Battery spot welding machine. Arduino based spot welder Features of making a timing relay timer for spot welding on arduino board

An acquaintance came, brought two LATRs and asked if it was possible to make a spotter out of them? Usually, upon hearing such a question, an anecdote comes to mind about how one neighbor is interested in another, whether he knows how to play the violin and in response he hears “I don’t know, I haven’t tried” - and so I have the same answer - I don’t know , probably "yes", but what is a "spotter"?

In general, while the tea was boiling and brewing, I listened to a short lecture about how you shouldn't do what you don't need to do, that you need to be closer to the people and then people will reach out to me, and also briefly plunged into the history of auto repair shops, illustrated by savory stories from the life of "chiropractors" and "tinsmiths". Then I realized that a spotter is such a small "welder", working on the principle of an apparatus spot welding... It is used to "grip" metal washers and other small fasteners to the dented car body, with the help of which the deformed sheet is then straightened. True, there is still a "reverse hammer" needed, but they say that this is no longer my concern - all that is required from me is the electronic part of the circuit.

Having looked at the spotter schemes on the net, it became clear that we needed a one-shot that would "open" on a short time triac and supply mains voltage to the power transformer. The secondary winding of the transformer should provide a voltage of 5-7 V with a current sufficient to "grip" the washers.

To form a control pulse for the triac, different ways- from a simple discharge of a capacitor to the use of microcontrollers with synchronization to the phases of the mains voltage. We are interested in the simpler circuit - let it be "with a capacitor".

Searches "in the nightstand" showed that apart from passive elements, there are suitable triacs and thyristors, as well as many other "little things" - transistors and relays for different operating voltages ( fig. 1). It's a pity that there are no optocouplers, but you can try to assemble a capacitor discharge pulse converter into a short "rectangle" that turns on a relay, which will open and close the triac with its closing contact.

Also, during the search for parts, several power supplies with output constant voltages from 5 to 15 V were found - they chose an industrial one from the "Soviet" times called BP-A1 9V / 0.2A ( fig. 2). With a load in the form of a 100 Ohm resistor, the power supply produces a voltage of about 12 V (it turned out that it was already redone).

We choose from the available electronic "garbage" triacs TS132-40-10, a 12-volt relay, take several KT315 transistors, resistors, capacitors and begin to model and check the circuit (on fig. 3 one of the configuration steps).

The result is shown in Figure 4... Everything is quite simple - when you press the S1 button, the capacitor C1 begins to charge and a positive voltage appears on its right terminal, equal to the supply voltage. This voltage, having passed through the current-limiting resistor R2, enters the base of the transistor VT1, which opens and voltage is supplied to the coil of relay K1, and as a result, the contacts of relay K1.1 are closed, opening the triac T1.

As the capacitor C1 is charged, the voltage at its right terminal gradually decreases and when a level is less than the opening voltage of the transistor, the transistor will close, the relay winding will be de-energized, the opened contact K1.1 will stop supplying voltage to the control electrode of the triac and it will close at the end of the current half-wave of the mains voltage ... Diodes VD1 and VD2 stand to limit the arising impulses when the S1 button is released and when the relay K1 winding is de-energized.

In principle, everything works this way, but when controlling the open time of the triac, it turned out that it "walks" quite strongly. It would seem that even taking into account possible changes in all on-off delays in electronic and mechanical circuits, it should be no more than 20 ms, but in fact it turned out many times more and plus to this, the pulse lasts 20-40 ms longer, and then for all 100 ms.

After some experiments, it turned out that this change in the pulse width is mainly associated with a change in the supply voltage level of the circuit and with the operation of the transistor VT1. The first was "cured" by installing a simple parametric stabilizer, consisting of a resistor, a zener diode and a power transistor ( fig. 5). And the cascade on the VT1 transistor was replaced by a Schmitt trigger on 2 transistors and the installation of an additional emitter follower. The diagram took the form shown in Figure 6.

The principle of operation remains the same, added the ability to discretely change the pulse duration by switches S3 and S4. The Schmitt trigger is assembled on VT1 and VT2, its "threshold" can be changed within small limits by changing the resistances of the resistors R11 or R12.

When prototyping and checking the operation of the electronic part of the spotter, several diagrams were taken, according to which it is possible to estimate the time intervals and the resulting delays of the fronts. In the circuit at that time there was a timing capacitor with a capacity of 1 μF and resistors R7 and R8 had a resistance of 120 kΩ and 180 kΩ, respectively. On Figure 7 the top shows the state on the relay winding, below - the voltage across the contacts when switching the resistor connected to +14.5 V random coefficients divisions, so the "Volts" scale is not true). The duration of all pulses of the relay power supply was approximately 253 ... 254 ms, the contact switching time was 267 ... 268 ms. "Expansion" is associated with an increase in the shutdown time - this can be seen from Figures 8 and 9 when comparing the difference that occurs when the contacts are closed and opened (5.3 ms versus 20 ms).

To check the temporal stability of the formation of pulses, four consecutive switches were carried out with control of the voltage in the load (file in the same appendix). On a generalized Figure 10 it can be seen that all the pulses in the load are quite close in duration - about 275 ... 283 ms and depend on the place of the mains voltage half-wave at the moment of switching on. Those. the maximum theoretical instability does not exceed the time of one half-wave of the mains voltage - 10 ms.

When setting R7 = 1 kΩ and R8 = 10 kΩ at C1 = 1 μF, it was possible to obtain the duration of one pulse less than one half-cycle of the mains voltage. At 2 μF - from 1 to 2 periods, at 8 μF - from 3 to 4 (file in the appendix).

In the final version of the spotter, parts with the denominations indicated on the Figure 6... What happened on the secondary winding of the power transformer is shown in Figure 11... The duration of the shortest pulse (the first in the figure) is about 50 ... 60 ms, the second - 140 ... 150 ms, the third - 300 ... 310 ms, the fourth - 390 ... 400 ms (with a timing capacitor capacity of 4 μF, 8 μF, 12 μF and 16 μF).

After checking the electronics, it's time to do the hardware.

A 9-ampere LATR was used as a power transformer (right on rice. 12). Its winding is made with a wire with a diameter of about 1.5 mm ( fig. 13) and the magnetic core has an inner diameter sufficient for winding 7 turns from 3 parallel folded aluminum busbars with a total cross section of about 75-80 sq. mm.

We carry out the disassembly of the LATR carefully, just in case, we “fix” the entire construct in the photo and “copy” the conclusions ( fig. 14). It's good that the wire is thick - it is convenient to count the turns.

After disassembling, we carefully inspect the winding, clean it of dust, debris and graphite residues using a paint brush with a hard bristle and wipe it soft cloth slightly moistened with alcohol.

We solder a five-ampere glass fuse to terminal "A", connect the tester to the "middle" terminal of the coil "G" and supply 230 V to the fuse and the "nameless" terminal. The tester shows a voltage of about 110 V. Nothing hums and does not heat up - we can assume that the transformer is normal.

Then we wrap the primary winding with fluoroplastic tape with such an overlap so that at least two or three layers are obtained ( fig. 15). After that, we wind a test secondary winding of several turns with a flexible wire in isolation. Having applied power and measuring the voltage on this winding, we determine the right amount turns to obtain 6 ... 7 V. In our case, it turned out that when 230 V is applied to the terminals "E" and "unnamed" 7 V at the output is obtained at 7 turns. When power is applied to "A" and "unnamed", we get 6.3 V.

For the secondary winding used aluminum tires "well, very used" - they were removed from the old welding transformer and in some places they had no isolation at all. In order for the turns not to close among themselves, the tires had to be wrapped with a serpyanka tape ( fig. 16). The winding was carried out so that two or three layers of coating were obtained.

After winding the transformer and checking the operability of the circuit on the desktop, all the parts of the spotter were installed in a suitably sized case (it looks like it was also from some kind of LATR - fig. 17).

The terminals of the secondary winding of the transformer are clamped with bolts and nuts M6-M8 and brought out to the front panel of the case. These bolts on the other side of the dashboard hold the power wires going to the car body and the hammer back. Stage appearance home check shown on Figure 18... At the top left are the mains voltage indicator La1 and the main switch S1, and on the right is the pulse voltage switch S5. It switches the connection to the network or the "A" terminal, or the "E" terminal of the transformer.

Fig. 18

At the bottom are the connector for the S2 button and the terminals of the secondary winding. The pulse width switches are installed at the very bottom of the case, under hinged lid (fig. 19).

All other elements of the circuit are fixed on the bottom of the case and on the front panel ( fig. 20, fig. 21, fig. 22). It doesn't look very neat, but here the main task was to reduce the length of the conductors in order to reduce the influence of electromagnetic pulses on the electronic part of the circuit.

The printed circuit board was not divorced - all the transistors and their "strapping" are soldered to a breadboard made of fiberglass, with a foil cut into squares (visible on fig. 22).

Power switch S1 - JS608A, allowing switching of 10 A currents ("paired" outputs are paralleled). There was no second such switch and S5 was installed at TP1-2, its outputs are also paralleled (if you use it with the mains power off, it can pass quite large currents through itself). Pulse duration switches S3 and S4 - ТП1-2.

S2 button - KM1-1. Connector for connecting wires of the button - COM (DB-9).

Indicator La1 - ТН-0.2 in the corresponding installation fittings.

On Figures 23, 24 , 25 the photographs taken when checking the operability of the spotter are shown - a furniture corner with dimensions of 20x20x2 mm was point-welded to a tin plate 0.8 mm thick (fastening panel from the computer case). Different sizes"Patches" on fig. 23 and fig. 24- this is at different "cooking" voltages (6 V and 7 V). The furniture corner is welded tightly in both cases.

On fig. 26 the reverse side of the plate is shown and it can be seen that it warms up through and through, the paint burns and flies off.

After giving the spotter to a friend, he called about a week later, said that he had made a reverse "hammer", connected and checked the operation of the entire apparatus - everything is fine, everything is working. It turned out that long duration pulses are not needed in operation (ie, elements S4, C3, C4, R4 can be omitted), but there is a need to connect the transformer to the network “directly”. As I understand it, this is so that with the help of carbon electrodes it is possible to heat the surface of the dented metal. It is not difficult to make the power supply "directly" - they put a switch that allows you to close the "power" terminals of the triac. A little confused by the insufficiently large total cross-section of the veins in the secondary winding (according to calculations, more is needed), but since more than two weeks have passed, and the owner of the device has been warned about the “weakness of the winding” and does not call, then nothing terrible has happened.

During experiments with the circuit, a version of the triac was tested, assembled from two thyristors T122-20-5-4 (they can be seen on picture 1 on the background). The connection diagram is shown in fig. 27, diodes VD3 and VD4 - 1N4007.

Literature:

1. Goroshkov BI, "Electronic devices", Moscow, "Radio and communication", 1984.
2. Mass radio library, Ya.S. Kublanovsky, "Thyristor devices", M., "Radio and communication", 1987, issue 1104.

Andrey Goltsov, Iskitim.

List of radioelements

In some cases, instead of soldering, it is more profitable to use spot welding. For example, this method can be useful for repairing rechargeable batteries consisting of several batteries. Soldering causes the cells to heat up excessively, which can lead to cell failure. But spot welding does not heat up the elements so much, since it lasts for a relatively short time.

The Arduino Nano is used to optimize the whole process in the system. This is a control unit that allows you to effectively manage the power supply of the installation. Thus, each welding is optimal for a specific case, and energy is consumed as much as necessary, not more, and not less. The contact elements here are copper wire, and the energy comes from a conventional car battery, or two if more current is required.

The current project is almost perfect in terms of complexity / efficiency. The author of the project showed the main stages of creating a system, having laid out all the data on Instructables.

According to the author, a standard battery is sufficient for spot welding of two 0.15 mm thick nickel strips. For thicker strips of metal, two batteries are required in parallel. The pulse time of the welding machine is adjustable and ranges from 1 to 20 ms. This is sufficient for welding the nickel strips described above.

The author recommends making the payment to order from the manufacturer. The cost of ordering 10 such boards is about 20 euros.

Both hands will be engaged during welding. How do you manage the entire system? With a footswitch, of course. It's very simple.

And here is the result of the work:

Your attention is a diagram welding inverter, which you can assemble with your own hands. The maximum current consumption is 32 amperes, 220 volts. The welding current is about 250 amperes, which allows you to cook without problems with a 5-wire electrode, the arc length is 1 cm, which passes more than 1 cm into low-temperature plasma. The efficiency of the source is at the level of the store, and maybe better (I mean inverter).

Figure 1 shows a diagram of a welding power supply.

Fig. 1 Schematic diagram power supply

The transformer is wound on a Sh7x7 or 8x8 ferrite
The primary device has 100 turns of 0.3mm PEV wire
Secondary 2 has 15 turns of PEV wire 1mm
Secondary 3 has 15 turns of PEV 0.2mm
Secondary 4 and 5 with 20 turns of wire PEV 0.35mm
All windings must be wound across the entire width of the frame, this gives a noticeably more stable voltage.

Fig. 2 Schematic diagram of a welding inverter

Figure 2 shows a diagram of a welder. The frequency is 41 kHz, but you can try 55 kHz. The 55kHz transformer is then 9 turns by 3 turns, to increase the PV of the transformer.

41kHz transformer - two sets Ш20х28 2000nm, gap 0.05mm, newspaper gasket, 12vit x 4vit, 10kv mm x 30 sq mm, copper tape (tin) in paper. The transformer windings are made of copper sheet 0.25 mm thick and 40 mm wide wrapped for insulation in paper from cash register... The secondary is made of three layers of tin (sandwich) separated by fluoroplastic tape, for isolation between themselves, for better conductivity of high-frequency currents, the contact ends of the secondary at the output of the transformer are soldered together.

The L2 choke is wound on a Ш20х28 core, ferrite 2000nm, 5 turns, 25 sq. Mm, a gap of 0.15 - 0.5mm (two layers of paper from the printer). Current transformer - current sensor two rings K30x18x7 primary wire threaded through the ring, secondary 85 turns wire 0.5mm thick.

Assembly of welding

Transformer winding

The winding of the transformer must be done using copper sheet 0.3mm thick and 40mm wide, it must be wrapped with 0.05mm thick thermal paper from the cash register, this paper is strong and does not tear as usual when winding a transformer.

You tell me, why not wind it with an ordinary thick wire, but not because this transformer operates on high-frequency currents and these currents are displaced onto the surface of the conductor and does not use the middle of the thick wire, which leads to heating, this phenomenon is called Skin effect!

And you have to fight with it, you just need to make a conductor with a large surface, this thin copper sheet has this and it has a large surface through which the current flows, and the secondary winding should consist of a sandwich of three copper tapes separated by a fluoroplastic film, it is thinner and all these are wrapped layers into thermal paper. This paper has the property of darkening when heated, we don’t need it and it’s bad, from this, let the main thing remain that does not break.

You can wind the windings with a PEV wire with a cross section of 0.5 ... 0.7 mm, consisting of several tens of cores, but this is worse, since the wires are round and dock with each other with air gaps, which slow down heat transfer and have a smaller total cross-sectional area of ​​the wires combined in comparison with sheet metal by 30%, which can fit the windows of the ferrite core.

It is not the ferrite that heats up at the transformer, but the winding, so you need to follow these recommendations.

The transformer and the entire structure must be blown inside the case by a 220 volt 0.13 ampere or more fan.

Design

To cool all powerful components, it is good to use heatsinks with fans from old Pentium 4 and Athlon 64 computers. I got these heatsinks from a computer store doing upgrades, for only $ 3 ... 4 apiece.

The power oblique bridge must be done on two such radiators, the upper part of the bridge on one, the lower part on the other. Screw the bridge diodes HFA30 and HFA25 onto these radiators through a mica gasket. IRG4PC50W must be screwed without mica through KTP8 heat-conducting paste.

The leads of the diodes and transistors must be screwed to meet each other on both radiators, and between the leads and the two radiators, insert a board that connects the 300-volt power circuit with the bridge parts.

The diagram does not indicate it is necessary to solder 12 ... 14 pieces of capacitors of 0.15mk 630 volts to this board in the 300V power supply. This is necessary so that the transformer surges go into the power circuit, eliminating the resonant current surges of the power switches from the transformer.

The rest of the bridge is connected to each other by surface mounting with short conductors.

The diagram also shows snubbers, they have capacitors C15 C16, they must be of the K78-2 or SVV-81 brand. You cannot put any garbage there, since snubbers play an important role:
the first- they muffle the resonant emissions of the transformer
second- they significantly reduce the losses of IGBTs when turning off, since IGBTs open quickly, but close much slower and during closing, the capacitance C15 and C16 is charged through the VD32 VD31 diode longer than the closing time of the IGBT, that is, this snubber intercepts all the power on itself, preventing heat from escaping on the IGBT key three times than it would have been without it.
When the IGBT is fast open, then through the resistors R24 R25 the snubbers are smoothly discharged and the main power is allocated on these resistors.

Customization

Supply power to the PWM 15 volts and at least one fan to discharge the capacitance C6, which controls the response time of the relay.

Relay K1 is needed to close the resistor R11, after the capacitors C9 ... 12 are charged through the resistor R11, which reduces the current surge when the welding is switched on to the 220 volt network.

Without resistor R11 for a straight line, when turned on, a large BAC would have been obtained during charging a capacity of 3000mk 400V, for this this measure is needed.

Check the operation of the relay closing the resistor R11 2 ... 10 seconds after the power is applied to the PWM board.

Check the PWM board for the presence of square-wave pulses going to the HCPL3120 optocouplers after both relays K1 and K2 are triggered.

The pulse width should be the width relative to the zero pause 44% zero 66%

Check the drivers on optocouplers and amplifiers driving a square-wave signal with an amplitude of 15 volts, make sure that the voltage on the IGBT gates does not exceed 16 volts.

Apply 15 Volt power to the bridge to check its operation for the correct manufacture of the bridge.

In this case, the consumption current should not exceed 100mA at idle.

Verify the correct phrasing of the power transformer and current transformer windings using a two-beam oscilloscope.

One beam of the oscilloscope is on the primary, the second on the secondary, so that the phases of the pulses are the same, the difference is only in the voltage of the windings.

Apply power to the bridge from power capacitors C9 ... C12 through a 220volt 150..200W light bulb, having previously set the PWM frequency to 55kHz, connect the oscilloscope to the collector emitter of the lower IGBT transistor to look at the waveform so that there are no voltage surges above 330 volts as usual.

Start downgrade clock frequency PWM until a small bend appears on the lower IGBT key indicating transformer oversaturation, record this frequency at which the bend occurred, divide it by 2 and add the result to the oversaturation frequency, for example, 30kHz oversaturation is divided by 2 = 15 and 30 + 15 = 45, 45 is and there is the operating frequency of the transformer and the PWM.

The current consumption of the bridge should be about 150mA and the lamp should barely glow, if it glows very brightly, this indicates a breakdown of the transformer windings or an incorrectly assembled bridge.

Connect at least 2 meters of welding wire to the output to create additional output inductance.

Apply power to the bridge already through the 2200 watt kettle, and set the current strength to the PWM at least R3 closer to the resistor R5 on the light bulb, close the welding output, check the voltage on the lower key of the bridge so that there is no more than 360 volts on the oscilloscope, while there should be no noise from the transformer. If there is one, make sure that the current transformer is correctly phased, pass the wire in the opposite direction through the ring.

If the noise remains, then you need to place the PWM board and the driver on the optocouplers away from the noise sources, mainly the power transformer and the L2 choke and the power conductors.

Even when assembling the bridge, the drivers must be installed next to the radiators of the bridge over the IGBT transistors and no closer to the resistors R24 R25 by 3 centimeters. The connections between the driver output and the IGBT gate should be short. The conductors from the PWM to the optocouplers should not run close to sources of interference and should be as short as possible.

All signal wires from the current transformer and going to the optocouplers from the PWM should be twisted to reduce the noise level and should be as short as possible.

Then we begin to increase the welding current with the help of the resistor R3 closer to the resistor R4, the welding output is closed on the key of the lower IGBT, the pulse width increases slightly, which indicates PWM operation. More current - more width, less current - less width.

There shouldn't be any noise, otherwise they will failIGBT.

Add current and listen, watch the oscilloscope for overvoltage of the lower key, so as not to exceed 500 volts, maximum 550 volts in the surge, but usually 340 volts.

To reach the current, where the width sharply becomes the maximum, it is said that the kettle cannot give the maximum current.

Everything, now we go straight without a kettle from minimum to maximum, watch the oscilloscope and listen so that it is quiet. Reach the maximum current, the width should increase, emissions are normal, not more than 340 volts usually.

Start cooking, at the beginning 10 seconds. We check the radiators, then 20 seconds, also cold and 1 minute the transformer is warm, burn 2 long electrodes 4mm bitter transformer

Radiators of 150ebu02 diodes noticeably warmed up after three electrodes, it is already hard to cook, a person gets tired, although it is great to cook, the transformer is hot, and no one else is cooking. The fan, after 2 minutes, the transformer brings to a warm state and you can cook again until it drops.

Below you can download printed circuit boards in LAY format and other files

Evgeny Rodikov (evgen100777 [dog] rambler.ru). If you have any questions when assembling the welder, write to E-Mail.

List of radioelements

The timer of the time relay is a device with which you can adjust the time of exposure to current, impulse. Timer timer for spot welding measures the duration of exposure welding current on the parts to be connected, the frequency of its occurrence. This device is used for automation welding processes, production of a weld, in order to create various designs from sheet metal... It controls the electrical load in accordance with a given program. Time relay is programmed for contact welding in strict accordance with the instructions. This process consists in setting the time intervals between certain actions, as well as the duration of the welding current.

Principle of operation

This time relay for spot welding will be able to turn on and off the device in a predetermined mode at a certain frequency on a constant basis. In simpler terms, it carries out the closing and opening of contacts. The rotation sensor is used to set the time intervals in minutes and seconds after the expiration of which it is necessary to enable or disable welding.

The display serves to display information about the current switch-on time, the period of exposure to the metal of the welding machine, the number of minutes and seconds before switching on or off.

Types of timers for spot welding

Timers with digital or analogue programming can be found on the market. The relays used in them are different types but the most common and inexpensive are electronic devices. Their principle of operation is based on a special program that is written on a microcontroller. It can be used to adjust the delay or turn-on time.

Time relays are currently available for purchase:

• with shutdown delay;
• delayed to turn on;
• adjusted for the set time after energizing;
• set for the set time after the impulse has been given;
• clock generator.

Time relay accessory

To create a timer relay for spot welding, you will need the following parts:

• Arduino Uno board for programming;
• prototyping board or Sensor shield - provides easy connection, installed sensors with a board;
• female-to-female wires;
• a display that can display at least two lines with 16 characters in a row;
• relay that switches the load;
• a steering angle sensor equipped with a button;
• power supply for supplying the device electric shock(during testing, you can power it via USB cable).

Features of creating a timer relay timer for spot welding on arduino board

For its manufacture, you must clearly follow the scheme.

At the same time, it would be better to replace the frequently used arduino uno board with the arduino pro mini, since it has a significantly smaller size, costs less and, at the same time, it is much easier to solder the wires.

After collecting all component parts timer for contact welding on arduino, you need to solder the wires that connect the board to the rest of the elements of this device. All elements must be cleaned of plaque and rust. This will significantly increase the operating time of the relay timer.

You need to choose a suitable case and collect all the elements in it. It will provide the device with a decent appearance, protection against accidental shock and mechanical stress.

At the end, it is necessary to install the switch. It will be needed if the owner of the welding decides to leave it unattended for a long time in order to prevent fire, damage to property in case of emergencies. With its help, leaving the premises, any user can without special efforts disconnect the device.

"Note!

The 561 resistance welding timer is a more advanced device, as it is created on a new modern microcontroller. It allows you to more accurately measure the time, set the frequency of turning on and off the device. "

The 555 resistance welding timer is not as perfect and has a limited functionality. But it is often used to create such devices, since it is cheaper.

To better understand how to create welding machine it is worth contacting the employees of the company. In addition, we propose to consider the scheme for creating this device. It will help you understand the principle of operation of the device, what and where to solder.

Conclusion

The timer for spot welding on arduino is an accurate and high-quality device that, with proper use, will last for many years. He is enough simple device, so it can be easily mounted on any welding. In addition, the spot welding timer is easy to maintain. It works even in severe frost, it is practically not affected by negative manifestations of the natural environment.

You can assemble the device yourself or contact the professionals. The latter option is more preferable, since it is guaranteed to provide the final result. The company will test the elements of the device, identify problems, eliminate them, thus restoring its operability.