Alternator welder

[I_Love_Plasma]

The mower its going on is a old thing. so it prolly aint got much.

HAHA put it on a Scag "Turf Tiger 48" it's got a 25amp alt! pretty good

[blasphemy000]

I kinda skimmed through this so I'm sorry, but what diode trio are you talking about removing? The ones for the regulator or the ones for the output? I've never delt with a regulated alternator, I'm a Mopar guy so all my alts are external even in their automotive sense. The internal output rectifier will handle whatever the alternator can throw at it though. Most diodes that are rated at high amperage are also rated for a voltage way higher than what anybody would need for welding. I have some diodes here I was going parallel together to use to convert an old "buzz-box" to DC and they are 60a and I think 600v each. I never had my alternator apart but I'm sure the voltage on the rectifier diodes is way higher than the alternator is capable of putting out even when there isn't an arc struck. If the thing has regulator diodes separate from the output diodes then I have no idea about those as I've never had to work with an internally regulated one before.

[Rivets]

I kinda skimmed through this so I'm sorry, but what diode trio are you talking about removing? The ones for the regulator or the ones for the output? ......

Blasphemy,

Yes, they feed the "+" side of the coil on a GM "N" type regulator.
Packaged as a trio, each one connected to a stator phase junction at one end, and the other ends connected together to feed the coil.

See schematic in post #38 above.

Cheers,
rivets

[bobwills]

Well i got my alternator going today. The way I hooked it up was how someone said to do it earlyeir on here. I hooked the field and sensor wire together and hooked it to my charger. The alternator was hooked to a old 1/4 hp electric motor. Turning the altornator at maybe 1500 rpms. I turned the charger on 2 amps and guess what i got 50 something volts out of it. Never messed with the regulator or anything. So i turned the charger off and it cept the 50v. So what all have i found out about it. Also does the diod trio or whatever i have to take out keep the alternator from keeping producing current when the feild is turned off when its taken out or what?

[parkour]

You can check out the schematic of the GM alternator.. http://mightymo.org/public_html/imag...re/DelcoSI.jpg It appears to me that the diode trio provides an isolated, lower voltage drop path for self excitation current to flow so that the alternator can self start without an external power supply being connected, while at the same time loads are attached to the main alternator output. (it's plausible for a 70's era vehicle that such a thing would be important) The residual polarization in the rotor should be enough to get it going. This is how cheap self "regulating" mains power generators work (residual mag, not diode trio)

It would be a trivial matter to convert this to a self starting (no external electric supply needed), adjustable constant *voltage* supply. You could make it a current limited supply (like a buzz box) (more like constant power than CC or CV)) by powering the field externally from a stable power source, or if you add a current shunt (precision low resistance resistor (usu just a spec length and gage of copper)), and some control circuitry, you can make a voltage limited, current regulated supply.

I did this with a 12v power system, LM393 comparator, mcp14e4 mosfet gate driver, and an FQP50N06L mosfet. The circuit switches the field on and off to give me an auto selecting voltage or current regulated supply. I read two potentiometers with the 393, and also the output voltage and output current. When both were below the set point, the circuit would switch the field on, but when one or the other got above set point, the circuit would switch the field off. The current shunt I used was 4' of #4ga copper, and dropped 1mV per amp of current. I selected that to minimize power dissipation at the 400 amps of output I was designing for. It's still 160 watts lost in 4' of copper at 400 amps.

[bobwills]

Ha not really sure what any of this means but are you saying the voltage regulator needs nothing done to it then since its oveasly not doing its job. And do i still need to get rid of the diod trio. And without it will the current stop when the cuttent running to it is shut off.

[blasphemy000]

If you're getting 50v OCV(open circuit voltage) with about 2 amps of input current to the field coil I would go ahead and raise the input to about 6-8 amps and try striking an arc with it using some 1/16 or 3/32 rods. If it won't hold an arc put 10-12 amps into the field. If it still won't hold an arc then either the alternator just doesn't have enough power or the regulator is holding it back. With a 50v OCV though I would say that the regulator just isn't working due to a lack of feedback. I could be completely wrong though, but I would give it a try just to see if it works.

[parkour]

I was merely describing what I thing the purpose of the diode trio is. Beyond that I was just musing into the keyboard.

But I agree with blasphemy about why you are seeing 50 volts; lack of feedback to the regulator. If you connect #2 to the output, it should immediately drop to 13.8 volts. But this is actually an interesting thing. You should be able to use it as a weldernator just as it is with nothing connected to it other than the belt, the work clamp to the BAT post and the electrode holder to the case. You would simply adjust the amps with the throttle lever. The engine does have a governor... right?

[blasphemy000]

Adjusting the amps with the throttle isn't the best idea. I'm sure it would work but it's not ideal. It's better to keep the alternator spinning at a constant speed and adjust the output by varying the input with a rheostat between the battery charger and the field coil.

[bobwills]

I was thinking that I should try it tonight with a set of jumper cables and a 1/16" 7018. Got some be a good little test. I doubt it will work though cause its only hooked to a 1/4 hp electric motor now. But still gonna try it. And I tryed putting 8 amps to the field but it didnt raise the voltage any. And after all this i still dont know what a diod trio does. Someone dumb it down a bit caise i dont understand all that technical jarend, Sorry. Just like say what differs the alternator with it in and then what it does when its out. Also so when i turn the charger off it keeps producing current. How would i make it stop when i turn the feild off. Got an idea of something to try though too.

[blasphemy000]

If you wired it up the way I showed you in the diagram I drew in paint the output current should stop as soon as the field power is removed. If it keeps producing current after the battery charger(field current) is turned off then maybe there is an internal capacitor holding a charge inside it and keeping power to the field. I really don't have a clue why it would continue to make power after the field current is switch off. It shouldn't be doing that.

[bobwills]

Yeah i did wire it feild and sensor wire together. Maybe if i seperate the 2 though it might stop. Need to try that next chance i can. If its that way ill put another switch on the sensor wire so when i want it off i can just flip it off too. Im not really sure though

[parkour]

Yea, I don't think it's going to work very well with the 1/4 hp motor.

The diode trio is what powers the field. If you leave it, the alternator will be able to produce output without anything connected to it. If you remove the diode trio, you will have to power the field externally. If it is producing current even after you disconnect the charger, it is because the alternator is functioning normally. The only way to get it to stop is to stop spinning it. Once it gets going, it is self sustaining as long as it is spinning.

[bobwills]

No its not suspose to. Just using it because its easyier than messing with a gas motor when im Messing with it. And ok. So thats good. Thats why i need to remove the diod trio. Now i get it. Guess that will be the next part of the build

[bobwills]

Well last night i hooked it up and put a pair of jumper cables on it to see if it would weld. It didnt. But it was just on my little test motor. So might build a little mount to try it on a bigger motor that will turn it much faster so i can get the full output out of it. That or take the diod trio out of it so i can control it. Lol. But dont know where to start on that or what it looks like. What yall think i should do.

[bobwills]

Ok so i finally got a chance to get the alternator opened up. Makes it much easyier having something to look at. So ive hooked a wire up to the regulator and ran it to the outside where i can ground it out. Now im to the diod trio. So i looked up what that looks like and came up with the picture below. Is that it. And for it do i just remove it or do i bypass it or something.

http://www.pico.com.cn/images/Diodes...ios/8A-200.jpg

[parkour]

Thats it. What to do with it depends on what you wish to accomplish.

[DaveO]

At the risk of butting in, I'd like to suggest a reality check at this point. I don't mean to be critical of anybody, or in any way question or criticize anyone's motives or capabilities. I'm hesitant to post this, even. This is not targeted specifically at any one person, but to anyone thinking they can simply read an internet post and then lash together a TIG welder.

I'll admit- when this thread started I looked for an alternator of the right type, actually found one at a junk yard (they prefer to be called "automotive dismantlers", btw) not too far from here. Then I realized the desire to have a welder clouded my judgement. I appreciate and admire the knowledge and skill that members on this board have: they can take totally unrelated parts, connect a few wires, and a TIG welder comes out the other end! My hat is permanently off to those guys, but I admitted to myself that at least in this case I am not one of them, as much as I'd like or wish to be.

The reality check is this: if you're thinking of a DIY TIG welder, and you ALREADY HAVE the built-in knowledge of the electrical systems required, then maybe you could pursue this kind of DIY project. Merely owning some spare parts does not qualify you.

If you can only get there because enough guys help you and draw diagrams and show pictures with arrows pointing the way, then isn't it time to wonder if you're swimming in the wrong end of the pool. If you need more than a little nudge to get you going, then please just buy a Harbor Freight TIG welder and be done with it. It's on sale this week for $229, and comes with a warranty and a torch. Better yet buy an Everlast, it's a better machine.

Yes, everyone should learn, and desire to learn, and push their personal envelope. I know and do a lot of things because I didn't listen to people when they said No. But get the learner's permit before you attempt to drive the Indy 500. Don't burn down your house or kill yourself just to save a few bucks. The world's most expensive TIG welder is still cheaper than your funeral.

OK, off the soap box.

[bobwills]

Well for one im not making a tig if you read the posts and two im just making it for them times you need to do some welding where you aint got electric. And also just because it would be awesome to have. And no I dont know all about it but hey you got to learn somewhere. I dont see any other 16 year olds trying this or know about arc like ive picked up or buying tools and getting them for christmas since a young age. But yeah i didnt know nothing about altornators before the start of this but I can tell you one thing and that is that Ive sure learned alot form everyones input on here. And to everyone Thank you very much. Everyones been a huge help.

[parkour]

Gabe,
I'm not familiar enough with the electricals of the early Delco alternators to give you really good guidance on how to mod one for welding, but I did find a page that describes the process.
http://www.huv.com/jon/jeep/Welder/on-board-welder.html

With this design, you control amps with engine rpm. You could use a high wattage 12v light bulb in place of the resistors.