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  #11  
Old 07-20-2010, 12:47 PM
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Hobweld Hobweld is offline
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Quote:
Originally Posted by digger doug View Post
Ken,
I don't understand the Original post.

What are you trying to accomplish ? do you want to smooth
out the welding voltage somewhat ?
Yes
are you trying to make
a "stiffer" supply so that the short arc current goes up ?
Yes
Or/and fixing this "single wire gun switch" problem ?
I still will be using the single wire original gun but need to reduce/lower the voltage fed to the pcb. So the drive part of the pcb doesn't misread it.
Does that make sense?
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  #12  
Old 07-20-2010, 01:05 PM
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Bob, you need to look at the drawings again and read post # 4
It's not a good idea to parallel bridges especially if they are not the same.
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Last edited by GWIZ; 07-20-2010 at 02:31 PM.
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  #13  
Old 07-20-2010, 01:55 PM
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Quote:
Originally Posted by Hobweld View Post
I still will be using the single wire original gun but need to reduce/lower the voltage fed to the pcb. So the drive part of the pcb doesn't misread it.
Does that make sense?

No, not to me, why change from the original, just because of
a switch change ?

It seems odd to me that the power supply is fed with an ever changing
voltage, unless they are using it to make changes to the drive motor
speed (independent of the rheostat setting) based on how low the
arc pulls the transformer voltage down. (and wether or not you are
set in hi or low voltage)
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  #14  
Old 07-20-2010, 02:16 PM
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There is a few options but here is what you wanted.
Here is the added relay BUT depending on where the power taps for reversing the polarity are located the added relay will have to be located at the down stream side of the taps.
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  #15  
Old 07-20-2010, 02:52 PM
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Quote:
Originally Posted by GWIZ View Post
Bob, you need to look at the drawings again and read post # 4
It's not a good idea to parallel bridges especially if they are not the same.
You're right, GWIZ! I didn't read it carefully. Hobby I think the reason your wirefeed is running too fast with the xtra cap is that the effect is to increase the voltage on that line. In that case, I don't think you need an additional bridge to power the pcb. just a pot in series with the line to the wirefeed. Adjust it to the same voltage as is there without the extra cap and you're done.
As to paralleling the bridges, GWIZ, you are correct if both circuits are in use at the same time. I had believed that Hobby was interested in adding a second gun (something I apparently misread or dreamed up). In that case either bridge one OR bridge two would be in circuit, never both at once.
Hobby I think you need to take a dvm and go through the circuit paying attention to the voltage on the wirefeed controller input with and without the extra capacitor. I think you're fooling it to believe that the wirefeed pot has been turned up on the front panel. a series trimpot should take care of it.

I'm not sure I understand why you want the extra cap in the original welding circuit Hobby? I'm pretty sure the welding engineers put in the correct value at the factory. That cap DOES smooth the DC but it also changes the rise and fall times in the circuit and may mess with your weld beads. As I recall the traditional circuit element to add was an inductor, not a capacitor.
I think I'll quit now before I get in any more trouble.

DrBob
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  #16  
Old 07-20-2010, 02:54 PM
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Quote:
Originally Posted by GWIZ View Post
There is a few options but here is what you wanted.
Here is the added relay BUT depending on where the power taps for reversing the polarity are located the added relay will have to be located at the down stream side of the taps.
GWIZ
Thanks, this unit is shielded gas only no reversing taps.

Ken
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  #17  
Old 07-20-2010, 03:09 PM
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Quote:
Originally Posted by DrBob View Post
You're right, GWIZ! I didn't read it carefully. Hobby I think the reason your wirefeed is running too fast with the xtra cap is that the effect is to increase the voltage on that line. In that case, I don't think you need an additional bridge to power the pcb. just a pot in series with the line to the wirefeed. Adjust it to the same voltage as is there without the extra cap and you're done.
As to paralleling the bridges, GWIZ, you are correct if both circuits are in use at the same time. I had believed that Hobby was interested in adding a second gun (something I apparently misread or dreamed up). In that case either bridge one OR bridge two would be in circuit, never both at once.
Hobby I think you need to take a dvm and go through the circuit paying attention to the voltage on the wirefeed controller input with and without the extra capacitor. I think you're fooling it to believe that the wirefeed pot has been turned up on the front panel. a series trimpot should take care of it.

I'm not sure I understand why you want the extra cap in the original welding circuit Hobby? I'm pretty sure the welding engineers put in the correct value at the factory. That cap DOES smooth the DC but it also changes the rise and fall times in the circuit and may mess with your weld beads. As I recall the traditional circuit element to add was an inductor, not a capacitor.
I think I'll quit now before I get in any more trouble.

DrBob
DrBob
I appreciate the added input. The main reason was to get a little more punch to help wet out the puddle better.

Pic 1 from this.....

Pic 2 to this.
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  #18  
Old 07-20-2010, 03:23 PM
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Per my old linde mig supply:
1. Wetting is more inductance. Not neccesisarily affecting current
(or wire speed).

2. More voltage is more "punch" (total heat input), up it and you need
to increase wire speed as well.

EDIT: your only going to get so much from a wall socket.

If this is a 220 vac unit, your only gonna get so much thru that
(transformer) core.
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  #19  
Old 07-20-2010, 03:43 PM
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Quote:
Originally Posted by Hobweld View Post
"Actually the motor negative is going to the negative on the bridge, but the way the original diagram is drawn, appears to connect to the positive, maybe I should have redrawn it to show it passing past the positive connection. I didn't draw the original diagram, it was a download from manufacturers website" His words.

Ken
You already know that your posted drawing is a bit wrong.

It's ok to tap off the AC side and feed a second bridge, but in your drawing the minus sides are connected to both bridges.
You can not connect the plus or the minus sides of one bridge to the other.
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  #20  
Old 07-20-2010, 06:24 PM
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Quote:
Originally Posted by GWIZ View Post
You can not connect the plus or the minus sides of one bridge to the other.
I didn't think I fully understood what was going on in that drawing but that part bothered me right away.
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