Foot Controller DIY - I need help!

[Lfernando84]

Gentleman, I have this brazilian brand name Bambozzi WMI 208 TIG AC/DC welding machine with a 5 pin connector for TIG HF start. I bought a very common foot controller (since this brand does not have one) but, of course, I have to adapt it. I've watched all Youtube videos of DIY foot pedals, I've seen hundreds of schematic images on google search and I've tried myself to make this pedal to work with my machine but with no success, so I need help.
My pedal controller has two linear rotary potentiometers: one external and one internal. Both B103 (10KOhms). It has two plugs: one for the switch with two pins and another for the amperage control with 3 pins.
Since my machine has a 5 pin aviation plug, I have to figure it out what pin does what and I did (kind).
From the inside, there's two green wires (pins 1 and 3) for the switch, one black wire (pin 2), one red wire (pin 4) and one blue wire (pin 5).
Using a multimeter on continuity mode, none of the pins are connected to the machine ground (the chassis).
On DC voltage mode, my multimeter shows:
14.7 volts on pins 5 (blue) and 4 (red)
14.7 volts on pins 4 (red) and 2 (black)
0 volts on pins 5 (blue) and 2 (black)
So:
4-5 = 14.7V
4-2 = 14.7V
2-5 = 0V

I tried to connect one potentiometer (10kOhms) like this:
Machine Pot
Pin: 2(black) ------ 1
Pin: 4(red) --------- 2 (whiper)
Pin: 5(blue) -------- 3

Though it changes those 14,7 voltages (checking with multimeter) and lights up the foot controller on the panel, it doesn't change the numbers on amperage display.
I tried changing the wires, tried wiring two potentiometers as a voltage divider, even tried with 2.2K and 1K potentiometers, but nothing worked. Run out of ideas here and reaching my machine's company customers service, they didn't want to help me aswell.

 

[tommullin]

Isnt there usually a switch that needs to make contact too? Are you making continuity between 1&3?

 

[voipio]

Is there an instruction manual available for this machine? Most welder manuals have some sort of schematic, which tend to deal with printed circuit board connections, rather than individual component level details, but these crude schematics can be helpful.

On your voltage measurements between the various pins, polarity isn't mentioned e.g. was pin 5 positive with respect to pin 4, or vice versa?

As a first guess, I would disconnect the existing potentiometer connections and connect the plug's pin 5 to both potentiometers at pin 3, provided this is the pin closest to the potentiometer wiper at the minimum settings. If that is the case, connect the external potentiometer's pin 1 to pin 4 on the plug. Next, connect the outside potentiometer's pin 2 to the internal potentiometer's pin 1. Lastly, connect the internal potentiometer's pin 2 to the plug's pin 2. That way, the external potentiometer should set the maximum current, whilst the internal potentiometer controls the current between 0 and the maximum set by the other potentiometer. Please note that this is just an educated guess. There may also need to be an external link that "tells" the welder that a welding pedal is connected.

 

[Madis Moppel]

Same welder although in different housing is available also from Italian Manufacturer AWELCO with designation TIG 200 AC/DC PULSE. I suspect that both companies have ordered the welder from Asia as white label product. AWELCO lists foot pedal with order no 95900. Unfortunately with quick googleing I wasn't able to find any documentation for TIG 200 AC/DC PULSE. Maybe with additional search something can be found.

 

[Lfernando84]

Isnt there usually a switch that needs to make contact too? Are you making continuity between 1&3?

Yes, that's right. I have continuity on 1 and 3. Both are green wires inside of the machine

 

[Lfernando84]

Same welder although in different housing is available also from Italian Manufacturer AWELCO with designation TIG 200 AC/DC PULSE. I suspect that both companies have ordered the welder from Asia as white label product. AWELCO lists foot pedal with order no 95900. Unfortunately with quick googleing I wasn't able to find any documentation for TIG 200 AC/DC PULSE. Maybe with additional search something can be found.

Never heard of them. It's exactly the same panel and connector!

 

[Lfernando84]

Is there an instruction manual available for this machine? Most welder manuals have some sort of schematic, which tend to deal with printed circuit board connections, rather than individual component level details, but these crude schematics can be helpful.

On your voltage measurements between the various pins, polarity isn't mentioned e.g. was pin 5 positive with respect to pin 4, or vice versa?

As a first guess, I would disconnect the existing potentiometer connections and connect the plug's pin 5 to both potentiometers at pin 3, provided this is the pin closest to the potentiometer wiper at the minimum settings. If that is the case, connect the external potentiometer's pin 1 to pin 4 on the plug. Next, connect the outside potentiometer's pin 2 to the internal potentiometer's pin 1. Lastly, connect the internal potentiometer's pin 2 to the plug's pin 2. That way, the external potentiometer should set the maximum current, whilst the internal potentiometer controls the current between 0 and the maximum set by the other potentiometer. Please note that this is just an educated guess. There may also need to be an external link that "tells" the welder that a welding pedal is connect

Yes, I am Sorry for that one... The pin 4 (red) is positive in relation pin 5 (blue) and in relation with pin 2 (black).
The users manual has nothing on schematics or connectors info. Pretty poor, actualy. The schematic that Ive attached, Ive found on Internet, but It doesnt work.
I will try your schematic.

 

[voipio]

OK, those measurements and polarities seem to be consistent with pin 4 being a +15V supply, and pin 2 or pin 5 being the negative supply. My suggested connection scheme is based on pin 5 (blue) being 0V supply, and the black wire (pin 2) being the signal lead from the pedal to the welder, but it's possible that they could be the other way round.

Check that the potentiometer resistance tracks are continuous, and of the expected resistance, between the pins that you have labelled 1 and 3 on the pots (potentiometer pins should be disconnected for this measurement), as they can burn out if sufficient current flows. The PCB circuit, if designed propely, should avoid this happening, but it's always worth checking.

 

[Lfernando84]

That way, right? I've just tried. Doesn't work. They bring the 14.7 volts down to 12.X volts on max (think that this might have to do with their values? - both 10k).
When I turn on the welder with this schematic plugged in, the "pedal foot" indication light on panel is on, witch is fine, but when I rotate Ex pot or In pot to the minimum anti-clockwise (or other way around, don't remember), the light on panel goes off, witch is odd, and the amps display number doesn't change its value at all...
OBS: Already checked the pots and they're just fine and continuous.

 

[voipio]

Your schematic interpretation of the description I gave in posting #3 is correct :-)

The panel "pedal" light going off could be because the welder senses the presence of the pedal when there is a non-zero voltage on the signal line, and turning the external knob fully anticlockwise sends a 0V signal.

Although the panel current display can reflect pedal position, this isn't true on all welders. It may be that your welder is one on which this doesn't happen. Try striking an arc, and see if pedal position influences it. If this doesn't seem to work, try swapping the connections to pins 2 and 5 over, so blue from plug pin 5 goes to the internal pot's pin 2, and black from plug pin 2 goes to pin 3 on both potentiometers. Hope that makes sense.

 

[Lfernando84]

I will try that and come back with an answer...
In the meanwhile, theres this guy on YouTube with simillar problem:

 

[500e]

There is a manual and parts Dload on the mirror site says to follow and gives email contact
Worth a try

 

[Lfernando84]

There is a manual and parts Dload on the mirror site says to follow and gives email contact
Worth a try

Sorry, what site? The italian Brand? I already sent them an e-mail asking for help.