Fwd: wireless foot pedal for TIG welder

[Jeff Sturges]

Hi all,  FYI...  In case anyone is interested in working on this, pls contact Avery directly.  

Jeff Sturges

Founder & Conductor, Mt Elliott Makerspace
Director's Fellow, MIT Media Lab

---------- Forwarded message ----------
From: Curt Malouin <cu...@redpandalab.com>
Date: Mon, Aug 4, 2014 at 9:54 AM
Subject: Fwd: wireless digital potentiality
To: Jeff Sturges <jeff.s...@gmail.com>

Hi Jeff.

Avery (see below) stopped by the Green Garage today looking for someone to help with an electronics project.  He’s a welder/metalworker who wants to develop a wireless remote controller for TIG welding machines.  Sounds like an Arduino/wireless project.  He is willing to pay someone to help him.  I thought you might know someone and/or be able to point him in a good direction, so I gave him your name (hope that’s OK).

Hope things are going well!

-curt

Begin forwarded message:

From: Avery Marriott <averym...@gmail.com>

Subject: wireless digital potentiality

Date: August 3, 2014 at 7:55:44 PM EDT

To: in...@redpandalab.com

Reply-To: Avery Marriott <averym...@gmail.com>

Your Name: Avery Marriott

Your Email: averym...@gmail.com

Subject: wireless digital potentiality

Message: Hello Curt,
My name is Avery, Jon the owner of Beard Balm suggested that I speak with you in regards to building a wireless foot pedal to control the amperage of a tig welding machine.

--

Curt Malouin

cu...@redpandalab.com

[Jody Raiford]

They already make these.

They cost between $500 and $1500, though, and only Miller and Lincoln seem to have them readily available.

An Arduino/etc. build might be able to beat that (assuming that they charge that because they can, not because it's actually expensive to make), and/or if you can make one that works on different machines.

Anybody with skill points in electronics able to comment about what it would actually take to make something like this? 

Miller's version

Lincoln's Version

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[eric©]

I'm still trying to figure out the point of a wireless control since you're still tethered to the machine anyways with the electrode and ground leads...

Eric

[Drew]

@eric: I think the point is to eliminate the possibility of current
traveling through the operator between his hand and foot. Or else it
might be to control a welding robot of some sort.

The foot pedal part is easy. Almost anything that can create any kind
of signal will do. TV remote control, or RC car controller are two
possibilities.

The hard part is in the welder end. Specifically finding a relay
switch that can handle high currents.

http://www.millerwelds.com/education/articles/images/Fig.2modernTIGwelder.jpg

shows a TIG DC max of 200 amps.

For comparison, I have a 1500 watt invertor which I got for power
outages. It uses 12 volt batteries for input. Input currents are
expected to be ~ 100 amps. The specs permit 4 guage wire in a pinch,
but strongly recommend 0 guage wire. I got about 6 feet of it from a
welding supply shop. Whatever you come up with for a switch should
probably have twice the cross section or better. There also may be
inductance issues.

In spite of which I don' t think it has to cost $500+ to build this
device - so long as you don't need it for anything related to legal or
insurance purposes (OSHA, etc.)

[Roger S]

For wireless you will need to come up with some kind of protocol or other way to ensure that the signal gets through and that there aren't false activations.  Currents of the magnitude around welders give off lots of interference.

[Nathaniel Bezanson]

Roger's got it, interference is the killer. Welders in general, TIG in particular, are really just big RF jammers with the convenient side-effect of heating metal in a controlled fashion. It's possible for radios to work in that environment, but difficult to make them work reliably. Infrared isn't much better, even with narrow filters and modulation, the light coming off a welding arc will just plan saturate most receivers. There's a reason these controls are wired! Making a remote one is a daunting task indeed. Can you do it? Sure, but I wouldn't bet my job on it.

-Nate B-

[Jeff Sturges]

Hi all, thanks for feeding info to this idea.  I cc'd Avery so that he can read all of this, add some thoughts, etc.

From my discussion with Avery, the pedal has 5 contacts - ground, positive (on/off),, and then the three legs of a pot.  According to Avery, the pedal does not run any high voltage/amperage through it. (I know nothing about TIG pedals myself, and very little about TIG welders).  

Based on my limited experience, I suggested the following:

- a pedal or some foot-to-leg mechanism that uses a spring loaded pot talking to an Arduino analog pin

- The pedal Arduino would have a Zigbee shield 

- another Ard/Zig combo would mounted on the TIG, talking to it via Arduino controlled digipot to give the amp/gas signal(?), and digital I/O pins for the positive on/off  

However, based on what Roger and Nate mentioned, I imagine that the TIG might cause a ton of RF jamming, so perhaps the Zigbee is an unwise option?  Still worth trying, or no?

Are any usable frequencies are unaffected by the RF disruption of the TIG?

I wonder what the $500-$1500 pedals use for their wireless?  

Thanks for tossing this around!

Jeff Sturges

Founder & Conductor, Mt Elliott Makerspace
Director's Fellow, MIT Media Lab

@eric: I think the point is to eliminate the possibility of current
traveling through the operator between his hand and foot. Or else it
might be to control a welding robot of some sort.

The foot pedal part is easy. Almost anything that can create any kind
of signal will do. TV remote control, or RC car controller are two
possibilities.

The hard part is in the welder end. Specifically finding a relay
switch that can handle high currents.

http://www.millerwelds.com/education/articles/images/Fig.2modernTIGwelder.jpg

shows a TIG DC max of 200 amps.

For comparison, I have a 1500 watt invertor which I got for power
outages. It uses 12 volt batteries for input. Input currents are
expected to be ~ 100 amps. The specs permit 4 guage wire in a pinch,
but strongly recommend 0 guage wire. I got about 6 feet of it from a
welding supply shop. Whatever you come up with for a switch should
probably have twice the cross section or better. There also may be
inductance issues.

In spite of which I don' t think it has to cost $500+ to build this
device - so long as you don't need it for anything related to legal or
insurance purposes (OSHA, etc.)

 

They already make these.

- - - - 0 

They cost between $500 and $1500, though, and only Miller and Lincoln seem to have them readily available.

An Arduino/etc. build might be able to beat that (assuming that they charge that because they can, not because it's actually expensive to make), and/or if you can make one that works on different machines.

Anybody with skill points in electronics able to comment about what it would actually take to make something like this? 

Miller's version

Lincoln's Version

[Drew]

What about laser light and|or a fiberoptic cable?

[agm...@gmail.com]

I think that a fibre *cable* sort of defeats the whole “wireless” concept, though it does remove the possibility of current through a human.

Laser light (through free air, I assume you are suggesting) would work, but it would need relatively narrow optics to avoid the same fate as the IR system already proposed. Narrow optics mean tight aiming between the transmitting and receiving ends, so the pedal would probably be best bolted down or exceedingly heavy so as not to move during use.

--
Andrew G. Meyer
<agm...@gmail.com>