Adjusting rheostat for wire feed in semi-automatic machines. How to set up a semi-automatic welding machine

landscaping 15.06.2019

landscaping

Semi-automatic welding is very convenient device for work at home and in small workshops. You can work with it in any conditions, no special preparation of the workplace is required, it is compact almost like a conventional inverter.

Unlike manual arc welding, for work with it high qualification of the welder is not required. Correct setting welding semiautomatic device allows you to perform high-quality work and a low-skilled welder.

Depending on the type of material to be welded, its thickness, it is necessary to correctly set the wire feed speed, shielding gas. Further, the welder needs to evenly drive the torch along the seam, and a high-quality weld will be obtained. All the difficulty lies in correct selection welding parameters for a specific material.

For a high-quality setting of a semiautomatic welding machine, an understanding of the characteristics of welding is required, it is also necessary to understand the features of a semiautomatic device.

Semi-automatic welding machines allow you to work with almost any metals and their alloys. They can weld non-ferrous and ferrous metals, low carbon and alloy steel, aluminum and coated materials, are capable of welding up to 0.5 mm thick, can weld even galvanized steel without damaging the coating.

This is achieved due to the fact that flux, flux-cored wire or shielding gas, as well as welding wire can be fed into the welding area, and the supply is automatic, everything else is done as in manual arc welding.

Semi-automatic welding machines are produced in different classes, but they all consist of:

control unit;
power supply;
welding wire feeder with coil;
welding torch;
power cables.

In addition, there must be a cylinder with a reducer and an inert gas (carbon dioxide, argon or mixtures thereof), a flux funnel.

The wire feed mechanism consists of an electric motor, a gearbox and feed or pull rollers.

Before performing work, it is necessary to securely ground the welding machine and only then start setting up. The semi-automatic welding machine must be connected to a gas-balloon system with protective gas.

It is necessary to check the presence of the welding wire in the coil, if necessary, recharge it and stretch it to the torch handle. The gas supply rate has great importance during the welding process.

Therefore, it also needs to be installed. LPG equipment has reducers indicating gas consumption in liters. This is very convenient, you just need to set the required flow rate within 6-16 liters.

The operating instructions for the device give recommendations on how to properly set up a semi-automatic welding machine, what current to cook a particular metal, and at what speed to feed the wire.

The instructions should have special tables in which everything is described. If you set all the parameters in accordance with them, then everything should work out.

In practice, there can be difficulties. A lot of parameters influence the quality of semi-automatic welding. If the supply network does not meet the standards, then the power supply will produce the wrong voltage and current, the parameters will be unstable.

The temperature of the environment, the thickness of the metal, its type, the condition of the surfaces to be welded, the type of seam, the diameter of the wire, the volume of gas supply and many other factors affect the quality of the semi-automatic welding.

Setting the current and wire feed speed

First of all, the strength of the welding current is set, which depends on the type of material being welded and the thickness of the workpieces. This can be found in the instructions for the semi-automatic or found in the relevant literature.

Then the wire feed speed is set. It can be adjusted stepwise or continuously. With stepwise adjustment, it is not always possible to select optimal mode work. If it is possible to choose a device, buy a semi-automatic welding machine with continuously variable wire feed speed.

The control box must have a wire feed forward/reverse switch. When all the settings have been made in accordance with the operating instructions for the semiautomatic device, you need to try working on a draft sample with the same parameters. This must be done because the recommendations are averaged, and in each individual case the conditions are unique.

At high speed the wire supply, the electrode simply will not have time to melt, there will be large deposits or shifts from above, and at low it will burn out without melting the metal being welded, the weld bead will sag, depressions or breaks will appear.

Parameter adjustment

The adjustment of the current or voltage depends on the thickness of the workpieces. The thicker the work piece, the greater the welding current. In simple devices semi-automatic welding current adjustment is combined with wire feed speed.

In professional semiautomatic devices, the adjustments are separate. The correctness of the setting can only be determined empirically by making an experimental seam on a test piece. The roller must be of normal shape, the arc is stable, without spatter.

In some models of semi-automatic devices, there is an adjustment of the inductance (arc settings). With a small inductance, the temperature of the arc drops, the depth of penetration of the metal decreases, the seam becomes convex.

This is used when welding thin metals and alloys that are sensitive to overheating. With a large inductance, the melting temperature rises, the weld pool becomes more liquid and deep. The seam bead becomes flat. Welding in this mode is used for thick workpieces.

The wire feed speed switch in models capable of working with different diameters requires additional adjustment taking into account the specific thickness of the wire.

Having set the optimal settings for welding the workpiece today, it may turn out that the next day they will become suboptimal because the quality of the network has changed or the position of the workpiece on the work table has changed.

That is, setting the modes is a permanent and individual process, because it also depends on the manner of work of the welder himself.

Common Mistakes

A distinct crack indicates an error in the settings of the semi-automatic welding machine. Loud clicks indicate that the solder feed rate is low. It is necessary to increase the feed rate until the crack disappears.

Heavy spattering of the metal is often observed. This is due to insufficient insulating gas in the area of the weld pool. It is necessary to increase the gas supply, adjust the semi-automatic gearbox.

There are lack of penetration or seam burns. Is it due to being too low or too high voltage arc, adjustable by setting the voltage or inductance.

The uneven width of the weld bead is related to the speed of the torch and its position relative to the seam, that is, it is related to the technique of the welder.

Some people think that it is not worth buying expensive welding machines when you can assemble them yourself. At the same time, such installations can work no worse than factory ones and have fairly good quality indicators. In addition, in the event of a breakdown of such a unit, it is possible to independently and quickly eliminate the breakdown. But in order to assemble such a device, you should be thoroughly familiar with the basic principles of operation and the constituent elements of a semi-welding machine.

semi-welding machine transformer

First of all, it is necessary to determine the type of semi-automatic welding machine and its power. The power of the semiautomatic device will be determined by the operation of the transformer. If threads with a diameter of 0.8 mm are used in the welding machine, then the current flowing in them can be at the level of 160 amperes. Having made some calculations, we decide to make a transformer with a power of 3000 watts. After the power for the transformer is selected, its type should be selected. Best for this the device is suitable a transformer with a toroidal core, on which the windings will be wound.

If you use the most popular W-shaped core, then the semiautomatic device will become much heavier, which will be a minus for the welding machine as a whole, which will need to be constantly transferred to different objects. In order to make a transformer with a power of 3 kilowatts, you will need to wind the winding on an annular magnetic circuit. Initially, the primary winding should be wound, which starts with a voltage of 160 V in steps of 10 V and ends at 240 V. In this case, the wire must be at least 5 square meters in size. mm.

After the winding of the primary winding is completed, the second winding should be wound over it, but this time it is necessary to use a wire with a cross section of 20 sq. mm. The voltage value on this winding will be on the reading of 20 V. By this creation, it is possible to provide 6 steps of current regulation, one mode of standard operation of the transformer and two types of passive operation of the transformer.

Adjustment of the semi-welding machine

To date, there are 2 types of current adjustment through the transformer: on the primary and secondary windings. The first is the regulation of the current on the primary winding, carried out using a thyristor circuit, which often has many disadvantages. One of these is a periodic increase in the pulsation of the welding machine and the phase transition of such a circuit from the thyristor to the primary winding. Adjusting the current through the secondary winding also has a number of disadvantages when using a thyristor circuit.

In order to eliminate them, you will have to use compensating materials, which will make the assembly much more expensive, and besides, the device will become much heavier. After analyzing all these factors, we can conclude that the current regulation should be carried out along the primary winding, and the choice of the circuit to be applied remains with the creator. To ensure the desired regulation on the secondary winding, you need to install a smoothing choke, which will be combined with a 50 mF capacitor. This setting should be done regardless of the scheme you use, which will ensure efficient and trouble-free operation of the automatic welding machine.

Wire feed adjustment

As with many other welding machines, it is best to use pulse-width modulation with feedback control. What gives PWM? This type modulation will normalize the speed of the wire, which will be adjusted and set depending on the friction that is created by the wire and the landing of the device. In this case, there is a choice between feeding the PWM controller, which can be carried out by a separate winding or fed from a separate transformer.

The latter option will result in more expensive scheme, but this difference in cost will be insignificant, but at the same time, the device will gain a little weight, which is a significant disadvantage. Therefore, it is best to apply the first option. But if it is necessary to weld extremely carefully, at a small current, then, consequently, the voltage and current passing in the wire will be just as small. In case of great value current, the winding must create the appropriate voltage value and transmit it to your regulator.

Thus, an additional winding can fully satisfy the needs of a potential user in the maximum current value. Having become acquainted with this theory, we can conclude that the installation of an additional transformer is extra cost money, and the desired mode can always be supported by an additional winding.

Drive Wheel Diameter Calculations for Wire Feeder

Through practice, it has been determined that the unwinding speed of the welding wire can reach values from 70 centimeters to 11 meters per minute, with a wire diameter of 0.8 mm. We do not know the subordinate value and the speed of rotation of the parts, therefore, calculations should be made according to the available data on the unwinding speed. To do this, it is best to do a small experiment, after which it is possible to determine right amount revolutions. Turn on the equipment at full power and count how many revolutions it makes per minute.

To accurately catch the turn, fasten a match or ribbon to the anchor so you know where the circle ended and began. After your calculations are done, you can find out the radius using the formula familiar from school: 2piR \u003d L, where L is the length of the circle, that is, if the device makes 10 revolutions, you need to divide 11 meters by 10, and you get an unwinding of 1.1 meter. This will be the length of the unwind. R is the radius of the anchor, and it must be calculated. The number "pi" should be known from school, its value is 3.14. Let's take an example. If we counted 200 revolutions, then by calculation we determine the number L = 5.5 cm. Next, we calculate R = 5.5 / 3.14 * 2 = 0.87 cm. So, the required radius will be 0.87 cm.

Functionality of a semi-welding machine

Best done with minimum set functions such as:

The initial supply of carbon dioxide into the tube, which will first fill the tube with gas and only then supply a spark.
After pressing the button, wait about 2 seconds, after which the wire feed automatically turns on.
Simultaneous shutdown of current with wire feed when you release the control button.
After all that has been done above, it is necessary to stop the gas supply with a delay of 2 seconds. This is done in order to prevent the metal from oxidizing after cooling.

In order to assemble the welding wire feed motor, you can use the wiper gearbox from many domestic cars. At the same time, do not forget that the minimum amount of wire that should be pulled out per minute is 70 centimeters, and the maximum is 11 meters. These values must be followed when choosing an anchor for winding out the wire.

The gas supply valve is best chosen among the water supply mechanisms from all the same domestic cars. But it is very important to ensure that this valve does not leak after some time, which is very dangerous. If you choose everything correctly and correctly, the device under normal operation can last about 3 years, while it will not be necessary to repair it many times, as it is quite reliable.

Welding semiautomatic device: scheme

The scheme of the semi-automatic welding machine provides all the points of functionality and makes the semi-automatic welding machine very convenient to use. In order to set the manual mode, the switch relay SB1 must be closed. After you have pressed the control button SA1, turn on the switch K2, which, using its connections K2.1 and K2.3, will turn on the first and third keys.

Next, the first key activates the supply of carbon dioxide, while the key K1.2 starts to turn on the power supply circuits of the semi-automatic welding machine, and K1.3 completely turns off the engine brake. At the same time, during this process, relay K3 begins to interact with its contacts K3.1, which, by its action, turns off the power supply circuit of the engine, and K3.2 unbends K5. K5 in the open state provides a two-second delay in turning on the device, which must be selected using resistor R2. All these actions take place with the engine turned off, and only gas is supplied to the tube. After all this, the second capacitor turns off the second switch with its impulse, which serves to delay the supply of welding current. After that, the welding process itself begins. The reverse process when releasing SB1 is similar to the first one, while providing a delay of 2 seconds to turn off the gas supply of the semi-automatic welding machine.

Ensuring the automatic mode of the semi-automatic welding

First you need to familiarize yourself with what the automatic mode is for. For example, it is necessary to weld a rectangular layer of a metal alloy, while the work must be perfectly even and symmetrical. If you use the manual mode, then the plate will have a seam with a different thickness along the edges. This will cause additional difficulties, since it will be necessary to align it to the desired size.

If you use the automatic mode, then the possibilities increase a little. To do this, you need to set the welding time and amperage, and then try your welding on some unnecessary object. After checking, you can make sure that the seam is suitable for welding the structure. After that, we turn on the desired mode again and start welding your metal sheet.

When you turn on the automatic mode, use the same SA1 button, which will carry out all processes like manual welding, with the only discrepancy that you will not need to hold this button to put it into operation, and all switching on will be provided by the C1R1 chain. It will take from 1 to 10 seconds for the full performance of this mode. Work this mode very simple, for this you need to press the control button, after which welding is turned on.

After the time set by the resistor R1 has elapsed, the welding machine will turn off the flame itself.

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.

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 the welding wire is located above.

The device includes an electric motor direct current with a gear reduction mechanism, as a rule, an electric motor with a gearbox from a UAZ or Zhiguli car 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 a prototype of a factory semi-automatic device, they revealed some shortcomings that prevent high-quality welding: premature failure of the output transistor of the motor speed controller circuit due to overload; the absence in the budget scheme of the engine braking machine on the stop command - the welding current disappears when it is turned off, and the engine continues to feed the wire for some time, this leads to excessive wire consumption, the risk of injury, 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.

Device Specifications:

2. Electric motor power - up to 100 watts.

3. Deceleration time 0.2 sec.

4. Start time 0.6 sec.

5. Speed control 80%.

6. Starting current up to 20 amperes.

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.

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 transistor VT1 with collector spark reduction circuits 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 the 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 R8. 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 resistor R11 and capacitor C5. The second purpose of capacitor C5 is to eliminate the burning of contacts K1.1 of relay K1. After supplying the 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 volts and a current of 8-12 amperes, the VD4 diode bridge is selected for 2x current. If there is a semi-automatic secondary winding of the corresponding voltage on the welding transformer, power is supplied from it.

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

Field-effect transistor analogue of IRFP250 with a current of 20-30 Amperes and a voltage above 200 Volts. Resistors type MLT 0.125, R9, R11, R12 - wire. Install the resistor R3, R5 of the type SP-3 B. The type of relay K1 is indicated on the diagram or No. 711.3747-02 for a current of 70 Amperes and a voltage of 12 Volts, their dimensions are the same 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 TL431 CLP.

The solenoid valve for inert gas supply Em.1 is standard, for a supply voltage of 12 volts.

Adjustment of the circuit of the wire feed regulator of the welding semiautomatic device Start by 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, adjust the minimum speed with the resistor R5 - first set the slider of the resistor R3 to the lower position, with a gradual increase in the value of the resistor K5, the engine should gain minimum speed.

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. The heating of the transistor and the diode bridge does not exceed 60 degrees Celsius.

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 welding transformer voltage 12-16 volts. An inert gas supply valve can be connected to capacitor C6 and will also be switched on after mains voltage is applied. Power supply of power networks and electric motor circuits should be performed with a stranded wire in vinyl insulation with a cross section of 2.5-4 mm.kv.

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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. A solenoid valve is installed to turn on the gas. 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.

In the laboratory "Automation and Telemechanics" of the Irkutsk Regional CDTT, a more modern circuit of the wire feed regulator has been developed, the fundamental difference of which from the factory ones is the presence of a braking circuit and a double supply of the switching transistor in terms of starting current with electronic protection.

The circuit diagram of the wire feed controller includes a current amplifier 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 choose the best option for controlling the engine speed, depending on its power modification and power supply voltage.

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 small - only to reduce the vibration of the armature of the relay K1, a large value will create inertia when braking the motor. Resistor R9 limits the current through the relay winding when the power supply voltage is increased.

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. Recovery mode - transferring energy back to the network allows you to stop the motor in a short time. 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 a printed circuit board made of single-sided fiberglass with a size of 136 * 40 mm (Fig. 2), except for the transformer and 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.

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 of 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 electrical network, 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 the 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.
The use of a single-phase welding transformer in the circuit 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 electronic circuit start welding transformer.

When the mains voltage is applied to the anodes of the triacs through the automatic three-phase machine SA1, the 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 likelihood of an operator being struck by high voltage from the mains in the event of a wire insulation failure. 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 during start-up at 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 TS-270 type, the windings are previously removed, and in their place a winding with a cross section of at least 2 times the secondary one 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:

The reliability of modern semiautomatic devices often fails the wire feed speed controller of the welding semiautomatic device; the circuit is not always reliable and mechanical

some also often fail.

A malfunction of this unit leads to significant malfunctions in the operation of the semi-automatic device, loss of working time and hassle with the replacement of the welding wire. The wire at the outlet of the tip is stuck, you have to remove the tip and clean the contact part for the wire. A malfunction is observed with any diameter of the used welding wire. Or a large feed may occur when the wire comes out in large portions when the power button is pressed.

Malfunctions are often caused by the mechanical part of the wire feed regulator itself. Schematically, the mechanism consists of a pressure roller with an adjustable degree of wire pressure, a feed roller with two grooves for wire 0.8 and 1.0 mm. A solenoid is mounted behind the regulator, which is responsible for shutting off the gas supply with a delay of 2 seconds.

The feed regulator itself is very massive and is often simply fixed on the front panel of the semiautomatic device with 3-4 bolts, essentially hanging in the air. This leads to distortions of the entire structure and frequent malfunctions. Actually, "curing" this drawback is quite simple by installing some kind of stand under the wire feed regulator, thereby fixing it in its working position.

On factory-made semi-automatic devices, in most cases (regardless of the manufacturer), carbon dioxide is supplied to the solenoid through a dubious thin hose in the form of a cambric, which simply “dubes” from cold gas and then cracks. It also causes work to stop and needs repair. Masters, based on their experience, advise replacing this supply hose with an automotive hose used to supply brake fluid from the reservoir to the brake master cylinder. The hose perfectly withstands pressure and will serve indefinitely.

The industry produces semiautomatic devices with a welding current of about 160 A. This is enough when working with automotive iron, which is quite thin - 0.8-1.0 mm. If you have to weld, for example, elements of 4 mm steel, then this current is not enough and the penetration of the parts is not complete. For these purposes, many masters purchase an inverter, which, together with a semi-automatic device, can produce up to 180A, which is quite enough for a guaranteed weld of parts.

Many try with their own hands, through experiments, to eliminate these shortcomings and make the operation of the semiautomatic device more stable. Quite a lot of schemes and possible improvements of the mechanical part have been proposed.

One of those proposals. This, modified and tested in the work, the wire feed speed controller of the semi-automatic welding circuit is proposed on the integral stabilizer 142EN8B. Thanks to the proposed scheme of operation of the wire feed regulator, it delays the feed for 1-2 seconds after the gas valve is triggered and slows it down as quickly as possible when the power button is released.

The downside of the circuit is the decent power given off by the transistor, heating the cooling radiator in operation up to 70 degrees. But all this is plused by the reliable operation of both the wire feed speed controller itself and the entire semiautomatic device as a whole.

From this article you will learn where and for what welding processes an inverter semiautomatic device is used, as well as what are its disadvantages and advantages.

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Three-phase diesel generators

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Wire feed speed controller for semi-automatic welding

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.

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 the 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. A solenoid valve is installed to turn on the gas. When using a prototype of a factory semi-automatic device, they revealed some shortcomings that prevent high-quality welding: premature failure of the output transistor of the motor speed controller circuit due to overload; the absence in the budget scheme of the engine braking machine on the stop command - the welding current disappears when it is turned off, and the engine continues to feed the wire for some time, this leads to excessive consumption of the wire, the risk of injury, the need to remove excess wire with a special tool.

In the laboratory of "Automation and Telemechanics" of the Irkutsk Regional DTT Center, a more modern wire feed regulator circuit has been developed, the fundamental difference of which from the factory ones is the presence of a braking circuit and a double supply of the switching transistor for inrush current with electronic protection.

Device Specifications:
1. Supply voltage 12-16 volts.
2. Electric motor power - up to 100 watts.
3. Deceleration time 0.2 sec.
4. Start time 0.6 sec.
5. Speed control 80%.
6. Starting current up to 20 amperes.

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 transistor VT1 with collector spark reduction circuits 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 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 R8. Recovery mode - transferring energy back to the network allows you to stop the motor in a short time. At a complete stop, the speed and reverse current will be set to zero, this happens almost instantly and depends on the value of 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 supplying the 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 wire feed regulator circuit is made on a printed circuit board made of single-sided fiberglass with a size of 136 * 40 mm, except for the transformer and motor, all parts are installed with recommendations for possible replacement. The field-effect transistor is installed on a radiator with dimensions 100 * 50 * 20.

The DA2 comparator has a complete analogue of foreign-made TL431 CLP.
Solenoid valve for supplying inert gas Em.1 is standard, for a supply voltage of 12 volts.

The scheme has been tested on different types of electric motors, with similar power, the braking time mainly depends on the mass of the armature, due to the inertia of the mass. The heating of the transistor and the diode bridge does not exceed 60 degrees Celsius.

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. turning on HL1 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 volts. An inert gas supply valve can be connected to capacitor C6 and will also be switched on after mains voltage is applied. Power supply of power networks and electric motor circuits should be performed with a stranded wire in vinyl insulation with a cross section of 2.5-4 mm.kv.

List of radio elements

Vladimir 22.02.2012 08:54 #

The circuit does not ensure the maintenance of stable engine speed, regardless of the power in the load and the voltage in the network. To solve this problem, it is not enough to stabilize the gate voltage.
Limiting the current to 25A, according to the rating of R9, will not save anything. Even the resistor itself - 62.5 watts will be dissipated on it. But not for long ... There is no talk of a transistor.
Chain R7, VD2 is meaningless.
There is no recovery mode in the circuit. Quote: "... consists in the load of the reverse current of the electric motor during rotation by inertia ..." just a pearl.
Tellingly, there is no photo of the assembled board ...

Grigory T. 25.02.2012 13:37 #

Message from Vladimir

Limiting the current to 25A, according to the rating of R9, will not save anything.

And how do you like the fake trimmer R8?
There are too many blunders in the scheme to seriously discuss it.

Dmitry 26.02.2012 14:24 #

Yes, this scheme is complete crap, I assembled it a couple of months ago, only in vain I bred the board, there is nothing good in it. I assembled part of the regulator from the PSU on the LM358 and KT825, and I’m satisfied, the speed is regulated smoothly, and there is sufficient power at low speeds, the disadvantage is that it is necessary to remove heat from the transistor.

yuri 03/21/2012 17:32 #

I struggled with setting up this circuit for several days. If the engine starts, then the speed is regulated normally, but starting at low speed is a problem, there is not enough voltage, and if the variable is unscrewed all the way, then this is no longer adjusting the wire feed, but really just crap

Scheme of a semi-automatic welding machine

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 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

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

Trimmer resistor R5 allows you to choose the best option for controlling the engine speed, depending on its power modification and power supply voltage.

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 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. Recovery mode - transferring energy back to the network allows you to stop the motor in a short time. 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 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

Field-effect transistor analog IRFP250 with current 20. 30 A and voltage above 200 V. Resistors type MLT 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.

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

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 of 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.

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

Switching the connection of the power transformer T2 to the mains occurs with 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 the 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 homemade 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.

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 mains filters to reduce impulse noise. When using a semi-automatic welding machine in domestic 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".

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

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

Triac optocouplers U1.1. U1.3 perform galvanic isolation of the mains from the electronic control circuit, allow a simple method to 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 the triacs, it is useful to shunt their control circuit 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 VD3 diodes. 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 TS-270 type, the windings are previously removed, and in their place a winding with a cross section of at least 2 times the secondary one 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

On the cathodes of 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:

Source: Radio amateur 7 "2008

Pilot (yesterday, 01:32) wrote:

preference should be given to an engine with permanent magnets, since it has a pronounced dependence of the EMF on the rotor speed.

I would even say not just pronounced, but linear.

If we rotate the engine with something extraneous, like a generator, then some kind of voltage will appear on its outputs. If we apply the same voltage to this motor, then it will rotate at about the same speed as we rotated it. When the motor rotates, the back-emf that occurs in the armature is directed against the supply voltage and they are compensated.

In a real engine, when the shaft is loaded, the speed decreases due to the voltage drop on the ohmic resistance of the winding, this resistance is, as it were, connected in series between the power source and the ideal engine. By the way, if you feed a DCT with permanent magnets from a current source, then we get a stable torque on the shaft, this can also be useful. Yes, that's the resistance of the windings of the same motor from the wipers, very small and much less than the output resistance of a primitive source. With a good voltage stabilizer, they can be neglected. You can make a source with a negative output impedance, equal to the resistance windings, this is done, for example, in cassette recorders, stability will be better, but for our task this is IMHO, superfluous. As for the feedback from the tachogenerator, this task is not as simple as it seems at first glance.

Damn, what a stream of consciousness turned out, sorry.

And the scheme in the topic does not inspire confidence in me.

#17 Pilot

Members

339 messages

City: Cherkasy region Talnoe

Wire feed stabilization - diagram

Practice is good, but without theory it is useless. I will try to explain in a simplified way, why does the engine, with an increase in the load on the shaft, reduce the speed? According to the laws of physics, in order for the engine to deliver a certain power, it must consume the same power from the power source, taking into account the efficiency of the engine. Since the load on the engine is not constant in time (hose bending, wire sticking, etc.), it can be concluded from this that the supply voltage should change proportionally, depending on the load and stable rotor speed. A stabilized voltage source does not meet these conditions. Based on the above, I have developed a PWM motor speed stabilizer with hard feedback that meets all these requirements. The circuit is quite simple, although a bit complicated to set up. Details can be found here http://www.chipmaker. __1#entry709142

#18 dan_ko

Members

1447 messages

City Dnepropetrovsk

Wire feed stabilization - diagram

Pilot (today, 14:42) wrote:

from this we can conclude that the supply voltage should change proportionally, depending on the load

I would not make such a conclusion.

Depending on the load, the current consumed by the motor changes. Thus, the power consumption changes. Even if we make a full-fledged feedback from the tachometer, we will be surprised to find that in the entire range of loads, with constant speed, the voltage on the motor will change very little.

I will not discuss your scheme, so as not to produce flood and flame.

What is a diagram of a semi-automatic welding machine?

Semi-automatic welding device.

semi-welding machine transformer

First of all, it is necessary to determine the type of semi-automatic welding machine and its power. The power of the semiautomatic device will be determined by the operation of the transformer. If threads with a diameter of 0.8 mm are used in the welding machine, then the current flowing in them can be at the level of 160 amperes. Having made some calculations, we decide to make a transformer with a power of 3000 watts. After the power for the transformer is selected, its type should be selected. The best for such an apparatus is a transformer with a toroidal core, on which the windings will be wound.

Adjustment of the semi-welding machine

Welding semiautomatic device with thyristor control.

Wire feed adjustment

Diagram of a transformer with primary and secondary windings.

As with many other welding machines, it is best to use pulse-width modulation with feedback control. What gives PWM? This type of modulation will normalize the speed of the wire, which will be adjusted and set depending on the friction created by the wire and the landing of the device. In this case, there is a choice between feeding the PWM controller, which can be carried out by a separate winding or fed from a separate transformer.

With the latter option, a more expensive circuit will turn out, but this difference in cost will be insignificant, but at the same time the device will gain a little weight, which is a significant minus. Therefore, it is best to apply the first option. But if it is necessary to weld extremely carefully, at a small current, then, consequently, the voltage and current passing in the wire will be just as small. In the case of a large current value, the winding must create an appropriate voltage value and pass it to your regulator.

Thus, an additional winding can fully satisfy the needs of a potential user in the maximum current value. After reviewing this theory, we can conclude that installing an additional transformer is an extra cost of money, and the desired mode can always be supported by an additional winding.

Drive Wheel Diameter Calculations for Wire Feeder

Scheme for calculating the welding transformer.

Through practice, it has been determined that the unwinding speed of the welding wire can reach values from 70 centimeters to 11 meters per minute, with a wire diameter of 0.8 mm. We do not know the subordinate value and the speed of rotation of the parts, therefore, calculations should be made according to the available data on the unwinding speed. To do this, it is best to do a small experiment, after which it is possible to determine the required number of revolutions. Turn on the equipment at full power and count how many revolutions it makes per minute.

Functionality of a semi-welding machine

Characteristics of welding transformers.

It is best to do it with a minimum set of functions, such as:

The initial supply of carbon dioxide into the tube, which will first fill the tube with gas and only then supply a spark.
After pressing the button, wait about 2 seconds, after which the wire feed automatically turns on.
Simultaneous shutdown of current with wire feed when you release the control button.
After all that has been done above, it is necessary to stop the gas supply with a delay of 2 seconds. This is done in order to prevent the metal from oxidizing after cooling.

In order to assemble the welding wire feed motor, you can use the wiper gearbox from many domestic cars. At the same time, do not forget that the minimum amount of wire that should be unwound per minute is 70 centimeters, and the maximum is 11 meters. These values must be followed when choosing an anchor for winding out the wire.

Welding semiautomatic device: scheme

Ensuring the automatic mode of the semi-automatic welding

Scheme of the device of the welding inverter.

When you turn on the automatic mode, use the same SA1 button, which will carry out all processes like manual welding, with the only discrepancy that you will not need to hold this button to put it into operation, and all switching on will be provided by the C1R1 chain. It will take from 1 to 10 seconds for the full performance of this mode. The operation of this mode is very simple, for this you need to press the control button, after which welding is turned on.

After the time set by the resistor R1 has elapsed, the welding machine will turn off the flame itself.