Making a cold heat soldering iron

cold_heat

Cold Heat soldering irons are pretty cool. They heat up in seconds and cool down just as quickly. [photozz] shows us how we can make one from stuff we probably have sitting around right now. Cold Heat soldering irons work off of resistance, the tip material heats very quickly when electricity is passed through the two halves. Upon assessing what he had lying around, [photozz] realized that graphite would work much the same way.  He modified a regular soldering iron with a new two piece graphite tip, and powered it with an old pc power supply. The end result is quite nice, though it still needs some kind of temperature control.  You may recall seeing other electrical uses for graphite, such as making quick and dirty light.

Comments

  1. spaceballs3000 says:

    Very nice!
    I like.

  2. Cadero says:

    Nice one, I think I’m gonna try it out ^_^

    I remember making an arc lamp with 2 pieces of pencil(and a large power supply, a pc psu will probably die, or it just won’t work…), but you should use very dark sunglasses/welding glasses; I was a bit blinded for a couple of hours, seeing white spots everywhere -_-‘

  3. bill says:

    Do these really work? I mean, are the solder joints stable? I see television commercials for these, and always say “yea, right”, because we all know how truth in advertising works.

  4. atrain says:

    Another problem is if you short something with this thing you can blow it up, so you don’t want to use this for any fine work.

    The coldheats were awful, the tips were so fragile + expensive…

  5. AudioCra-Z says:

    I have been given 2 Coldheat’s already. I have come to hate them. Sometimes you will “arc” on the point you are soldering, instead of heating it up. I applaud for somebody being creative to make their own, but the general problems with these will be the same. Can only use them on non electronic soldering. And, yes, I have broken a tip while trying to maintain a good contact with what I was working with multiple times.

  6. Ilial says:

    This doesn’t look very ESD safe.. I’ve had one of the Radioshack ones a few years ago, and remember it being very frustrating to use.
    Still, great idea, and I applaud the DIY-ness of this project.

  7. brian says:

    I was interested by the Cold Heat irons, but I’ve read that they’re terrible for electronics.

    I wonder though if they might be useful for making battery packs?

    One isn’t supposed to use a conventional soldering iron to attach tabs or wires to cells because of the risk of melting various plastic parts inside. There are special spot-welders that deliver high temperatures to a very small point that are intended for this.

    It seems like the cold heat iron might also be able to do the same thing by heating the terminal very quickly, limiting the time that the heat has to conduct through metal pieces to the plastic parts.

    Any thoughts? Better ways to do this?

  8. tjh says:

    i remember getting a cold heat for Christmas and immediately throwing it away. this is an interesting project but is there really a need for a ‘cold’ soldering iron?

    someone should hack the cold heat into something useful

  9. Morden says:

    I tried the coldheat, it kept creating solder bridges between the forks and shutting down. also the thing never really was fast enough to heat up contacts as I would have liked.

  10. Matt says:

    I have a coldheat, and I have found that it is a lot better with nimh batteries. The instructions specifically say not to use them, and they will probably damage the tip or some internal circuitry, but it is worth it. Nimh batteries can supply extra current, so the tip heats up faster and gets hotter, making it easier to get a good joint. Eventually the tip will start to glow red and the plastic that holds it will start to melt. You should stop before that happens. Also, since the tip gets hotter with nimh batteries, it will not cool down as fast, so be careful not to burn youself.

    To comment on the lead light, I found a way to get much brighter, whiter light. I used a PSU at either 5V or 12V (I can’t remember). I connected the ground wire to a penny, then connected a positive wire to a short piece of lead using an alligator clip to hold the lead. The lead should be abut 1/2″ to 1″ long for the most light. To use it, gently press the tip of the lead against the penny. Most of the light will be made near the tip, so as the graphite burns away you can feed the lead towards the penny and get consistent light. It works kind of like an arc welder or maybe an arc lamp (but I don’t think there was actually that much arcing). The penny acts as a reflector so you don’ blind yourself and it helps to concentrate the light. It would be really cool if there was some way to autofeed the graphite and make a usable lamp.

  11. steve says:

    Give me an old fashioned adjustable Weller any day. this sounds like a cool project and I admire the work and thought that went into it, but I do enough soldering that I really do need a pro soldering station.

  12. ehrichweiss says:

    I loved how easy the commercial version worked UNTIL the tip broke and I couldn’t just go out to buy a replacement. I may try this project though.

  13. arthur92710 says:

    The only part from the coldheat thing that I liked was the solder. Does anyone know what kind it was?

  14. Haku says:

    I bought a 4-AA ColdHeat portable iron last year because it was on sale and it looked like it could be useful, found it annoying trying to make both halves of the tip make contact with what I was soldering and it didn’t last me very long as when I tried to use it like a conventional iron it got too hot and the plastic holding the tip melted and the internal contacts shorted the batteries out – rendering the whole thing completely useless.

    I haven’t bothered looking at them ever again, though a few weeks ago I picked up a couple of 3-AA portable Antex irons very cheap which work very well for quick soldering jobs as they aren’t coldheat irons.

  15. Jay says:

    Tried the cold heat deal a few years ago and couldn’t get it to work for the life of me. I replaced it with a simple butane iron. Works like a champ. As far as a “good” soldering iron I prefer a Metcal station. If you haven’t had the pleasure of using one it makes surface mount cake to solder.

  16. Man On Fire says:

    it also means you’re putting voltage across a potentially voltage sensitive joint. not a good idea. and the cold heat irons they sell suck.

  17. hmmmm says:

    hmmm i had a cold heat iron it broke the day i got it i replaced it with a radio shack 4-batterie iron.the odd thing bout my iron is if u un screw the tip it looks like a light bulb.i had to mod the switch other wise you have 2 keep presure on the switch.stock up on batteries for it though

  18. hmmmm says:

    and its not a cold heat

  19. Andrew says:

    Cold heat things are junk. Give me a baby metcal iron any day.

  20. fartface says:

    Cold heat irons suck. You cant solder anything decently with them and they have a very small working range.

    Spend your money on a real soldering station and you get the 15 second heat up time. My Weller station heats up faster than I can get a part ready for soldering.

  21. Roly says:

    Nothing new under the sun. From the valve era…

    http://ozvalveamps.elands.com/scopeirons.htm

    “An iron with high AC current flowing through the tip was not suited to solid-state, and the emergence of CMOS was the last nail in the Scope coffin.”

    All the moreso in this case because one side of the tip will be connected to mains ground.

  22. GJG says:

    yeah my cold heat melted the day i got it too, only i got it at home depot, i ran back there as fast i could and told them it was a piece of crap. Funny thing is the solid solder i was using never melted but the plastic on the cold heat did! I ran back to home depot as fast i could and told them it was crap. Seriously a soldering iron that melts before the solder?! The thing was also very hot to the touch the only time i buy its on tv garbage is if a cheap chinese nock off is at the dollar store and if it actually doesnt break itself or does what it says. I bought a soldering iron for a dollar and havent replaced it yet, the cold heat garbage was like 30 or 25 if i remember.

  23. Ashton says:

    I’ve been saving up to buy a Weller, but this idea beats the hell out of my crappy radio-shack iron. I built two of these last night, and it works pretty well. I used two cotter pins, screwed into a small piece of wood, one flat and the other angled down to wards the other to form a triangle once the lead is inserted. The cotter pin triangle works better than my first attempt at duplicating his design (I used a piece of tile to separate the lead) I tried to use a large diameter piece from a wooden pencil but it didn’t get hot enough, but 0.7mm mechanical pencil lead worked great. I also mounted a push switch so that the lead pieces could be directly touching, instead of using the solder to bridge the connection.

  24. heretic says:

    i got myself one of those a few months ago.
    didn’t expect much, but it’s better than i expected.
    takes some time until you get used to it, but that’s just the same with “normal” soldering irons.

    since it’s an entirely different technology, you can’t expect it to work just like the soldering irons you’re used to. if you’ve broken a tip, you’ve clearly not read the manual.

    that said, the cold heat is not suitable for anything smaller than e.g. a DIL IC.
    it’s OK if you need something that runs on batteries, but by far no match for a decent soldering station.

  25. GarageScientist says:

    Ahh, now that’s a good idea ashton (.7mm mechanical pencils) If you could get two mechanical pencils with metal tips, then I’m sure you could modify them to minimize the gap near the tip. (On each one, taper one side flat on a belt sander or something.) So that they fit closely together like: \/ but at a VERY acute angle.

  26. Ken williams says:

    I have used one of these and for their designed jobs they work very well.In model railroading the building of brass rolling stock where a number of parts are to be soldered to a piece of brass or copper, you want to heat right where you are soldering without heat transfer like you get with an iron or torch, causing the other parts to fall off as you are adding more parts in the same area. The heat and voltage are only between the the two probes

  27. Whoa, interesting read. I just now stumbled on your website and am already a fan. :)

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