I admit I have spent a lot of time on this, to the point where doing overtime at work could have bought me a pro one... but I have learnt a lot and it has been worth it, and I have a working version now The pro element is very big, and has a huge surface area (didnt think of winding it like that) but it has a few problems. It needs to be in a tube, its going to be very long and hard to hold. That element would probably be run at 500-650c I have about 100 meters left of nichrome, Ive wasted a lot so far with different attempts, so I dont really mind short element life as it costs me nothing to make a new one. The woodburner idea could work but you need loads moer power. All the metal your using needs to get hot, or it will be cooling the elemement. When its hot, it has a big surface area and will disipate a lot of the heat you put in. For my 50w element, I have 20mm long by 4mm OD of surface area, and all the connections to it are well insulated. Element temperature is now about 800c, so it could be more efficient, but also a 75w element wouldnt hurt it with this design. If you do make one the important, hard to find things are insulation. Clay pipe triangles are great for the handle, mine is a 63mm diameter one. edit: pictures I need a lot of practice with it, I tryed to solder the ic back but it took a while so im sure its dead from overheating.
Yeah. I looked up the RadioShack desoldering iron that seems to work for everyone else (it has to melt solder and suck it away, after all), and it's 45 watts. It's got a lot of metal, but I think the long tube may be insulated. I'm not sure, I need to see one up close. I think I'm gonna pick one up and see how it goes. Oh, and nice work on that prototype!
The tube isn't insulated, it's just made of a metal that conducts heat poorly (I think it's Iron). It's also really thin-walled. Interestingly enough, the heating element on the RS desoldering iron is a length of nichrome wire wrapped around a copper cylinder, insulated with a bunch of sheets of what (i think) is mica. as far as being hard to hold, it's just a matter of how it's built. For the professional models, the handle isn't actually in contact with the center tube. the airgap and convection prevent the handle from heating up. _____handle_________ |________________________________ |air - - - - - - - - - - - - - -> Element |________________________________ |___________________
Homsetly your probably better off with a needle point soldering iron. But I think a ceramic tube would make the best element support. I have an idea for an element.
Yeah, that's more sensible for a $10 item. I might even remove that tube, or at least cut it down, so that I can get a higher temperature. I don't want to gimp the desoldering capability, though. I have an average solder sucker, works great, but it might be handy to have one built into the tip. I can always re-extend the metal tube with some high temperature tubing, say, silicone. I'll need some anyway...another reason to place a US Plastics order!
It worked but not too well. Currently I cant desolder anything more than 4 pins or bigger than 5x5mm. Air temperature is upto 430c. I am going to try 2 elements (to give better surface area) but it will be very similar to the previous one. I will use some copper to support the second one. TO-220 packages are impossible, regulator leads are too big and too much solder. I tryed remaking the element at 55w but it didnt really help. I think air temperatures (at this flow rate) need to be 500-550c. Lower flow rates may even help, I found I was heating up a lot of the pcb. Also as I am heating the air in a very small space very quickly, it expands rapidly, meaning the smallest possible flow from a pump and I get enough flow, maybe too much. I think PWM is the best way to control it, and a push to make button in the handle would be a good safety feature - incase pump fails. I had one element explode from overheating, if your element is not enclosed its also a very good idea to wear safety glasses. I was refering to the handle size, mine being under 10mm wide makes it very easy to point at the component. Mine does not heat up at all, after switching the element off any part can be touched within seconds
After some thinking I have the answer! (which is now v5) wish I thought of it sooner but anyay... The element is 1mm ID, 1.8mm OD. It fits perfectly in the ceramic tube (2mm ID, 8.6m OD) pictured on the last version and a 3R (50w at 12v). Length is slightly shorter than the 63mm handle, allowing it to be stretched (allows better air contact, prevents shorts between each turn) to the handle length. I may need to increase power, maybe to 100w or higher, but im sure that the increased length (63mm v 20mm) will give the air more time to heat up, reduced diameter will allow better contact with air, and higher air restriction will give me slightly more control. The contact with ceramic will definatly prevent the element overheating, but it should still be able to get very hot. Cant test it untill tomorrow.
One good source for silicone tubing is your local hobby shop. Gas RC vehicles use silicone for fuel tubing because it generally has to run through hot areas (around the engine). Plus, they sell it cheap. Cut the tube on the desoldering iron down to ~1/2 inch and connect the silicone tubing there. Less thermal mass, and less crap in the way. Anyone willing to mail me some nichrome wire?
Silicon tubing won't go much higher than 500F so won't handle tip temp. solder but will handle molten but slightly cooled solder.
I'm going to leave it at the top first. I'd like to preserve the desoldering function if possible. Sure, if I cut it down I could still attach the bulb at the end of a piece of tubing, but that might not be so fun. Also, as hydro_electric_655 said, silicone tubing may not handle the tip temperature of a 45 watt iron. I'll test it though. Any recommendations as to alternatives to silicone? PTFE should go a good bit higher, but is a bit pricey. I can't melt the PTFE tip on my solder sucker with my 210 watt soldering gun (at least not easily) so I think it can handle 45 watts.
I just want to point out that wattage doesn't bear too much of a relationship to temperature. Thermal mass and thermal loading is much more important. All you'd need to use silicone tubing is a drop of 100-300 def f, which shouldn't be too divicult to design. Just use a stub of a metal tube with boor thermal resistance to feed the silicone tube. Incidentially, teflon (PTFE) starts to outgass carcinogens at 480 deg f.
Okay, bad example. In any case, my 210-watt iron does get very hot, and that was my point. Pfft minor detail.
Well, I just snagged a 1.45 lb (!!!) reel of nichrome wire off ebay for $24.00 . Don't know when I'll get it, but expect developments within the week. I'll probably build the power supply first.
thats a LOT of wire. what size is it? mine is 0.38mm diamter, 125 grams is several hundred meters. v5 didnt work, temperatures upto 480c but almost no airflow, didnt manage to desolder anything (although i didnt try any really small smd resistors). Had to turn it off because the wood handle was starting to make smoke. I think in this case higher wattage would help. 72 watts has 2/3rds of the wire length, so will be much less restrictive, however I know the ceramic is getting to 200-300c which the wood is touching. I am going to try and get some clay tomorrow to make the element properly. Im told that the local diy shop definatly has some, and if not an exhaust repair kit would work from another shop but possibly more expensive.
Looks dry, but add some water and its perfect. Working on v6 now Will also be making a high-airflow version for larger components - which could probably be easyer. Also, quite an interesting idea. I could shape some of this fireclay around different chip packages, and build an element into it, specific for each chip size. While it would be contact heating/soldering, I think it could work very well for large smd components.
The wire I bought is Is .0125 in wide x .0045 in. thick. (I think). The person selling the wire made a typo in the auction. In any case, it's 5.5 ohms a foot, which means the cross-sectional area of the wire is somewhere in the range of 28-30 gauge (your wire should be ~27 gauge). Not much news on my end. I'm doing a lot of work with brass tube, and am currently working on a spot welder for that reason. It's always fun working with 500A +. Things you normally think of as good conductors (like a 1/8" x 1" steel bar) start acting like big resistors, and get nice and hot. That, and the fact that the lights dim when you turn it on. Still waiting for my wire.... All I need to do at this point is file the contacts (the two brass screws on the jaws to the right) to a point. I'd do it now, but I try not to run the drill press at night. It upsets the neighbors. LOTS of heavy wire. The arms on the jaws (1/8" x 1" steel bar) actually heat up when you run it for more than 10 seconds.
I picked up that RadioShack desoldering iron today. Took it apart, stuffed some desoldering braid in the tip to increase surface area. I don't have an air source hooked up yet, but using the included vacuum bulb I was able to push and pull air well enough to melt a good amount of solder.
But it works great! I'm gonna dig around and find my old aquarium air pump tonight. I'll also get some silicone tubing. All Electronics used to have windshield wiper fluid pumps for $3.50, maybe I'll pick one up next order and try to make a powered desoldering iron.
Windshield fluid pumps are designed for a fluid. They'll overheat with air, and wouldn't move much anyways, as liquid behaves much differently than air. At best, you'll probably get less than ~.1 psi air pressure. What you want is a diaphram pump. I've got one of these. Got it surplus, with a torn diaphram. a few cents of cyanoacrylate fixed it up.
