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3d Printed knob turner - remote TIG amp control!

By combining 3d parts, gyro, and a stepper, I made a programmable foot pedal for my cheap GTAW welder! General remote knob turner.

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I wanted to add amperage control via foot pedal to my uber-cheap new gas tungsten arc welding (GTAW) machine. I was not enthusiastic about the ~$50+ pricetag for the simple pedals. Furthermore, the cheap pedals require removing and matching the default amperage control pot on the front of the unit and passing through leads from the pedal pot.

While I'm not usually too attached to warranties, this GTAW kit was scarily cheap and came with a 30d return period, so I had the aim to not modify the unit in the eventuality that it failed.

So I got to work on coupling an MPU6050 gyroscope (for angle) with a stepper, instead. This approach is appealing, as I was able to easily add min/max current cutoff knobs that relate to the full pedal deflection, allowing for precise control.

I'm excited about the prospect of adding other programmable features, such as modifiable timed current pulse settings for welding.

This project is also easily modifiable for any fine remote motion

Intent

Remotely control a knob -- controlling GTAW amperage in this case -- using a tilt sensor to create a simple foot pedal. 3d printed gears and mounting allow adjustment of gear ratios and mounting style to suit a wide variety of motion tracking and remote control projects. 



Result

Process

An immediate difficulty I encountered was that the gear generator linked from Hackaday seemed to require money to download models. 

I found this DXF exportable gear generator online instead: http://hessmer.org/gears/InvoluteSpurGearBuilder.html

From there, I imported the model into InkScape:

This allowed me to save it as an SVG, which TinkerCad can take as an input:

I originally was at a gear ratio of about (1 : 3) and using a memsic2125 accelerometer, but I ended up on (1 : 1.3) and an MPU6050 gyroscope to measure the angle. 

In the end, i used an Arduino clone, an MPU6050 gyroscope, a SparkFun EasyDriver, a stepper motor, and the 3d printed parts.

I used the on-chip Digital Motion Processing of the MPU6050 to get filtered angle measurements. This is mapped to the min/max stepper limits coming from the potentiometers. 

All in all, I'm extremely pleased to have a fun and hackable alternative to a purchased GTAW foot pedal for amperage control. It's pleasing to think that I can easily program in current pulsing functionality, a display, or more advanced features on a future whim. I'm working to remedy MPU6050 DMP FIFO Buffer Overflows on long stepper moves, general stabilization, and pulsed current routines next!

mpu6050easysteppercontrol.txt

Arduino code -- still dealing with the MPU6050 buffer overflowing from time to time, I believe from long stepper moves.

plain - 11.91 kB - 02/19/2019 at 05:49

Download

  • 1 × GY-521 / MPU6050 Gyroscope
  • 1 × STEPPER Power Management ICs / Motion, Motor and Servo Control
  • 1 × Sparkfun EasyDriver
  • 1 × Arduino Nano clone

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Discussions

Dan Maloney wrote 02/19/2019 at 16:37 point

That's really clever! Gets the job done without having to buy the foot pedal, and doesn't void the warranty.

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Rami wrote 02/19/2019 at 19:29 point

Thank you! It was really enjoyable to put it together.

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