schematics resistance soldering?

Hi,
I'm planning to build my own resistance soldering unit. Is there someone who has a schematic of i.e. the American Beauty or Hotip units?
Thanks.
Regards, Richard Netherlands
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KingRichard wrote:

There's hardly anything to require a scematic. They're just a low-voltage high-current transformer with multiple taps. Most are activated by a footswitch on the 115 VAC input. I've seem some that use an autoformer on the input, driving a low-voltage high-current transformer, to give continuous variable output.
A straight autoformer is NOT suitable, as it gives NO isolation from the power line (which is dangerous at best).
So, all you really need is a suitable transformer, a high current output switch (or a set of binding posts), a fuse or circuit breaker (on the input), and a footswitch (on the input).
Dan Mitchell ===========
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Daniel A. Mitchell spake thus:

I'd like to contribute my project, which I just recently finished and used successfully. As Dan says, the unit is simplicity itself.
Here's what I did, and it works very well: for the variable voltage source, I used an ordinary light dimmer, the garden-variety type available at any hardward store or home-improvement place.
Now before someone says "But you're not supposed to use those--they're for AC only!", let me say that, yes, that's what they say: they're not supposed to be used for inductive loads (motors, transformers, etc.). However, it works, and works well, and shows no signs of failure: no overheating, buzzing noises, smoke, etc. I suspect that it may be giving me half-wave rectified AC, but in any case, it works.
The rest is simple: I used a big old honking "filament" transformer, with multiple 12-volt windings which can be wired together either in series or parallel (I chose parallel for higher current). The thing is rated at 14.6 A wired that way, which is *way* overkill. However, it's what I had, so I used it. (You could use a much lower-rated transformer, which would be cheaper and easier to find.)
The rest is just the working end of the electrodes. I got some thin (1/8") copper-clad welding rod and used that for one electrode. The end can be ground down to any shape you like. The other electrode is just an alligator clip.
You'll find as you experiment with your unit that the trick is to use little enough current. It's very easy to use enough current to turn your workpiece red-hot or even vaporize it if it's small enough!
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David Nebenzahl spake thus:

[...]
Whoops--forgot one important detail: the footswitch. Mine's homemade (out of an old office hole punch). This may be the hardest part to find. (Old guitar effects box footswitches are a possibility.)
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I made one out of a foot switch I bought at a Grainger Supply store, a car charger, and a Weller soldering pin that screws apart, I bought at Radio Shack. Take the positive lead from the charger to the foot switch and the lead from the foot switch to the soldering pin. I put a cooper coated carbon rod, bought at a welding supply store, in place of the rod of the soldering pencil. Take the negative lead from the charger and connect it to a heavy duty alligator clip. Place the negative clip on one side of your piece and hold the soldering pencil carbon rod opposite the negative. Touch the foot switch for just a couple of seconds. Piece soldered together. Charger costs $25, solder pencil costs $10, foot switch $20, box of carbon rods $12. It helps to file the carbon rod to a fine point because it helps eliminate arcing and makes a cleaner connection and you can get closer to your work.

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Jeff Hensley wrote:

I run my carbon rods into a pencile sharpiner.
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David Nebenzahl wrote:

How about an old sewing machine footswitch?
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Greg Procter spake thus:

Good idea. Problem with those is that they're rheostats, not switches. But I'll bet one of them could be hacked into a switch pretty easily.
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David Nebenzahl wrote:

Some may well be rheostats, others have a built-in autoformer (just a filter choke with exposed windings, and a wiper, much like a lot of the early tinplate train transformers). Either MIGHT work, depending on the 'downstream' circuitry, but might also prove hard to control. An intersting experiment.
Dan Mitchell ===========
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David Nebenzahl wrote:

My one includes a switch as well as a rheostat - for "off/rheostat on". It's from a very old 'Singer'.
Regards, Greg.P.
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The very simple Res. Soldering outfits are nothing more than a low voltage/high current transformers, heavy wire leads and a handpiece. No rheostats. Period! Full power on no power.
My AB unit has an autotransformer feeding the low voltage/high current transformer. Foot switch included with it is a simple on-off pedal. You dial the power setting you want on the faceplate of the transformer unit, then step on the foot switch to get that power.
Nothing complicated. Actually, I use that same foot switch for other electic tools I use (like my flex shaft Dremel).
And foot switch pedals are readily available for about US $25. http://mocro-makr.com has one for sale.
Peteski
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David Nebenzahl wrote:

Here's a whole list of readily available footswitches, from relatively cheap to heavy duty industrial.
http://www.grainger.com/Grainger/searchresults.jsp?QueryString=footswitch&search_type=keywordandcatmfgindx
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Rick Jones spake thus:

http://www.grainger.com/Grainger/searchresults.jsp?QueryString=footswitch&search_type=keywordandcatmfgindx
Sorry, doesn't work ("your session has expired"), since it's cookie-driven. (I hate cookies.) But I'll take your word for it.
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David Nebenzahl wrote:

Grrr! OK, just go to www.grainger.com and enter "footswitch" in the search. I got dozens of hits, from about $12 on up to $100+ for the explosion-proof stuff.
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Greg Procter wrote:

Most of these had both a switch and a (sort-of) variac (autoformer) built in, to give variable speed control to the motor. With a suitable low-voltage transformer 'downstream' of the footswitch, this might work. The switch would need adequate current capacity (for the input side of the transformer). I also question the advisability of the 'variable' feature ... it might be difficult to control soldering heat dependably and repeatably (which is important).
So, yes, it might work, depending on the switch and other circuitry, perhaps well, perhaps not. There are too many vairiables to give a better answer. You'll just have to experiment.
Dan Mitchell ==========
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Daniel A. Mitchell spake thus:

Not true; most of them (maybe all?) were rheostats. I just opened up the footswitch left over from my last broken sewing machine, and it has a rheostat. I've seen a bunch of these, and have never seen any with an autotransformer. A rheostat would be much cheaper and does the job adequately, so no reason for the manufacturer to go to all that trouble.
In any event, I was suggesting hacking one of these to make it into a simple on-off footswitch. Wouldn't be hard, judging from the innards of the one I just opened up. (You *definitely* wouldn't want to control the heat with a foot-operated rheostat; you'd never be able to get the exact same setting.)
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This article might offer something:
http://www.trainweb.org/bristol-s-gauge/Projects/rsu.html
Good luck with your project!
Bill Bill's Railroad Empire http://www.billsrailroad.net
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Hi,
Thanks for all the replies. At this moment I'm building a RSU from a 6v/26A transformer and using an old sewing footswitch.
Regards, Richard

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