Homemade Resistance Soldering Unit

I tried posting this earlier, but I got an error message when I went to
post it. So, I am not sure the first message went anywhere. If this is
a double post, I apologize.
I am attempting to build a resistance soldering unit from a small car
battery charger. I am following these directions:
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I am using a 12v 6a charger that, I think, is too small. I can just get
two pieces of .005 brass sheet soldered together before the charger
circuit breaker shuts off the charger. The charger will run for about
6-7 seconds. This should heat it up within 3 seconds. I would like to
solder up to around .025 brass sheets together too. I found a 12/30/75
amp charger at Menards that is probably my next step. But I would like
to be able to vary the current coming out. Do I need a variac for this?
Does this go on the input (110v) or the output (12v) side of the
charger? What specs (volts/amps/watts) should I look for on this? I
also know that I could use a filament transformer of around 6.3v 6-20
amps on the secondary in place of the battery charger. Any suggestions
on which is better? I KNOW that using a light dimmer switch for the
adjustment setting is a bad idea.
I already know that American Beauty and PBL sells these. But for around
$500 for a 250 watt model, I think I will screw around with this some
more. I am bidding on a 300 watt model on ebay right now.
I also searched around the Internet for more instructions. But
everything I found was pretty vague. I am electronics illiterate, but I
can usually figure stuff out with some clear directions.
ANY help on this would be greatly appreciated.
THANKS!
Mike
Reply to
mj
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You're not getting nearly enough current from a small battery charger. One 500-watt resistance soldering box (Wassco Glo-Melt model 105-B2) has voltage taps from 1.0 to 5.8 volts -- which, at 500 watts would be 500 to 86 amps.
You might try a soldering gun --without the tip. My (old) Weller D-550 delivers 240 or 325 watts at 1.5 volts. That's 160 and 216 amps -- if the load resistance is low enough to accept it. There's one ;ike it on EBay right now:
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Looks like current production D550's are rated at 260/200 watts. The D650 is rated at 300/200 watts. You might also try a 150 from HF( item 42685) for $9.99. You could use two or more in series or parallel to get more heat.
The tubes on the Weller are threaded 7/16-14 so you could connect to it with a couple of bolts. Use very heavy wire like #4 welding cable, automotive ground braid or copper strip for (short) connections from soldering gun to work and stinger. The issue isn't overheating the wire, but minimizing voltage drop everywhere but in the load itself.
Yes, a variac would be the best control. With a variac, I'd tape the trigger down on the gun and use the variac to control it. A foot switch might be handy too.
Reply to
Don Foreman
Hi Don, Yeah...I had thought about using a soldering gun for the power pack. But I sort of like the portability of the soldering iron that I already have built. I have a foot control, but it is a simple momentary ON (while the pedal is to the metal) or Off (foot off the pedal). The thing is, this setup works. I am just not getting the current I need at the end of the carbon. I am hoping to get some more replies before I throw more money at this. I "think" a larger charger with a variac will work. If you don't mind taking a look at this auction, I am looking at this variac:
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This would go on a 12/30/75 amp charger something like this one from Amazon:
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One of the things that I don't understand (I don't understand a lot of what I am doing, this is only one of them) is which side does this go on? The 110v or the 12v side? My guess is the 110v side.
Thanks for the reply.
Mike
Reply to
mj
Definitely on the primary (110v) side. Just remember that the Variac does NOT isolate the output from the 110v input. I'm sure your aware but thought I'd mention it. The output of the soldering gun would be AC but the charger, of course, is DC. I had considering building one but also using a DC cap in the circuit to give it just a bit more "punch". I've not looked inside one of the commercial units to verify if those are done that way or not. Respectfully, Ron Moore
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Reply to
Ron Moore
That'll work.
Uh....I think you're right to wait for more replies.
Right.
Reply to
Don Foreman
They're not. They're AC. AC heats just as well as DC, why rectify it?
You're right that DC with a cap would have more punch -- if you want divots in your sheetmetal.
Reply to
Don Foreman
I was thinking of the welder mech that is used to link batteries into packs. Don't know why I was thinking that. I'm sorry, I not sure what you were referring to that is not DC output, unless it is the resistance welder and not the charger. Once again, my mind was on the wrong box. Great article on the shopbuilt resistance soldering device. I may have to build one, just to have one in case..... The Variac would be great to control current, especially with the soldering gun, which may be too much anyway. Sorry about my confusion. Respectfully, Ron Moore
Reply to
Ron Moore
Interesting idea, I never thought of that approach. Have you done this and did it work?? How well compared to a commercial unit like the American Beauty??
Reply to
Bradford Chaucer
You would use the variac on the 120 v side of the stepdown transformer so it is feeding thtransformer a variable input voltage. Never on the output.
That said, you are still taking the wrong approach, the transformer in that battery charger is still to high a voltage output and to low a current. You want like a big asses old4-5 v filament transformer with a 100 amp output!!
Reply to
Bradford Chaucer
Right, it's the resistance soldering device, soldering guns and otherwise. The Wassco I mentioned is also AC. Capacitive discharge DC works great for spotwelding batteries.
Gunner has mentioned soldering heavy wires by pressing a 250-watt gun (sans tip) up against the splice and pulling the trigger, using the current to heat the wires. I've never tried that, but it sounds neat. The tip on a 250 watt gun is a few inches of about 1/8" square copper and it get real hot right quick.
Reply to
Don Foreman
I do that all the time. I have to solder the center pins on coax connectors and have 2 notches filed in the part of the gun the tip attaches to. Just stuff the pin in and pull the trigger about 2 sec and it is melting solder. Slip it over the end of the wire and pull the trigger again and it is a done deal. The pins stick in the gun tight enough that when you pull the gun off it tests the connection too. I have also used it to solder car battery cables etc. but you have to remove the tip for that. My PACE Kit has resistance soldering tweezers that are wonderful for DB connectors. The wire leads in those is about 14GA. I have never measured the voltage and current in it though.
Glenn
Reply to
Glenn
I haven't, and I don't have an American Beauty to compare it to -- but I do have an old 500-watt Wassco. I use a little O/A torch for silverbrazing small stuff, but I certainly do a resistance soldering experiment if you'd care to define the experiment.
Gunner has soldered wires together by pressing a soldering gun (sans tip) against a splice to be soldered.
My priority job right now is to fix the Reznor unit heater in my shop that doesn't wanna light off until I smack it with a pipe. I think it needs a new gas valve or gas valve controller after a mere 20 years of service. I thought it just needed a new thermocouple -- until I discovered that it doesn't even use a thermocouple. Uses flame rectification for flame proving and that seems to be working because the ignitor quits sparking once the pilot is lit.
Unnnnggghhh. Wanna fixit before it gets cold in MN. A cold shop is not a happy shop.
Reply to
Don Foreman
Hi Bradford, Actually from what I've read on using a filament transformer is that a 6.3 v with anywhere from 6-20 amps is "supposed" to work. I don't know how well this concoction is going to work compared to a commercial unit, but I am willing to throw around $100 at it to find out.
I am looking around for a filament transformer on ebay. Unless you have an old tube type TV set that you could pull one out for me. LOL.
Earlier you had asked how this setup compares to an American Beauty. I don't know. I've never gotten my hands on an AB or any other commercial units for that matter. The one that I am looking at from PBL is a 300 watt unit. From my rudimentary electronics knowledge, a 6v (or there abouts) transformer with even 20 amps on the output is 120 watts, correct? (6 x 20). Your idea of using a 4-5 volt / 100 amp output would get me up to 400-500 watts. Where I would find something that big, I have no idea.
Mike
Reply to
mj
Bradford, My unit works...sort of. It ran long enough to get two pieces of .005 brass sheet strips soldered together before the internal breaker kicked in. It takes a little bit for it to cool before I could try it again. Even soldering the .005 strips took about 5-6 seconds. The commercial units will do it in about 3. I just need more power coming out of the carbon rod, which I "think" is more amps and maybe lower volts. Mike
Reply to
mj
That's right, lower voltage, higher current. When the voltage is too high, you will just get arcing and pitting of the parts and electrodes.
As to transformers, keep poking about on Ebay. I picked up some a while back.
Reply to
Bradford Chaucer
Do a search on Microwave Oven Transformers in RCM. A typical MWO transformer is good for about 1000 watts. The secondary is fairly easy to remove and a new secondary can be wound on. You get about one volt per turn so you don't have to have many turns.
I can find Mircowave Ovens for two or three dollars at the St. Vincent de Paul that are guaranteed to be defective. I have only purchased two, but both of those had good transformers.
Dan
Reply to
dcaster
I recently measured the voltage across the tip of my 250-watt Wen soldering gun - it's 0.175 volts rms or so (starts lower, then rises as the copper tip heats and increases in resistance). To achieve the stated 250 watts, the current will be 250/0.175= 1,429 amps. This could almost be used for spot welding (where 4,000 amps is more common), and the resulting magnetic field can pick up small pieces of iron (~50 grams).
For the record, the Wen Soldering Gun (Model 250, bought in 1963) consists of a big AC power transformer with a one-turn secondary made of 3/8 inch brass rod. The open-circuit voltage (with tip removed) is 0.275 volts rms, for 118.9 volts rms in, so the transformer winding ratio is 435:1. The gun was manufactured under US patents 2,701,835 and 2,680,187. Go to to get copies.
The Weller soldering gun is almost identical, although the tip of the Wen is instead made of 0.164" diameter (~AWG #6) plated round copper wire.
Joe Gwinn
Reply to
Joseph Gwinn
Joe is right. I'd assumed 1.5 volts because it illuminates the little penlight bulbs, but my measurement just now agrees with Joe's. They must have another winding for the light bulbs.
Thanks, Joe!
Rather than buy a battery charger, I suggest the two courses most likely to work are:
1: Dan Caster's suggestion of putting a new secondary on a discarded microwave oven. If the size and weight aren't a problem, that would certainly work. (Be sure to strip the high voltage secondary off completely. ) Make that 1 or 2 turn secondary out of insulated heavy braid or copper strip, or several (half a dozen) bits of #12 copper wire in parallel.
2: buy two or three HF soldering guns at $9.99 each, connect them in series. 0.175 volts may not be enough to push much current thru thin brass.
Neither of these courses will cost half as much as the battery charger, and both are much more likely to work.
Reply to
Don Foreman
My rapidly disappearing short term memory may be causing me repeat this here, but a soldering gun also makes an ersatz demagnetizer for stuff small enough to fit inside the loop formed by the tip, like say a screwdriver. Just remember to move the steel part away before releasing the trigger.
My rapidly disappearing short term memory may be causing me repeat this here, but a soldering gun also makes .... Aw, shite!
Happy New Year!
Jeff
Reply to
Jeff Wisnia
I've heard of doing this too. And I might have access to an old microwave. The one in our kitchen needs to be replaced one of these days. This might be a good excuse to replace it.
Then all I need to do is figure out how to rewire the secondary....
But I am sure you guys will be able to explain that to me LOL.
Thanks Mike
Reply to
mj

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