DIY welder almost finished but

chuckinnc

10 µW
Joined
Mar 17, 2019
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5
My DIY tab welder is waiting on the final piece, I need to know what would be the best weld voltage so I can wind the 1100w transformers secondary. I see utube videos that have anything from 1v output to ones using 12v battery, so weld voltage can vary alot. Does anyone know the open circuit voltage of a factory made welder, or maybe should I scrap the idea and go with a battery powered welder?
 
can we assume you are using a microwave transformer style welder? if so, what switching are you using? that will impact the welding power.

note that a diy transformer based welder usually ends up in the bin because they suck.
 
chuckinnc said:
My DIY tab welder is waiting on the final piece, I need to know what would be the best weld voltage so I can wind the 1100w transformers secondary. I see utube videos that have anything from 1v output to ones using 12v battery, so weld voltage can vary alot. Does anyone know the open circuit voltage of a factory made welder, or maybe should I scrap the idea and go with a battery powered welder?

I have 2.8V and everything works just fine. You need to measure how many volts you have in one wind. 3-4V is ok for yout transformer.
You will get 280-350 amps based on your secondary wire AWG.
You have timer circuit?
 
The control board came from ebay, I installed it in a old ups case, the green knob/readout adjust the timer, red knob/readout adjust the 120v power level going to the input of a transformer, the board has a triac that sets power cycle of the 120vac, I assume it will probably stay at 100% & only need to use the timer to control weld time. That is if I stay with this type (120v)
welder, the 12 volt battery types look interesting so I am trying to decide on completing this one or changing to DC type.

I have several 1100 watt input (120v) transformers. Trying to decide how much round wire I can thread in a square transformer
hole, smaller wire with more turns would fit better than large 2 ga. wire with 1-2 turns, output wattage would be the same
 
chuckinnc said:
The control board came from ebay, I installed it in a old ups case, the green knob/readout adjust the timer, red knob/readout adjust the 120v power level going to the input of a transformer, the board has a triac that sets power cycle of the 120vac, I assume it will probably stay at 100% & only need to use the timer to control weld time. That is if I stay with this type (120v)
welder, the 12 volt battery types look interesting so I am trying to decide on completing this one or changing to DC type.

I have several 1100 watt input (120v) transformers. Trying to decide how much round wire I can thread in a square transformer
hole, smaller wire with more turns would fit better than large 2 ga. wire with 1-2 turns, output wattage would be the same

I use 3 AWG wire (25mm2) and its ok so far. Of course i cannot weld thick nickel with this. Also electrodes are very important.
Its ok for some small power battery packs.
 
Wire diameter has a huge impact on the power.
More turns means more volts means more power when resistance stays the same.
 
flippy said:
Wire diameter has a huge impact on the power.
More turns means more volts means more power when resistance stays the same.

Yes but you can make 3-4 turns with thick wire.
More turns means more volts but less power.
 
Wow, great link, best article I have found yet. Well if I cant weld battery tabs properly then I can always use the unit for resistance soldering station. I have a small American Beauty brand 250w resistance solder station for connectors and it does a good job, so 1400w should be amazing. Anyway I know my efforts in this project will be used in on way or another.
 
Once you have a large transformer, you can even put a few turns of smaller wire through the secondary window, and leave some airspace. It is good to tie-wrap the secondary or it will vibrate a lot, but as long as it doesn't vibrate through the wire insulation, it will still be fine.

You can lower the watt output of a large transformer, but if you have a small unit, the max watts are when the windows are filled with copper. Once you know what to look for, keep an eye out for a large microwave.

You can buy a 1500W one on ebay for $50ish, but be patient and you'll find one for free.
 
I have 2 same transformers. Will try to use them in parallel when i catch some time. I guess amperage should be higher but im not sure about this.
 
I managed to find 1750VA (i guess its about 1400W right? )transformer, removed secondary and rewind 3 turns with 35mm2 wire.
Welding power is much higher now - i need to wait for new control board (i burned old one :D ) so i can test with different nickel strips.
However transformer is very noisy. Im not sure why - vibrations (because its not fixed anywhere) or something else.
 
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