Soldering hair dryer with his own hands. And a little bit of theory.
I have wanted to make a soldering iron for a long time. I am not interested in a ready-made one. Since I am busy remaking ATX power supply in the lab, it became possible to get 24-25 volts at currents up to 8 amps. Realistically, my hair dryer works up to 5 amps. As a compressor I used a hybrid of an axial fan, designed in a case (volute) on the principles of the centrifugal fan. There were also simple centrifugal fans, but I was curious to try this version. The idea turned out to be quite workable. Blows as well as my other centrifugal fans, even in the presence of aerodynamic drag (the main problem of axial fans). I recommend it, if you can not find a suitable turbine.
- Heater power 110 watts.
- Voltage of power supply adjustable within 24,2 volt.
- Current consumption up to 4.8 amps.
The heater can work with lead free solder from boards. Smaller stuff all the more. I also got the composite video output connector from the same board. The video processor did not. The trivia from the boards with ordinary solder can be taken already at 75 watts of power quite comfortably. You can go even lower if you lower the fan speed. Forty-some microcircuits are quite removable at full power. Phone boards are easy.
Where do you start?
Decide on the power you can and want to get. Less than 100 watts doesn’t make much sense. If you do the rest of the stuff right though, that’s good enough for small stuff. I went for 100-110 watts. Rebooting the video processors is not enough.
Second. How much current you can get from the power supply. That will affect the choice of nichrome for the coil. I have 0.4mm nichrome. If memory serves, it was sold on the market as a 1.5kW tile coil. I found it to be optimal. Thin wire doesn’t hold its shape well, thick wire requires a lot of current to get enough temperature. For a wire of 0.4 mm you need a current of about 3.5 – 5.5 amperes. The wire should heat up to a yellow glow approximately. If the wire is blown intensively, its temperature will decrease. Let’s remember that wire diameter unambiguously determines the current. But the power will have to be gained by voltage. Since my PSU for this purpose produces about 24 volts, I stopped at that. Resistance of cold coil turned out to be about 3 ohms. In the warmed up state, according to the calculations – about 4. The coil does not care what kind of current, DC or AC. You can power it directly from the transformer with a dimmer to adjust it. But then the transformer will be humming. And it must have enough power and a winding made thick enough to hold the selected current.
An important element is the fan. Axial fans can be used as a last resort, but they do not do a good job of pushing air through mazes. Their job is to blow in a straight line. Therefore, a centrifugal fan is preferable for a hair dryer. It is precisely designed to push air through considerable aerodynamic resistance. It so happened that some time ago I was at an acquaintance, he showed me a heating system of his design. Where there is also a centrifugal fan. Homemade, too. It turned out that he made both possible mistakes there for fans of this kind. Wrong direction of rotation for an impeller from a vacuum cleaner and wrong design of the volute for it. I am not a fan designer at all, but I studied physics at school, I have an idea of how it works. Well, like a hackneyed theme for a long time, preparing the article, I went to google. And, to my surprise I found that almost a third of pictures on this topic contains one of two or both errors at once. That’s why I will give my schemes, so that nobody should be confused. Moreover, it makes direct sense for beginners.
This is the general principle of construction of centrifugal fans. Three different variants of possible impellers are shown. There are actually more variants, but that’s enough for us. Please note these are three different impeller options. Just partially shown. It is by no means one. As you can understand from the diagram, the impeller is supposed to “push” the air apart, thereby creating pressure. (Oh, those “google boneheaders”, drawing things they don’t understand themselves).
The red one (1) is the best. Green (2) is worse. Blue (3) is worse than the previous two, but will work. If the direction of rotation of the impeller is different, just mirror the schematic.
I did almost the same thing, only the impeller was an axial fan.
The impeller, of course, works by “blowing” air in. The difference from a simple axial fan is that energy for twisting the air flow is not lost in vain, but is used according to the centrifugal principle. In theory, such things should be patented.
This hybrid works quite adequately. It is a bit noisy, but it depends on your luck. The point is that with small diameter of the impeller (both axial and centrifugal) to provide sufficient air flow it is necessary to give high revolutions of the engine. With all the ensuing consequences. With a large impeller could be quieter, but the convenience of the hair dryer will be lower.
If you will create a turbine, as I suggested, when choosing the basis for the fan, you should give preference to small-sized, with a high speed, preferably straight blades (with saber-shaped will work worse). The more blades the better. The steeper their tilt (angle of attack) the better. I used an impeller from a very old video card. 12 volt, about 1,5 watts. The diameter of the impeller is 37mm. Use what you can find. Experiment.
Suitable centrifugal fans in almost finished form, or as donors of the impeller with a motor for my snail. You can put it not as I have “flat”, but perpendicular to the hair dryer. That’s what I did in my first attempts. And the turbine from the laptop was very decent. And it is quieter too. But it is already pretty worn out and designed for 3.5 volts, so I went the other way.
My hybrid compressor is bigger.
The main body of the snail is made of styrofoam. It doesn’t matter what it is, even if it’s wood. You can see the structure well enough. By the way, if you plan to make a protection for the impeller, I highly recommend not drilling small holes in the top cover. Want to know why – google the device of a mechanical hand horn from the war. Noise will be three times higher than with the version shown.
I used a 18650 battery case as the sleeve for the hair dryer. Mining technology on the type shown in this video (from someone else’s YouTube channel):
Only I did not bother with drilling, as the author suggests, through the sleeves. Drilled with a small drill bit. Re-drilled it to 4mm. Corrected with a nail file if the center of the hole was out of alignment. Using a step drill, drilled further, dressing with a nail file at each step, if necessary. I also made the bushing differently. From some chandelier threaded tube with two thin nuts. I riveted one nut on the end so it wouldn’t rotate, and clamped the other. I insert the fixed nut from the inside of the battery cup. I cut off the extra thread for beauty. You can do without the sleeve, but the flow will be worse. Not a jet but a divergent torch. I don’t recommend to use too fine one. In my opinion, 7-10 millimeters inside diameter would be more convenient. Also there is no need to create unnecessary resistance to air.
I have mica inside of 18650 cup. The coil was wound on the plate of glass fiber glass 14 mm wide. Nichrome diameter of 0.4 mm. I wound 16 turns. You will be oriented to a different voltage supply, the number of turns will have to pick up. The ends are bent 90 degrees. Leave the ends longer, then cut to fit. And this coil must be put on a ceramic tube. I bought it at Mitinskoe Radio Market at one time. The diameter is 4mm. In principle, almost any will do, but if the diameter is very different, you may have to experiment with the width of the plate for winding. One end of the coil is passed through a ceramic tube. The coil, put on the ceramic tube should be “twisted”, shifting each next coil in relation to the previous one. If you manage to untwist these 16 coils by a couple of turns, it is not bad. Since the length of the coil is not long, you should try to arrange it more evenly. To increase air heating, I additionally inserted an impeller made of galvanized iron (can be tin), which further twists air flow against the helix rotation, improving heat exchange. And at the same time serves for some alignment of the ceramic tube inside the cup. The resulting spiral should fit freely inside the cup with mica. But it is desirable that it does not bump around too much. It is quite tightly inserted in my cup.
In the picture you can see the very impeller to twist the airflow and you can see how I terminated the nichrome. I halved it, twisted it a little, put on and flattened brass tubes from 0,7-8 kerf lugs (you can use tubes from antenna, for example). Ends wrapped thin copper wire, soldered, soldered silicone wire from a heater (in principle you can use regular), and also covered the place of soldering with brass tubes. All this is needed to reduce the nichrome heat in the area of contact with the wire. On top of the tubes made of fiberglass fabric. You can find it in dead energy savers, for example. You can use mechanical clamps instead of soldering. Whatever you can find. Keep in mind, the helix and the air screw impeller must be insulated to avoid short circuits to the housing and to each other.
The further “body” was assembled from a pipe (used in furniture and design cases) and a car cigarette lighter case (it is not bad to put it on a battery cup), fortunately I have accumulated several of them after my experiments with the infrared soldering iron. Use what you find, it is not important. I connected the tube to the cigarette lighter housing by soldering. There is not much heat, it will hold. The ends of the body cut crosswise to get a kind of collet, to clamp the cup from 18650 through a piece of fiberglass tape, or just fiberglass cloth for insulation.
I soldered the air duct shell from tin. A plate is soldered on top of it (I used foil fiberglass) to which the fan is attached with screws. I cut the threads for the fixing screws right in it.
In this picture the coil is not completely screwed in.
The final look is more or less like this. This picture more or less shows how the rest of the wire was shaped. This is not the final version, still without the impeller.
A little bit about power
The fan is powered from the standby. It is triamped there. I had a 12 volt converter with Chinese settings. The fan is switched on together with the PSU fan. And heating is switched on with key Ps-On (upper right corner of PSU). And firstly we switch off the heating with this key after work and after the hair dryer cools down we switch off the power (from behind). The toggle switch is designed to switch the fan speed. Not yet implemented, there was no need to overheat the air flow. I plan to just power the fan with a diode or two (I’ll have to try), and the tumbler would just pass the diodes, shorting them. The lower the flow rate, the hotter the air will get.
A little bit about the connector.
I used a male/female COM connector. I got it off the board somewhere. I unsoldered it this way: two groups of three pins for heating (more than enough for 5 amps), one for the fan. Then I fixed and insulated with thermal adhesive.
Thus PSU is stabilized (if not running at maximum voltage), the fan power is stabilized, therefore the output air temperature is stabilized.
I am satisfied with the circuit. It is enough for hobby purposes. At the maximum temperature the metal pipe near the handle is getting pretty hot, but my hand can stand it. In normal operation the tube is just warm. I.e. nothing will melt there. The airflow through the tube does the job of cooling it down. And it is desirable to place the air duct as I have, closer to the handle. So that there was no air backflow from the hot zone. The hair dryer was tested by turning it off after the maximum heat. It was just de-energized. Along with the fan. Nothing melted.
For beginners: start constructions of this kind, you need to get into the pantry, closets, etc. and contemplate the previously accumulated wealth. And with a high degree of probability will be found something that can be easily enough to use. My point is that the design doesn’t have to be exactly the same as mine.
How to quickly convert a soldering iron into a soldering iron
To repair and assemble chips, you need a soldering iron. It allows you to solder and disassemble miniature SMD components by heating the solder locally in a selected area. If it is not available, you can get out of the situation on a temporary or permanent basis by converting a regular electric soldering iron into a hair dryer.
- soldering iron;
- snail fan;
- duct tape;
- thin wire;
- 12 V power supply.
Conversion of soldering iron into a hair dryer
You need to remove the parts that are unnecessary for the soldering iron. First remove the handle to remove the inner rod, which does not perform any important function other than supporting the power cable.
It is also necessary to remove the stinger. The removed parts are not thrown away. They can be put back in later if the soldering iron is needed.
The handle of the tool is put back on. It is important that it serves as a tube, so if the handle is plugged or has a very small hole, the edge will have to be sawed off.
The power cable coming out of the handle is bent and taped with duct tape or very sticky duct tape. To the end of the tube is attached a fan snail outlet. This is also taped over.
Such an attachment is quite sufficient, as there will be no mechanical stress on the fan. It is necessary to tape the soldering iron joint tightly so that all the air from the fan comes out clearly into the tube.
If you had to cut part of the wire with the plug when disassembling the soldering iron, you can now twist it back together, or better yet, solder the joint securely insulated. To keep the wires from the coil and the soldering iron coil from dangling, they can be tied to one of the eyelets on the fan.
There are vents on the body of the soldering iron right in front of the handle. You don’t need them for the blow dryer. To close them, all you have to do is wrap a strip of foil around them and tighten it with wire.
To work the soldering dryer, you need to plug it into a socket, and connect the fan to a 12V power supply. The coil will blow air through the housing with the heating coil, giving at the output more than enough heat to melt the solder.
The homemade device is not as easy to operate as a factory soldering iron, but it is free, provided the snail is available. At any time you can equip it back with a stinger even without removing the fan. The main thing is not to forget to remove the foil on the vents. For amateur soldering boards such equipment is quite enough.