DIY-Welder - Build your own Arc, MIG and TIG welder Page hits:

First prototype was using a 200A alternator and an 18HP B&S engine:

A basket-case riding mower, but it has a good 18HP B&S engine. 2nd pic is simplified mower controls.

Here's the control panel and alternator installed:

Installed control board and an output terminals. The alternator is mounted to the right. Inside the mower frame are filter capacitors and a hand-wound reactor.

So far, only MIG has been tested. It works very well. These are the first test welds on 1/8" steel. First weld lasted about 2 seconds before the pulley spun off the alternator. Second weld was better. 0.030 wire, 19.5V probably about 100A. Could have used a bit more current.

I tested arc welding with the board set to MIG, worked ok, but needs arc firmware to work right:

  7014 rod, 28V, about 60A. Did half a rod then the whole rod turned red from too much current.

Update 7-12-2008:  Added arc firmware and did some more arc welds:

 5/64" 6013 rod, DCEN, 1/8" steel, OCV 36V, too much current caused spatter.  3/32" 7018 rod. Tried higher OCV (45V.). Still current a bit high. The top left was DCEP and is cleaner. Bottom trace had too much current still and has big blob of weld hanging down. Need to adjust current range a bit..

After these 4 welds, checked alternator and it was barely warm. Control board heat sink was still room temp. Works well. The 18HP engine has no problem with the load. What was surprising was the alternator can output 48V with no problem. It can do 32 volts at idle with no load. The current sensing has been redone so I have more control over the current slope.

Here is a test of the complete setup for MIG. The wire feeder needs more top speed as it is just too slow on 12V. Will need to power with 24V or get a faster geared motor.