I would like to make a basic hot air soldering iron. Basicly metal tips are either too big, or dont have enough surface area (higher wattage might help here though). My current iron is only 18w, my gas one is 50w which is better but not enough control at the tip (not temperture). My gas iron tips have disintergrated (catalyst too). I thought about using the blowtorch tip, with a 8cm long peice of brass pipe on the end. While the output heat is about right, the body of the iron gets hot quickly. Some attempts by other people: http://dansworkshop.com/SMT Hot Air Pencil.shtml http://hans-w.com/surfacem.htm http://usbmicro.com/odn/documents/ACC430664DD26DDE5986574AAA62775FDFF29EA1.html http://www.gideontech.com/content/articles/297/2 Plan: Air pump/compressor probably from a pet shop should be suitable, or one of the car battery powered tire pumps. Flow should be about 0.25-1liter/min. I would like it to run on 12v or 5v, while it will be temp controlled or atleast calibrated for a specific temperature, I would like to get upto 400c air temps, and 600-900c element temps (adjustable). I can buy some NiChrome wire to make an element, which is partly the reson im posting here, I am not sure what swg is best. Also is there anywhere I can buy it in lower quantitys than here? I might be wrong, but wouldnt the wire have to be quite thick to stand 4A+ at high temperatures? I dont think even the standard 0.7/1 wire used on breadboard is rated for 2A? That would also mean it has to be very long to get enough resistance? Electrical plan: I would use a pic to control it with high temperature thermistor/thermocouple imputs (one in coil, one on output). A lm338T regulator would possibly be adequate (5A version) although the K version would be better rapid want 8x more £ for it Output voltage and curent measurement would be nice too. As I want to use a pic nyway, I could ouput all of this (temps included) to a lcd. Testing using some random peice of wire as an element: Most/all of the heat is generated in the coiled part. ~10w (5vx2A) is barley enough to maintain 300c with no airflow. blowing on the coil decreases it to 100c. instantly Also higher the temperature the resistance increases. 2.4A at ambient, 1.4A at 320c - but this shouldnt happen with propoer element wire. I think 20W will be needed to maintain 500c with no airflow. 30-40w+ atleast is needed to keep that with 0.25-1l airflow. Ill find out how to work that out later. I tryed it at 12v x 4A (max 40w). current dropped to 2A at 300c , reached 530c measured, while one part was glowing very dark red, then thermocouple insulation melted So I would like the wire to be thich enough to support itself. The airflow would be best inside the coil. Anyone know of a material I could build the coil around, thats an electrical insulator, high temperature and preferably available as some cheap product. I was thinking clay, but I dont have any, and it could easly crack.
Well porcelan is great stuff. It is gonna take a fair amount of energy to generate good heat. I would expect this to be very effective but definately something worth a try. I would say you would want to get a soldering station later on. But if you can make an array of graphite pencil lead. Trust me it can handle high current and high temps no prob. Just hit up your local paper store or office store and get like .9 or 1.2 mm pencil lead. And get some clay find a local kiln somewhere make 2 rings to hold the lead so air can flow and glue them to a tube. Then something and such. I have use 480 watts through wooden pencil lead. Glows bright yellow and white then melts and burns the 1/4" copper supports.
The resistance of graphite is far too low, for a 0.5mm length about 1R per 50mm, maybe less my multimeter isnt very accurate. Graphite is very brittle so below 0.5mm its not really useable, it would be very difficult to connect several lengths in series. For NiChrome wire, 0.3mm diameter seems to be about perfect, although I think that will not be able to support itself very well. The resistance of copper wire is also far too low, a 2foot length of 0.27mm was less than 0.7R.
as for nicrome wire, I would suggest salvaging some instead of buying, there are a lot of cheap sources in houeshold appliances: hot plates, hairdryers, toasters, clothes irons, as for PIC regulation, PWM would be your best bet. use a digital output temp sensor, (or one that puts out the temp in millivolts, and use a PIC with A/D) then ajust the PWM as nessecary.
Argos sells an air pump or two that could be perfect. Intended for pumping car tires, and 12v. Might have a look tomorrow. I still need something to wind my element around that can withstand high temperatures. Ill probably use something ceramic (possibly a 10w resistor cut down the middle into quaters), doesnt need to be hollow, it will be fixed inside a peice of copper pipe which will have the air blowing through it. this should give better heat transfer too. Household appliances tend to use 240v so not really suitable. Not sure about regulation yet. I think I will be lazy and adjust element temperature by air flow. I dont have any 5A+ transistors or regulators so this is much easyer (and cheaper). I will probably get the 28swg nichrome wire, still looking for somewhere to buy a smaller quantity. Found about 10 shops, only one that does the right quantity only sells 0.1mm which is far too small
I made a few elements 3R (48w), and 7.1R (20w), although I have plenty of nichrome wire spare. Also found a 2mm OD peice of ceramic tube. ID is wide enough to get a thermocouple down too. Using the 3R (48w) element, and blowing on it, the thermocouple stays around 450c. I had to give it more airflow than I wanted, becuase some parts of the element dont contact the ceramic too well, which gives a few hotspots. When its in a tube, the air flow will be forced along the element, so less will be needed, although im not sure 50w will really be enough, so I might make a 75-100w element.
I've seen the interior of those pumps. They have a working lifetime of about 1-4 hours (running), and make a huge ammount of noise. They're basically total trash. You want a diaphram pump. Ebay is a great source of nichrome wire. Incidentally, some professional hot air stations are 400-500w, so more power may not be a bad thing. You can use PWM to regulate a 500w element to 100w of heat output, but you can't get 500w output from a 100w element.
Not sure. the pumps are basicly a cheap small motor/impeller. The impeller is attached drectly to the motor shaft. If it fails I can just get a better motor, infact I think I have a couple that would be adequate. ebay had one uk seller of nichrome, and although it would have been a lot cheaper they were 5 day listings. I could make a 500w element, although it would probably be best to use a higher input voltage, or several smaller ones (72w x6). I think the higher wattage stations generally have a large mass around the element, which would limit maximum temperature and take a lot longer to heat up if a smaller element was used. The element Im using to test has quite a low mass, so it should work but it really all depends on how much airflow I get and the thermal resistance of element-to-air/air-to-pcb. Just had first test with the pump. With element at 12.5W (5v) air temperature is 60-80c. At 72W (12v) parts of the element get red hot very quickly, so Im going to space it out a bit more. And I think I killed my psu I remember it being rated higher, its a basic AT psu, but its only 8A. Also the voltage was dropping to 9-10v, giving only 45w. I found another psu rated 36A, which should allow the element to work at 75w Also, I think it could be very easy to preheat the air with another element. This would be a lot easyer than increaasing the power of the main element. Also as it wont be operating at nearly as high temperature, this could then be made around wood or plastic.
Uh... I think your math is wrong. Power (watts) is volts * amps. 12 v @ 8 amps is 96 watts, and if you were drawing enough power to drag the power supply output to 9-10v, I would imagine you were using a good deal more current than that. In any case, why are you constraining yourself to shopping for UK nichrome sellers? Considering that the actual product is quite lightweight, international shipping is fairly inexpensive. There's dozens of people selling nichrome wire in America.
I had the pump 1-2A and my hub (upto 1A) running from the psu aswell. It was working ok with the pump at 5v, but with it at 12v it was too much and went very soon after. Theres also a small chance the element shorted but I doubt it (as thats the main problem atm, I have been very carefull about it), although Ive remade it and shouldnt be possible now. Its a very old AT style psu, the outputs for it have probably always been that low, I know that it definatly was low with just the router. 1) I dont really trust americans. Laws are a lot looser so even buying from shops is a lot more risky. 2) postage costs 3) surface mail sucks, airmail costs a lot. Just got back from work, gonna set up the other psu soon and hopefully Ill be able to use it and get some pics too.
Didnt get round to testing last night, I forgot the pump is so noisy and people wanted to sleep :/ Done some tests today and found: Air temperature really varies a LOT around the 8mm outlet. I need a better element design. The wound-element-in-center-of-a-brass-tube has several problems, eg. element wont stay exactly where you want it. this creates an area where air can flow easyer, which doesnt heat up so much, and one where there is much less airflow, about the correct temperature. This is very inefficient, although the temperatures I was hoping for seem to be possible with current element. Lowest measurement was 90c, whilst hottest was 170c, repeatable in different areas of the outlet. As I have very little insulation material, Im going to try an unsupported element, 4mm ID with airflow directed into it, no tube around it to control flow. sorry my camera is a bit crappy, will try my phone camera next time. The element looks a lot hotter than it really is in these pics. It was bright orange about 900c and not nearly as white as the bottom picture shows.
Any one know the name of this type of insulation? Id like to know if possible what temperature it can stand before it melts. Im guessing 300-450c, was from an old soldering iron. My new 96w element. First try was a bit disapointing, seemed about the same as the last element. Airflow is about the same but much more dense, so I will lower it a bit (quieter pump ) Temperature range across the outlet seems a smaller too.
That is your problem. You can't have half of th element contacting the ceramic. You need much less contact with the ceramic support. And your other problem is that the heat tube is the same size as the nozzle the nozzle needs to be much smaller. Maybe .25 mm The only way to secure metal at that temp is screw on. Ill go make my own with a 480 watt element right now.
an element exploded earlyer not really sure why but the current was normal almost 8A but it was a lot hotter, part of it melted - its springy so a small molten part landed on me, another part landed inside the psu. I think the tubed version worked better, so I am starting a 3rd. The main problem is getting the heat into the air - small coils of wire dont have nearly enough surface area. Idealy the element would be about 600-700c with the air output 350-500c. This is the start of my 3rd attempt The copper box will have 3 elements totaling about 125w. 15mm air inlet, 4mm outlet. I should braze it together but as I have no high temperature flux it will be held together mechanicly. The inlet end will be soft soldered as it wont get nealy as hot. For the handle, this copper box will be fixed betwen two peices of wood. The element will be self supported, the ceramic in the picture will be cut into 6mm lengths, 2.5mm either side of the holes in the box.
"That insulation" looks like glass fiber braid, goot (as you guessed), to something like 1000 deg f. Melts when glass melts, though the actual working temperature varies quite a bit depending on type. Considering the size of your element, and how hot you're running it, you have way too much airflow. It's not a heat gun, it's a soldering tool. A good test for airflow is to get a couple of small SMT components (0805 resistors or such. Pick the really small ones), and see if you can blow them around your work surface. Ideal airflow is just before they begin to move. You don't trust americans?... But wait... I'm american... Everything I've said is a lie... Quick! Run Away!
Size of element? you were telling me to use a 500w one I tested it with some 0603 resistors, i dont think its possible not to blow them around as the wiegh 0.0001 grams each, but your right, I had far too much airflow, so I made lots of changes. First test worked very well, although I decided to use 20w it gave outlet temperatures around 130c. Also the element was around 650c or less, only just glowing. this was a very small 1R length of nichrome at 5v. My multimeter loses a lot of accuracy below 1R and is unable to measure below 0.5R so I will use 12v for the next one. changes: Ceramic pipe for the handle, 6.3mm OD, 2mm ID, 80mm long. 1mm length of copper wire goes through the middle of pipe, one end attached to bottom of element to hold it in the center. This is important to stop the element moving away from the air flow. 3.1R element, at 12v this is 46w, which I think is about perfect. This is 2.5mm ID and 20mm long. Most importantly I changed the air hose which is now very easy to squash so I can use it to regulate the air flow. Its 70mm of ceramic away from the element so it cant get hot.
I know you're trying to roll your own here, but have you considered something cheaper/easier such as this? It seems several people have done it with quite a bit of success. There's one on Engadget, too. The difference being they kept the bulb attached, drilled a hole in the back of it and inserted the tube there. This is supposed to stop the tubing from melting after you shut it off...otherwise you have to keep the pump on to prevent heat from building up. I'm thinking about trying one, and if I like it, I'll use some high temperature silicone tubing or something. I know US Plastics has "low temperature" silicone tubing that does 500 F, about 80-90 cents per foot (or 40-50p I estimate), it would certainly get the job done. I'm thinking I'll try it since it would be easier and a lot more elegant than anything I could put together in a reasonable amount of time. Edit: After closer examination, the RadioShack desoldering iron could be made with parts from around the home. Some bits of tubing brazed together and a nozzle of some sort. Oh, and some brass bar, threaded, so it screws into any soldering iron. The heat from a low wattage iron wouldn't be anywhere near enough to melt the solder from the brazed joints, especially not if you have a long tube on the top to suck the heat away. Actually, that may be a bad idea...I bet you could get a higher temperature by shortening that tube. Hmm...time to see if there's anything in my basement I could use to make one. There's only three generations of useful crap to sort through! PS, didn't mean to hijack or anything, I just got started on a rant. Hopefully something in my rant can give you ideas.
Heh, some confusion here. I've been assuming that you're running the element at a maximum of 100-200 deg f above the desired air temp. You're running it yellow hot (somthing like 1800f, or 1000 deg above the desired air temp. The longevity will be crap, but it'll get the air real hot, real fast. As I understand it, profesional hot air stations don't even run their heating elements above the curie point, so you need a big element, with a lot of surface area. You feed it a lot of power, and then regulate the crap out of it with PWM or something. *edit* whoops, The curie point is the temperature at which the heating element begins to emit light... IOW, when it starts to glow. I should also point out that every homemade hot air tool I've seen on the internet uses a fish tank pump as an airsource, so that should give you an idea of the ammount of airflow you want (though a little more couldn't hurt). Incidentally, here's what a professional element looks like, courtesy of www.sparkfun.com ***Don't kill me for hot linking***
In case anyone's interested, here are pictures of tonight's little foray into throwing together a hot air attachment for a soldering iron. Actually, a wood burner or hot knife multi-tool, since most new soldering irons don't use screw in tips. I took a 3" piece of pipe, drilled a hole and stuck that rivet-like thing in there. I'm not really sure what it is, but I have quite a few of them like that. It's solid, so I tapped the other side and it screws into the iron. I then brazed (okay, soldered) it into the pipe, just for good measure. I figured the heat would spread out enough not to melt the solder when the iron was on, I was wrong! No big deal though. In retrospect, the rivet-thing fit in real snug, and with the tightening to the iron, it would have transferred heat just fine. I also stuffed a bit of steel wool down near the tip, to help transfer heat into the air, as instructed by several tutorials for the RadioShack iron. The assembly got hot enough to melt the solder around the immediate area of contact, but not further down the pipe or at the tip. The tip wasn't enough hot enough to burn newspaper, and the neck was hot enough to only brown newspaper, where it used to burn it quickly. I tried blowing into the back of the tube since I have no air supply yet. I got some good flow, which I felt with my finger on the other end. It was hot enough to give a first degree burn if I kept it there long enough, but not hot enough to melt solder. I think the main problem is that there is too much metal conducting heat away too fast. I'll try cutting the pipe piece down. I could also try replacing the air nozzle assembly with a barbed nipple, like one for connecting 1/8" tubing. Even after all that, I might just find that this little 25 watt wood burner just isn't hot enough. I might also try stuffing the length of the tube, loosely, with steel wool to increase surface area with the air. Ideally I would use desoldering wick, braiding removed, and stuffed in like steel wool. It would conduct quite a bit of heat into the air, I think. Anyway, just some ideas. Seems like you're going for building something much more high end, and I wish you luck.
