Modifying foot pedal

[sebring115]

I have a foot pedal on my chinese Tig that is just a linear Pot wired as a 3 wire potential divider. I want to be able to limit the current of the welder so that I can for example set full scale of the foot pedal to 60 amps. Whats the best way of doing this on the pedal? When I have the pedal in use the power on the welders front panel is switched out and has no effect.

Thanks

Mark

 

[shenion]

Add a potentiometer (R2) in series with the existing one (R1).

 

[Will_Davis]

Very Interesting.

As I do NOT have a foot pedal option on my SIP welder for current setting I could disconnect the existing Pot ( or fit a manual selector switch on ISET ) and then plug this circuit in?

I think "Its a cunning plan and it may just work"

 

[sebring115]

Thanks for that, had kind of confirmed what I thought. The linear pot fitted at the moment seems to measure 11k4 which seems odd, but I presume a 10k rotary pot would be fine.

It had crossed my mind to alter the connections inside the welder so that the panel power pot did something similar (so becomes r2) and then use a switch just to disconnect out the foot pedal (R1)when its not being used.

Cheers

Mark

 

[justmental]

i am going to be removing my potentiometer that controls the amps on my foot pedal
being on the side makes it a pain have caught it many times now.
going to make a small box for it and extend the cables so it can be put by the welder so amps can be adjusted without having to keep grabbing hold of the pedal.

 

[zedhead]

Aah, this explains an issue I've had with my Chinese tig... I fitted a foot pedal last week, and couldn't understand why I could quite clearly get more power through than was dialled in on the control panel!

 

[sebring115]

Justmental.

Picking up on your point it would therefore make sense to add a pot in at the connector on the machine, no mods needed anywhere, just an additional pair of connectors between the machine and foot pedal.

Wondering if one of these would do:-http://www.maplin.co.uk/standard-potentiometers-2205 part number FW02C.

These also look like the plugs I have on my machine
http://www.maplin.co.uk/audio-locking-connectors-chassis-plug-line-socket-997 (will have to check though)

 

[justmental]

can see what you mean but i want the best of both worlds being able to adjust at the bench top and by the pedal or near me if i am all wrapped inside a car doing a roll cage.

As for the connectors you are on about are they are style i will be using.
i am going to do a short connection from the box with a plug then a longer cable to plug into the foot pedal so if i damage the cable i can plug it in near the pedal.
save having any down time might just even make a second cable.

 

[sebring115]

so is you max power pot wired like Shenion suggests? Do you know what resistnace it is?

 

[justmental]

yes it is wired as mentioned but has no markings on it from what i can see.
i will be making a start on it at the weekend

 

[shenion]

Use the same value pot that is in the pedal for the second one.

 

[rohart]

Justmental - does/will your pedal have a switch to start the current ?

The pedal I made did, and I was forever clicking the current on when I was getting ready to weld. It didn't matter much until I changed from an auto-dark lid to a plain flip down mask. Then I flashed myself a few times.

So I put an override switch in the bench box. With this off, I can mess with the pedal underfoot, knowing that I won't start the arc.

 

[justmental]

Justmental - does/will your pedal have a switch to start the current ?

The pedal I made did, and I was forever clicking the current on when I was getting ready to weld. It didn't matter much until I changed from an auto-dark lid to a plain flip down mask. Then I flashed myself a few times.

So I put an override switch in the bench box. With this off, I can mess with the pedal underfoot, knowing that I won't start the arc.

what i am doing is removing them amp aduster from the pedal and putting it to a length of cable so i dont have to keep bending over to adjust it.
will post some pics over the weekend as getting the cable and plugs to do it on friday.

 

[rohart]

My pedal started off as a bench control. I thought I'd check I could make it work before making up a pedal. The bench box had one knob to set the range, and another to set the max amps in that range.

That worked, so I made a pedal to take over the max amps knob. The pedal connected through the bench box, and still does.

That's when my second auto-dark bit the dusk and I opted for plain lenses and a flip visor. Well, I was totally unable to flip it without dislocating my neck, so I needed to set up my torch ready to strike, then flip down the lid, then go. If I tried using the button on the torch, the whole torch would move before I was ready to go. Result - disaster.

So, then I put a micro-switch into the pedal. That worked great. But.... I kept hitting the micro switch and starting the arc when I was making myself comfortable. Must have flashed myself a few times.

And that's why I put an override switch into the bench box. But it's not needed if you use an auto-dark, because you don't have your lid up at that stage.