Spot Welder
BackThis is a fairly simple project but if you have no experience with electronics then I wouldn't attempt it. The first thing you are going to need to do is find a so called "dead" microwave. I got mine from my good friend Oscar. The unit I got was a vary large microwave so that usually means a large transformer is used.
Next thing you will want to do is dissemble the microwave but before you start this I would recommend letting the microwave sit unplugged for about 36 hours. The reason for this being is that there is a vary large and potentially deadly capacitor in the microwave. After you have the shell off the microwave you should have one side with allot of electronics on it and one with nothing but the microwave cavity. Don't go cutting wires yet. Make sure to get a good pair of wire cutters that have insulated handles. You can also optionally use some thick rubber gloves if you wish.
What you will be looking for is a big square (normally bigger than your fist). There should be four wires coming off it. Carefully snip each wire with your wire cutters and try and leave a good piece of insulated wire attached to the transformer. I would recommend you have some one with you well you do this but have them stand three or four feet back from you. This way if you would happen to get shocked some one would be able to call for help. After you get all the wires sniped and you make sure you removed all the screws that hold the transformer down take it out of the microwave. This may be a little difficult as the transformer will likely be magnetized.
Don't worried about touching the transformer because if you got all the wires cut there is no current in the transformer at all. After you have the transformer out make sure to keep the rest of the microwave as there are some other usefully parts on it. Next step is to get a hack saw, hammer, and a small piece of round bar. Take the hacksaw and cut the secondary windings (the big bunch of very fine wires). Make sure not to damage the primary windings with the hack saw.
I would also recommend putting a piece of news paper on your working area. This will help after the next step. After you have it cut all the way threw you will want to use the hammer and small round bar to knock out the windings from the transformer. After that's done you will know why I told you to put the news paper down. Next get an old cord of some sorts (the kind that plug in the wall. Lamp cord works well). Cut it off the lamp or what ever you found and strip both of the wires (if there is more than two, one of them should be green.
Strip the two that aren't green). Attached one of the non-green wires to one terminal on the primary coil and then put the other non-green wire on the other post (make sure the cord isn't plugged in when your doing this). Next get a small piece of insulated wire (the gauge of the wire isn't important) and wrap it threw where the secondary coil used to be (I would start with three wraps). Hook one end of the insulated wire to the + on your tester and hook the other end to the - on the tester and make sure the tester is set to ac volts.
Make sure both of the end are not close to each other then plug in the lamp cord to the wall. If you did this right it should read about four volts on your tester. If it's not close to four volts unplug the cord from the wall and wrap the insulated wire around one more time and check again. When you are near four volts make sure the plug isn't plugged in and take the insulated wire off the unit making sure to remember how many wraps of wire you had put on. The only step left is to get some four gauge wire (this can be bought from your local car audio store) and wrap it around the unit the same amount of times you did with your small insulated wire. At this point that's all I can tell you. I still have to make a clamp to hold the wire to the mettle. I will say this. Never ever touch the four gauge wire you just used well the unit is plugged in.
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