Inverter build NEED A BIT OF HELP

[Samuel1477]

Hello everyone. Before I start I must say this. I know the risks involved when handling  high currents. I am a hobbyist. Also a welder. I got my hands on a old welder. I want to do 1 of two things. What I really want to do with it is turn it in to a power inverter. Is that possible? If not I want to upgrade it to a digital welder with a arduino or something along those lines. I only want to know if I can use either one of the two transformers or are they completely different? Would I be better off just doing a welder upgrade?

[Siwastaja]

No, you can't turn it into an inverter.

You sure can digitalize the controls but are you sure you want to do this? What's wrong with the old knobs, switches, potentiometers?

[jonpaul]

Vague posts with little info will not get good responses.

The OP should please  give us details of the "old welder" MIG? TIG? Spark gap? Tube/valve? High Freq? How many KVA?

Control of on/off or control of power?

With respect to the welders expertise, high power inverters have lethal bulk power eg 360 VDC, and need special equipment to design and debug safely.

Kind Regards,

Jon

[Samuel1477]

Millermatic 250 mig Welder sorry I should have put that in my original post it is an analog welder

[Samuel1477]

My mistake millermatic 210

[penfold]

Millermatic 250 mig Welder sorry I should have put that in my original post it is an analog welder

Interesting idea, you could readily replace the tap changer with just a big triac doing some phase angle control, or maybe use two or three of the taps to give a better control range for lower currents, then the world's you lobster as far as implementing stuff like pulse mode, phase angle stuff is relatively easy to do. I'm guessing SC-MIG isn't too sensitive to waveform? (depends on the size of the output inductance though)

The wire feed would just be pretty straight forward,

[Samuel1477]

So I have all the components from the welder I just have to build a case for it. Once I have that done then I'm thinking of bypassing the control board and just using an arduino. I do need a few components, digital readouts and a pot for the wire speed. This is possible right?

[penfold]

So I have all the components from the welder I just have to build a case for it. Once I have that done then I'm thinking of bypassing the control board and just using an arduino. I do need a few components, digital readouts and a pot for the wire speed. This is possible right?

You'll need something to interface from the Arduino to actually switch the motor power (MOSFET h-bridge for instance) and some sensors to give you something to display.
If you're monitoring output voltage then you will need some galvanic isolation, and depending if you want to know the voltage at the input to the rectifier, output of the rectifier or at the output of the unit the nature of the voltage sensing will be slightly different.
Current can be easily enough done with a current transformer at the output of the transformer (measuring the AC).

As prior warning, it won't be the easiest project because there will be a lot of EMI that will easily couple into your circuits if they're not designed well.

[strawberry]

1:could upgrade to 3phase transformer for smooth weld and power
2:digital readout (Vpeak, Vrms or Vavg)
3:feeder speed sensor for speed stabilization
4:antistick protection
5:AC converter for aluminium welding

if you want to build basic welding inverter, start here http://danyk.cz/svar_en.html (difference is TIG/MMA constant current but MIG is constant voltage but everything else is the same)
if something more: hot start, pulse, HF start...