Electronics > Projects, Designs, and Technical Stuff

Yet another spot welder circuit

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beduino:

--- Quote from: texaspyro on April 04, 2019, 03:36:31 am ---Also, no matter what you do, expect to kill a lot of FETs getting this thing to work.

--- End quote ---
I have yet another tricky idea to drive transformer primary in my spot welder by using pulse train described above,
but instead of triac or thyristors in anti-parallel I used so far without any problem-my idea is to use AC mosfet switch driven directly from MPU by gate drive transformers ;)

I used this concept of GDT with 100kHz PWM on two MPU pins in my current roof LED lights project, where AC mosfet switch block 230VAC and GDT with 100k resitor on AC mosfets gate does the job, but it is low current needed.
In the case of spot welder 230VAC mains can draw much higher currents on transformer primary, but still oders of magnitude lower than in capacitor based spot welder, so I do not expect any fireworks in my new spot welder project but will see soon  :-/O

Virus:
Yesterday I found KWeld schematic and I shamelessly ripped off some ideas, specially what's concerning about measuring the voltages in both terminals of the welder and the positive terminal of the capacitor in order to see if I can replicate that pulse length to joules calibrations method by myself or see if I can get something worth of processing out of measuring these voltages.
Any comments on this?

Virus:
I am making the PCB, will update when it's ready.

Doctorandus_P:
The simplest would be to use a modified microwave transformer and combine that with a EUR 10 Spotweld timer from Ebay / Ali / China / Whatever.

beduino:

--- Quote from: Doctorandus_P on April 07, 2019, 09:16:01 am ---The simplest would be to use a modified microwave transformer ...

--- End quote ---
Nope, in many cases those microwave transformer  have aluminium primary windings, so forget about decent quality ;)

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