Breath Controller to Operate a Welder?
Please excuse the length of this message.
A couple years ago I picked up a used EWI4000 wind controller for personal use. While this is a device with built in sound generation, it has a Midi out for controlling other modules and devices. I have and electronics background and followed the breath controller posts but I have no "hands on" experience with Midi.
I am hoping that your creativity and knowledge of Midi can help someone in need.
I am a member of several welding forums. On one of the forums a member recently asked about using some sort of mouth-operated device to control a welder. The member is a triplegic (he has use of one arm and only very gross motor skills in the other). He unable to use his welder effectively with available technology.
Based on the responses, there does not seem to be a ready-made solution and other than some hypotheticals, no viable options are emerging. After thinking about it I believe a breath controller may be a very appropriate technology to use. I just don’t have the know-how.
The member is using a TIG (Tungsten Inert Gas) welding process. In Tig, the operator holds a “torch” between the fingers (somewhat like a very fat pencil or soldering iron). The torch is connected to the welder through a power cable, and a shielding gas hose. The other hand is used to hold a very thin filler wire.
When the torch is very close to the target metal (fractions of an inch), the operator normally steps on a pedal to initiate an electric arc from a tungsten electrode. This essentially melts the base metal. By varying the foot pedal up/down, the operator can vary the current (heat) put into the weld site. Also, while the pedal is pressed, Wire is had fed into the arc zone to melt and add filler to fuse with the metal being welded. An inert gas flows over the weld site to displace oxygen and prevent oxidation.
The process resembles electric soldering except that the operator is wearing a face shield, gloves and protective gear.
The member does not have the ability to manage a foot control. There is a small torch-mounted control available that allows fingertip control of arc-start and amp-control but the member does not have the motor skills to use that option.
I do not have particulars on his welder model, but I have an older Tig welder and the pedal has a small micro switch to initiate the arc and 10K potentiometer to control the amperage (the max amperage is pre-set at the welder and the pedal varies between min/max). I suspect his model has something similar.I believe those are the only parameters that need to be controlled.
The key issues here are providing the user with a comfortable, effective method of controlling the welding process and has the granularity to allow the user to customize arc initiation, arc stop, and amperage.
Solutions might include:
*Bite-Hold to initiate and continue weld – Bite release to stop the weld.
*Momentary Bite to trigger weld-on process and second momentary Bite to stop
*Breath to vary the amperage.
*I am not sure if some sort of pitch-bend or velocity would offer any benefits but they might provide user customizable preferences.
* A wireless option might be beneficial. However, the Tig process puts a lot of current (sometimes hundreds of amps) into the weld zone. Because of the proximity of the sensors to the weld zone (AC, DC, pulsed, varied frequency) I don’t know about interference if some sort of wireless solution is envisioned.
This project is above my skill-set but I started out thinking about a breath controller that controls a keyboard volume pedal. That addressed the amperage control but not the stop/start.
After days of searching I found the "MIDI to Potentiometer" board on this site:
This "variable Pot" looks like the type of item I am trying to assemble but when I follow the link, it takes me to this site, but I am unable to find the item.
Any ideas you may have would be appreciated.
If any promising (and affordable) options pop up, I can try and prototype on my welder.
Thanks for your time.
However, it's not certain that the digital potentiometer used in the design (MCP42010) is an appropriate substitute for the pot in the welding pedal. You'll have to check out the MCP42010 datasheet and make sure that the electrical specs are adequate (digipots tend to be pretty limited as far as voltage and current are concerned).
I hope this helps.
It seems like the two main main challenges are 1) finding an appropriate way to interface the welding machine so that amperage is controlled, and 2) finding a breath controller that is agreeable to the user. The stuff in between is mostly a programming problem, and could probably be accomplished with an Arduino or variant.
Thanks for your response.
As you can probably tell, my knowledge set is on the periphery of the various technologies. I know just enough to believe that a solution is close at hand, but with my current skillset, just out of reach.
I have spent hours on-line, using all kinds of search term permutations and following leads. I began to notice how many websites and search hits linked back to this site or mentioned/used/recommended your products. Just this morning, googling MIDI and Animatronics’ led me back here to: http://blog.highlyliquid.com/category/animatronics/.
I took that as a good sign. After looking over the site, I was impressed with how responsive you are to questions. I was hoping (but didn’t expect) that I would find the perfect solution here. But, the information here has given me some reliable reference info and I have learned new things along the way.
In my case, although bread-boarding up a “proof of concept” solution can be fun, I would prefer to use proven, commercial or finished products since I will be testing a prototype and hopefully delivering a stable, reliable and easy- to-use product.
The goal is to provide the user with a solution while meeting three key requirements:
1) Provide an effective user control/ interface
2) Protect the user from potentially hazardous conditions
3) Protect the equipment from any possibility of damage from a badly engineered solution.
An effective solution has to fit within these guidelines.
Item 1: The solutions I have seen proposed so far are just ideas. I don’t think much thought has been put into usability, calibration and customizing the solution to meet the user’s abilities/preferences. I believe breath controllers and MIDI effectively address this.
Item 2: Safety is a key feature of the MIDI environment. Think of it this way - What industry currently has workers routinely operating mouth-controlled devices connected to high voltage, high amperage equipment (thousands of watts)? Add to this walking over power cables, poor/ungrounded electrical setups and often working in open- outdoor job-sites with high humidity/rain/lightning risk etc. Now, THAT is a hazardous environment. Who does this - Electronic musicians when they walk out on stage and use breath controlled wind instruments, or use breath controllers to add expression to keyboards.
Addressing Item 3 has been the most difficult. The current pedal has 2 functions:
1) Initiate/stop welding arc (currently a micro-switch in an 18 VAC circuit)
2) Control welding amperage with a 10K, 2 watt linear pot.
Originally, I was expecting to replace these functions with solid state components. However, introducing electronic circuits into an existing welder circuit (which is proprietary and not fully documented) introduces the potential for bad outcomes (or warranty issues etc.). I am now leaning toward using a hybrid Digital-to-Analog approach that preserves the original welder control architecture.
A MIDI controlled relay, servo or solenoid operating a microswitch easily satisfies the switch issue.
Item 2 got a little trickier. As you mentioned, the step granularity of digital pots (128 steps) may be too rough for smooth arc amperage control. Plus, even if higher resolution devices exist, I don’t know how effective they would be at replicating the continuously variable pedal behavior expected.
I am now leaning toward Midi controlled motorized pots (probably servo or steppers). That way, I further insulate the user-side electronics and circuits from the welder electro-mechanical functions and don’t introduce any possibility of creating a bad outcome.
To drive the pot, am now exploring MIDI-to-Servo controllers: YEI Technology produces a MIDI based servo controller (SERVOCENTER) that is set up to handle 16 servos and has a 14 bit resolution (16384 servo positions). I believe this device can handle both the microswitch on/off and servo-controlled pot in a single device. It is overkill (16 servo controlled outputs) but seems quite robust and well thought out at a price point under $100. And, who knows, as this process progresses, it might be useful to have expansion capability to handle other functions (change other welding parameters or turn the welder on/off).
Anyway, thank you for your time and patience. The quality of information on this site has been very helpful.
Keep up the good work.
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