The device has been in use for 5 years now, and by the way it works well, although the CA is not used very often. The transformer from which the welding machine is made was torn out of a strong microwave oven- like the fan that is installed to cool the windings. The secondary winding has been removed from the transformer without affecting the network winding (). The next step to take is winding the new secondary winding with a thick cable (under 10 mm in diameter).
Both the transformer and the fan are screwed to the plywood. A board with two holes is attached in front of the transformer, through which both ends of the secondary winding are inserted. Plywood is also a kind of screen that stops cold air from the welding site. Next to the transformer, as can be seen in the photographs, a timer is used to adjust the power-off time.
The transformer is turned on using a foot pedal - then the operator will have both hands free to work with the electrodes and the part. The electrodes are made of an 8 mm copper rod, which is threaded. The cable clamp is made from cut copper tube.
Welding machine in action
The fan starts working from the very moment the plug is inserted into the socket, since the transformer becomes very hot during operation. Next, we install two electrodes opposite each other, press the pedal, switching the voltage on the timer, which gives it some more time to supply the trans. Here this switch is used only for unintentional long pressing of the pedal or unwanted blocking of the button.
Cross section of the secondary winding, more precisely the quantity coil turns, select experimentally. When powered by 220 V, it does not blow out fuses (even 10 A) and does not cause the light to blink at startup.
Naturally, the welding voltage is low and the electrodes can be handled with your bare hand, but it is better to wear protective gloves, since the electrodes heat up from long-term operation.
Power welding machine depends on the transformer - a microwave oven is usually 800-1200 watts, so the larger the transformer, the better. When welding, a large current is created - 1-2 kA or more at a voltage of 1-8 V. The higher the current, the better connection, because the welding time is very short, and when it comes to long-term welding with low power, it will result in a blackened area.
Let's continue the cycling topic.
When I rode a bicycle to work, it was inconvenient to carry it in a backpack - my back sweats. Carrying it on the trunk is inconvenient - the package slips and tries to get into the spokes. You need a small basket for the trunk that would keep small loads from falling. Since they don’t make such small baskets, I decided to make them myself. To assemble such a basket you need resistance welding, which can also weld batteries.
The process of assembling the trunk basket, batteries, and welding itself is described below.
"Weld body"- transformer from a microwave oven.
The secondary winding was removed with a hacksaw, and the plates between the primary and secondary were removed. I recommend a hacksaw; a Dremel or grinder can easily damage the primary winding, but it is still needed. A PV3 wire of 70 square millimeters was inserted (stuffed, hammered) into the window of the secondary winding in 4 hands, 1 meter is enough. The wire goes very hard, it took two people to refuel.
On the wire gas burner Tinned copper tips were soldered, but it was not possible to solder purely copper ones. Electrodes are attached to the tips - 10 squares of copper for welding batteries and rectangular ones for welding rods or sheets. 
In the case of rectangular electrodes, they allow you to weld both wire, if the electrodes are placed plane to plane, and a sheet if you turn the top electrode at an angle, as in the photo.
Rectangular electrodes are plates from the installation kit for current transformers; they were not useful during electrical installation, but here they are.
"Welding Brains" - homemade timer on the PIC16F628A microcontroller, the link to which is in the title of the review.
I purchased it from the Chinese Super Electronic market, it’s not the first time I’ve made it there, and I don’t think it’ll be the last. When ordering $15-30, it is sent by mail with a normal track, well packaged, and does not mess with the package. Moreover, his prices are usually minimal or close to them.
In addition to picukha, it was purchased
- , 10 items, 5 pieces each - $2.7 lot 50 pieces.
- 50 pcs $1.28
- 10 pieces 4.8$
- 10 pcs 1.6$
- - 10 pcs 13.8$
Based on the diagram from
The power part was taken from the circuit, and it was decided to write the firmware myself.
I didn’t like the use of two buttons in the circuit - it’s faster and more convenient to control the encoder, the shutter speed range is small.
I have already reviewed the power supply; a 5V stub has been added to it. Two supply voltages 5V main and 12V control go to the controller. When the power is turned off, the 12V voltage begins to drop first; it goes through a resistive divider to the controller leg (blue trimmer, set to 3V). The controller sees zero on the leg, saves the parameters and goes to sleep.
The output of the PIC leg gives a signal to the optocoupler, the optocoupler opens the thyristor, which in turn turns on the trans primary. No heating of parts was noticed. It is possible to use a solid state relay, as in the previous article on this resource. I also used a solid body in my previous welder, but the optocoupler + thyristor is smaller and cheaper when purchased in 10-piece quantities.
The encoder was purchased
It already has pull-up resistors, the encoder not only rotates but is also pressed.
When you press the encoder, the number begins to blink smoothly (I changed the brightness according to a sinusoid) - it shows the number of pulses up to 9, that is, you can cook with a repeated or triple pulse, the pause between pulses is equal to the pulse duration, the duty cycle is 50% in general. When you press the encoder again, it remembers the parameter into memory (checks whether it has changed) and goes back to the operating mode.
Indication on two LED seven-segment indicators, dynamic indication.
When welding, you usually need both hands free; to start welding, a pedal was made - a bell button.
When turned on, the timer for 1 second shows and reminds the number of pulses.
Then the shutter speed indication
.2 -0.02sec
0.2 -0.2 sec
2.2 -2.2 sec.
maximum 9.9 seconds, minimum 0.01 sec.
When the pedal is pressed and the shutter speed is worked out, - - is displayed
The tweezers should not twitch when working out the shutter speed, it didn’t work out very clearly.
timer operation 1.33 min
Physically, the timer is assembled in the housing of the HP printer power supply; a board is used from it as a supporting element and a power connector, fuse and filter capacitors at the input.
Something is assembled on stands, something is glued with hot glue, in general, all the elements of the collective farm. Oddly enough, everything works.
The faint of heart and perfectionists should not look at photos of offal
Welding nails 4+4mm.
Result after
Welding result
Luggage racks, 1 kg of 3 mm galvanized wire was enough for both racks, price about $1.5-2
My cell is 4*4cm, my wife’s bike bag cell is 5*5cm 
Welding batteries for screwdrivers 
Galvanizing residues 
UPD.
Added larger photo 
Brief description of the principle of operation and assembly:
Resistance welding is the process of forming a permanent welded joint by heating the metal passing through it electric shock and plastic deformation of the connection zone under the action of compressive force. (Vicki)
That is, a large current and compression force are needed. In industrial devices, the compression force and current are regulated electronically; there are welders with hydraulic compression. The simplest ones are those where you squeeze with your hands, as in my version. Current is still needed. The transformer from the microwave allows you to replace the secondary winding; instead of the step-up winding, we install a step-down winding. Voltage of great importance does not have, the current is sufficient. When using larger transformers, damage to the wiring is possible; the primary winding currents in the microwave transformer are around 15-20 amperes, a good home option.
In addition to the power part, which provides current and sometimes pressure, sometimes an electronic part is needed. Can be placed in the primary winding circuit breaker at 16A, as in the driveway panel, and using it with your hands “by eye” set the time delay of the current effect on.
For example like this 
If you want a little convenience, holding both with both hands, you can add a button. But not every button can withstand currents of 15 amperes; for this you can use a solid-state relay or a starter. If the starter coil or solid state relay input is low voltage, not 220V, then a power supply is needed. This option is in the next picture. 
The power supply provides 12 or 24 or any other safe voltage, it turns on the relay/starter through the K button, it is convenient to press with your foot and the button does not burn out.
For long shutter speeds of the order of 2-5 seconds and large details, this is acceptable. But when welding batteries, plates 0.1-0.2 mm thick are usually used and short dwell times of about 0.01-0.1 seconds are required. Such shutter speeds are difficult to work out manually; exceeding the shutter time will burn out the plates, and sometimes even the battery, and they are not cheap.
To ensure repeatability of the result, an electronic timer is installed, which generates the necessary short exposures.
The next picture shows a circuit with a timer. 
In total, almost the most advanced option - a transformer with a replaced secondary, a timer button, a power supply, you can combine it to your taste. For example, if the timer is 220V, then a power supply is not needed, but your leg may get fried if there is 220V on the pedal.
Brief assembly instructions:
-Find a microwave, disassemble it, remove the trans (it is 2/3 of the weight of the microwave).
-Check whether the primary winding is alive, it is usually wound with a thicker wire, ring. Do not turn on! High voltage may appear on the secondary winding and transformer housing.
-Carefully remove the winding with the thinnest wire, if the thick one is live. Clamp it in a vice, cut it with a hacksaw or any other not very powerful tool, the remains will be knocked out.
-Remove the shunts (plates between the primary and secondary windings).
-There are several more turns of the filament winding. It can also be deleted.
-Wind the secondary winding into the vacant window. For welding batteries, 35 squares of copper are enough, for thicker materials 70-100mm. You may have to remove the factory insulation and insulate with heat shrink/duct tape. Two or three turns is usually sufficient. The wire is called PV3*70 or welding wire. Maybe PV5*70, but I haven’t seen those.
-End the wire. Typically, tinned copper lugs and copper lugs are used. You can crimp or solder them or both.
-Attach electrodes to the ends of the wire. To weld batteries, 10 squares of copper (PV3*10) are enough. For thicker metals, electrodes are made from copper rod large diameter, sharpened at the ends. The better the connection between the electrodes and the wire and the shorter the wire, the greater the current and the better the welding.
- Add a timer, button, body to taste. You can add an LED to the upper electrode arm to illuminate work area. You can add another winding of 3-5 turns and solder a 5V buzzer to it (the white wire is in my photo), it will beep when welding.
Link to firmware
RV2 adjust to 3v, lower log. 0 and the command goes to save to memory.
Motor-encoder, two buttons to turn it, a trigger button and an encoder button
ports B for indicator - ABCDEFG-2345610
I have sc56-11gwa indicators, that is, a common cathode.
Oscillograms
The title shows the shutter speed in seconds.
In the first, the shutter speed is 0.01 sec, pulses one by one manually, to the right 5 pulses of 0.01 each
the rest are all 5 pulses automatically after a pause equal to the shutter speed. 
Welding an electric bicycle battery
This is a video from a previous welder, there are 3 turns * 35mm
The wire is thinner and more flexible, the essence is the same.
Plate 0.1*4mm Planning to buy +138 Add to favorites I liked the review +160 +286
A simple welding machine for electrical arc welding Anyone can do it at home, without using any specialized equipment or circuits. All we need is just two microwave ovens that can be found in a landfill or two transformers from them.
We disassemble the microwaves and take out the transformers.
These transformers are step-up, that is, they convert 220 Volts into a voltage of about 2.5 kV, necessary for the operation of the magnetron. Therefore, their secondary winding contains a less thick wire and with a larger number of turns. Such a transformer has a power of about 1200 W.
To assemble an arc welding machine, we do not have to disassemble the core of these transformers. We will simply cut down and drill out the secondary high-voltage winding. Usually this winding comes from the top, and the primary winding is 220 V from the bottom.
The tool we need for our work.
Making a simple welding machine from a microwave with your own hands
We take the transformer and secure it so that it does not move. We take a hacksaw and cut off the secondary winding on both sides of both transformers. If you decide to repeat, be careful not to damage the primary winding.
Then we drill the winding with a drill with a metal drill, thereby relieving the internal stress of the metals, making it easier to knock out the remains.
We knock out the remnants of the winding.
We have two transformers with 220 V windings. The transformer on the left, above the winding, has a current shunt that separates the windings. To increase power, they also need to be knocked out. Such manipulation will increase the power of the transformer by 20-25 percent.
There is also a small low-voltage winding made of a pair of wires between the large windings - we also throw that out.
We take a stranded wire in plastic insulation with a cross-section of six squares and a length of 11-12 meters. You can take a more stranded wire, not coarse like in my example.
I wound about 17-18 turns on each transformer, 6 rows high and 3 layers thick.
The windings are connected in series. I wound everything with one wire, but you can wind each transformer separately and then connect it. The entire winding is very tight and should not dangle.
After winding is completed, we connect the high-voltage 220 V windings in parallel. I used automotive grade ferrules, insulated with heat shrink tubing.
I plug in the entire structure and measure the voltage on the secondary that I wound. The result was about 31-32 Volts.
Then I took wooden board and screwed both transformers with self-tapping screws to make a single unit.
When welding, I will use 2.5 mm electrodes and weld two pieces of iron 2 mm thick.
I'm happy with the result; it's quite suitable for household needs, considering that I actually got everything for free.
Watch the video of making an arc welding machine
IN Lately I quite often began to encounter lithium-ion batteries in various devices. Sometimes it even came to assembling batteries, and I connected the elements by soldering. However, I wanted to take a more correct path and use a resistance welding machine for this.
Buying a ready-made welder, even on Aliexpress, has choked me to death, since I very rarely need to weld batteries, and the device is expensive. Therefore, I decided to assemble such a device myself, and at the same time enjoyed the process.
There are many methods for assembling a resistance welder with your own hands. You can use a car battery, or a transformer from an old microwave. There are also various ways manage welding current and the duration of the welding pulse. In the simplest case, you can simply connect two thick wires to the car battery, from copper wire make electrodes, connect it all together and weld by hand, measuring the time “by eye”. You can make control based on Arduino or a specialized time controller, a relay from a motorcycle, etc.
Well, I decided to make a welding machine based on a transformer from a microwave oven (microwave). In any case, it will be more compact and lighter than a car battery. And I bought a controller that doses both current and pulse duration on Aliexpress because it’s inexpensive, and that’s already ready product, which you don’t need to assemble yourself.
I bought an old 750-watt microwave transformer on Avito for 600 rubles.
I also bought 1 meter of multi-core at the market power cable with a cross section of 25 squares for 125 rubles. More precisely, I took 2 meters (with a margin), but one is enough.
On Aliexpress I bought: a controller with a 40-amp triac (no more needed for welding 18650 batteries), a 9-volt AC transformer to power the controller, a foot pedal for convenient control, and also the most expensive thing - wires with connectors (on this part it was possible to save money by making electrodes from thick copper wire and connecting them, for example, through a terminal block to power wires) + electrodes (copper needles). In general, from what you bought on Ali, you only need a controller and a transformer alternating current at 9 volts, the rest is optional.
AC Transformer:
Foot pedal:
Cables with connectors and handles with collet clamps:
The first step is to get rid of the secondary winding of the transformer. It is located at the top and is wound with a thin wire. You just need to saw off the winding with a hacksaw.
After this, the remaining wires can be easily drilled out with a thick drill.
If your transformer has such additional packages of metal plates, they also need to be removed.
Now you need to take a thick cable and insert it into the place of the former secondary winding, making two turns. Thus, we will get a step-down transformer from a step-up transformer. The output voltage is now only about 2 volts, but the current has increased many times - tens or perhaps even hundreds of amperes. This voltage is safe for humans, and it’s okay if you accidentally touch the powered electrodes with your hand.
The ends of the cable are clamped into terminals and insulated with heat shrink.
We connect cables with handles to them.
Now, according to the diagram, you need to assemble the rest of the electrics.
The foot pedal comes with a 10 cm piece of wire, so I replaced it with a long one so that the pedal could be placed on the floor.
The power wires were connected using a terminal block. It was possible to sleep.
The wires were connected to the transformer through removable terminals so that it could be easily disconnected.
Well, I simply soldered two wires to the controller, although it would have been better to screw them onto screws and round terminals, but I didn’t have those on hand, unfortunately.
In general, the circuit is assembled and can be connected to the network. Please note that the controller is powered by an AC transformer and not direct current.
When turned on, the digital indicator and various LEDs light up.
The left knob sets the pulse duration (from 1 to 50, each unit is equal to 20 milliseconds). The right knob sets the power, ranging from 30 to 99%.
When you press the pedal, the circuit turns on set quantity milliseconds
To weld the tape to the battery, you need to press the electrodes tightly against the surface. The surfaces of both batteries and tapes must be absolutely clean, without dirt, glue, oxides, etc. Otherwise the tape will not be welded.
I have no experience in resistance welding there was none, so all the parameters had to be selected experimentally, training on an unnecessary battery. A properly welded tape holds well and comes off when force is applied, leaving a small piece on the battery. The pulse duration and current strength depend on both the power of the transformer and the thickness of the nickel tape - possibly also on other conditions.
Traces of experiments:
I began to get more or less correct welding with parameters 35/70. But I think it would be better for me to take a more powerful transformer; it would be possible to shorten the pulse duration and there would be less overheating. However, we still need to experiment.
From 2 transformers from an old microwave oven, you can make a useful device for your home workshop and garage with your own hands - resistance spot welding.
Contact spot welding makes it possible to work with a wide variety of metals and their alloys, which makes it universal for everyday use.
First of all, we remove the transformers from the microwave body. After this, you will need to carefully remove the “native” secondary winding without damaging the primary.
The easiest way to “painlessly” remove the secondary winding is to cut off the protruding turns with a grinder.
After this, using an electric drill, you need to drill a hole inside the transformer and pull the remaining wires out with narrow-nose pliers.
Main stages of work
After we have removed the secondary winding from the transformer, we remove everything unnecessary, including metal spacers. Only the secondary winding should remain.
The same operation will need to be done with the second transformer. Then the master welds both transformers together.
Instead of a secondary winding on two transformers, the author uses a thick multi-core cable, which is intended for a welding machine. It is enough to make only two turns. The secondary windings are connected in parallel.
A piece of channel 160 mm wide is used as the base. You need to drill a couple of holes with a diameter of 8 mm in it, then screw on the perforated profile. You also need to weld two corners with holes to the channel.
Spot Welding Assembly
Four holes must be drilled in the base. Then we install the transformers, having previously connected two primary windings in parallel. We do everything the same as with secondary ones.
