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, do 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 easy 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 an 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). Note that the cooked green mass is very sticky, and to keep your fingers and tools from sticking, sprinkle with dry talcum powder from time to time.
Around the tip, tightly roll a 30 mm long tube of copper foil - 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 insulation of the winding 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 amateur will always need a can of compressed air so that you can blow out the dust from 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.
The working voltage of soldering irons can have a different range of values - from 220V and below. The trend towards stricter safety requirements has led to the fact that only powerful soldering irons use the full voltage of the household network for operation. It's not just about safety. A malfunction of a high-voltage tool (insulation breakdown, short circuit) can damage the radio equipment, for which a soldering iron is used.
The most widespread for the repair of various devices are soldering irons with voltages of 24, 36 and 42V. Such voltages are safe for both people and equipment.
Where is a low-voltage soldering iron needed?
To carry out work on the repair of automotive devices, electric soldering irons are produced with a lower voltage - 12V. This is the voltage of the vehicle electrical system. If the repair is carried out away from a service station or garage, then only the car's battery can serve as a voltage source. A breakdown of electrical equipment on a trip is fraught with a call to a tow truck, if this happened not on additional equipment (radio tape recorder, car refrigerator), but in the on-board network itself.
Power limits
The use of low-voltage soldering irons comes up against a fundamental limitation on the permissible power of the tool, because, according to the elementary law of electrical engineering, with a decrease in voltage for the same power, more current is required. So, a soldering iron with a power of 40 W at a voltage of 36 V consumes a current slightly more than 1A, and a 12-volt one will require more than 3 amperes. This requires a large diameter of the supply wires, firstly, according to the permissible heating of the wires, and secondly, according to the voltage drop across them.
Soldering iron connection 12V
To connect third-party electrical devices in most cars, there is only one option - through the cigarette lighter socket.
Before using it to connect a powerful soldering iron, you should study the car's wiring diagram in terms of the purpose and power of the fuses. Many car models have electrical equipment in which other devices are included in the cigarette lighter power circuit. For example, on the popular VAZ-2109 model, rear window heating is included in the cigarette lighter circuit, and exceeding the permissible current consumption can lead to blown fuses and inoperability of part of the car's electrical equipment.
Thus, a powerful electric soldering iron must provide for connection directly to the battery. This also achieves a reduction in the voltage drop across the switching elements and connecting wires.
Important! Using a powerful soldering iron for a long time can discharge the battery to a critical value. It is necessary to remember this and avoid discharging.
Soldering iron selection
When purchasing a low-voltage soldering iron, you need to imagine the purpose for which it will be used. A tool with a power of up to 40 W can only be used for soldering electronic equipment and thin wires. The car's power wiring has a large wire size and is an efficient heat sink. It is almost impossible to perform reliable soldering of such conductors with a low-power 12 volt soldering iron, especially in cold weather.
The temperature of the soldering iron tip must be at least 300-400 ° C. At lower temperatures, the solder will be difficult to melt. It is good if the soldering iron is equipped with a power regulator, but such models are much more expensive.
All parts of the soldering iron should look solid and reliable. The tip and handle of the tool should be firmly in place and not wobbly. The connecting wires of a good and high-quality tool have great thickness and at the same time good flexibility. It is inconvenient to use the tool when soldering miniature radioelements and applying efforts to bend the supply wires.
DIY soldering iron
If there is a desire to do something with your own hands and the ability to work with tools, you can make a 12 volt soldering iron yourself. It will look a little unpresentable, but the reliability is much higher than that of cheap Chinese instruments.
To make a homemade soldering iron you need:
- Powerful (at least 10W) 5-6 ohm wirewound resistor;
- Copper rod with a diameter corresponding to the diameter of the inner hole of the resistor;
- Copper bar is thinner for the tip. You can grind a section of a thick bar, but then, if the sting is burned, you will have to change the entire element completely;
- Insulating material for the soldering iron handle (textolite, plywood);
- Connecting wires with a cross section of 1-1.5 mm2;
- Plug for cigarette lighter socket.
After collecting the heating element, wires are soldered to it, and the handle is attached with a metal clamp through an asbestos gasket.
Video
Soldering electronic circuits often requires special care when heating the leads of semiconductor elements. They are very demanding on temperature.
In addition, sometimes when debugging a circuit, you have to solder with the power connected. In this case, it is dangerous to use a regular soldering iron powered from a 220 Volt network. For such cases, it is better to use an electric soldering iron that operates on a voltage of 12 volts.
The soldering iron, designed for 12 volts, can operate on both AC and DC.
A soldering iron working on direct current can even be connected to the vehicle's on-board network, provided that its power does not exceed the design power of the car wiring.
There are many low voltage soldering iron designs on the market. You can distinguish them by the mandatory inscription on the body, on the packaging.
This voltage must also be indicated in the technical data of the instrument. If you have an unnecessary 220 volt soldering iron, you can make a 12 volt one yourself.
Alteration of an old soldering iron
In order to remake a standard soldering iron, you need to disassemble it, remove the heating element. Instead, a nichrome thread with a thickness of 0.02-0.20 mm should be wound on a mica substrate. The thread can be removed from any old electrical appliance, such as a hair dryer.
The length of the filament is selected experimentally depending on the thickness and the required degree of heating of the soldering iron. When winding the thread, make sure that the threads do not come into contact with each other.
The sequence of work is as follows:
- after selecting the length of the wire, the turns are fixed using some kind of heat-resistant glue;
- the thread from both ends is connected with wires to the power source. It can be a 12 volt converter, a battery for a power tool, or a car battery;
- the case of a new 12 volt soldering iron must be assembled and it will not differ in any way from the previous one.
In order not to accidentally turn on the tool to the 220 volt network, it is recommended to make a catchy, well-visible inscription on the handle - "12V".
From resistor
You can make a miniature homemade 12 volt soldering iron using fixed metal film resistors, for example, a 2 W MLT-2.
They work even with overload up to 6-10 times, so it is not difficult to achieve a power from them up to 12-20 watts. But a significant part of it will be wasted on heat exchange with air due to the relatively large surface area of the resistor. For manufacturing, you need a resistor with a nominal value of 24-27 ohms.
One of its thick enough leads will serve as a soldering iron tip, the second - as a contact for the power wire.
The resistor housing near the tip contact must be stripped of paint and tightly wrapped with a second supply wire. The working circuit of the soldering iron is ready.
It only remains to place it in a case that will be convenient to use. For this, the resistor is wrapped in a heat-resistant heat-insulating material, for example, glass cloth, and placed in a plastic tube of a suitable diameter.
Use in a car
In modern cars, there are few such units and parts that can be repaired on their own, outside the garage or workshop. Most likely, these can be damaged wiring harnesses at the bends.
Such malfunctions are easy to fix right on the road. It is enough to remove the excess insulation and twist the wires, then protecting the twist with insulating tape.
But the car's wiring works in very difficult conditions. It is susceptible to vibrations, frequent changes in temperature and humidity, especially in winter.
Under these conditions, contact in the twist can be lost, and when using conventional single-wire electrical circuits, the loss of contact can unpredictably affect the behavior of the vehicle.
To prevent this undesirable phenomenon, it is recommended to solder the twist. For this you need a car soldering iron powered by a cigarette lighter.
Almost all car cigarette lighters are powered by a wire line designed for a current of up to 15 A. This is quite enough to connect a soldering iron with a power of up to 100 watts. And more is unlikely to be required. The cigarette lighter itself is also being converted into a pallet. It turns out a miniature infrared hair dryer.
In cars of earlier production, soldering may be needed to repair mounting blocks for relays and fuses, to solder terminals to wires that are broken during use.
Sometimes there are situations when the owner simply cannot do without a simple soldering iron. For example, you need a multicore cable for an outlet, or from a burnt-out appliance. At such moments, you have to either borrow a tool, or postpone the case indefinitely. After all, not everyone wants to buy an expensive soldering iron or soldering station, if he is not a repairman. However, there is a simple way out of this situation - to assemble a small soldering iron on your own, it is just suitable for small work. The manufacturing process does not take much time and effort, but you can save some amount of money and gain invaluable experience. Next, we will tell you how to make a do-it-yourself soldering iron at home. You will be offered several designs, and you can choose the one that suits you best.
Idea # 1 - Using a resistor
The first and simplest technology for making an electric soldering iron with your own hands is using a powerful resistor. The device will be designed to operate at voltages from 6 to 24 volts, which will allow it to be powered from various current sources, and even make it a portable version powered by a car battery. In order to make your own instrument, you will need the following materials:
To make a soldering iron yourself from a resistor at home, you must follow these steps:
- At the end of a thick copper rod, you need to drill a hole and drive the thread under the screw using a tap. It is also necessary to cut a groove for the retainer, which in our case is the spring ring. This can be done using a triangular file or a metal hacksaw.
- From the second end, drill a hole with a diameter like a thin rod, which will act as a tip of a mini soldering iron.
- All elements of the rod must be assembled into one piece, as shown in the photo.
- The resistor is prepared for attaching the soldering iron tip, which must be inserted and secured from the back with a screw and washer.
- From a textolite or plywood plate, you need to make a comfortable handle with a seat for a resistor and a wire with your own hands. To do this, use a jigsaw to cut out two identical halves of the handle and make holes and indentations for the screws and nuts.
- A power cord must be connected to the heater terminals. It must be screwed onto the screws so that the contact is reliable.
- The finished homemade soldering iron is twisted and checked.
We draw your attention to the fact that with such a portable gun you can easily solder microcircuits and even do it yourself. It can work not only from the power supply, but also from the battery. On the forums, we met a lot of reviews where this homemade version was connected from a 12 Volt cigarette lighter, it is also very convenient!
Please note that when first turned on, all soldering irons may smoke and stink for a while. This is normal for any model, as some elements of the paintwork will fade. It will stop afterwards.
Video instruction for making the simplest electrical appliance
Idea number 2 - The second life of a ballpoint pen
There is another unusual, but at the same time simple idea of how to make a soldering iron with your own hands from scrap materials for soldering small parts or smd components. In this case, again, it will be useful to us, but now it is not a PEV (as in the previous version), but an MLT, with a capacity of 0.5 to 2 watts. 
So, first you must prepare the following materials:
- A ballpoint pen of the simplest design.
- Resistor with characteristics: resistance 10 Ohm, power 0.5 W.
- Double-sided textolite.
- Copper wire with a diameter of 1 mm, it can be wound from an old choke or you can buy a single-core copper wire in insulation from an electrician store and carefully remove it with a clerical knife
- Steel or copper wire with a diameter of no more than 0.8 mm.
- Wires for connecting to the network.
Making a soldering iron from a pen at home is quite simple, you just need to follow these steps:
- Remove the paint layer from the surface of the resistor. This operation can be carried out using a skin, a file or a file, in extreme cases, a knife. The main thing is not to overdo it so as not to damage the resistor. If paint is difficult to remove, connect the product to a regulated power source and heat slightly.
- 2 wires come out of the barrel, cut one of them and drill a hole in this place for a copper wire (diameter 1 mm). To prevent the wire from touching the cup (this must be avoided), make a countersink with a thicker drill, as shown in the photo below. In addition, you need to make a small cut for the wire directly on the resistor cup. A triangular file will again help you with this.
- Bend the steel wire into a ring-shaped handle, about the same diameter as the drank on the cup. If you have copper wire, then you need to clamp the cup in it and twist it with pliers so that the contact is reliable, but do not overdo it, otherwise you will remember the case. Remember that the wire must be free of varnish insulation.
- Carefully cut the board out of the double-sided PCB with your own hands, exactly the same as shown in the example in the photo. It is not necessary to buy a new PCB sheet. You can use a jigsaw to cut a suitable piece from any unnecessary double-sided board. Or do without it altogether: twist the wire with wires, and attach them to the handle using superglue. The main thing you need to pay attention to is that the distance between the heating element and the handle is more than 5 cm, otherwise the plastic may melt.
- Next, you need to assemble a homemade soldering iron from a pen, which should not cause difficulties.
- It remains to install a thin tip in the seat. To prevent the copper wire from burning through the resistor, you need to make a protective layer from a piece of mica or ceramic between the back wall and the tip.
- The last thing to do is to connect the homemade product to a 1 A power supply and a voltage of no more than 15 Volts using wires.
That's the whole technology of creating a homemade mini soldering iron at home. As you can see, there is nothing difficult in making this tool, and you can easily cope with it, and all materials can be found at home by disassembling old equipment or looking for them in the bins.
How to make a more complex mini soldering iron model at home?
Video review of a device with nichrome wire, operating from 12 volts
Idea # 3 - Powerful Impulse Pattern
This option is suitable for those who are already more or less familiar with radio engineering and know how to read the corresponding diagrams. A master class on making a homemade pulse soldering iron will be provided following the example of this circuit: 
The advantage of this tool is that the tip heats up within 5 seconds after turning on the power, while the heated rod can easily melt the tin. At the same time, it can be made from a switching power supply from a fluorescent lamp, slightly improving the board at home.
As in the previous examples, first we will consider the materials from which you can make a do-it-yourself soldering iron at home. Before assembling, you must prepare the following tools at hand:
All you need is to connect the tip to the secondary winding, which, in fact, is already part of it. After that, one of the ballast leads must be connected to the primary winding of the transformer and all elements of the circuit must be fixed in a reliable case, which will save you from accidental electric shock, since the circuit contains a life-threatening voltage of 220 volts!
The principle of operation of this design is that the ballast from the lamp creates an alternating voltage that is applied to the primary winding of the transformer and decreases to low values, while the current increases many times. One turn, which is, in fact, the tip of the soldering iron acts as a resistor on which heat is dissipated. When the button is pressed, the current is supplied to the circuit, and rapid heating occurs, after the button is released, the sting cools down quickly, which is very convenient, since you do not need to wait long for the tool to heat up and cool down.
Idea # 4 - Simple wire version
There is another option for making a miniature soldering iron - using nichrome wire. To do this, you will need:
Manufacturing process:
- Drill a hole in the block for a copper wire 3 times larger than its diameter.
- Place a piece of copper wire in it so that it protrudes about 5 cm and secure it there with a thick plaster putty, let it dry.
- Put insulation on the copper rod, which is a sting, and wind the required amount of nichrome wire, leaving a distance between the turns. Put insulation on the ends as well and bring them closer to the handle. Then connect to strands with wires. Tape them to the handle with duct tape.
That's all, you have another simple and reliable do-it-yourself soldering iron design.
We still recommend using either the first or the second option, which is clearer and easier to manufacture. As for the transformer version, although it is more powerful, it is still not so convenient to use. We hope that these photo instructions were useful for you and in the end we recommend that you definitely watch all the video examples in which the assembly process is discussed in more detail!
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