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Mr.RC-Cam

Sparky: A Little Stick Welder with Big Features

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trying to find a schematics, I guess you have not found them either?

I did not find schematics to this welder.  Having them would have saved a lot of time developing the Sparky Project.
 

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Is the potentiometer just a constant voltage divider or is it driven with some sensing feedback?

The current setting POT  is sourced by the PWM chip's feedback path. I originally planned to use the ESP32's DAC to control weld current but had to abandon that idea because of the welder's feedback configuration. The MCP45HV51 digital POT was a convenient solution.

 

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1 hour ago, Mr.RC-Cam said:

The current setting POT  is sourced by the PWM chip's feedback path. I originally planned to use the ESP32's DAC to control weld current but had to abandon that idea because of the welder's feedback configuration. The MCP45HV51 digital POT was a convenient solution.

 

A crazy idea: use A/D to convert the feedback and use that to calculate the output....naah :-)...digital POT is way easier...

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An accurate schematic of the welding machine's PWM controller board could help us design alternate current control solutions. I don't have the free time to reverse-engineer the controller board, but perhaps someone else will volunteer to do that.

 

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Weld Current Calibration Notes:

The PWM controller board has a multi-turn trim Pot that affects the Welding Current.  See photo:

Current_Pot1_800.jpg

 

But before any attempts to change the trim Pot's factory setting it is important to understand how it interacts with the front panel's Current Adjustment.

The front panel current setting changes the gain of the PWM based inverter. This is the user's control for adjusting the weld current. It has a end-to-end range of about 60 Amps.

The internal trim Pot is used to apply a constant offset to the Weld Current. It can "move" the weld current up or down about 60 Amps. It's a "factory" calibration adjustment for setting the minimum weld current. And since it is an offset, that means it also affects the absolute maximum current.

Although far short of the advertised 200A specification, it's possible for Sparky to achieve 125A (short current). When the trim Pot is calibrated to allow 125A maximum current the minimum current will be about 65A. If a lower minimum current is needed then the maximum current will be reduced by the same amount.

Adjusting the trim Pot means that the machine's top cover must be removed. This exposes dangerously high voltages to the world. The unprotected circuitry can harm (or kill) you! Do NOT proceed with adjusting the trim Pot until you have had proper training with working on high voltage equipment. Proceed at your own risk.
 

 

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Great project! I like it!
I was planing on doing something similar for same welder. Is it possible to implement hot start function and anti-stick? It would make this welder even more useful!

Many strong welds! :)

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Is it possible to implement hot start function and anti-stick?

Those are on the future feature wish list. Not sure when I'll have the free time to add them. However, any developer is welcome to roll up their sleeves and tackle it. This is an open source project so contributions are welcome.

Some special Arc control actions (scratch-start, lift-start) are being added in hogthrob's TIG software. His code might be useful for adding the new stick functions too.
https://github.com/thomastech/Sparky/pull/6

- Thomas

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