It is possible to save on the purchase of a semi-automatic welding machine if you assemble it yourself. At the same time, you can get high-quality welding for critical structures, for example, a car, which will in no way be inferior to an expensive device bought in a store. Do-it-yourself welding equipment is available for high-quality welding and obtaining strong joints.

Semiautomatic option No. 1 "Assemble from scratch"

The scheme below has been tested, several welding machines have been assembled and successfully operating according to it, which have been buzzing uninterruptedly for more than one year. You can cook with or without carbon dioxide.
The above diagram is specially simplified so that even a beginner who does not have special knowledge can handle the assembly.

The power transformer Tr1 is wound on a 10A laboratory autotransformer. We leave the primary winding of the trance unchanged, but the conclusions for adjusting the current are located after fifteen turns. The secondary consists of two windings of thirty turns
Inductor L1 can be wound on a frame from a television transformer with a copper bus in two windings of thirty turns each)
Trans Tr2 pick which one you find at 13V, three-ampere.
M2 engine - for supplying an electrode-wire, you can take it from the wipers of an old car.
M1 engine - fan from the system unit (computer) - cooling system.
R4 - wire movement regulator.
The relay for turning on the power transformer can be omitted, it is also possible to do without a relay for the brake system of the feed motor.

Option number 2. We take as a basis the MMA welder.

As a basis in a homemade semiautomatic device, you can take an ordinary inverter direct current for domestic work which is not expensive. For example, the MINIONE inverter is suitable for this purpose.

Avrora Minione 1600

You need to assemble a rectifier for the minivan, which consists of powerful diodes, a choke and a powerful capacitor with a capacity of about 50 microfarads. Purchase a hose, broaching mechanism, which is sold separately. As a brake for a coil with filler material, you can take an ordinary rubber band from an old tape recorder (if there is one on the farm). It is necessary so that when the feed stops, the coil does not continue its rotation on its own.

welding wire 08G2S

To power the wire feed regulator, you can use a circuit that consists of automotive relays, a 12V power supply used for ceiling lighting, a DC rectifier (diode block). The regulator is connected to an electric motor that rotates the coil. The whole structure can be fixed in metal frame and cook with pleasure! A huge plus is that the inverter, which is used as a base for a home-made semi-automatic machine, can always be removed and used as a regular MMA welding.

Semi-automatic welding made by hand from improvised means. The semi-automatic welding machine can be used to repair vehicles, build a greenhouse frame, and manufacture metal products.

The welding semiautomatic device is applied in different areas: in construction, in mechanical engineering, in the manufacture of metal structures and in installation work.

Selection rules

Preliminary it is recommended to choose a gun and a cylinder of carbon dioxide. Shielding gas can be used if desired. Experts recommend considering the features of the functioning of the mechanism that feeds the wire. Before deciding how to make a semi-automatic welding machine, you should find out its components. Pistol and canister necessary elements welding machine. Experts advise to carefully approach the choice of a gas cylinder. Initially, you can use a carbon dioxide fire extinguisher, but such a replacement is short-lived.

With the help of a gun, the wire wound from the reel is fed to the welding zone. This device is connected to a hose that supplies gas. The substance is supplied to the nozzle of the gun by means of an electromagnetic valve, which is triggered by the short circuit of the wire in contact with the surface of the gun.

A gun for a homemade welding machine is chosen based on personal preferences. Experts do not recommend purchasing cheap devices in which a low-quality gas hose is installed. Semi-automatic welding machines can be equipped with a CO2 gas system. In the operation of this equipment, the use of gas is necessary in order to obtain high-quality seams. Carbon dioxide is supplied to the welding area, which protects it from the effects of nitrogen and oxygen. The seams made by the apparatus with gas contain little slag.

Gas welding can be replaced with flux-cored wire. The advantages of this system are the absence of the need for gas and the speed of the work process, but the quality of the seams is low. Gas protection necessary if high demands are placed on products.

The apparatus that feeds the wire can be assembled using the windshield wiper motor in cars. A roller is put on the shaft. It can be prevented from sliding along the drive roller if the structure is additionally pressed with a firmly fixed satellite roller.

Welding, for which semi-automatic welding is used, requires the use of a rectifier. It is chosen depending on the method of winding the corresponding transformer. The manufacture of a welding machine with 2 windings will require the use of 2 diodes "DL161-200". A bridge rectifier circuit will require 4 diodes. A capacitor (30000x63V) helps smooth out voltage ripples.

In a DC circuit, in order to enhance the stability of the arc after the rectifier diodes, it is necessary to install a choke wound on the transformer core with about 20 turns of wire. The core section is 35x35 mm. The diameter of the wire must not be less than that used for the secondary winding in the transformer. The power supply of the electric motor, which is used in the wire feeder, comes from a power supply in which the current is 5 A and the output voltage reaches 12-15 V.

Welding semiautomatic devices are additionally equipped with:

• electromagnetic start for inclusion;
• electrovalve for gas;
• wire feed sleeve.

Additional work

Do-it-yourself semi-automatic machines can be of high quality and reliable if all the nuances are thought out. You can adjust the wire feed speed during the operation of the welding machine using a variable resistor. The gas supply valve will open synchronously with the switching on of the transformer of the apparatus after pressing the "Start" button.

The scheme according to which the semiautomatic device will be made by hand can be changed taking into account the available parts.

The rectifier block contains:

• throttle;
• bridge rectifier (200 A);
• an electrolytic capacitor with a capacity of 22,000 microfarads or more (63 V).

The inductor is necessary to filter the variable component of the device. When using the transformer "TC - 270", 60 turns of the winding are sufficient. To one end of the throttle of the welding machine, it is necessary to connect the “+” of the rectifier, and to the other end of the “+” of the capacitor and a cable that will supply the “+” of the rectifier, which is equipped with a semi-automatic welding machine, to the wire. The gun must be wired to one of the valve contacts. The minus of the rectifier and the 2nd contact of the valve must be connected to the product.

Make a semi-automatic welding machine yourself without extra costs it is possible using the solenoid valve from the Zhiguli car. By pressing the button, the master will be able to turn on the MPP, the wire will be fed to the gun head, closing the circuit of the electrovalve, which is responsible for the gas supply. The supply of the substance supply valve and the MPP motor is carried out using an additional transformer (200 V). It is recommended to close access to the “stuffing” of the device in order to welding work were safe.

visibility 893 views

On sale you can see a lot of semi-automatic welding machines of domestic and foreign production, used in the repair of car bodies. If you wish, you can save on costs by assembling a semi-automatic welding machine in a garage.

Wire feed speed controller for semi-automatic welding

The set of the welding machine includes a housing, in the lower part of which a single-phase or three-phase power transformer is installed, a device for drawing a welding wire is located above.

The device includes a DC electric motor with a gear reduction mechanism, as a rule, an electric motor with a gearbox from a UAZ or Zhiguli windshield wiper is used here. The copper-plated steel wire from the feed drum, passing through the rotating rollers, enters the wire feed hose, at the exit the wire comes into contact with a grounded product, the resulting arc welds the metal. To isolate the wire from atmospheric oxygen, welding takes place in an inert gas environment. To turn on the gas installed solenoid valve. When using the prototype of the factory semiautomatic device, some shortcomings were revealed in them that prevent high-quality welding. This is a premature overload failure of the output transistor of the motor speed controller circuit and the absence of an automatic engine brake on the stop command in the budget circuit. The welding current disappears when it is turned off, and the engine continues to feed the wire for some time, which leads to excessive consumption of the wire, the risk of injury, and the need to remove excess wire with a special tool.

More than modern scheme wire feed regulator, the fundamental difference of which from the factory ones is the presence of a braking circuit and a two-fold margin of the switching transistor in terms of starting current with electronic protection.

Part circuit diagram The wire feed controller includes a current amplifier based on a powerful field-effect transistor. A stabilized speed setting circuit allows you to maintain power in the load regardless of the mains supply voltage, overload protection reduces the burning of the motor brushes during start-up or jamming in the wire feeder and the failure of the power transistor.

The braking circuit allows almost instantly stop the rotation of the motor.

The supply voltage is used from a power or separate transformer with a power consumption not lower than the maximum power of the wire pulling motor.

The circuit includes LEDs for indicating the supply voltage and the operation of the electric motor.

Device characteristic:

• supply voltage, V — 12…16;
• electric motor power, W - up to 100;
• braking time, sec - 0.2;
• start time, sec - 0.6;
• adjustment
• revolutions,% - 80;
• starting current, A - up to 20.

Step 1. Description of the semi-automatic welding regulator circuit

The electrical circuit diagram of the device is shown in fig. 1. The voltage from the motor speed controller R3 through the limiting resistor R6 is supplied to the gate of a powerful field-effect transistor VT1. The speed controller is powered by an analog stabilizer DA1, through a current-limiting resistor R2. To eliminate interference, possible from turning the slider of the resistor R3, a filter capacitor C1 is introduced into the circuit.
The HL1 LED indicates the on state of the welding wire feed regulator circuit.

Resistor R3 sets the feed rate of the welding wire to the place of arc welding.

Trimmer resistor R5 allows you to select best option regulation of the engine rotation speed depending on its modification of power and voltage of the power source.

Diode VD1 in the voltage regulator circuit DA1 protects the chip from breakdown if the polarity of the supply voltage is reversed.
The field effect transistor VT1 is equipped with protection circuits: a resistor R9 is installed in the source circuit, the voltage drop across which is used to control the voltage at the gate of the transistor, using the comparator DA2. At a critical current in the source circuit, the voltage through the tuning resistor R8 is supplied to the control electrode 1 of the comparator DA2, the anode-cathode circuit of the microcircuit opens and reduces the voltage at the gate of the transistor VT1, the speed of the motor M1 will automatically decrease.

To eliminate the operation of protection against impulse currents that occur when the brushes of the electric motor spark, capacitor C2 is introduced into the circuit.
A wire feed motor is connected to the drain circuit of the transistor VT1 with circuits for reducing the sparking of the collector C3, C4, C5. A circuit consisting of a VD2 diode with a load resistor R7 eliminates the reverse current pulses of the motor.

The two-color LED HL2 allows you to control the state of the electric motor: with a green glow - rotation, with a red glow - braking.

The braking circuit is made on the electromagnetic relay K1. The capacitance of the filter capacitor C6 is chosen to be small - only to reduce the vibration of the armature of relay K1, a large value will create inertia when braking the electric motor. Resistor R9 limits the current through the relay coil when increased voltage power source.

The principle of operation of braking forces, without the use of reverse rotation, is to load the reverse current of the electric motor during rotation by inertia, when the supply voltage is turned off, to a constant resistor R11. Recuperation mode - transferring energy back to the network allows you to a short time stop the motor. At a complete stop, the speed and reverse current will be set to zero, this happens almost instantly and depends on the value of the resistor R11 and capacitor C5. The second purpose of the capacitor C5 is to eliminate the burning of contacts K1.1 of relay K1. After applying mains voltage to the control circuit of the regulator, relay K1 will close the circuit K1.1 of the electric motor power supply, the drawing of the welding wire will resume.

The power supply consists of a network transformer T1 with a voltage of 12 ... 15 V and a current of 8 ... 12 A, the diode bridge VD4 is selected for a double current. If there is a semi-automatic secondary winding of the corresponding voltage on the welding transformer, power is supplied from it.

Step 2. Details of the semi-automatic welding regulator circuit

The wire feed regulator circuit is made on printed circuit board from one-sided fiberglass with a size of 136 * 40 mm (Fig. 2), except for the transformer and the motor, all parts are installed with recommendations for possible replacement. The field effect transistor is mounted on a radiator with dimensions of 100 * 50 * 20 mm.

Field-effect transistor analogue of IRFP250 with a current of 20 ... 30 A and a voltage above 200 V. Resistors of the MLT type 0.125; resistors R9, R11, R12 - wire. Resistors R3, R5 set type SP-ZB. The type of relay K1 is indicated on the diagram or No. 711.3747-02 for a current of 70 A and a voltage of 12 V, they have the same dimensions and are used in VAZ vehicles.

Comparator DA2, with a decrease in speed stabilization and transistor protection, can be removed from the circuit or replaced with a KS156A zener diode. The VD3 diode bridge can be assembled on Russian diodes of the D243-246 type, without radiators.

The DA2 comparator has a complete analogue of foreign-made TL431CLP.

Solenoid valve for inert gas supply Em.1 - regular, for a supply voltage of 12 V.

Step 3. Adjustment of the semi-automatic welding regulator circuit

The adjustment of the wire feed regulator circuit of the semi-automatic welding machine begins with checking the supply voltage. Relay K1, when voltage appears, should operate, having a characteristic click of the armature.

By increasing the voltage at the gate of the field-effect transistor VT1 with the speed controller R3, check that the speed starts to grow at the minimum position of the resistor R3 slider; if this does not happen, correct the minimum speed with the resistor R5 - first set the engine of the resistor R3 to the lower position, with a smooth increase in the value of the resistor R5, the engine should gain minimum speed.

Overload protection is set by resistor R8 during forced braking of the motor. When the field-effect transistor is closed by the comparator DA2 during overload, the HL2 LED will go out. Resistor R12 at a power supply voltage of 12 ... 13 V can be excluded from the circuit.
The scheme has been tested on different types electric motors with similar power, the braking time mainly depends on the mass of the armature, due to the inertia of the mass. Heating of the transistor and diode bridge does not exceed 60°C.

The printed circuit board is fixed inside the body of the semi-automatic welding machine, the engine speed control knob - R3 is displayed on the control panel along with indicators: HL1 on and a two-color engine operation indicator HL2. Power is supplied to the diode bridge from a separate winding of the welding transformer with a voltage of 12 ... 16 V. The inert gas supply valve can be connected to capacitor C6, it will also turn on after the mains voltage is applied. The power supply of power networks and electric motor circuits is to be carried out with a stranded wire in vinyl insulation with a cross section of 2.5 ... 4 mm2.

Starting circuit of the welding semiautomatic device

Characteristics of the semi-automatic welding machine:

• supply voltage, V - 3 phases * 380;
• primary phase current, A - 8 ... 12;
• secondary open circuit voltage, V — 36…42;
• no-load current, A - 2 ... 3;
• open circuit voltage of the arc, V - 56;
• welding current, A - 40 ... 120;
• voltage regulation, % — ±20;
• switching on duration, % - 0.

The wire is fed into the welding zone in the semi-automatic welding machine using a mechanism consisting of two steel rollers rotating in opposite directions by an electric motor. To reduce the speed, the electric motor is equipped with a gearbox. From the conditions of smooth adjustment of the wire feed speed, the rotation speed of the DC electric motor is additionally changed by the semiconductor wire feed speed controller of the semi-automatic welding machine. An inert gas, argon, is also supplied to the welding zone to eliminate the effect of atmospheric oxygen on the welding process. The mains supply of the semi-automatic welding machine is made from a single-phase or three-phase mains, a three-phase transformer is used in this design, recommendations for power supply from a single-phase network are indicated in the article.

Three-phase power allows the use of a smaller cross-section winding wire than when using a single-phase transformer. During operation, the transformer heats up less, the voltage ripple at the output of the rectifier bridge decreases, and the power line is not overloaded.

Step 1. Operation of the semi-automatic welding start circuit

The connection of the power transformer T2 to the mains is switched by triac switches VS1 ... VS3 (Fig. 3). The choice of triacs instead of a mechanical starter allows you to eliminate emergency situations when contacts break and eliminates the sound from the "clapping" of the magnetic system.
Switch SA1 allows you to disconnect the welding transformer from the network during maintenance work.

The use of triacs without radiators leads to their overheating and arbitrary switching on of the semi-automatic welding machine, so triacs must be equipped with budget radiators 50 * 50 mm.

It is recommended to equip the semi-automatic welding machine with a 220 V fan, its connection is parallel to the mains winding of the T1 transformer.
A three-phase transformer T2 can be used ready-made, for a power of 2 ... 2.5 kW, or you can buy three transformers 220 * 36 V 600 VA, used for lighting basements and metal-cutting machines, connect them according to the star-star scheme. In the manufacture of a home-made transformer, the primary windings must have 240 turns of PEV wire with a diameter of 1.5 ... 1.8 mm, with three taps 20 turns from the end of the winding. The secondary windings are wound with a copper or aluminum bus with a cross section of 8 ... 10 mm2, the amount of PVZ wire is 30 turns.

Taps on the primary winding allow you to adjust the welding current depending on the mains voltage from 160 to 230 V.
Use in a single-phase circuit welding transformer allows the use of an internal electrical network used to power home electric furnaces with an installed power of up to 4.5 kW - the wire suitable for the outlet can withstand currents up to 25 A, there is grounding. The cross section of the primary and secondary windings of a single-phase welding transformer in comparison with a three-phase version should be increased by 2 ... 2.5 times. A separate ground wire is required.

Additional regulation of the welding current is carried out by changing the angle of the triac turn-on delay. The use of a semi-automatic welding machine in garages and summer cottages does not require special network filters to reduce impulse noise. When using a semi-automatic welding machine in living conditions it should be equipped with an external noise filter.

Smooth regulation of the welding current is carried out using an electronic unit on a silicon transistor VT1 with the button SA2 "Start" pressed - by adjusting the resistor R5 "Current".

The connection of the welding transformer T2 to the mains is carried out by the SA2 "Start" button located on the welding wire supply hose. The electronic circuit through the optocouplers opens the power triacs, and the mains voltage is supplied to the mains windings of the welding transformer. After the appearance of voltage on the welding transformer, a separate wire feed unit is turned on, the inert gas supply valve opens and when the wire coming out of the hose touches the workpiece to be welded, an electric arc is formed, the welding process begins.

Transformer T1 is used to power the electronic starting circuit of the welding transformer.

When mains voltage is applied to the anodes of triacs through an automatic three-phase machine SA1, a transformer T1 for supplying the electronic start-up circuit is connected to the line, the triacs are in the closed state at this time. The voltage of the secondary winding of the transformer T1, rectified by the diode bridge VD1, is stabilized by the analog stabilizer DA1, for stable operation of the control circuit.

Capacitors C2, C3 smooth out the ripple of the rectified supply voltage of the starting circuit. The triacs are turned on using the key transistor VT1 and triac optocouplers U1.1 ... U1.3.

The transistor opens with a positive polarity voltage from the DA1 analog stabilizer through the "Start" button. The use of low voltage on the button reduces the chance of injury to the operator high voltage mains, in case of violation of the insulation of wires. The current regulator R5 regulates the welding current within 20 V. Resistor R6 does not allow reducing the voltage on the mains windings of the welding transformer by more than 20 V, at which the level of interference in the mains increases sharply due to the distortion of the voltage sine wave by triacs.

Triac optocouplers U1.1 ... U1.3 perform galvanic isolation of the power supply from the electronic control circuit, allow simple method adjust the opening angle of the triac: the greater the current in the optocoupler LED circuit, the smaller the cutoff angle and the greater the current of the welding circuit.
The voltage to the control electrodes of the triacs is supplied from the anode circuit through the triac of the optocoupler, the limiting resistor and the diode bridge, synchronously with the mains phase voltage. Resistors in optocoupler LED circuits protect them from overload at maximum current. The measurements showed that when starting at the maximum welding current, the voltage drop across the triacs did not exceed 2.5 V.

With a large spread in the turn-on slope of triacs, it is useful to shunt their control circuits to the cathode through a resistance of 3 ... 5 kOhm.
An additional winding is wound on one of the rods of the power transformer to power the wire feed unit with an alternating current of 12 V, the voltage to which should be supplied after the welding transformer is turned on.

The secondary circuit of the welding transformer is connected to a three-phase DC rectifier on diodes VD3…VD8. Installation of powerful radiators is not required. The circuits for connecting the diode bridge with the capacitor C5 should be made with a copper bus with a cross section of 7 * 3 mm. The inductor L1 is made on iron from the power transformer of tube TVs of the TC-270 type, the windings are previously removed, and in their place a winding with a cross section of at least 2 times the secondary is wound, until full. Between the halves of the transformer iron of the throttle, lay a gasket made of electrical cardboard.

Step 2. Installation of the semi-automatic welding start circuit

The starting circuit (Fig. 3) is mounted on a circuit board (Fig. 4) with a size of 156 * 55 mm, except for the elements: VD3 ... VD8, T2, C5, SA1, R5, SA2 and L1. These elements are fixed on the body of the semi-automatic welding machine. The circuit does not contain display elements, they are included in the wire feed unit: the on indicator and the wire feed indicator.

Power circuits are made with an insulated wire with a cross section of 4 ... 6 mm2, welding circuits - with a copper or aluminum bus, the rest - with a wire in vinyl insulation with a diameter of 2 mm.

The polarity of the holder connection should be selected based on the conditions of welding or surfacing when working with metal with a thickness of 0.3 ... 0.8 mm.

Step 3. Adjustment of the start-up circuit of the semi-automatic welding machine

The adjustment of the starting circuit of the semi-automatic welding machine begins with a voltage check of 5.5 V. When the "Start" button on the capacitor C5 is pressed, the open circuit voltage must exceed 50 V DC, under load - at least 34 V.

On the cathodes of the triacs, relative to the zero of the network, the voltage should not differ by more than 2 ... 5 V from the voltage at the anode, otherwise replace the triac or optocoupler of the control circuit.

If the mains voltage is low, switch the transformer to low voltage taps.

When setting up, safety precautions must be observed.

Download printed circuit boards:

Welding semi-automatic functional device, which can be purchased ready-made or made from. It should be noted that the manufacture of a semi-automatic apparatus from an inverter device is not an easy task, but it can be solved if desired. Those who set themselves such a goal should study the principle of operation of a semiautomatic device well, look at thematic photos and videos, and prepare everything necessary equipment and accessories.

What is required to convert the inverter into a semi-automatic

To remake the inverter, making it a functional semi-automatic welding machine, you must find the following equipment and additional components:

• inverter machine capable of generating a welding current of 150 A;
• a mechanism that will be responsible for feeding the welding wire;
• the main working element is a burner;
• a hose through which the welding wire will be fed;
• hose for supplying shielding gas to the welding area;
• a coil with welding wire (such a coil will need to be subjected to some alterations);
• an electronic unit that controls the operation of your homemade semi-automatic device.

Special attention should be devoted to the alteration of the feeder, due to which the welding wire is fed into the welding zone, moving along a flexible hose. In order for the weld to be of high quality, reliable and accurate, the speed of wire feed through the flexible hose must match the speed of its melting.

Since when welding using a semiautomatic device, wire from different materials and different diameters, its feed rate must be regulated. It is this function - the regulation of the welding wire feed speed - that the feeding mechanism of the semiautomatic device should perform.

Internal layout Wire spool Wire feeder (view 1)
Wire feed mechanism (view 2) Attaching the welding sleeve to the feed mechanism Construction of a homemade torch

The most common wire diameters used in semi-automatic welding are 0.8; one; 1.2 and 1.6 mm. Before welding, the wire is wound on special coils, which are prefixes of semi-automatic devices, fixed on them with the help of simple structural elements. During the welding process, the wire is fed automatically, which significantly reduces the time spent on such a technological operation, simplifies it and makes it more efficient.

The main element of the electronic circuit of the semi-automatic control unit is a microcontroller, which is responsible for regulating and stabilizing the welding current. It is from this element of the electronic circuit of the semi-automatic welding machine that the parameters of the operating current and the possibility of their regulation depend.

How to remake an inverter transformer

In order for the inverter to be used for a homemade semiautomatic device, its transformer must be subjected to some alterations. It is not difficult to do such an alteration with your own hands, you just need to follow certain rules.

In order to bring the characteristics of the inverter transformer in line with those required for a semiautomatic device, it should be wrapped with a copper strip, on which a thermal paper winding is applied. It must be borne in mind that for these purposes it is impossible to use an ordinary thick wire, which will be very hot.

The secondary winding of the inverter transformer also needs to be redone. To do this, do the following: wind a winding consisting of three layers of tin, each of which must be insulated with a fluoroplastic tape; solder the ends of the existing winding and the hand-made winding to each other, which will increase the conductivity of the currents.

The design used to include it in a semi-automatic welding machine must necessarily provide for the presence of a fan, which is necessary for effective cooling of the device.

Setting the inverter used for semi-automatic welding

If you decide to make a semi-automatic welding machine with your own hands, using an inverter for this, you must first de-energize this equipment. To prevent such a device from overheating, its rectifiers (input and output) and power switches should be placed on radiators.

In addition, in that part of the inverter housing where the radiator is located, which heats up more, it is best to mount a temperature sensor, which will be responsible for turning off the device if it overheats.

After all the above procedures are completed, you can connect the power part of the device to its control unit and connect it to the electrical network. When the mains indicator lights up, connect an oscilloscope to the outputs of the inverter. Using this device, it is necessary to find electrical impulses with a frequency of 40–50 kHz. The time between the formation of such pulses should be 1.5 μs, which is regulated by changing the voltage value supplied to the input of the device.

It is also necessary to check that the pulses reflected on the oscilloscope screen have rectangular shape, and their front was no more than 500 ns. If all checked parameters correspond to the required values, then the inverter can be connected to the electrical network. The current coming from the output of the semiautomatic device must have a strength of at least 120 A. If the current strength is less, this may mean that a voltage is supplied to the equipment wires, the value of which does not exceed 100 V. In the event of such a situation, the following must be done: test the equipment by changing the current (in this case, it is necessary to constantly monitor the voltage on the capacitor). In addition, the temperature inside the device should be constantly monitored.

After the semi-automatic has been tested, it is necessary to check it under load. To make such a check, a rheostat is connected to the welding wires, the resistance of which is at least 0.5 ohms. Such a rheostat must withstand a current of 60 A. The current supplied to the welding torch in this situation is controlled using an ammeter. If the current strength when using a load rheostat does not correspond to the required parameters, then the resistance value of this device is selected empirically.

How to use a welding inverter

After starting the semi-automatic device that you assembled with your own hands, the current value of 120 A should appear on the inverter indicator. If everything is done correctly, then it will happen. However, the inverter display may show eights. The reason for this is most often insufficient voltage in the welding wires. It is better to immediately find the cause of such a malfunction and promptly eliminate it.

If everything is done correctly, then the indicator will correctly show the strength of the welding current, which is regulated using special buttons. The adjustment interval for the operating current, which is provided, is in the range of 20–160 A.

How to control the correct operation of the equipment

So that the semi-automatic welding machine that you assembled with your own hands serves you long time, it is better to constantly monitor temperature regime inverter operation. To implement such control, it is necessary to press two buttons simultaneously, after which the temperature of the hottest radiator of the inverter will be displayed on the indicator. Normal operating temperature the one whose value does not exceed 75 degrees Celsius is considered.

If this value is exceeded, then, in addition to the information displayed on the indicator, the inverter will emit an intermittent sound signal, which should be immediately paid attention to. In this case (as well as in case of breakage or short circuit of the thermal sensor) electronic circuit The device will automatically reduce the operating current to 20A, and an audible signal will be emitted until the equipment returns to normal. In addition, a malfunction of DIY equipment may be indicated by an error code (Err) displayed on the inverter indicator.

A semi-automatic welding machine is a fairly popular device among professional and home craftsmen, especially those involved in body repair. This unit can be purchased ready-made. But many owners of inverter welding machines are wondering: is it possible to convert the inverter into a semiautomatic device so as not to buy another welder? Making a semiautomatic device from an inverter with your own hands is a rather difficult task, but with a strong desire it is quite feasible.

To assemble the unit, you will need the following items:

• inverter welding machine;
• burner, as well as a special flexible hose, inside which a gas pipeline passes, a wire guide, power cable and electrical control cable;
• mechanism for uniform automatic wire feed;
• control module, as well as a motor speed controller (PWM controller);
• protective gas cylinder (carbon dioxide);
• solenoid valve for cutting off gas;
• coil with electrode wire.

To assemble a home-made semiautomatic device from a welding inverter, the latter must generate a welding current of at least 150 A. But it will have to be slightly upgraded, since the current-voltage characteristics (CVC) of the inverter are not suitable for welding with electrode wire in a shielding gas environment.

But more on that later. First you need to make the mechanical part of the semiautomatic device, namely the wire feed mechanism.

Wire feed mechanism

Since the feeder will be placed in a separate box, it is ideal for this purpose. computer system case. In addition, you do not need to throw away the power supply. It can be adapted to the operation of the broach mechanism.

First, you need to measure the diameter of the wire spool or, having outlined it on paper, cut out a circle and insert it into the body. There must be enough space around the reel to accommodate other components (power supply, hoses and wire feeder).

The wire pulling device is made from a windshield wiper mechanism from a car. Under it, it is necessary to design a frame that will also hold the pressure rollers. The layout must be drawn on thick paper in real scale.

Advice! The connector for connecting the burner hose and the hose with the burner itself can be made by hand. But it would be better to buy ready kit which has an affordable price.

The feeder should be installed in the housing so that the connector is in a convenient location.

In order for the wire to be fed evenly, all components must be fixed exactly opposite each other. The rollers must be centered in relation to the hole for the inlet fitting, which is located in the connector for connecting the hose.

as roller guides use suitable diameter bearings. on them with lathe a small groove is machined along which the electrode wire will move. For the body of the mechanism, you can use plywood 6 mm thick, textolite or durable sheet plastic. All elements are fixed on the basis, as shown in the following photo.

Used as primary wire guide axially drilled bolt. The result is something like a wire extruder. At the inlet of the fitting, a cambric reinforced with a spring is put on (for rigidity).

The rods on which the rollers are fixed are also spring-loaded. The clamping force is set using a bolt located below, to which the spring is attached.

Advice! If for some reason you do not have the opportunity to make a wire pulling mechanism with your own hands, then you can buy it in China. 12 V and 24 V mechanisms are available for sale. This case, since you are using a power supply from a computer, you will need a device powered by 12 V.

The basis for fixing the bobbin can be made from a small piece of plywood or textolite and trimmed plastic pipe suitable diameter.

Mechanics control scheme

To achieve good quality seam when welding, it is necessary to ensure the wire feed with a certain and constant speed. Since the motor from the wiper is responsible for the feed rate of the equipment, a device is needed that can change the speed of rotation of its armature. Suitable for this turnkey solution, which is also available in China and is called

Below is a diagram from which it becomes clear how the speed controller is connected to the engine. The regulator of the controller with a digital display is displayed on the front panel of the case.

Next, you need to install relay control gas valve . It will also control the start of the engine. All of these elements must be activated by pressing the start button located on the burner handle. In this case, the gas supply to the place of welding should be ahead (by about 2-3 seconds) of the start of the wire feed. Otherwise, the arc will ignite in the environment atmospheric air, and not in a shielding gas environment, as a result of which the electrode wire will melt.

A delay relay for a homemade semiautomatic device can be assembled based on the 815th transistor and capacitor. To get a pause of 2 seconds, a 200-2500 uF capacitor will be enough.

Advice! Since the power comes from a computer PSU that outputs 12 V, instead of self-manufacturing module, you can use an automotive relay.

It is placed in any place where it will not interfere with the operation of moving parts, and is connected to the circuit according to the diagram. You can use an air valve from GAZ 24 or buy a special one designed for semiautomatic devices. The valve is responsible for the automatic supply of shielding gas to the burner. It turns on after pressing the start button located on the semi-automatic burner. The presence of this element significantly saves gas consumption.

But as already noted, the current-voltage characteristics (CVC) of the inverter are not suitable for the full operation of the semiautomatic device. Therefore, in order for the semi-automatic prefix to work in tandem with an inverter, in its wiring diagram minor changes are required.

Changing the I-V characteristic of the inverter

There are many schemes to change the I-V characteristic of an inverter, but the easiest way to do this is as follows:

• assemble the device using choke from the lamp daylight according to the scheme below;

• to connect the assembled device, you will need to assemble another block according to the following scheme;

• In order to prevent the inverter from triggering the overheating sensor, an optocoupler must be soldered (in parallel) to it, as shown in the following diagram.

But if the welding current is controlled in the inverter with a shunt, then you can assemble a simple circuit of three resistors and a mode switch, as shown below.

As a result, the conversion of a welding inverter into a semiautomatic device will cost 3 times cheaper than an already finished unit. But of course, for self assembly the device will need to have certain knowledge in the radio business.