We offer you, as an option, to make a miniature 12-volt electric soldering iron from available materials using available equipment with your own hands. It will be very convenient for working with small-sized working material - when soldering the leads of various microcircuits, parts of micro-earpieces, handheld electronic clocks (or, for example, making it yourself) and any other miniature elements of modern radio electronics.
Homemade microelectric soldering iron
The set of materials required for the product is quite small. You will need: copper wire for a soldering iron tip; copper foil, nichrome wire and a tin tube - a casing for an electric heater; plastic heat-resistant handle; electric cord in heat-resistant insulation; office silicate glue and talcum powder for electrical insulating mass.
You may have some problem with copper foil. But it is quite solvable. If there is no foil, then it is not difficult to find foil fiberglass, from which printed circuits and boards are made (if printed circuits or boards are not lying around anywhere, then fiberglass can be bought for 200 rubles in a radio store). You can separate the layer of foil from fiberglass by heating it with an iron. It is difficult to pry off the edge of the foil at the beginning, and then, after the iron, you will easily wind the foil onto a round stick. In this case, the main thing is to pull the foil evenly.
Necessary equipment: electric or, tweezers, pliers, nippers, plates or planks for coating with adhesive mass, rags for wiping hands and tools.
The miniature soldering iron will be powered from a household power supply through a 220/12 volt step-down transformer, the secondary winding of which should deliver 1 ampere of current to a 12-ohm load. For example, the transformer TVK-110L, used for frame scanning in old tube TVs ("Record-B300", "Vesna-308" and the like), is quite suitable. will not work for this purpose.
For a soldering iron tip, take a piece of copper wire 40 mm long and 1.5 mm in diameter. Grind one end of the wire in the form of a dihedral corner with a solution of 40˚, then tin the edges of the corner ("cheeks" of the sting). The manufactured tip will be inside the heating element.
Now prepare a special electrical insulating mass: knead talcum powder on office silicate glue (liquid glass) until a thick dough. With this mass, you will apply thin layers of insulation on a cylindrical surface using any devices (tweezers, planks, plates). Please note that the cooked green mass is very sticky, and to keep your fingers and tools from sticking, sprinkle them with dry talcum powder from time to time.
Tightly roll a 30 mm long tube of copper foil around the tip - the base for the heating element (the tip of the tip with a length of 10 mm will stick out from it). Cover the tube carefully with a thin layer of insulating material. Then, holding over a gas or electric hob (temperature should be 100-150˚), dry until the electrical insulation test is completely "baked".
Wrap a heating coil made of nichrome wire 350 mm long and 0.2 mm in diameter on the prepared base of the heating element. Lay the coils tightly to each other in one layer. Do not forget to leave the straightened ends - wire leads: one - 30 mm long, the other, "barbed" - 60 mm. Cover the winding with a protective electrical insulating layer and repeat the drying process in full.
When the winding insulation is dry, wrap the long ("bar") end of the wire back and, pressing it firmly against the surface of the tube, apply a third layer of your doughy mass and repeat the drying process again. The soldering iron heating element is ready.
Also cover the two ends of the wire protruding from the heating element up to half of their length with electrical insulating compound (the remaining halves will be connected to the wires of the electrical cord). This operation will require special patience and accuracy from you: often it is necessary to additionally fill the remaining microcavities with a crude "dough" due to an oversight or carelessness and each time to dry over a burner.
The final design procedure is the assembly of the microelectric soldering iron. Pull the electric cord in heat-resistant insulation through the inner cavity of the plastic heat-resistant handle and screw the ends of your nichrome electric heater to its bare conductors.
And now, finally, the last procedure for coating and drying: insulate the bare joints of the electric heater with the electric cord. After that, mount the electric heater in a suitable size tin protective cover and connect the cover with the handle.
After the test turn-on and warm-up, your miniature 12 volt soldering iron will be ready for work.
When working with soldering, any radio amateurs will always need a can of compressed air so that they can blow dust off the board. In the article, you will learn how you can make such a can at home.
Now watch this helpful video:
A soldering iron designed for 12 volts from your own car-horse can be made in an hour or two, which can be very useful in the household of a home craftsman. The basis of the heating element will serve as ... you will not believe - resistor PEV-10 or PEV-7.5!
This design is just an example, and the flight of fancy of crazy pens is unlimited here. The main thing here is to have two copper rods of different diameters and the SEV resistor itself.
Found a description of such an original design on the net. Here, damn it, live and learn! How many years I have been fond of electronics, various crafts, but I have not heard about this and I would not have doped it myself.
Indeed, if you find yourself not in the garage, you will need to solder something in some device of your car, because you will not have 220 volts at hand. So such a homemade soldering iron, made by hand in an hour, can very much help you out in such a situation. And if you have a powerful old transformer with a 12-volt output lying around, this wonderful soldering iron will also work at home!
SEV resistors
These resistors are of high power. I remember that when I worked as a radio installer at the factory, we had 36 volts of soldering irons and they were then regulated in a primitive way: through the serial connection of such huge resistors to their power circuit, like these, but only with cylindrical regulation. For this, resistors of the PPG-25G type were used. With a decrease in temperature, part of the energy was dissipated on this resistor, and given that we had 40 W soldering irons, these resistors were heated oh-oh-oh.
Here is Russian ingenuity! In fact: resistors made of ceramics, designed for enormous heat (I know, I am telling you as a practitioner), are made firmly, reliably - it is quite possible to use it as a heating element of a soldering iron. The number in the name means the power of the resistor, if you haven't guessed.
Homemade soldering iron design
Well, now it remains only to fix the tip for the soldering iron inside the PEV-10 (PEV-7.5) resistor, and attach a handle to its terminals. And, as I mentioned, the conclusions, like everything else in these resistors, are made for centuries - you will tear off figs!
This is how the sting is made, together with a body that transfers heat, from two copper rods inserted into the resistor.
In the large rod, recesses are drilled on both sides: for the tip itself and for the fastening bolt. Then the threads are cut into them. The thread is also cut on the tip of the future soldering iron.
On the large rod, you need to make a groove for the retaining steel ring, then put it on.
After that, the design of the tip and the heating element of the soldering iron are assembled together.
Hehe, cheap and cheerful! 🙂 Looks like it? Hände hoch! 
On my own I will add that after assembly, the resistor can be wrapped with an asbestos cord to reduce heat loss.
The author made the handle from two identical halves of a textolite plate. Material with a thickness of 3-5 mm is suitable. Grooves are made in the plates for the supply wire.
A little weak point of the soldering iron is the resistor contacts. They are not made of steel, but copper, unfortunately. Therefore, they have a certain flexibility, and the author of the design speaks about this. So don't push too hard when soldering! But if you wish and skill, you can strengthen the fastening by putting on two round clamping brackets over the resistor in the contact area, clamping the resistor itself with brackets in this way. And already their ends are screwed to the plates. The brackets can be sealed with fluoroplastic tape.
Well, the finished design! 
Resistor PEV resistor for soldering iron
For a 40 W soldering iron powered by a car battery, the resistance of the resistor should be about 5.1 ohms (it will generate about 30 watts of power). This is taking into account the resistance of the wires (approximately 1 ohm). With this resistance, the soldering iron is normally warmed up if the battery voltage is higher than 12 V. and does not overheat at the maximum (14.4 V).
If the soldering iron is supposed to be connected through an automatic thermostat (with a thermocouple installed on the tip), then the resistance of the resistor can be reduced to 3.6 ... 4.7 ohms. Then it will heat up faster - not 2 ... 3 minutes, but only 40 seconds. And domestic PEV's are practically insensitive to overcurrents. For other supply voltages, the resistance of the resistor must be different, as can be seen from the table.
Now in stores you can buy soldering irons for every taste and color. However, sometimes you want to create something with your own hands, especially if you have enough free time. Today's step-by-step review, which is for the editorsHomius sent by Leonid Vladimirovich Orenburkin from the city of Tver, will tell you about how to make a 12 V soldering iron from what almost every home craftsman who is keen on homemade products has at hand.
Having worked for a long time as an electrician in RES (regional power grids), I had to quit for health reasons, so I had more than enough free time. At first I did not know what to do with myself. And then one day the idea came to my mind to equip a small workshop. This was the beginning of my hobby for homemade products. Making one of these, I would like to describe in my article in the hope that it will be interesting to someone.
To begin with, a wooden shank was taken (it is better to take a birch or maple), chiseled "under the arm" and sanded. You can give it any shape, but for the first time I didn’t do unnecessary work. It should also not be made too long, although this is a matter of taste.
Next, a drill with a thick drill entered the work, on which I marked the hole stop with the help of electrical tape. A depth of 2-3 cm was enough for a 12V mini-soldering iron. A hole made in the center of the handle from the end will serve for installing the power socket and pulling wires to the heating element.
An identical hole was drilled on the back side, which will serve to install the soldering iron tip.
Preparing the grooves for the supply wire
At a distance of 2-3 cm from the edge where it is planned to install the socket for the power plug, we make markings for two holes (on opposite sides). For the convenience of measuring the distance, you can use the same drill with the depth marked with electrical tape. Having determined the locations of the holes with a marker, we again take up the drill, but with a thinner drill.
Drilling under the wires should be done at a slight angle - so it will be easier to stretch them later. As a result, it should turn out so that the wire enters from the end and under a small break is laid further, to the opposite end of the handle, on which the soldering iron tip will be located.
Now you need to make sure that the wires stretching from the power socket along the handle do not interfere with the work with the soldering iron. To do this, from the holes to the edge where the sting will be located, I cut the grooves. This is easy to do with an ordinary clerical knife. Of course, if the handle were made of pine, it would be much easier to cut along the fibers, but this material was "swept away" immediately. The reason for this was that additional coating of the handle was not planned, which means that there was a possibility that the hands could get dirty in the resin during work.
When the grooves are cut, it is advisable to work on them a little with an ordinary round file. Indeed, despite the handicraft production of a 12 V soldering iron, they are supposed to work, which means that accuracy will not be superfluous here. As a result, we got a handle with holes on both sides and grooves for the wire, which is ready for further work - assembling the filling of the device for soldering wires.
Soldering iron power socket installation, wire pulling
To the usual socket, suitable for the adapter from the old TV, I soldered 2 wires - red and black, which were first pulled through the center, and then routed along both sides of the handle through thinner holes. The socket for connecting the plug from the power supply was immersed in the handle from the end, and then fixed with hot glue. It cools down quickly, after which the connection becomes quite rigid.
Of course, you could immediately pull the wires from the adapter by cutting off the plug, but I decided that the option with a detachable power supply would be much more convenient not only during storage, but also during operation. And, running a little ahead, I can say that I made the right decision.
Choosing a copper conductor from a cable for a soldering iron tip
The tip should not be too thick so that the adapter has enough power to warm it up. However, too thin will be inappropriate here - it will bend at the slightest pressure, which is completely unacceptable. The optimum thickness was determined by trial and error. In my case, it was 2.7 mm in diameter.
Cutting off a piece of copper conductor of a suitable length, I installed it in the hole prepared in the handle (on the opposite side from the power socket). It was previously filled with stucco. This material, in addition to rigid fixation of the tip, plays another important role. By absorbing heat, it will not let the wood burn out under the influence of high temperatures during the operation of the soldering iron.
Choosing a power supply with a 12V output for a soldering iron
All adapters have differences in output current strength, therefore, the length of the heating element in each case will have to be measured empirically. In my case, the output was 12 V / 1 A. In fact, more current for a miniature soldering iron is not required, so I was quite pleased with such a power supply.
Measurements of the length of nichrome, sufficient for the operation of a soldering iron
The thin nichrome wire that was used to make the heating element had to be connected to the power supply in order to understand how long it should be. To do this, I screwed 2 screws into the bar, between which it was pulled. Further, with the help of "crocodiles", which gradually shifted, I determined the size at which the soldering iron will heat up to the melting point of the solder. In other words, nichrome should be red hot.
Tip preparation, heater installation
Now it was necessary to isolate the sting from the nichrome. For this, a fiberglass cambric was used. He was dressed on a copper core until about the middle, after which he was fixed at the edges with a thin copper wire. It is worth noting that you do not need to remove the ends of it - they should stick out about 4-5 cm. In further work, this will be useful to us.
A thin nichrome wire, measured in length earlier, was wound over the fiberglass; its ends were twisted with copper veins located at the beginning and at the end of the cambric. The result is a complete heating element capable of raising the tip temperature to the required temperature.
It is worth noting here that the longer the length of the tip from the heater to the working edge is, the longer the temperature rise will take. With a small power supply unit and a too long soldering iron tip, it is possible that the device will not reach operating temperature at all. But here you can experiment and calculate everything so that you end up with a kind of soldering station, which has lower operating temperatures for working with microcircuits and other SMD elements.
Final assembly of the soldering iron powered by 12V
For the final stage of assembly, 2 more pieces of thin heat-resistant cambric were needed. They were dressed on "mustaches" of thin copper conductors, to which a heating element was attached. Their free ends were twisted with wires coming from the power socket. After that, I thought that it would be nice to install a small toggle switch on the handle, which would turn off the voltage supply to the heater without pulling the power supply from the outlet or the socket in the handle of the soldering iron. But these are already particulars. If any of the readers will collect such a device, it is worth bearing in mind this possibility.
Final touches: enhancing the look of a homemade soldering iron
In general, here you can do with two pieces of electrical tape wrapped around the handle, which will fix the supply wires. But this is already a matter of taste. Someone wants to wrap the handle completely with electrical tape or use other materials that will give the product an interesting appearance, this will not affect the performance of the soldering iron in any way. In any case, all electrical work has already been completed. You can proceed to the first connection of the soldering iron to the network and check it.
What happens when you turn on for the first time: some of the nuances that need to be taken into account
When a ready-made soldering iron powered by 12 V is first connected to the network, and the nichrome gets hot, the fiberglass under it begins to smoke heavily. This should not be scared - the insulating layer will not be able to burn out. I mentioned this because one of the "masters" tried to tell me that the soldering iron, assembled according to my method, is inoperative. And he made such a conclusion only on the basis of the appearance of smoke after the initial supply of power to the heater.
After just a minute, the fiberglass will stop smoking. After waiting a little, you can try to melt the solder. And here there is one more nuance. If the power of the soldering iron is not enough to melt a thick tin bar, this does not mean that the manufactured soldering iron is inoperative. For such a material, high power and temperature are required. It is worth taking a thin tin wire as solder. With her, work will go more fun.
Soldering iron 12 Volt Is a low-voltage soldering iron, the heating element of which is designed for an operating voltage of 12 volts. A 12 Volt soldering iron is used to connect wires and parts of various kinds to each other by soldering.
The undoubted advantage of a 12 Volt low-voltage soldering iron, in comparison with a 220 V household soldering iron, is a low operating voltage and, therefore, a certain safety when performing work.
A 12 Volt soldering iron is widely used, for example, in radio engineering, when soldering radio elements to printed circuit boards. Its use here prevents damage to pick-up current-sensitive radio components and radio components. Also, a 12 Volt soldering iron is convenient to use in a car, for example, when soldering wires, since in a normal state, the car's battery is charged somewhere at 12.6 Volts. In order to use a 12 Volt soldering iron directly in a car, you need an adapter, or an adapter, which is usually inserted into the cigarette lighter. It is for these purposes that they use special automotive soldering irons.
Features of 30w Rexant soldering irons
Today, the main elements of the soldering iron are being modernized in order to improve their performance. Ceramic rods are increasingly being used instead of copper ones. This allows you to speed up the process of heating the tip of the device. There are other types of soldering tools: induction soldering iron and pulse soldering iron, which differ in the way of heat transfer.
Soldering iron 12 Volt buy today it is not a big deal, the widest selection of these tools on the shelves of stores and online stores. Everyone can choose a tool to their liking. For example, a 12 volt Rexant soldering iron or a soldering station has a main unit in its kit that allows you to adjust the heating temperature of the tip, and the electric soldering iron itself is designed for a power of 8 watts.
And in conclusion, it should be recalled that during the process of soldering parts, soldering smoke is emitted. This smoke contains lead and rosin vapors, which have an adverse effect on the human body. Long-term inhalation of such smoke can lead to allergic and asthmatic reactions, or the so-called "soldering" disease. It is necessary to strictly observe sanitary norms and rules and as often as possible ventilate the rooms in which harmful solder and flux vapors accumulate. It is also not recommended to continuously solder for a long time.
It is primarily economic considerations that motivate home (and not only) craftsmen to assemble a soldering iron with their own hands. A simple 220 V soldering iron for ordinary small adhesive work is better, of course, to buy. However, it is also possible to modify it without disassembling it in order to extend the life of the sting. But the "ax" for 150-200 W, which can be used to solder metal water pipes, is no longer 4.25, but ten times more. And not Soviet rubles, but evergreen conventional units. The same problem arises if you need to solder out of the accessibility of the power supply from a 12V car or a pocket lithium-ion battery. How to make a soldering iron yourself for such cases, and not only for such, is discussed in today's publication.
What is smd
Sub Micro Devises, sub-miniature devices. You can clearly see smd by opening a mobile phone, smartphone, tablet or computer. Using smd technology, tiny (possibly smaller than a match cut) components without wire leads are soldered onto pads, in smd terminology called polygons. The polygon can be equipped with a thermal barrier that prevents heat spreading along the paths of the printed circuit board. Here the danger is not only and not so much in the possibility of delamination of the tracks - the piston connecting the layers of the installation can break from heating, which will render the device completely unusable.
A soldering iron for smd should be not only micropower, up to 10 watts. The heat reserve in its sting should not exceed that which the soldered part can withstand. But long soldering with a too cold soldering iron is even more dangerous: the solder does not melt, but the part is warming up. And the soldering mode is significantly influenced by the external temperature, and the more, the lower the power of the soldering iron. Therefore, soldering irons for smd are made either with a time limit and / or the amount of heat transfer during soldering, or in operational, during the current technological operation, by adjusting the temperature of the tip. Moreover, it must be kept 30-40 degrees above the melting point of the solder with an accuracy of literally up to 5-10 degrees; this is the so-called. permissible temperature hysteresis of the tip. This is very much hindered by the thermal inertia of the soldering iron itself, and the main task in designing one is to achieve its lowest possible time constant for heat, see below.
It is possible to make a soldering iron at home for any of these purposes. Incl. and powerful for soldering steel or copper plumbing, and accurate enough mini for smd.
Note: in fact, in a soldering iron, the tip is the working (tinned) part of its rod. But, since there are other different rods, for the sake of clarity, we will consider the entire rod as a sting. If the working part of the soldering iron is pushed onto the rod, it is called a tip. Let's assume that a tip with a rod is also a sting.
Simplest
For now, let's not get into the complexity. Let's say we need a regular 220V soldering iron without any fuss. We go to choose and see the difference in prices reaches 10 or more times. We figure out why. First: a heater, nichrome or ceramic. The latter (not "alternative"!) Is practically eternal, but if the soldering iron is dropped on a hard floor, it can crack. The tip of soldering irons on ceramics is necessarily non-replaceable, which means that you need to buy a new one. And the nichrome heater, if the soldering iron is not forgotten to be turned on at night, lasts more than 10 years; with occasional use - over 20. And in extreme cases, it can be rewound.
The difference in price has now decreased to 3-4 times, what else is the matter? In a pity. Nickel-plated copper with special additives dissolves little with solder and burns very slowly in the soldering iron holder, but is expensive. Brass or bronze heats up worse, and smd cannot be soldered with them - the temperature hysteresis cannot be driven back to normal due to the much worse thermal conductivity of the material than copper. The red-copper sting is eaten by solder, and swells rather quickly from copper oxide, but it is cheaper.
Note: A tip made of electrical copper (a piece of winding wire) is unsuitable for a conventional soldering iron - it quickly dissolves and burns. However, for smd, such a sting is the very thing, its thermal conductivity is maximum possible, and thermal inertia and hysteresis are minimal. True, it will have to be changed often, but the sting is a match or less.
Burning and swelling of the red-copper tip can be fought with just accuracy: after finishing work and letting the soldering iron cool down, the tip is removed, chipped from oxide, tapping on the edge of the table, and the channel of the soldering iron holder is blown out. Solder dissolution is worse: it is often inconvenient to grind the sting and it works quickly.
You can make a soldering iron tip made of ordinary red copper several times more resistant to the action of molten solder without sharpening its working end, but forging it to the desired shape. Cold copper is perfectly forged with an ordinary metalwork hammer on the anvil of a table vise. The author of this article has had a forged tip in the ancient Soviet EPCN-25 for more than 20 years, although this soldering iron is in operation, if not every day, then certainly every week.
Simple of a resistor
Payment
The simplest soldering iron can be made from a wire-wound resistor; this is a ready-made nichrome heater. It is also easy to calculate: when dissipating the rated power in free space, the wire resistors heat up to 210-250 degrees. With a heat sink in the form of a sting, the "wireworm" holds a long-term power overload by 1.5-2 times; the temperature of the tip will be at least 300 degrees. It can be increased to 400, giving a power overload of 2.5-3 times, but then after 1-1.5 hours of operation, the soldering iron will need to be allowed to cool down.
Calculate the required resistance of the resistor by the formula: R = (U ^ 2) / (kP), where:
R is the required resistance;
U is the operating voltage;
P is the required power;
k is the power overload factor indicated above.
For example, you need a 220V 100W soldering iron to solder copper pipes. Heat transfer is large, so we take k = 3.220 ^ 2 = 48400. kP = 3 * 100 = 300. R = 48400/300 = 161.3 ... Ohm. We take a resistor of 100 W 150 or 180 Ohm, because There are no 160 Ohm "wireworms", this rating is from a range of 5% tolerance, and "wireworms" are not more accurate than 10%.
The opposite case: there is a resistor for power p, what power can you make a soldering iron out of it? What voltage should it be powered from? Remember: P = U ^ 2 / R. We take P = 2 p. U ^ 2 = PR. We take the square root of this value, we get the operating voltage. For example, there is a 15W 10 ohm resistor. The soldering iron power comes out up to 30 watts. We take the square root of 300 (30 W * 10 Ohm), we get 17 V. From 12 V, such a soldering iron will develop 14.4 W, you can solder trifles with low-melting solder. From 24 V. From 24 V - 57.6 W. The power overload is almost 6 times, but occasionally and for a short time it is possible to solder something big with this soldering iron.
Manufacturing
How to make a soldering iron from a resistor is shown in Fig. above:
- We select a suitable resistor (pos. 1, see also below).
- We are preparing the details of the sting and fasteners to it. A groove on the rod is selected under the annular spring with a file. Threaded blind holes are made for the bolt (screw) and the tip, pos. 2.
- We assemble the rod with the tip into the sting, pos. 3.
- We fix the sting in the heating resistor with a bolt (screw) with a wide washer, pos. 4.
- We attach the heater with a sting to a suitable handle in any convenient way, pos. 5-7. One condition: the temperature resistance of the handle is not lower than 140 degrees, the resistor leads can be heated to this temperature.
Subtleties and nuances
The soldering iron described above from 5-20 W resistors was made by many (including the author in the days of his pioneering youth) and, having tried it, they were convinced that they could not work seriously. It heats up unbearably for a long time, and solders only a trifle with a poke - a layer of ceramics interferes with heat transfer from the nichrome spiral to the sting. That is why the heaters of factory-made soldering irons are wound on mica mandrels - the thermal conductivity of mica is orders of magnitude higher. Unfortunately, it is impossible to roll mica into a tube at home, and winding 0.02-0.2 mm nichrome is also not for everyone.
But with soldering irons from 100 W (resistors from 35-50 W), the matter is different. The thermal barrier made of ceramics in them is relatively thinner, on the left in the figure, and the heat reserve in the massive sting is an order of magnitude larger, because its volume grows in cube sizes. It is quite possible to qualitatively solder the joint of copper pipes 1/2 ″ 200 W with a soldering iron from a resistor. Especially if the sting is not prefabricated, but one-piece forged.
Note: wirewound resistors are available for power dissipation up to 160 W.
Only for a soldering iron, it is necessary to look for resistors of the old types of PE or PEV (in the center in the figure, in production so far). Their insulation is vitrified, withstands repeated heating to light red without loss of properties, it only darkens, cooling down. The pottery is clean inside. But the C5-35V resistors (on the right in the figure) are painted, inside too. It is completely impossible to remove the paint in the channel - the ceramics are porous. When heated, the paint is charred and the sting sticks tightly.
Soldering iron regulator
The example with a low-voltage soldering iron from a resistor is given above for good reason. The PE (PEV) resistor from trash or from the iron market most often turns out to be of an unsuitable rating for the current voltage. In this case, you need to make a power regulator for the soldering iron. This is much easier these days, even for people who have the most vague idea about electronics. The ideal option is to buy a ready-made universal voltage and current regulator TC43200 from the Chinese (well, Ali Express, or else), see fig. on right; it is inexpensive. Allowable input voltage 5-36 V; output - 3-27 V at a current up to 5 A. Voltage and current are set separately. Therefore, you can not only set the desired voltage, but also adjust the power of the soldering iron. There is, for example, a 12 V 60 W instrument, but now you need 25 W. We set the current to 2.1 A, the soldering iron will go to 25.2 W and not a milliwatt more.
Note: for use with a soldering iron, it is better to replace the standard TC43200 multiturn regulators with ordinary graduated scale potentiometers.
Impulse
Many people prefer pulse soldering irons: they are better suited for microcircuits and other small electronics (except smd, but see further). In standby mode, the tip of the pulse soldering iron is either cold or warms up a little. Soldered by pressing the start button. At the same time, the sting quickly, in fractions of a unit s, heats up to operating temperature. It is very convenient to control the soldering: the solder spreads, squeezed out the flux from the drop - released the button, the tip cooled down just as quickly. You just need to have time to remove it, so as not to be soldered there. The danger of burning a component with some experience is minimal.
Types and schemes
Pulsed heating of the soldering iron tip is possible in several ways, depending on the type of work and the requirements for the ergonomics of the workplace. In amateur conditions, or for a small individual IP, an impulse soldering iron is more convenient and affordable to make one of the tracks. schemes:
- With a current-carrying sting under current of industrial frequency;
- With an insulated sting and its forced heating;
- With a high frequency current-carrying sting.
Electrical schematic diagrams of pulse soldering irons of the indicated types are shown in Fig: pos. 1 - with a current-carrying sting of industrial frequency; pos. 2 - with forced heating of the insulated tip; pos. 3 and 4 - with a high frequency current-carrying sting. Next, we will analyze their features, advantages, disadvantages and methods of implementation at home.
50/60 Hz
The scheme of a pulse soldering iron with a tip under a current of industrial frequency is the simplest, but this is not its only advantage, and not the main thing. The potential at the tip of such a soldering iron does not exceed fractions of a volt, so it is safe for the most delicate microcircuits. Until the induction soldering irons of the METCAL system appeared (see below), it was the power frequency pulses that a significant part of installers in the electronics production worked with. Disadvantages - loudness, significant weight and, as a result, poor ergonomics: a shift longer than 4 hours. the workers got tired and started making mistakes. But there are still a lot of pulsed power-frequency soldering irons in amateur use: Bison, Sigma, Svetozar, etc.
The device for a 50/60 Hz pulse soldering iron is shown in pos. 1 and 2 fig. Apparently, for the sake of saving on production costs, manufacturers most often use transformers on cores (magnetic circuits) of type P (pos. 2) in them, but this is far from the optimal option: in order for the soldering iron to solder like EPCN-25, the transformer power needs 60-65 watts. Due to the large stray field, the transformer on the P-core in the short-circuit mode heats up very much, and the heating-up time of the tip reaches 2-4 s.
If the P-core is replaced with an SHL from 40 W with a secondary winding made of a copper bus (pos. 3 and 4), then the soldering iron can withstand an hour's work with an intensity of 7-8 rations per minute without unacceptable overheating. For operation in the mode of periodic short-term short-circuits, the number of turns of the primary winding is increased by 10-15% against the calculated one. This design is also advantageous in that the tip (copper wire with a diameter of 1.2-2 mm) can be attached directly to the terminals of the secondary winding (pos. 5). Since its voltage is a fraction of a volt, this further increases the efficiency of the soldering iron and lengthens its operating time before overheating.
Forced heating
The scheme of a forced heating soldering iron does not require special explanations. In standby mode, the heater operates at a quarter of the rated power, and when the start is pressed, the energy accumulated in the capacitor bank is thrown into it. Disconnecting / connecting to the battery capacity, you can rather roughly, but within acceptable limits, dose the amount of heat emitted by the sting. The advantage is the complete absence of an induced potential on the sting, if it is grounded. The disadvantage is that on commercially available capacitors, the circuit is realizable only for resistor mini-soldering irons, see below. It is mainly used for occasional work on non-component-rich hybrid assembly boards, smd + conventional printed wiring in through-pistons.
At high frequency
Pulse soldering irons at increased or high frequencies (tens or hundreds of kHz) are very economical: the thermal power at the tip is almost equal to the nameplate electric inverter (see below). They are also compact and lightweight, and their inverters are suitable for powering continuous heating mini-soldering irons with an insulated tip, see below. Heating the tip to operating temperature - in a fraction of a second. Any thyristor voltage regulator 220 V can be used as a power regulator without modifications. They can be powered by a constant voltage of 220 V.
Note: for power over approx. A 50 W HF pulse soldering iron is not worth doing. Although, for example. computer IPBs are available with a capacity of up to 350 W or more, but it is almost impossible to make a sting for such a power - either it will not warm up to the operating temperature, or it will melt itself.
A serious drawback - the operating frequencies are affected by the influence of the tip's own inductance and the secondary winding. Because of this, an induced potential of more than 50 V can appear on the sting for more than 1 ms, which is dangerous for CMOS components (CMOS, CMOS). There is also a significant drawback - the operator is irradiated by the power flow of the electromagnetic field (EMF). You can work with a 25-50 W pulsed HF soldering iron for no more than an hour a day, and up to 25 W - no more than 4 hours, but no more than 1.5 hours in a row.
The simplest way to implement a 25-30 W pulsed HF soldering iron inverter for ordinary adhesive work is based on a 12 volt halogen lamp power adapter, see pos. 3 fig. with diagrams. The transformer can be wound on a core of 2 K24x12x6 ferrite rings folded together with a magnetic permeability μ of at least 2000, or on an E-shaped magnetic core made of the same ferrite with a cross section of at least 0.7 sq. see Winding 1 - 250-260 turns of enameled wire with a diameter of 0.35-0.5 mm, windings 2 and 3 - 5-6 turns of the same wire. Winding 4 - 2 turns in parallel to a wire with a diameter of 2 mm or more (on a ring) or braid from a television coaxial cable (pos. 3a), also paralleled.
Note: if the soldering iron is more than 15 W, then it is better to replace the MJE13003 transistors with MJE130nn, where nn> 03, and put them on radiators with an area of 20 sq. cm.
The version of the inverter for a soldering iron up to 16 W can be made on the basis of a pulsed starting device (IPU) for LDS or filling a burned-out economy light bulb, respectively. power (do not beat the flask, there are mercury vapors!) Refinement is illustrated by pos. 4 in Fig. with diagrams. What is highlighted in green may be different in the IPU of different models, but we do not care. We need to remove the starting elements of the lamp (highlighted in red in pos. 4a) and short-circuit points A-A. We get a diagram of poses. 4b. In it, a transformer is connected in parallel to the phase-shifting inductor L5 on the same ring as in the previous one. case or on W-shaped ferrite from 0.5 sq. cm (item 4c). Primary winding - 120 turns of wire with a diameter of 0.4-0.7; secondary - 2 turns of wire D> 2 mm. A sting (pos. 4d) from the same wire. The finished device is compact (pos. 4e) and can be placed in a convenient housing.
Mini and micro resistors
A soldering iron with a heating element based on an MLT metal-film resistor is structurally similar to a wire-wound resistor soldering iron, but it is designed for power up to 10-12 W. The resistor operates with a power overload of 6-12 times, because, firstly, the heat sink through a relatively thick (but absolutely thinner) sting is larger. Secondly, MLT resistors are physically several times smaller than PE and PEV. The ratio of their surface to volume acc. increases and heat transfer to the environment is relatively growing. Therefore, soldering irons on MLT resistors are made only in mini and micro versions: when you try to increase the power, the small resistor burns out. Although MLTs for special applications are produced for power up to 10 W, it is really possible to make on our own only a soldering iron on MLT-2 for small discrete components (placers) and small microcircuits, see, for example. video below:
Video: micro-soldering iron on resistors
Note: a chain of MLT resistors can also be used as a heater for an autonomous battery-powered soldering iron for ordinary welding, see next. video clip:
Video: Cordless Mini Soldering Iron
It is much more interesting to make a mini soldering iron from an MLT-0.5 resistor for smd. The ceramic tube - the MLT-0.5 body - is very thin and almost does not interfere with heat transfer to the sting, but it will not miss the heat pulse at the moment it touches the landfill, which is why smd components often burn out. Having picked up the tip (which requires quite a lot of experience), you can slowly solder the smd with such a soldering iron, continuously monitoring the process in a microscope.
The manufacturing process of such a soldering iron is shown in Fig. Power - 6 W. Heating is either continuous from the inverter described above, or (better) with forced heating with direct current from a 12 V power supply.
Note: how to make an improved version of such a soldering iron with a wider range of applications is described in detail here - oldoctober.com/ru/soldering_iron/
Induction
The induction soldering iron is today the pinnacle of technical advances in the field of metal soldering with eutectic solders. In essence, an induction heated soldering iron is a miniature induction furnace: the HF EMF of the inductor coil is absorbed by the tip metal, which is heated by Foucault's eddy currents. It is not so difficult to make an induction soldering iron with your own hands if you have a source of high-frequency currents at your disposal, for example. computer switching power supply, see eg. plot
Video: induction soldering iron
However, the qualitative and economic indicators of induction soldering irons for conventional adhesive work are low, which cannot be said about their harmful effects on health. In fact, their only advantage is that the sting stuck to the clip in the body can be ripped out, for fear of breaking the heater.
Induction mini-soldering irons of the METCAL system are of much greater interest. Their introduction in the electronics production made it possible to reduce the percentage of defects due to errors of installers by 10,000 times (!) And lengthen the work shift to normal, and the workers left after it vigorous and capable in all other respects.
The device of the METCAL type soldering iron is shown at the top left in Fig. The highlight is the ferronickel coating of the tip. The soldering iron is powered by an HF of a precisely maintained frequency of 470 kHz. The thickness of the coating was chosen such that at a given frequency, due to the surface effect (skin effect), Foucault currents were concentrated only in the coating, which heats up strongly and transfers heat to the sting. The sting itself turns out to be shielded from EMF and induced potentials do not arise on it.
When the coating warms up to the Curie point, above which the ferromagnetic properties of the coating disappear in temperature, it absorbs EMF energy much weaker, but it still does not let RF into copper, because maintains electrical conductivity. Cooling down below the Curie point by itself or as a result of the outflow of heat to the soldering, the coating again begins to intensively absorb EMF and heats the tip. Thus, the tip maintains the temperature equal to the Curie point of the coating with literal precision to the degree. In this case, the thermal hysteresis of the tip is negligible. is determined by the thermal inertia of the thin coating.
In order to avoid harmful effects on people, soldering irons are produced with non-replaceable tips, tightly fixed in a cartridge of a coaxial design, through which it is fed to the HF coil. The cartridge is inserted into the soldering iron handle - a holder with a coaxial connector. Cartridges are available in types 500, 600 and 700, which corresponds to the Curie point of coverage in degrees Fahrenheit (260, 315 and 370 degrees Celsius). Main working cartridge - 600; The 500th is soldered especially small smd, and the 700th is the large smd and scattering.
Note: to convert Fahrenheit to Celsius, you need to subtract 32 from Fahrenheit, multiply the remainder by 5 and divide by 9. If it is necessary on the contrary, add 32 to Celsius, multiply the result by 9 and divide by 5.
Everything is great in METCAL soldering irons, except for the price of the cartridge: for "(company name) new, good" - from $ 40. "Alternative" ones are one and a half times cheaper, but they are produced twice as fast. It is unrealistic to make a METCAL tip yourself: the coating is applied by spraying in a vacuum; galvanic at Curie temperature instantly exfoliates. A thin-walled tube set on copper will not provide absolute thermal contact, without which METCAL simply turns into a poor soldering iron. Nevertheless, making an almost complete analogue of the METCAL soldering iron yourself, and with a replaceable tip, is difficult, but possible.
Induction for smd
The device of a homemade induction soldering iron for microcircuits and smd, similar in performance to METCAL, is shown on the right in Fig. Once similar soldering irons were used in special production, but METCAL has completely supplanted them due to better manufacturability and greater profitability. However, you can make such a soldering iron for yourself.
Its secret lies in the ratio of the shoulders of the outer part of the tip and the shank protruding from the coil into the interior. If it is as shown in fig. (approximately), and the shank is covered with thermal insulation, then the thermal focus of the tip will not go beyond the winding. The shank will, of course, be hotter than the tip of the tip, but their temperatures will change synchronously (theoretically, the thermhysteresis is zero). Once you have set up the automation with an additional thermocouple that measures the temperature of the tip of the tip, you can continue soldering calmly.
The timer plays the role of the Curie point. It is reset to zero by a signal from the thermostat for heating, for example, by opening a key shunting the storage tank. The timer is started by a signal indicating the actual start of the inverter: the voltage from the additional winding of the transformer of 1-2 turns is rectified and unlocks the timer. If the soldering iron is not being soldered for a long time, the timer will turn off the inverter after 7 seconds until the tip cools down and the thermostat issues a new signal for heating. The bottom line is that the thermhysteresis of the tip is proportional to the ratio of the times of the off and on heating of the tip O / I, and the average power at the tip is opposite I / O. Up to a degree, such a system does not keep the temperature of the tip, but it provides +/– 25 Celsius with a working tip of 330.
Finally
So what kind of soldering iron should you make? A powerful wirewound resistor is definitely worth it: there is nothing at all for it, it does not ask for it, but it can help out thoroughly.
It is also worth making a simple soldering iron for smd from an MLT resistor on the farm. Silicon electronics are exhausted, they are at a dead end. Quantum is on its way, and graphene is clearly looming in the distance. Both do not interface directly with us, like a computer through a screen, a mouse and a keyboard, or a smart phone / tablet through a screen and sensors. Therefore, the silicon framing will remain in the devices of the future, but only smd, and the present scattering will seem like something like radio tubes. And do not think that this is fantasy: only 30-40 years ago, not a single science fiction writer thought of a smartphone. Although the first samples of mobile phones were already there. And an iron or a vacuum cleaner "with brains" would not have occurred to the dreamers of that time even in a bad dream.
(1
estimates, average: 5,00
out of 5)