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Small DC TIG welder remote switch needed

Clambake

Mar 8, 2016
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I meant this test. Make sure the Pot's at mid range. It insures that this test can't pop anything because the opposite fixed un-shorted terminal will always see some resistance between it and the wiper.

Chris

I'll try it during my lunch break today
 

Clambake

Mar 8, 2016
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Make sure the Pot's at mid range. It insures that this test can't pop anything because the opposite fixed un-shorted terminal will always see some resistance between it and the wiper.

Ok Chris I ran this test.

When I jumpered Wiper to Pot hi I got a big arc at the torch. When I jumpered Wiper to Pot lo I got a very small spark at the torch. Both with pot dialed midway.

Does this mean I can put a microswitch between the Wiper and Pot lo? Is there a way to get rid of that small spark? Not 100% necessary but it would be nice.
 
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CDRIVE

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OK, I just want to wrap my head around this. Your results are somewhat as expected but not 100%. I expected no arc at all. What I expected was the same results that would be produced when without jumping anything and the Pot is set to 0, while not tripping the switch. Do you still get a small arc when the Pot is at max CCW prior to switching it off?

BTW, if this doesn't do the trick and even if it does, I still like Clark Kent's, AKA "Ed's" approach of hijacking that overload relay. ;)

Chris
 

Clambake

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I expected no arc at all.
You know I'm thinking maybe that tiny bit of current is how the welder senses a stuck electrode. When I was testing and got that spark, the buzzer would go off and the welder would act like it had a stuck electrode. Maybe the only way to get rid of that spark would be to somehow disable the stuck electrode sensing circuit.
 

CDRIVE

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Are you thinking that there will always be a tiny spark even though there's no current coming through the pot?

Yes, that's why I asked you to remove the jumper, turn the Pot to minimum but not OFF and test the arc. My guess is it produce a small arc similar to when you jumped the Pot wiper.

You know I'm thinking maybe that tiny bit of current is how the welder senses a stuck electrode. When I was testing and got that spark, the buzzer would go off and the welder would act like it had a stuck electrode. Maybe the only way to get rid of that spark would be to somehow disable the stuck electrode sensing circuit.

This only reinforces my opinion of Ed's approach. Energize the overload relay coil and kill the output entirely.

Chris
 

Clambake

Mar 8, 2016
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turn the Pot to minimum but not OFF and test the arc.

The control pot has a small amount of CCW rotation in the on/off switch click zone that can't be observed because the unit is powered down once the pot is rotated into that far left 3-5 degrees.

I guess if I want to observe the true effect the pot has when turned all the way down, I should jump the power switch pins so the unit remains powered up while the pot is rotated all the way CCW.
 

CDRIVE

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I'm wondering if triggering the overload relay is a guarantee that that stuck electrode sensing feature will be deactivated.
Is the stuck electrode feature something different than the overload feature? Or are you saying that when overload occurs it also sounds the Piezo until the electrode is unstuck? If that's the case it kinda puts the relay option in the undesirable category.

Chris
 

CDRIVE

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You know I'm thinking maybe that tiny bit of current is how the welder senses a stuck electrode. When I was testing and got that spark, the buzzer would go off and the welder would act like it had a stuck electrode. Maybe the only way to get rid of that spark would be to somehow disable the stuck electrode sensing circuit.

I just reread the above post. I'm not familiar with inverter arc welders so I can only speculate. What I think is this. An arcing contact is actually a rapidly intermittent connection. This is what actually generates the arc. When the electrode is stuck it is no longer an intermittent connection. Keeping this in mind it could also be possible that the circuit senses a steady state current vs an intermittent current that the arc produces. Hey, I'm guessing!

The control pot has a small amount of CCW rotation in the on/off switch click zone that can't be observed because the unit is powered down once the pot is rotated into that far left 3-5 degrees.

I guess if I want to observe the true effect the pot has when turned all the way down, I should jump the power switch pins so the unit remains powered up while the pot is rotated all the way CCW.

I don't think anything is going to be gained by doing that.

Here's another thought. Take a look at the data plate on the cooling fan and post the voltage and freq if it's AC.

Chris
 

Clambake

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Make sure the Pot's at mid range. It insures that this test can't pop anything because the opposite fixed un-shorted terminal will always see some resistance between it and the wiper.

I ran another test this morning with the (shorted wiper and lo) control pot at different settings while checking for spark at the torch.

The results were same small spark through all settings. If the electrode is held against the work there's an initial small spark, buzzer for the duration, fan loses power and there's a "pulsed" thunking consistant with the "stuck electrode" reaction this welder typically has.

I'm thinking this "pulsed" thunking might be the overcurrent relay being triggered on and off -perhaps using all the 24VDC the fan needs to run, resulting in it's losing power. When there's a stuck electrode during normal operation, the pulsed thunking manifests itself at the torchhead as intermittant current/no current.
 
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CDRIVE

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I was hoping that it was a 120VAC 60Hz fan. I guess it was too much to hope for. My next suggestion was going to be hard wiring the fan across the AC mains so it's always on when plugged in. Then I was going to suggest breaking the Pot Switch circuit and inserting your foot switch in series.

Personally, Id like Ed to come back and offer some additional wisdom. I believe he has more familiarity with inverter welders than I do. The only thing I know for certain is it's a Horror Freight product but I don't think it's exclusively theirs like many of their products. I did read the PDF user manual at their site but the item number was different than yours. This is meaningless for HF because I've seen identical items with different item numbers listed on the same page! Don't misconstrue these statement though. I have quite a few HF items and they do get the job done cheaper than anyone else can, with the exception of direct from China to you on Ebay. I do a lot of that too!

Sorry for digressing. Let's get back to your issue. It may be possible to move a bit further along the trail of the Pot circuit to completely kill any current at the torch. My problem is I don't know if this could be detrimental to the overload & stuck electrode functions. I don't want to be responsible for frying your welder. For example: Suppose we manage to kill the torch entirely. Let's also suppose you inadvertently make electrode contact with the work and then close the foot switch. I don't know if this scenario would defeat the safeguards built into that thing and make smoke!

Chris
 

Clambake

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could be detrimental to the overload & stuck electrode functions. I don't want to be responsible for frying your welder

Yes -and I have heard that inverter welders do fry. An old style welder with a seriously stuck electrode will just sit there and pile on the current until the stick melts. I think this little welder minus the stuck electrode sensing would burn up real quick.

I am thinking it may be possible that even with the main current shut off at the torch by activating the relay, that sensing circuit will still be active and sparky.

I've decided to go with the switch shorted pot leg idea. I am going to try to ignore the minor sparking.

If the little spark gets to be too irritating or causes problems, I'm going to bypass the main switch (your original idea) with the remote switch and just let the unit power completely down. It does work -I've tried it with a power strip -shuts off the torch right away.

So thanks for the help Chris and Ed!

By the way, I checked that little sensing spark's voltage with my DMM -it was 3VAC *and* 54VDC -I don't know if that means dual voltage or my DMM is messed up...
 

CDRIVE

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By the way, I checked that little sensing spark's voltage with my DMM -it was 3VAC *and* 54VDC -I don't know if that means dual voltage or my DMM is messed up...
More relevant would be the current delivered between the electrode and the work but you could fry your DMM measuring it.

Chris
 

73's de Edd

Aug 21, 2015
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Sir Clambake . . . . . . .

On your two . . . .LM324 . . .4 section operational amplifiers . . . . . being common as dirt / multi decade design workhorses . . . . flat pack I.C.'s that you identified . . . I would surmise that the one
near the "beeper" has two of its sections used for a window comparator, and the other two related to creating the beepers piezo drive signal.

Now, for the LM324 IC with the heavy YELLOW wire passing across it :
This 324 is close enough that it might be used a a variable oscillator followed by a pulse width modulator function related with the pots adjustment .
Evaluating that assumption would typically be requiring an oscilloscope savvy analysis . . . .OR . . .Mac Guyver'ing it by placing your DVM negative meter probe to ground
( any buss directly tied to pin 11 of the '324) and then MULTI twirl one lead of a .1 - - - - - thru a - - - - - - - 1 ufd poly/paper capacitor around the meters + probe and use the caps free lead to probe AC readings with .
Try probing pin 1 of the 324 while powered up and running the pot thru its extremes to confirm any AC voltage swing during that adjustment.
Then probe pin 7 for the same type of testing.
Then probe pin 8 for the same type of testing.
Then probe pin 14 for the same type of testing.
Finding voltage variance on those test points would tie that IC functioning to the pots adjustments . . . .and it is being the closest IC to the pot

Parte Deux:

You had not made any response in checking out the BLUE relays coil voltage.
Then . . . . . that might have been due to your not identifying its connections.
"Reading" as best as I can make out from the photo . . . . due to plated thru vias sometimes transfering connections to the other side of the board.
It is utilizing a SM1H-24v relay and I have placed one at the center of the photo for confirming its basing's contact terminals and coil layouts .
To the SPDT contacts I have assigned AC(armature common) and A1 is being its normally closed contact and the A2 as being its energized contact.
The coil is using assigned C1 and C2 designators. The GREEN path is an un-activated relay while the RED path is when its coil is energized.
So, if you look at the relays co-joining foil paths, the C1 connection passes up to be constantly connected to A1 terminal.
While the C2 terminal zags over and up to the top be constantly connected to A2 terminal.
So, overall, it looks like AC terminal is being the recipient of one or the other of the polaritys of the coil supply voltage.
As I am seeing it, the C1 terminal seems to be the negative or ground terminal while the C2 terminal is being the eventual recipient of an 24 Vdc.
I say eventual, because if you look at its foil's downward path, it initially connects to the first of a "scheiss pot" of 16 sequential series 68 ohm SM resistors
AND then it transitions to using nine 100 ohm resistors in series.
So in one relay position, all of that string could end up in parallel with the relay coil. BUT at that transition of 68's to 100's there must be a via that connects to circuitry at the other side of the board.
There is one GREEN ferrite coore with its heavy winding that connects to two of the HEAVY foil lands to the side of the the relay, with the copper wire seen on the one that is in the shape of a sideways numeral 1.
But that seems to be to far away as to be related. There is one white bisque 7 watt 4.7 ohm power resistor at the end of the relay and one electrolytic at the side of the relay near its coil which might be shunting it and
creating that engaged on off time constant that you are hearing . . . . .since I see no spike damping diode being used near the relay coil.
On the topic of toroids . . .specifically the YELLLOW cored one, I am seeing the output of the low voltage / high current power from the SMPS at the rear of the unit being looped thru it and it LOOKS that it is just one wire winding.
  • Can you confirm that it is not having one wire looped thru it for a current transformer function?
If not, that cored unit will just be used for RFI suppression.
  • Which then will take us back to the GREEN cored one . . . .is it just having a single winding on its core ?
I am trying to functionally account for the rather heavy gauge WHITE and BLACK wires that are routed towards the switch and then beside the LARGE raw DC filters.
  • Look at the mark up of the BLUE relay and note my assigned AC and then go right, just past theYELLOW case outline and tell me what the black device is? ? ?

Relating to post #52:
It says 12VDC .40 amps
I think that you are just finding yourself a common brushless computer fan being used there.

Relating to post #55:

"I've decided to go with the switch shorted pot leg idea. I am going to try to ignore the minor sparking."
Combined with . . . .
"By the way, I checked that little sensing spark's voltage with my DMM -it was 3VAC *and* 54VDC -I don't know if that means dual voltage or my DMM is messed up..."

Conceptually:
There is a series fed combination of high voltage and a BRUTE force variable DC voltage going to your electrode.
Your 54 Vdc seems right in range, within a particular positioning of the "power" control pot.
The 3VAC cold be in error due to the way some DVM's respond to a combined DC and AC voltage or the HV produce might be of such a narrow pulse width, that it
is responding with a decreased displayed value as compared to the meters EXPECTED sinusoidal waveform.
You will notice above, that I had you DC isolating your AC metering, for an expected symmetrical waveform (the oscillator portion) being in at least one part of that 324 circuitry.
A narrow pulsewidth waveform would give an erroneosly low reading in either situaton.

Functionally :
When you bring your "stick" in to your grounded work, the couple of KV's of high voltage initiate a small inter sparking, which creates an initial ionized path.
The 54 volts or so, at MULTI amp POWER capacity then sees that it NOW has a conductive path and it PUSHES in and . . .

ZZZZZZZZZapppppp . . . .
CreationOfAdamLong.gif


its ARC city ! . . . .with that initial sparking evolving into HOT plasma, until you pull the "stick" away.

Thassit . . . .

Techno Referencing:

eFZupjY.jpg


73's de Edd


.
 

CDRIVE

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Sir Clambake . . . . . . .


Functionally :
When you bring your "stick" in to your grounded work, the couple of KV's of high voltage initiate a small inter sparking, which creates an initial ionized path.
The 54 volts or so, at MULTI amp POWER capacity then sees that it NOW has a conductive path and it PUSHES in and . . .

ZZZZZZZZZapppppp . . . .
CreationOfAdamLong.gif


its ARC city ! . . . .with that initial sparking evolving into HOT plasma, until you pull the "stick" away.

Thassit . . . .

73's de Edd


.
Ed, reading this was like a Maxwell Smart moment. You know those little exchanges between him and the Chief. When the Chief says " Did ya get that Max? " and Max would say " Not quite Chief ". You know how the rest of the dialog goes.. :confused:

Anyway, on the up side I did comprehend the HV (ionization) initiation explanation! :)

Chris
 

Clambake

Mar 8, 2016
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You had not made any response in checking out the BLUE relays coil voltage.

It's true Edd. The reason I haven't done that test though is more logistic than anything else. To overheat the unit I have to do some heavy stick welding and that has to be done outside, and it's been raining pretty consistantly. TIG I can do inside, but I've never overheated the unit doing TIG.

BUT -I don't know if you saw my post #53. There I'm thinking that the welder's "stuck electrode" response is to pulse on/off that same blue relay -and I can simulate a stuck electrode easy, so I think there is now a way to do the test.

How would I go about controlling that relay, assuming shutting off the arc is what it does?
 
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Clambake

Mar 8, 2016
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and either "stick" a rod or do some heavy work to get the unit into "overload" condition

Oh ok -I guess you already figured the stuck electrode and overheat response would involve the same relay -at least I now have a way to simulate a stuck electrode without melting anything.
 
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