Ultra-budget spot welding of lithium batteries at home. Do-it-yourself welding inverter Features of creating a time relay timer for spot welding on an arduino board

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

To optimize the entire process, the system uses Arduino Nano. This is a control unit that allows you to effectively manage the power supply of the installation. Thus, each welding is optimal for a particular case, and as much energy is consumed as needed, no more, no less. The contact elements here are a copper wire, and the energy comes from a conventional car battery, or two if more current is required.

The current project is almost ideal in terms of complexity of creation / efficiency of work. The author of the project showed the main stages of creating the system, posting all the data on Instructables.

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

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

During welding, both hands will be occupied. How to manage the whole system? With a footswitch, of course. It is very simple.

And here is the result of the work:

Hello, brain! I present to your attention a spot welding machine based on the Arduino Nano microcontroller.

This machine can be used to weld plates or conductors, for example, to 18650 battery contacts. For the project, we will need a 7-12V power supply (12V recommended), as well as a 12V car battery as a power source for the welding machine itself. Typically, a standard battery has a capacity of 45 Ah, which is sufficient for welding nickel plates with a thickness of 0.15 mm. To weld thicker nickel plates, you will need a larger battery or two connected in parallel.

The welding machine generates a double pulse, where the value of the first is 1/8 of the second in duration.
The duration of the second pulse is adjusted using a potentiometer and is displayed on the screen in milliseconds, so it is very convenient to adjust the duration of this pulse. Its adjustment range is from 1 to 20 ms.

Watch the video, which shows in detail the process of creating a device.

Step 1: PCB Fabrication

Eagle files can be used for PCB fabrication, which are available at the following .

The easiest way is to order boards from PCB manufacturers. For example, on the site pcbway.com. Here you can buy 10 boards for about 20 €.

But if you are used to doing everything yourself, then use the attached schematics and files to make a prototype board.

Step 2: Installing the Components on the Boards and Soldering the Wires

The process of installing and soldering components is quite standard and simple. Install small components first, then larger ones.
The tips of the welding electrode are made of solid copper wire with a section of 10 square millimeters. For cables, use flexible copper wires with a cross section of 16 square millimeters.

Step 3: Foot Switch

You will need a footswitch to control the welding machine as both hands are used to hold the welding electrode tips in place.

For this purpose, I took wooden box in which the above switch is installed.

Your attention is presented with a diagram of a 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 makes it possible to weld without problems with a 5th electrode, the arc length is 1 cm, which passes more than 1 cm into a low-temperature plasma. source efficiency at the store level, or maybe better (meaning inverter).

Figure 1 shows a diagram of a power supply for welding.

Fig.1 circuit diagram power supply

The transformer is wound on ferrite Ш7х7 or 8х8
The primary has 100 turns of PEV wire 0.3mm
Secondary 2 has 15 turns of 1mm PEV wire
Secondary 3 has 15 turns of PEV 0.2mm
Secondary 4 and 5, 20 turns of wire PEV 0.35mm
All windings must be wound across the entire width of the frame, this gives a significantly more stable voltage.

Fig.2 Schematic diagram of the welding inverter

Figure 2 is a diagram of a welder. Frequency - 41 kHz, but you can try 55 kHz. Transformer at 55 kHz then 9 turns by 3 turns, to increase the PV of the transformer.

Transformer for 41kHz - two sets of W20x28 2000nm, gap 0.05mm, newspaper gasket, 12w x 4w, 10kv mm x 30kv mm, copper tape (tin) in paper. The windings of the transformer are made of copper sheet 0.25 mm thick, 40 mm wide, wrapped for insulation in paper from the cash register. The secondary is made of three layers of tin (sandwich) separated from each other by a fluoroplastic tape, for isolation from each other, for better conductivity of high-frequency currents, the contact ends of the secondary at the output of the transformer are soldered together.

Inductor L2 is wound on a W20x28 core, ferrite 2000nm, 5 turns, 25 sq.mm, gap 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 0.5 mm thick.

Welding assembly

winding transformer

The winding of the transformer must be done using copper sheet with a thickness of 0.3mm and a width of 40mm, it must be wrapped with thermal paper from a cash register with a thickness of 0.05mm, 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 it’s impossible because this transformer operates on high-frequency currents and these currents are forced out to the surface of the conductor and does not use the middle of the thick wire, which leads to heating, this phenomenon is called the Skin effect!

And you have to fight it, you just need to make a conductor with a large surface, that’s what a thin copper plate has 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 wrapped all these layers in thermal paper. This paper has the property of darkening when heated, we don’t need it and it’s bad, it won’t let it go and the main thing will remain that it doesn’t tear.

It is possible to wind the windings with PEV wire with a cross section of 0.5 ... 0.7 mm, consisting of several dozen cores, but this is worse, since the wires are round and dock with each other with air gaps that slow down heat transfer and have a smaller total cross-sectional area of ​​\u200b\u200bwires taken together compared to tin by 30 %, which can fit the windows of the ferrite core.

The transformer does not heat up the ferrite, but the winding, so you need to follow these recommendations.

The transformer and the entire structure must be blown inside the case by a fan of 220 volts 0.13 amperes or more.

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, only $ 3 ... 4 apiece.

The power oblique bridge must be made 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 heat-conducting paste KTP8.

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

It is not indicated on the diagram that you need to solder 12 ... 14 pieces of capacitors of 0.15 microns 630 volts to this board in a 300V 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 interconnected by surface mounting with conductors of short length.

The diagram also shows snubbers, they have capacitors C15 C16, they should be of the K78-2 or SVV-81 brand. You can’t put any garbage there, since snubbers play an important role:
first- they dampen the resonant emissions of the transformer
second- they significantly reduce IGBT losses during turn-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 for itself, preventing heat from being released on the IGBT key three times than it would be without it.
When IGBT is fast open, then through the resistors R24 R25 the snubbers are smoothly discharged and the main power is released on these resistors.

Setting

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

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 turned on in the 220 volt network.

Without the resistor R11 directly, when turned on, a large BAC would be obtained while charging a capacitance of 3000 microns 400V, for this this measure is needed.

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

Check the PWM board for the presence of rectangular pulses going to the HCPL3120 optocouplers after both relays K1 and K2 have been activated.

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

Check the drivers on optocouplers and amplifiers leading a rectangular signal with an amplitude of 15 volts to make sure that the voltage at the IGBT gates does not exceed 16 volts.

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

The current consumption in this case should not exceed 100mA at idle.

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

One beam of the oscilloscope 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 220 volt 150..200 watt bulb, having previously set the PWM frequency to 55 kHz, connect the oscilloscope to the collector emitter of the lower IGBT transistor to look at the signal shape so that there are no voltage surges above 330 volts as usual.

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

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

Connect a welding wire at least 2 meters long to the output to create an additional output inductance.

Supply power to the bridge already through a 2200-watt kettle, and set the current to the PWM at least R3 on the light bulb closer to resistor R5, close the welding output, check the voltage on the lower key of the bridge so that it is no more than 360 volts on the oscilloscope, while there should not be any noise from the transformer. If it is, make sure the correct phasing of the current sensor transformer, pass the wire through reverse side through the ring.

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

Even when assembling the bridge, the drivers must be installed next to the bridge radiators above the IGBT transistors and not closer to the R24 R25 resistors by 3 centimeters. Driver output and IGBT gate connections must be short. The conductors from the PWM to the optocouplers should not run close to noise sources and should be kept as short as possible.

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

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

There should not be any noise otherwise they will failIGBT.

Add current and listen, watch the oscilloscope for an excess voltage of the lower switch, so as not to exceed 500 volts, a maximum of 550 volts in the surge, but usually 340 volts.

Reach the current, where the width sharply becomes maximum, saying that the kettle cannot give the maximum current.

That's it, 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, no more than 340 volts usually.

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

The radiators of the 150ebu02 diodes noticeably warmed up after three electrodes, it’s already hard to cook, a person gets tired, although it’s cool to cook, the transformer is hot, and no one cooks anyway. The fan, after 2 minutes, the transformer brings to a warm state and you can cook again until swollen.

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 a welder, write to E-Mail.

List of radio elements

The time relay timer is a device with which you can adjust the time of exposure to current, pulse. Timer relay for spot welding measures the duration of exposure welding current on the parts to be joined, the frequency of its occurrence. This device is used to automate welding processes, the production of a weld, in order to create a variety of structures from sheet metal. It controls the electrical load in accordance with a given program. The time relay is programmed for resistance 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 the device on and off in a given mode with a certain frequency on an ongoing basis. In simpler terms, it carries out the closing and opening of contacts. With the help of the rotation sensor, the time intervals in minutes and seconds are set after the expiration of which it is necessary to turn welding on or off.

The display is used to display information about the current turn-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

On the market you can find timers with digital or analog programming. The relays they use are different types, but the most common and inexpensive are electronic devices. Their principle of operation is based on a special program that is recorded on the microcontroller. With it, you can adjust the delay or turn-on time.

Currently, you can purchase a time relay:

• with shutdown delay;
• with turn-on delay;
• set to the set time after energization;
• set to the set time after the impulse;
• clock generator.

Component for creating a time relay

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 ease of connection, installed sensors with a fee;
• wires of the mother-mother type;
• a display that can display at least two lines with 16 characters per line;
• a relay that switches the load;
• rotation angle sensor equipped with a button;
• power supply to supply the device electric shock(when testing, you can power it through the USB cable).

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

For its manufacture, it is necessary to strictly follow the scheme.

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

After collecting all constituent 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 impacts and mechanical impacts.

At the end, it is necessary to carry out the installation of the switch. It will be needed if the welding owner decides to leave it unattended for a long time in order to prevent fire, damage to property in case of emergencies. With it, leaving the room, any user can effortlessly turn off the device.

"Note!

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

The timer for contact welding on the 555 is not so perfect and has a reduced functionality. But it is often used to create such devices, as it is cheaper.

To better understand how to create a welding machine, you should contact the company's employees. In addition, we propose to consider the scheme for creating this device. It will help to understand the principle of operation of the device, what and where to solder.

Conclusion

The arduino spot welding timer is an accurate and high-quality device that, with proper operation, 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 the negative manifestations of the natural environment.

You can assemble the device with your own hands or turn to professionals. The latter option is more preferable, as it is guaranteed to provide the final result. The company will test the elements of the device, identify problems, fix them, thus restoring its performance.

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

To optimize the entire process, the system uses Arduino Nano. This is a control unit that allows you to effectively manage the power supply of the installation. Thus, each welding is optimal for a particular case, and as much energy is consumed as needed, no more, no less. The contact elements here are a copper wire, and the energy comes from a conventional car battery, or two if more current is required.

The current project is almost ideal in terms of complexity of creation / efficiency of work. The author of the project showed the main stages of creating the system, posting all the data on Instructables.

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

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

During welding, both hands will be occupied. How to manage the whole system? With a footswitch, of course. It is very simple.

And here is the result of the work: