to time it to rise to 10mA / 12mA.

But the current defiantly rises rapidly and then tapers off (like charging a CAP).

This is probably to stop debounce? Or quick refire signals?

(another reason why I switched to linuxcnc was I wanted to be able to use the halscope to learn a bit more about the timing of various elements {sure I could just hook up the oscilloscope..)
The following user(s) said Thank You: snowgoer540

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17 Feb 2021 01:22 #199118 by rodw
Replied by rodw on topic Powermax 45xp lost arc delay

snowgoer540 wrote: Also, here is a video I made when I was having the issue:


Something funny there in that video as there is preflow but no arc. Makes me think its another issue.

Have you got a 7i76e? I thought you were using a 7i96?

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17 Feb 2021 01:56 #199120 by snowgoer540

rodw wrote:

snowgoer540 wrote: Also, here is a video I made when I was having the issue:


Something funny there in that video as there is preflow but no arc. Makes me think its another issue.

Have you got a 7i76e? I thought you were using a 7i96?


Not preflow, what you are hearing is a failed pilot arc, and then the post flow. iPhone didn't really capture the really tiny spark/sputter of a failed pilot arc.

I know it's going to be tough, but you're just going to have to trust me, it was the MOSFET type SSR that caused the problem. It's 100% fixed and reliable now.

The table is wired with a 6i25 and 7i76 combo. I have a 7i96 in the wrapper because at some point I'd like to build another bigger table, and then sell this one (seriously just build the ~5' x ~10' to start if you're questioning it). I would probably rewire this table with the 7i96 and keep the 7i76 if I do. Seems it would make sense as I also have a 7i92 that I used to interface a pi4 to the 7i76 for some "just for fun" playing.

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17 Feb 2021 02:26 - 17 Feb 2021 02:31 #199122 by Nick7251

rodw wrote:

snowgoer540 wrote: Also, here is a video I made when I was having the issue:


Something funny there in that video as there is preflow but no arc. Makes me think its another issue.

Have you got a 7i76e? I thought you were using a 7i96?


Maybe you are getting who is who confused. I'm the OP and I indeed have the 7i96. Although the problem seems very very similar.

So if like to understand the "fix" better. I'm no electrical engineer. Is the fix to put a mosfet on the output ssr pin?

Edit: Nevermind. I reread and realized the "fix" in this post is the mechanical relay.
I haven't had a chance to get out to the table and try some of these suggestions out. Freezing the last couple days here.
Last edit: 17 Feb 2021 02:31 by Nick7251.

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17 Feb 2021 02:48 #199124 by rodw
Replied by rodw on topic Powermax 45xp lost arc delay

Nick7251 wrote: Maybe you are getting who is who confused. I'm the OP and I indeed have the 7i96..


Nah, I was referring to snowgoer. I thought he was using a 7i96 but on another thread I saw he had a 5i25/7i76 combo. If I got that wrong I am really confused :)

I decided to try using my Mesa 7i76e spindle relay while we are exploring this thread but I will post on another thread about that as I had some errors...

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17 Feb 2021 03:13 #199126 by Nick7251
The hard thing is that I could get it to work by moving the ground clamp closer to the cutting location for a while then the problem would pop back up. So I'd turn off the cutter and back on and that would sometimes allow it to cut again and sometimes not. Then I'd hit the pulse button and that seemed to get it to cut sometimes and sometimes not.

So I suspect none of those things actually effected anything and it was just intermittent and tricking me. Also the fact it is intermittent makes it hard to duplicate for serious testing and fixing.

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17 Feb 2021 03:14 - 17 Feb 2021 03:16 #199127 by rodw
Replied by rodw on topic Powermax 45xp lost arc delay

rodw wrote: I decided to try using my Mesa 7i76e spindle relay while we are exploring this thread but I will post on another thread about that as I had some errors...


Actually I resolved my error and its possibly relevant so I will post here.
I changed my torch on relay to be the 7i76e spindle enable relay. Removed the plasma cutter wires from my relay and connected to TB4-5 and tb4-6. Once I powered up the 7i76e, the torch came on unexpectedly so I switched off the plasma cutter. Then started up in a more orderly fashion and got a startup error from the plasma cutter which is described in the manual



Active Low seemed interesting and I was aware these digital relays are polarised so I swapped the wires around on the 7i76e and it is working perfect.

So I wonder if problems some people have been having using digital relays is becasue they have the wrong polarity?

I'm going to leave it this way and see how it goes...
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Last edit: 17 Feb 2021 03:16 by rodw.

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17 Feb 2021 03:18 #199128 by phillc54

Nick7251 wrote: The hard thing is that I could get it to work by moving the ground clamp closer to the cutting location for a while then the problem would pop back up. So I'd turn off the cutter and back on and that would sometimes allow it to cut again and sometimes not. Then I'd hit the pulse button and that seemed to get it to cut sometimes and sometimes not.

So I suspect none of those things actually effected anything and it was just intermittent and tricking me. Also the fact it is intermittent makes it hard to duplicate for serious testing and fixing.


Seems a lot similar to:
"It may be of importance to note: When this was all going on, with the SSR, I noticed that if i had the ground clamp near the torch I had a MUCH higher chance (but not always and the length of time the pilot arc was stable varied) of getting a reliable pilot arc. If I took the ground clamp off the table, it would never fire."
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