How to make resistance welding from an inverter. Do-it-yourself spot welding from an inverter. Homemade device from a microwave oven

Do-it-yourself spot welding from an inverter - is it a myth or reality? It is not at all easy to answer this question clearly. You can find many articles on this topic on the Internet. Their authors, as a rule, deal with the problems of altering electrical and electronic components. The question is how to create the necessary operating pressure on the electrodes, it seems to fade into the background. But it is, in fact, key, since we are talking about an effort of tens and sometimes hundreds of kilograms. Well, okay, let's take it in order.

The advantages of resistance welding are sufficient to make it attractive to those who intend to launch mass production of products or repair equipment at a professional level.

Good quality welded joint. It is ensured by the stability of parameters welding current and the pressure exerted on the parts being connected.
High speed process. It takes seconds to apply a suture. This is especially important when it comes to performing a large amount of work.
Operational simplicity. A properly manufactured resistance welding machine does not require special skills to use, and even a semi-skilled specialist can master the process.
The use of a spotter is justified when repairing automobile bodies. This device simplifies not only the welding process, but also the straightening of damaged parts.

The main obstacle to widespread adoption of the technology is the high cost of equipment. This gives many people the idea of making a resistance welding machine on their own.

Do you need an inverter?

In fact, using an inverter for these purposes is unjustified. After all, for resistance welding there is no need for direct current. If you already have it ready welding inverter The task of installing control circuits and manufacturing transformer coils of the required parameters is only somewhat simplified. With the same success, you can make equipment, as they say, from scratch.

What you need

It is not worth starting to solve such a problem without the necessary theoretical knowledge and practical skills. In words it all looks relatively simple. But if you know how to solder and know how to rewind the transformer coils correctly, you can try it. To do this you will need certain materials and tools.

Copper wire of a certain cross-section. Its cross-section and quantity can only be determined by performing preliminary calculations.
Material for making a tire. At worst, you can get by with the same wire, but it is more advisable to purchase a ready-made product.
Varnish to create an insulating layer on the wires and good insulating tape.
Multimeter for taking the necessary measurements.
Soldering supplies – soldering iron, flux, solder, etc.

Of course, you will have to purchase a ready-made welding inverter.

Transformer manufacturing

Figure No. 1 schematically shows the possible ratio of turns of the primary and secondary windings of the transformer necessary for resistance welding. A large number of outputs on the secondary winding is necessary in order to be able to roughly adjust the current parameters. But the presented circuit requires adjustment depending on the required current parameters. You can't do without preliminary calculations.

Theoretical and practical assistance

The number of turns can be calculated using this formula: N = 50/S. Where N is the number of turns, S is the core area in cm2. To simplify the task, it is recommended to use a ready-made calculator program. They can also be found online. For example, the OER program. This will help avoid mistakes and simplify the task. Since we are talking about designing equipment based on a ready-made inverter, you should first measure the parameters of the primary coil, make calculations, and only then begin manufacturing the secondary winding.

Carefully!

Care must be taken to ensure that both windings are grounded. After all, the resulting current power will be very high, and contact with live parts can be fatal.

Carefully insulate and cool well

When winding wire onto a coil, be sure to apply insulating varnish to its surface and lay the turns as tightly as possible. Otherwise it cannot be ruled out turn-to-turn short circuits and wire burnout due to overheating. Transformer cooling comes to the fore. For some reason, the authors of many articles are silent about this. It is possible that the installation of an additional cooling system consisting of radiators and fans blowing them will be required. If this is not taken care of, the equipment will simply fail due to overheating or even become a fire hazard. As an option, it is possible to install ready-made cooling systems used in electrical and electronics.

Control system installation

When installing the control circuit, it is recommended to use ready-made elements. They are already in the factory inverter. This will greatly simplify the assembly process and make the device convenient to use. But the capacity of its standard capacitors may not be enough. In this case, they will have to be replaced with parts that match the parameters. The current parameters in the resistance welding machine are adjusted in stages. Its accuracy will depend on the number of pins of the secondary winding and their pitch. This is necessary if equipment capable of operating in different modes is required.

It is important!

Installation of circuit components should be done using soldering. Detachable connections are not able to provide the required heat transfer mode. Their use makes sense only in cases where frequent replacement of any parts is expected.

Making pliers

Only when the transformer is ready does it make sense to start making contact clamps. Their design primarily depends on the nature of the work for which the equipment will be used. The gripper design will depend on its drive system and the expected size of the parts to be connected. An important part of the pliers are the contact tips. If the thickness of the sheet being welded is small, it is quite acceptable to use copper tips from a soldering iron. It is better if you purchase and install ready-made tips - they are available for sale and are convenient because they have a special shape that is well suited for the job. But if we are talking about steel sheet 0.5 mm or more and it is expected to apply connecting seams of considerable length; it is recommended to equip the tips with rollers.

Providing clamping force

Next we will have to solve the most practically difficult problem. The fact is that if you intend to create pressure on the welding tongs manually, it is better to refuse making contact welding. The efficiency of such a device will be low. The applied force at the welding site must be uniform and very significant.

In industrial settings, hydraulic or pneumatic systems are used for this. Making such a device yourself is extremely problematic. It makes more sense to purchase a ready-made booster, since they are available for sale. When making resistance welding with your own hands, it is easier to use amplifiers driven by compressed air. In this case, for their operation it will be enough to connect a conventional pneumatic compressor. It is optimal if the maximum force on the contacts reaches 100 kg or more. To change the pressure, you can use a separate regulator, or build it into common system device control.

Gas supply

To optimize welding conditions and improve the quality of the connecting seam, it is worth taking care of the gas supply to the working area. In the case of steel, this should be carbon dioxide. The selection of nozzle and its location depend on the size of the pliers, contacts and working area. The supply hose is secured so as not to interfere with the operation of other components of the device. It must be made of non-flammable, heat-resistant material and equipped with a control valve.

Concern for reliability and safety

For efficient work equipment, and in order to ensure safety standards, all components of the device must be carefully secured and insulated. It is recommended to use dielectric materials with good heat resistance and mechanical strength. It is also necessary to take care of integrating protective fuses into the electrical circuit. It is important to follow all recommended safety precautions when working on equipment.

What kind of apparatus is used, is it possible to make it yourself? Below we will try to answer all these questions.

Spot welding is used not only in production, but also at home.

On an industrial scale, the choice falls on this type of welding, when it is necessary to join alloys of non-ferrous metals, steel of various grades, when the sheets have different thickness, when creating profile blanks, for example, corners, etc.

At home, spot welding has found its application in repairs. household appliances, batteries, cables.

To reduce the cost of replacing system batteries, this machine can be used to weld batteries for laptops, screwdrivers and other mobile devices.

Welding of batteries occurs using conventional technology.

The welding process itself consists of heating a metal object to a state of plasticity, after which it is deformed, that is, connected.

To create a better quality seam, it is necessary to ensure consistency of the process, that is, constantly maintain the same speed of processing the object, and monitor the pressure.

These requirements apply more to manual welding, because at enterprises this process is performed automatically.

Heating metal objects occurs due to the passage of electric current, from which heat is generated on the surface.

In the place where the electrode came into contact with the surface, a liquid core begins to appear, formed from the melting of two parts.

When the current stops flowing (0.01-0.1 sec), then the core begins to solidify, thereby allowing both parts of the parts to be held.

To compress a metal sheet, pliers are used, which are divided into manual and suspended.

Hand pliers help generate current, which is subsequently supplied to the electrodes that clamp the workpiece. Hanging pliers are used in industry and are characterized by high productivity.

Resistance spot welding has a number of advantages:

Speed of work;
Safety of work is achieved due to low voltage;
The strength of the connection is ensured, but, unfortunately, not tightness;
You can make a welding machine yourself at home.

Process Features

Resistance spot welding is a simple process: current passes through the spot connection, generating heat.

At the same time, the condition of the contacts affects the quality of welding; any roughness or oxide can have an adverse effect.

See the video for the spot welding process.

When welding, it is necessary to take into account such properties of metals as thermal conductivity, resistance and melting point, since they are different, for example, iron will melt at a temperature of 1300 degrees Celsius, copper - 680, aluminum - 435, zinc - 1115, etc.

Electrodes also have certain requirements:

High rates of heat and electrical conductivity;
Strength;
Mechanical processing should be easy.

The quality of the weld seam also depends on the diameter of the electrodes; it determines the current density.

In order to visually correctly select the diameter of the electrode for the sheet being processed, it is necessary to multiply its thickness by two.

Resistance spot welding can be carried out not only in industrial scale, but also in everyday life.

To avoid having to use bulky equipment at home, manufacturers have released a compact device suitable for minor repairs, for example, household appliances, batteries or a car.

The device is called a spotter. It has two terminals, one of which is attached directly to the object, and the second to the electrode.

In this case, pliers are not needed. To ensure a better working process, it is advisable to select the power source so that it is located as close as possible to the welding site.

Despite the fact that the spotter is more of a hand-held device, it is quite functional.

The most simple devices, using single-phase current, are reliable and simple, but metal sheets with a thickness of more than 0.8 mm it will no longer be possible to connect.

More complex and powerful models use a transformer; it should be noted that they are more expensive. But the most expensive spotter is the inverter one.

In everyday life, you can get by with a cheaper device made by yourself.

Spot welding is characterized by the strength of the seam, which sometimes has to be removed by drilling. The drill is usually used when repairing a car.

It should be noted that there is a special drill for drilling spot welds. It is better to buy a drill rather than use some drill that you think is suitable. The price for such a drill is low. This work must be carried out carefully so that the body can be repaired in the future, rather than ordering a new one.

Diagram of a homemade welding machine

For everyday needs, there is no reason to buy a welding machine, especially since you can make it yourself.

The dimensions of such a device will directly depend on the needs. It is more convenient to assemble a medium-sized device. Below is a diagram of a point welding machine.

1 — modified OSM-1.0 transformer; 2 — conductor (duralumin rod with a diameter of 30, L300, 2 pcs.); 3 — liner (steel rod with a diameter of 10, L30, 2 pcs.); 4 — electrode (copper rod with a diameter of 12, L50, 2 pcs.); 5 — brass washer (2 pcs.); 6.12 — M6 screws; 7 handle; 8 - eccentric; 9 — cheek (2 pcs.); 10 - spring; 11 — output of half of the secondary winding (4 pcs.); 13 — textolite bushing (with a groove for the end loop of the spring); 14 — M8 bolt (6 pcs.); 15 — textolite washer (4 pcs.); 16 — insulating coating (varnished fabric or protective adhesive tape on a fabric basis, 2 pcs.); 17 — transformer casing.

The operation of the welding machine is based on the physical law of Lenz-Joule.

The meaning of the law is that the conductor begins to generate heat by passing through itself electricity, in an amount proportional to the resistance of the conductor material, the square value of the current and the time spent on the “passage” of the current.

Wires are selected taking into account this law.

Since resistance spot welding occurs due to an electric pulse, to create the device you will need a transformer, which is not recommended to be connected directly to the power source.

A rectifier bridge with a thyristor is required for proper connection.

The circuit of a homemade device involves the use of another power supply with a transformer and a rectifier bridge for more power.

The current is collected and the pulse is created using a capacitor.

The bridge of the first transformer is closed by a thyristor, which acts as a cathode.

It will remain open until the capacitor is completely discharged. “Impulse” is the beginning and end of the welding machine.

To create a more powerful device, the circuit changes slightly: it is necessary to add a semiconductor thyristor and a time relay.

Homemade welding machine

The circuit is the basis for creating a welding machine, and its “heart” can be considered a transformer, which will create the necessary voltage.

It’s worth noting right away that this element must be powerful with a minimum value of 700-800 watts.

You can make a homemade welding machine using an inverter, but this requires certain knowledge and skills. Using a transformer rather than an inverter is more in a simple way creating a homemade apparatus.

The transformer can be taken from the microwave. Moreover, an old device is suitable for this, or a microwave oven can be purchased specially second-hand.

The scheme of further actions is as follows:

You need to carefully remove the transformer from the microwave, removing all fasteners and disassembling the base;
The secondary winding from the microwave transformer must be knocked down. You can use any available tool: hammer, chisel, pliers, drill, etc. By the way, a drill should always be at hand when using spot welding. The secondary winding differs from the primary winding by a thicker wire. You also need to act carefully here so as not to damage the wire used for the primary winding;
It is necessary to make two or three turns of a new secondary winding. To obtain a current of 1000A, it is advisable to take a wire whose thickness will be at least 1 cm. Physically, it will not be possible to make more than three turns, so if necessary, add another transformer from a microwave, as mentioned above;
The next step is to check the winding for short circuits. A voltmeter is used for this. If none are found, then work can continue;
Next, the transformer from the microwave is checked with an ammeter. If the current exceeds 2000A, then it is necessary to reduce it in order to avoid future voltage drops.

Copper wire works well for electrodes. The thickness of the wire is selected so that the diameter of the wire does not exceed its diameter.

You can use two soldering irons, or rather their tips, which can be installed as electrodes.

Current losses can be reduced by shortening the length of the wire coming from the electrode.

The wire is connected to the electrode using a copper tip; a hole can be made by drilling, using a drill bit of 8.

If you solder the tip to the wire, you can avoid oxidation, which is inevitable when you turn it on for the first time.

When creating levers, you need to consider the following point: you need to create free movement the upper arm horizontally and vertically, this can be done using special openings in the body.

If desired, you can make the lower arm in the same way.

It is necessary to provide space for the on/off switch on the back cover of the device. After installing the toggle switch, the power cable is inserted.

To eliminate the possibility of the cable falling out, it must be made thicker and thicker.

The microwave transformer is attached to the base using self-tapping screws. A terminal is put on the mount and grounding is done. All connections must be carefully insulated.

To keep the upper arm raised, you can use a regular rubber band placed on two self-tapping screws.

Watch a video about do-it-yourself spot welding in our article.

A spotter is a welding unit used specifically for organizing spot welding, and also allows you to work on straightening thin sheet workpieces. This type of welding is especially common in workshops whose employees are engaged in straightening work that requires preliminary disassembly of the body. Using a spotter allows you to avoid the mandatory dismantling of the load-bearing parts of the car and straighten surfaces without using a reverse hammer (figure below).

In this case, the welding procedure is used for the purpose of point-fixing an additional holder on the restored surface, by pulling which it is possible to straighten the existing dent.

Spot Welding Properties

The design of this device is somewhat different from typical units with a continuously burning arc. You can make a spotter from a welding machine with your own hands only if you know the basic principles of the formation of the operating current. The fact is that with the contact welding method, heating occurs not by melting the metal, but by concentrating heat in a point zone between the workpiece and the electrode.

In the case of an incorrectly selected resistance welding mode (with a lack of experience on the part of the operator), sticking of the electrode is often observed, which can lead to unpleasant consequences in the form of a short circuit or even breakdown of the unit. That is why the spot welding machine is manufactured so that the welding time is strictly limited and does not exceed a second.

In addition, such a device is designed for small values of effective voltage (since ignition of the arc is not required in this case) and for significant operating currents. In this regard, the transformer (CT) included in its composition must also withstand high current loads, sufficient for high-quality heating of the welding site.

Features of the conversion

You can make a spot welding machine with your own hands without unnecessary effort if you use the option of converting it from an unnecessary welding device. When preparing for work, you will need to pay attention to the following points:

For an ordinary CT, the voltage when operating at idle (no-load), as a rule, is selected to be no more than 70 Volts;
In a situation with a spot welding unit, this figure should not exceed 6 Volts;
To implement this condition, a new secondary winding will be required, designed for a reduced output voltage.

Note! You can also make a new low-voltage coil by winding it over the existing secondary winding (if space allows).

Otherwise, it is better to unwind the old “secondary” and use its wire to form a new working winding.

Before doing spot welding with an updated transformer, it is advisable to familiarize yourself with existing types these electrical products and try to choose the most suitable one.

The cores used in welding transformers can have several different designs (picture below).

Among them, the following types of CT stand out:

With the so-called “W-shaped” or armored core;
With a rod base (in the shape of the letter “O”);
And finally, with a core made in the form of a torus.

Of all the listed options, the most suitable for the purposes under consideration is a transformer with a toroidal core, which has small dimensions and relatively light weight (see the figure below).

Additional Information. The cross-section of such a core in any transformer will be determined by the expected welding current.

For do-it-yourself spot welding to work properly, the output current of the unit must be at least 1000 Amperes. The latter means that a sufficiently thick wire must be used in the CT output winding. This requirement is fully satisfied by the selected version of the toroidal core, since there is plenty of space for placing the output winding in it.

Secondary winding

Selecting parameters

When remaking a CT, the main attention should be paid to the parameters of the secondary winding, which determine the output characteristics of the device (its load current, in particular). In this case, it is important to select a bus cross-section that would provide a current density of about 8 A/mm² (with a cross-sectional area of about 120 mm²). Since it is very difficult to handle such a thick busbar when winding on a torus, they are most often limited to a value of 80 mm².

Note! The specified cross-section can be obtained by putting together several wires of slightly less thickness.

To facilitate the conditions for converting a CT into a point unit, it is advisable to pre-calculate the amount of wire required for rewinding it. After this, it will be possible (based on the space occupied by the winding) to determine whether it will fit into the remaining space on the torus free space or not.

Important! In the case where the new winding does not fit into the torus, the old secondary coil will have to be completely disassembled (dismantled).

To make it easier to handle new wires during the winding process, it is recommended to wrap them insulating tape based on fabric. To determine the exact number of turns that affect the output voltage, we recommend using the method of test winding with a wire not large section in isolation.

Since the winding in this case is not connected to the load, the cross-section of the test wire of great importance does not have. Experience has shown that during rough tests it is sufficient to use no more than 10 turns. After winding them, the transformer should be connected to the network and the voltage produced by the test coil should be measured, after which it is divided by the number of turns. The result is a figure indicating the number of turns required to produce one volt of output.

Since in this case it is necessary to obtain 6 Volts, multiplying the number obtained from the test connection by 6, we obtain the required number of turns.

In order to make a new device with your own hands, you must first calculate the amount of wire required for rewinding the CT. After this, it will be possible (based on the space occupied by the bus winding) to determine whether it will fit into the free space remaining on the torus.

Winding diagrams and placement

The connection diagram and the order of placement of the “secondary” depend on the type of core selected. Given the toroidal base of the CT that we have declared, it is more convenient to divide it into two half windings connected in series (3 Volts each).

In order to increase the load capacity (increase the welding current), you can make two windings of 6 Volts each and connect them in parallel. In this case, the output voltage will not change, and the load current can be doubled. This design option allows us to solve the problem of the large cross-section of the secondary bus, which can then be reduced by half.

Various types of connections of such windings are shown in the picture below.

The order in which they are connected is very important to obtain the required output parameters, and mistakes made in this case can lead to completely different indicators. So, in particular, if you make a mistake during installation and turn on two windings in opposite directions, as a result they will be short-circuited to one another and will produce zero voltage at the output, which is equivalent to a short circuit.

At the ends of ready-made secondary windings, special tips should be equipped by crimping.

Control circuit

To control the welding process, short pulses are used, generated in a special electronic circuit. When manufacturing a spotter based on an old unit, it is also necessary to provide a control unit that allows switching a significant output current.

To solve this problem, manually generated pulses are applied to the primary winding of the CT (the simplest control circuit is shown in the figure below).

The disadvantages of such management include:

Using the button shown in the figure, the mains voltage is switched, which is extremely dangerous;
When mechanical contacts open, strong sparking occurs;
Even if you replace the mains switch with a traction relay from the starter, controlled by a push-button mechanism, then such a circuit, despite the improvement, will still be unfinished.

Note! To implement the traction principle, it is allowed to use a combination of “powerful starter plus automotive relay” (and the latter can be of any brand).

When this combination is selected, the relay is activated when a voltage of 12 Volts is applied, and its switching causes the power contactor to operate. However, this control option is not without drawbacks, since in this case it is not possible to precisely control the impact interval (pulse width).

For those who know the basics of electronics and know how to handle a soldering iron, something more complex in design, but reliable in operation, is suitable. electronic circuit controls (see photo below).

Here, operating pulses are supplied to the input winding of the CT from an electronic device - a thyristor, which opens when voltage is applied to its control electrode. The capacitor (C1) included in its circuit, with the button contact open, is charged through the elements V1-V4 of the diode bridge. When the button is pressed, the capacitance is discharged through resistor R1 and directly through the thyristor control electrode circuit, which causes it to turn on.

The electronic device will remain on until the capacitor is completely discharged (this interval can be adjusted with variable resistor R1). For the subsequent start operation, the button must first be released and then pressed again (its shutter speed determines the welding interval).

Transformer T1 can be of any type (with a voltage on the secondary winding of 12 Volts). The parameters of the thyristor must satisfy the operating conditions, that is, allow it to operate at voltages up to 400 Volts and currents of at least 50 Amperes. An electronic product of the T132-50 brand is quite suitable for these purposes.

In the final part of the review, we recall that welding equipment of the “spotter” type is most often in demand when body repair and similar works with sheet metal. In this regard, when choosing output power homemade unit thickness must be taken into account sheet material, with which you will mainly work.

Video

The spotter is pretty useful device, helping to significantly increase the efficiency and speed of work for car body repairs. But this unit has enough high cost with simplicity of design. Therefore, many craftsmen prefer to make a spotter from an old transformer or from a welding machine with their own hands.

When car body repairs, there is often a need to remove dents, for example, after an accident. For this purpose they use various ways: pulling out dents with suction cups, leveling with hammer blows from the back of the part, etc. In the latter case, the part must be dismantled to eliminate the defect.

The use of a spotter can significantly speed up and simplify the process of aligning car parts. This unit is a kind of contact spot welding, which can be used to weld washers, studs, bolts, hooks and other fasteners to damaged areas of the car body. Later, various tools are hooked onto them to level out the dents.

The spotter can also be used for soldering, heating, hardening and upsetting of leveled surfaces.

The design and principle of operation of the spotter

The spotter consists of the following elements:

a welding machine, which can be transformer or inverter type;
cables (power cable and ground cable);
welding gun (stadder);
electrode with an inertial hammer.

When you press a button on the studder, current begins to flow to it. Depending on the selected mode, the current supply can be constant or in the form of one short pulse. Next, the current flows to the electrode, which can have tips of different shapes.

The device is working according to the following principle.

The area on the car body that needs to be leveled is cleared of paint. You should also clean small area for connecting the ground cable.
Any fastener, for example, a washer, and is welded to the straightening site.
The alignment tool clings to the washer, after which the dent is pulled out.

Dent pulling can also be done without welding fasteners. In this case, a pointed tip must be installed on the electrode with an inertial hammer. The electrode is applied to to the right place parts, and the tip is welded to it with a short current discharge. Next, without lifting the electrode from the part, strike with a hammer in the opposite direction from the tip, thereby pulling out the dent (for aluminum, use reverse hammer it is forbidden). After eliminating the defect, the welded end of the electrode easily breaks off.

How and what to make a spotter from

The transformer for the spotter is noticeably different from the classic one welding transformer. During arc welding, the metal is heated by an electric arc, and during spot welding, heat is released due to the transition resistance in the electrode-metal section. This happens when arc welding if, for example, the wrong operating mode is set on the unit. In this case, the electrode sticks to the metal, which can cause damage to the device.

To prevent this from happening, spot welding is carried out in pulsed current supply mode(up to 1 second). And since spot welding does not require arc burning, the voltage in the spotter should be minimal (about 6 V), and the current should be high (at least 1000 A).

From a welding machine

It is impractical to make this unit from an inverter, if only because spot welding does not require direct current. In addition, you will have to redo the transformer in order to achieve high current levels. With such success, you can make a spot welding unit from scratch. If you have an inverter device, then it is better to use it for its intended purpose, and use a regular transformer welder for the spotter.

As for semi-automatic machines, all universal models of these units already have a pulse welding function, and no modification is required. But if you have a broken, ordinary semi-automatic machine, then the transformer in it will need to be remade.

Semiautomatic welding machine Aurora

Transformer conversion consists of removing the secondary winding and winding a new one. The spotter requires a welding current of 1000 A. If the calculations assume that the current density is 8 A per 1 mm 2, then its cross-section should be about 120 mm 2. But winding a wire of such a cross-section is quite difficult. Therefore, you can take a tire with a smaller cross-section, for example, 80 mm 2, if the device will not be used too intensively.

Advice! You can achieve the required cross-sectional area by stacking several thin tires together and wrapping them with fabric tape.

For determining the number of turns do the following.

Wind any conductor covered with insulation onto the magnetic core. 10 turns will be enough.
Connect the primary winding to the network, and measure the voltage on the improvised secondary.
The result obtained must be divided by the number of turns, that is, by 10. As a result, you will get a value that determines the number of turns to produce 1 V voltage. But since the spotter requires a voltage of 6 V, by multiplying the resulting value, you can find out the number of turns.

Based on the diameter of the wire with the required cross-section, you can determine whether this winding will fit into the free space between the primary and secondary windings of the transformer (not yet removed). If there is enough space, then the secondary can not be removed from the magnetic circuit, but a new winding can be wound on top of it. In this case, the welder can also be used for electric arc welding, and for point.

A modified transformer is not the only part required to make a spotter from a welding machine. You still need to add to it electronic discharge control unit and a small transformer to provide power to the module. Below is a diagram of the block that controls the spotter.

This scheme works as follows.

When the circuit is closed by switch S1, current begins to flow to the primary of transformer T1.
Next, the capacitor begins to charge. It is connected through a closed switch contact to a diode bridge.
The output transformer T2 will be de-energized until the switch button S is pressed. After this, the voltage from the capacitor through a variable resistor is supplied to the control electrode of the thyristor. Next, the voltage will be supplied to the primary of the output transformer, after which a pulse with the current required for welding will appear on its secondary winding.
After the capacitor is discharged, the module returns to its original state. To repeat the pulse, press the switch again.

After the control unit is ready, all components are placed in a plastic or metal case.

From battery

This device, made of a 12 V battery, is mobile and can operate regardless of the presence of an electrical outlet. To manufacture the unit you will need the following components.

The device is assembled according to the diagram below:

a ground cable is connected to the negative terminal of the battery, which must be in contact with the part prepared for repair;

the first relay contact is connected to the positive terminal of the battery;
the cable going to the welding gun is connected to the second contact of the relay;
a start button is installed between the first and third (connected to the battery positive) contact of the relay;
The solenoid relay must be connected to ground.

The cross-section of the cables should be about 100 mm 2, and their length should not exceed 1.5 m. The only drawback of this device is that the battery drains quickly and it takes time to charge it.

From the microwave

To make the device, you will need a transformer removed from the microwave. But for reliability it will be better if use two coils. The secondary winding should be removed from each transformer and instead, a couple of turns should be wound with a cable with a cross-section of at least 50 mm 2.

The primary windings of both transformers are connected in parallel. Next, the spotter control module, which was discussed above, is connected to the circuit. You can also simplify the design of the spotter if you include a time relay and a pull-in relay from the car in the circuit. You can find out how this is done in this video.

Important! Despite the low voltage - 6 V or less, the current obtained at the output of the transformer has huge values, about 1000 A, which poses a great danger to human life. Therefore, both windings of the transformer must be grounded.

Welding gun

To make a welding handle, no drawings are required. Best suited for this purpose body from glue gun . You will also need a copper rod with a diameter of about 20 mm.

On one side of the rod it is necessary to cut a thread (M14x1.5). Various welding attachments will be screwed onto it. A hole is drilled on the other side and tapped internal thread M8. The cable will be attached to this place. Also the details should make a few grooves so that it is better fixed inside the case.

All that remains is to find a suitable button, place it in the case and connect it to electrical diagram apparatus.

!

In this homemade product, AKA KASYAN shows the details of manufacturing a resistance welding machine.

Inverter type device. But the device itself is very complicated (in terms of operating mode).

The author had a need to weld nickel plates to lithium batteries.

It was this problem that was the starter of this project.

Many DIYers are familiar with resistance welding devices, which are a bulky transformer in the secondary winding of which several turns of a copper busbar or wire are wound.

They are usually made on the basis of a transformer from microwave oven.

To obtain high welding currents of several hundred and sometimes thousands of amperes.

An example of a Chinese welding machine. Maximum current 500A. Buy it - a couple hundred bucks.

And here is the author’s welder, with its light weight of 200g, it is capable of briefly creating currents of 200 - 220 amperes.

The inverter mode of operation in this class of devices is a little unusual. This technology is rarely used for resistance welding. In his version, the author uses a pulse circuit that is easy to implement.

That's how it burns!

A bonus is the low-voltage power supply of the device. You can connect this device to sources direct current(for example, a regular computer power supply).

When using a 12V battery, you will generally get autonomous and portable welding. Supply voltage range - up to 24 volts.

Appearance of the device this moment Not good. He has not yet acquired a body. (I quote the author).
The author assembled it for testing, therefore appearance Let's not pay attention.

Judging by the photographs, it burns right through the blade of the knife. This means that the contact of such welding is beyond doubt.

The push-pull circuit is very popular. An autogenerator, about which the author has many videos, there is no point in explaining the principle of its operation.

This device diagram was created using the service.

Materials and tools:

Two powerful field keys

Pulse transformer from a computer power supply.

Resonant capacitor 1-2uF X 300+ Volts.

The device is turned on using a weak button.

Soldering iron, rosin, solder, textolite.
Copper wires.
Throttle.

The operating frequency of the device depends on the inductance of the primary winding

and the capacitance of the resonant capacitor.

A satisfactory frequency range is from 20 to 50 kHz. Of course, if below 20K then we fall into the audible frequency range.

The greater the capacitance of the capacitor, the higher the current in the primary winding.

The author does not recommend installing capacitors with a capacity higher than two microfarads.
Then the frequency of the device will fall into the audio range.
This will result in a nasty whistling noise from the transformer.
IRFP150 transistors, analogs can also be used, with a current of 40A and a voltage of more than 50V.

The author recommends using keys in the TO247 housing. TO220 is also possible.
We attach a small radiator to the transistors. In the form of a plate.

We must isolate the keys themselves from the radiator.
The throttle is a must. It is wound into two one and a half millimeter wires.

The number of turns ranges from 10 to 30 pieces.

The power pulse transformer was confiscated from a classic ATX 450W computer power supply.

We remove the factory windings. To do this, I recommend heating it with a hair dryer.
So, the rewound primary consists of two loops of four turns each.