The Transformers

• To build a homemade arc welder you will need eight large transformers. These can be extracted from old microwave ovens and oftentimes appliance shops and random people will happily give you their old microwave ovens. Keep in mind that only transformers from microwaves of 950 watts or more will do. Once you have the transformers you must make one very important modification to them. Remove the secondary winding and replace it with a low voltage winding made out of no. 6 single conductor wire. Fit as many turns of the wire as possible. Because all of the transformers will be slightly different, you will need to pay close attention to them when building your cabinet so that the proper spaces are left for mounting each.
  
  

The Cabinet

• The cabinet design serves many functions. The top of it serves as a tray for storing loose materials like gloves, electrodes, clamps and other materials. Attached somewhere to the top of the case should be a carrying handle made form a 1 1/2" dowel because the machine will be quite heavy. Another function of the cabinet is to serve as a chassis for the transformers and electronics, so you will want ample cooling fans mounted in a way that provides sufficient air circulation to keep the transformers and other electrical parts cool. These fans can be gathered from the old microwaves as well. Another thing to keep in mind about the cabinet is that you should use good strong lumber and hardware when building it so that the weight of the parts is well supported, making for a cabinet that is sturdy and durable.
  
  

Electrical Parts and Schematics

• Once you have your transformers and your cabinet designed you need to acquire a few electrical parts from your local electronics store. These parts include; 600 pF 2kv ceramic, 0.1mf 400v epoxy, 22mf 250v electrolytic, IRKT71 SCR module, Lamp dimmer triac, RB152 1A bridge rectifier, Trigger diac, 1M Linear potentiometer and a 5k Linear potentiometer.
  
  Unless you are an electrical engineer, you will probably want to assemble the rest of the arc welder according to a schematic. The first reference for this article contains a schematic that can be completed with all of the parts above. However, there are several designs available online and, depending on your needs, you may want to use a different schematic or make modifications to an existing one. Once you have assembled the electronics, install them in your cabinet and your welder is ready to go.