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By the sheerest luck I've found enough parts to build a ~100W resistance soldering machine. I got the plans from an old NMRA Bulletin. (Would that our modern mags had so much good stuff in each issue).

At any rate, I need a source for carbon rods. And that leads to an aside, namely, there's a savvy electronics guy on this forum who's offered to answer questions, and I've mislaid his name/contact. Can anyone help me there?

The first question I want to pose is the diameter of the carbon rods. To those of you who happen to own one, can you give me the diameter and length? The only carbon rods I have to hand are 1/4" thick, and that seems a tad like overkill, but perhaps not. I'm not clear whether the face of the rod should be flat or pointed. It's for heat transfer, and not a consumable, as I gather it. I'm also wondering if common round tool-motor brushes would be suitable?

Your thoughts and help would be appreciated. If all else fails, I'll blind-order a set from Micro-Mark. It's the diameter that is the only number I'm lacking.

Les
 

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You can usually find carbon rods at a welding shop. Ask for Carbon Rod,1/8” diameter (Arch Gouging Carbon). They usually come in bulk at $15 per 100.
Until you find a source, try this. I've found that it works.

You can make a carbon rod from the guts of a standard, el-cheapo, alkaline, ‘D’ cell battery (carbon cell of course and not Nicad, NiMH or other rechargeable types). I found that the cheaper the battery the better. Name brands like Eveready or Duracell tend to have soft carbon rods that are pourous. The really cheap ones, like the off brands you get in a supermarket or with Chinese toys, seem to use much harder carbon. A hard carbon will last longer with resistance soldering. Take care when cutting a dry cell battery open because it can be a messy job. Use some sand paper or an old fashioned small plastic pencil sharpener to file a conical tip onto the working end of the carbon rod.
 

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Thanks, Carl.


That battery idea I like, at least until I get practiced up. (I know how to solder with an iron and torch). Now, where's that dead flashlight?


Les
 

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Posted By weaverc on 01/07/2009 7:29 PM
You can usually find carbon rods at a welding shop. Ask for Carbon Rod,1/8” diameter (Arch Gouging Carbon). They usually come in bulk at $15 per 100.
Until you find a source, try this. I've found that it works.

You can make a carbon rod from the guts of a standard, el-cheapo, alkaline, ‘D’ cell battery (carbon cell of course and not Nicad, NiMH or other rechargeable types). I found that the cheaper the battery the better. Name brands like Eveready or Duracell tend to have soft carbon rods that are pourous. The really cheap ones, like the off brands you get in a supermarket or with Chinese toys, seem to use much harder carbon. A hard carbon will last longer with resistance soldering. Take care when cutting a dry cell battery open because it can be a messy job. Use some sand paper or an old fashioned small plastic pencil sharpener to file a conical tip onto the working end of the carbon rod.




When I was young, my second cousin taught me how to do this to make arc lamps in flower pots.
 

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Les

I get my carbon electrodes for resistance soldering from MicroMark. They come in 0.078" diameter x 1 1/2" long, in sets of 6 electrodes.



Regards,

Rudy Allarde
Indian Springs, AL
 

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Rudy,

Thanks for posting the picture. Looks like yours is home-brewed too. I'm going to try to go with the battery cores Carl suggested; MM tacks on shipping fees 'n whatnot. And if I do, the whole thing will've cost me $2. It was an old Sears Battery charger, 10 amp. Even had the resettable automotive circuit breaker, which I'll use. It had a timer motor, I took it apart and obtained some good-looking brass contact strips which I want to try to use for track power pickups. The DC ammeter will go on the control panel. Here's an instance where the Bird of Paradise crapped all over me, it did.

The footswitch I'll make from a long-armed microswitch I've been saving for some years now.

Thanks for taking time to reply.

Les
 

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Dan,

According to the NMRA Bulletin, all you need is a 10 amp transformer. (Those are expensive, new, but as I posted earlier, I got one out of an old battery charger for $2.) The secondary winding is 12 volts, because of the charger. The old mag article I'm referring to used a 6V secondary from an old TV. So, if P=IE, then P= 10a x 6v, or about 60 Watts. The thermal output of a middling-to-smaller soldering iron, in other words. I got a 12v secondary, so P= 10a x 12v, or about 120 Watts, the size of a medium soldering iron.

If you will email me off post, I will try to scan the issue and send you the schematic. It's simple as falling off a log, so I'll describe it: You need an AC cord, a foot-operated switch (easy to build from a microswitch and a couple of boards & a spring). This connects to the primary (117v) windings of the transformer. IT IS VITALLY IMPORTANT FOR HEALTH AND ONGOING GOOD FORTUNE THAT YOU USE A POLARIZED PLUG--ONE THAT HAS A FAT BLADE ON ONE SIDE. You must wire the foot switch into the 'Hot/High/Black side of the AC line. If you don't know why, ask and I or others can tell you. But NEVER put a switch on the ground/return leg of an AC circuit unless you have an excellent reason. And then think twice.

Next, you need a fuse for the secondary (12v) side. Since I buy only the best junk, mine had a thermal fuse (instead of blowing, it just opens up for awhile, cools off and closes). It is rated at 12 amps. (Two amps more than the transformer is capable of putting out (without burning up) but that's Sears for you. Their idea appears to be: the fuse will trip before the transformer lets go. Anyway, you can smell a hot transformer, so it's not that bad. It takes awhile for a big transformer to die from moderate overload. Then you need to make a set of holders for the carbon rods. You need to use heavy gauge wire, the article said 8 ga, but I think they're a tad overcautious. I'm going to use 10ga. What it is, you don't want line loss in the leads to the carbon rods. The leads will be 6-8 feet long, probably. You wire one leg of the secondary of the transformer to one side of the fuse, and the other side of the fuse connects to one of the carbon rods. The remaining secondary wire connects directly to the lead of the remaining carbon rod.

Of course, you don't want your hands/body shorting out the 12v, so you need wooden holders. The article said the carbon rods should be made removable, so you can hold one in each hand for difficult-to-reach places. They neglected to mention how nice a pair of wooden handles would be in this case. There are instances of folks with undetected heart conditions that die from small amounts of electricity that many of us (not me) might ignore. I won't mention heat transfer from the rods to your fingertips, as you'll discover that all by yourself. So you want some sort of suitable wooden pincher-type arrangement, spring loaded, though the idea to resistance soldering is, you take your foot off the switch as soon as the solder begins to flow. I haven't tried resistance soldering yet, having learned about it on this board, and decided to try it out. I can torch and iron solder just fine.

Les
 

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Dean,

I went to your site and read Vance's article. I have some issues with it, but I don't want to go into any but the 30A fuse. You want a fuse smaller or equal to the current rating of the transformer secondary--to be fair, it wasn't stated what that current rating was--in order to save the transformer. ALL secondary wiring should be able to carry the current the transformer puts out, plus a bit.

On the upside, he's right about being careful around house AC. I emphasized that in my previous post. Some pixes of his article would help, are any available?

Also, using the dimmer control ahead of the transformer (on the primary side) is a most excellent idea. I believe a standard one will carry the current the primary will draw. I'm debating fusing the primary side on mine, as well as the secondary. (See my post, above).

Thank you for your helpful post, and I in no way mean to criticize or be negative about the contents therein, or inadvertently give offense.

Les
 

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Les,
I'm glad you found the web page helpful...other than making up the dimmer switch I didn't do anything with 120v AC....and the battery charger was not modified in any way, just hooked the soldering leads to the charger leads......I really do believe in the KISS (Keep It Simple Stupid) principle.......
I noticed I need update the page as I have used quite a bit and so far I've been more then pleased with the result... :) :) :)
 

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Posted By Dean Whipple on 01/09/2009 5:49 PM
Les,
I'm glad you found the web page helpful...other than making up the dimmer switch I didn't do anything with 120v AC....and the battery charger was not modified in any way, just hooked the soldering leads to the charger leads......I really do believe in the KISS (Keep It Simple Stupid) principle.......
I noticed I need update the page as I have used quite a bit and so far I've been more then pleased with the result... :)" src="http://www.mylargescale.com/DesktopModules/NTForums/themes/mls/emoticons/smile.gif" align="absMiddle" border="0" /> :)" src="http://www.mylargescale.com/DesktopModules/NTForums/themes/mls/emoticons/smile.gif" align="absMiddle" border="0" /> :)" src="http://www.mylargescale.com/DesktopModules/NTForums/themes/mls/emoticons/smile.gif" align="absMiddle" border="0" />









Dean,

I'm an utter failure at the KISS principle. As I said, perhaps in a different post, I have never 'resistance soldered'. I learned of it here. Then I happened to find a schematic and an article in an old NMRA Bulletin. The article didn't indicate rectifiers, which the battery charger has, giving an unfiltered ripple output, probably riding on a DC voltage. I'm guessing, I've never looked at one with a 'scope. Thus, I assumed AC was the way to go, as I know DC arc welding is different from AC; one is better for certain jobs than the other, I'm told, though I once did a lot of AC arcwelding.

I can't think why one would be superior to the other in this instance, perhaps you can explain.

I understand you 'made up' your own dimmer switch? I'm assuming a type of SCR circuit? I'd like to know the details on that. In any case, at first I thought of the old dimmer switches on the floorboard of cars.

Les
 

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Les,
I have know idea if AC or DC is best for resistance soldering, that's what Vance used so that's what I figured worked best... all I know is that it works great using an OLD Battery charger (not one of those fancy new electronic type battery chargers) and I can still use it for charging car batteries.... :) :)
As for the dimmer switch again Vance suggested it could be used and seeing as I'm in construction and I had a regular old dimmer switch for a light laying around....I just put it in a metal outlet-box (like you'd use in a house), I also added a foot switch to the extension cord that I made with a micro-switch a spring and a couple of pieces of 1/4" plastic I had laying around...... :) :) :)
Dean
 

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12 volts AC at 10 amp. That is about what the Aristocraft Ultima has inside it. Just tie to the transformer and bypass the fan, diodes!!!!

However, I think the Ultima has a 16 volt AC transformer as its DC output with no load is 22 volts (16 times 1.414 is 22.6). Many claim it was a battery charger, but the voltage output is too high for that.

So using a battery charger and tapping off the transformer would be a good pick as long as it has a 10 amp capability and had a full wave bridge.

PS, I have built my own power supplies so i know what to avoid and with a foot switch patched on the input, this should be used with a GFI for safer operation.
 

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Dean & Dan: (Boy, try to keep them straight in your head!)

Well, looks like we've agreed on one thing: none of us knows which is better, DC or AC for resistance soldering. Since I have a spot welder that is AC, and it works just great, I'd have to think it probably doesn't make any difference. When I build mine, which will be AC, I'll learn how to use it and post something.

Thanks for all the good info.

BTW, the GFI might be overkill if one used a 3-prong cord and grounded the case with the green wire. That's assuming the electrician wired in the ground lug on the outlet. (A bunch in my house aren't).

Les
 

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The purpose of the dimmer switch is that by lowering the input voltage to the power supply, the output voltage will then be reduced by a proportional amount...

But I'd be a little cautious using any model railroad power supply power pack with expensive electronics in it.....because, when you are Resistance soldering you are in effect shorting out the power supply to create the heat to melt the solder....and you might let the smoke out..... :) :)
 
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