An acquaintance came, brought two LATRs and asked if it was possible to make a spotter out of them? Usually, when hearing a similar question, what comes to mind is an anecdote about how one neighbor asks another if he knows how to play the violin and in response he hears “I don’t know, I haven’t tried” - 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 shouldn’t do, that you need to be closer to the people and then people will be drawn to me, and also briefly plunged into the history of car repair shops, illustrated with delicious tales from the life of “chiropper” and “tinsmith”. Then I realized that a spotter is a small “welder” that works on the principle of a spot welding machine. Used for “grabbing” metal washers and other small fastening elements to the dented car body, with the help of which the deformed sheet is then straightened. True, they also need a “reverse hammer”, but they say that this is no longer my concern - only the electronic part of the circuit is required from me.
Having looked at spotter diagrams online, it became clear that we needed a one-shot device that would “open” on short time triac and supply mains voltage to the power transformer. The secondary winding of the transformer should produce a voltage of 5-7 V with a current sufficient to “grab” the washers.
To generate a triac control pulse, use different ways– from simple capacitor discharge to the use of microcontrollers with synchronization to the mains voltage phases. We are interested in the simpler circuit - let it be “with a capacitor”.
Searches “in the nightstand” showed that, in addition to passive elements, there are suitable triacs and thyristors, as well as many other “small 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 includes a relay, which will open and close the triac with its closing contact.
Also, while searching for parts, we found several power supplies with DC output voltages from 5 to 15 V - we chose an industrial one from “Soviet” times called BP-A1 9V/0.2A ( Fig.2). When loaded with a 100 Ohm resistor, the power supply produces a voltage of about 12 V (it turned out that it had already been converted).
We select TS132-40-10 triacs, a 12-volt relay from the available electronic “garbage”, take several KT315 transistors, resistors, capacitors and begin to prototype and test the circuit (on Fig.3 one of the setup stages).
The result is shown in Figure 4. Everything is quite simple - when you press the S1 button, capacitor C1 begins to charge and a positive voltage equal to the supply voltage appears at its right terminal. This voltage, having passed through the current-limiting resistor R2, is supplied to the base of the transistor VT1, it opens and voltage is supplied to the winding of relay K1, and as a result, the contacts of relay K1.1 close, opening triac T1.
As capacitor C1 charges, the voltage at its right terminal gradually decreases and when it reaches a level less than the opening voltage of the transistor, the transistor will close, the relay winding will be de-energized, the open 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 are installed to limit the pulses that occur when the S1 button is released and when the relay winding K1 is de-energized.
In principle, everything works like this, but when monitoring the time of the open state of the triac, it turned out that it “walks” quite a lot. 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 to be many times more and plus this, the pulse lasts 20-40 ms longer, and then for all 100 ms.
After a little experimentation, it turned out that this change in pulse width is mainly due to a change in the supply voltage level of the circuit and the operation of transistor VT1. The first one was “cured” by installing wall-mounted inside the power supply of a simple parametric stabilizer consisting of a resistor, a zener diode and a power transistor ( Fig.5). And the cascade on transistor VT1 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, the ability to discretely change the pulse duration using switches S3 and S4 has been added. The Schmitt trigger is assembled on VT1 and VT2, its “threshold” can be changed within small limits by changing the resistance of resistors R11 or R12.
When prototyping and testing the operation of the electronic part of the spotter, several diagrams were taken, from which time intervals and the resulting delays of edges can be assessed. At that time, the circuit had a timing capacitor with a capacity of 1 μF and resistors R7 and R8 had a resistance of 120 kOhm and 180 kOhm, respectively. On Figure 7 the top shows the state on the relay winding, the bottom shows the voltage at the contacts when switching a resistor connected to +14.5 V (the file for viewing by the program is in the archived appendix to the text, the voltages were taken through resistor dividers with random division coefficients, so the “Volts” scale not true). The duration of all relay power pulses was approximately 253...254 ms, the contact switching time was 267...268 ms. “Expansion” is associated with an increase in shutdown time - this can be seen from pictures 8 And 9 when comparing the difference that occurs when closing and opening contacts (5.3 ms vs. 20 ms).
To check the temporal stability of pulse formation, four sequential switchings were carried out with control of the voltage in the load (file in the same application). 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 where the half-wave of the mains voltage occurs 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 kOhm and R8 = 10 kOhm with C1 = 1 μF, it was possible to obtain a duration of one pulse of 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 attachment).
The final version of the spotter was equipped with parts with the values indicated on Figure 6. What happened on the secondary winding power transformer, 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 tackle the hardware.
A 9-amp LATR was used as a power transformer (right on rice. 12). Its winding is made of wire with a diameter of about 1.5 mm ( Fig.13) and the magnetic circuit has internal diameter, sufficient for winding 7 turns of 3 parallel folded aluminum tires with a total cross-section of about 75-80 sq. mm.
We disassemble the LATR carefully, just in case we “fix” the entire structure in the photo and “copy” the conclusions ( Fig.14). It’s good that the wire is thick - it’s convenient to count the turns.
After disassembly, carefully inspect the winding, clean it of dust, debris and graphite residues using paint brush with hard bristles and wipe with a soft cloth slightly moistened with alcohol.
We solder a five-amp glass fuse to terminal “A”, connect the tester to the “middle” terminal of coil “G” and apply a voltage of 230 V to the fuse and the “unnamed” terminal. The tester shows a voltage of about 110 V. Nothing buzzes or gets hot - we can assume that the transformer is normal.
Then we wrap the primary winding with fluoroplastic tape with such an overlap that we get at least two or three layers ( Fig.15). After this, we wind a test secondary winding of several turns with a flexible wire in insulation. By applying power and measuring the voltage on this winding, we determine required quantity turns to obtain 6...7 V. In our case, it turned out that when 230 V is supplied to the “E” and “unnamed” terminals, 7 V is obtained at the output with 7 turns. When power is applied to “A” and “unnamed”, we get 6.3 V.
For the secondary winding, “very used” aluminum busbars were used - they were removed from an old welding transformer and in some places had no insulation at all. To prevent the turns from shorting with each other, the tires had to be wrapped with sickle 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 functionality of the circuit on the desktop, all the parts of the spotter were installed in a suitable housing (it seems that it was also from some kind of LATR - Fig.17).
The terminals of the secondary winding of the transformer are clamped with M6-M8 bolts and nuts and are brought out to the front panel of the housing. Power wires leading to the car body and the “reverse hammer” are attached to these bolts on the other side of the front panel. Appearance at stage home check shown in Figure 18. At the top left are the mains voltage indicator La1 and the mains switch S1, and on the right is the pulse voltage switch S5. It switches the connection to the network of either terminal “A” or terminal “E” of the transformer.
Fig.18 
At the bottom there is a connector for the S2 button and the secondary winding leads. Pulse duration switches are installed at the very bottom of the case, under the hinged lid (Fig. 19).
All other elements of the circuit are fixed to the bottom of the case and the front panel ( Fig.20, Fig.21, Fig.22). Doesn't look very neat, but here main task there was a reduction in 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 wired - all transistors and their “piping” were soldered to breadboard made of fiberglass, with foil cut into squares (visible on Fig.22).
Power switch S1 - JS608A, allowing switching of 10 A currents ("paired" terminals are paralleled). There was no second such switch, so S5 was installed as TP1-2, its terminals are also paralleled (if you use it when the mains power is turned off, it can pass quite large currents through itself). Pulse duration switches S3 and S4 - TP1-2.
Button S2 – KM1-1. The connector for connecting the button wires is COM (DB-9).
Indicator La1 - TN-0.2 in the corresponding installation fittings.
On drawings 23, 24 , 25 photographs taken when checking the functionality of the spotter are shown - a furniture corner measuring 20x20x2 mm was spot welded to a 0.8 mm thick tin plate (mounting panel from a computer case). Different sizes"piglets" on Fig.23 And Fig.24– this is at different “cooking” voltages (6 V and 7 V). In both cases, the furniture corner is welded tightly.
On Fig.26 The reverse side of the plate is shown and it is clear that it heats up through, the paint burns and flies off.
After I gave the spotter to a friend, he called about a week later and said that he had made a reverse “hammer”, connected it and checked the operation of the entire device - everything is fine, everything works. It turned out that long-duration pulses are not needed in operation (i.e. elements S4, C3, C4, R4 can be omitted), but there is a need to connect the transformer to the network “directly”. As far as I understand, this is so that the surface of the dented metal can be heated using carbon electrodes. It is not difficult to supply power “directly” - they installed a switch that allows you to close the “power” terminals of the triac. The insufficiently large total cross-section of the cores in the secondary winding is a little confusing (according to calculations, more is needed), but since more than two weeks have passed, and the owner of the device was warned about the “weakness of the winding” and did not call, then nothing terrible happened.
During experiments with the circuit, a version of a triac assembled from two T122-20-5-4 thyristors was tested (they can be seen in Figure 1 in the background). The connection diagram is shown in Fig.27, diodes VD3 and VD4 - 1N4007.
Literature:
- Goroshkov B.I., “Radio-electronic devices”, Moscow, “Radio and Communications”, 1984.
- Mass radio library, Ya.S. Kublanovsky, “Thyristor devices”, M., “Radio and Communications”, 1987, issue 1104.
Andrey Goltsov, Iskitim.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad | |
|---|---|---|---|---|---|---|---|
| To picture No. 6 | |||||||
| VT1, VT2, VT3 | Bipolar transistor | KT315B | 3 | To notepad | |||
| T1 | Thyristor & Triac | TS132-40-12 | 1 | To notepad | |||
| VD1, VD2 | Diode | KD521B | 2 | To notepad | |||
| R1 | Resistor | 1 kOhm | 1 | 0.5 W | To notepad | ||
| R2 | Resistor | 330 kOhm | 1 | 0.5 W | To notepad | ||
| R3, R4 | Resistor | 15 kOhm | 2 | 0.5 W | To notepad | ||
| R5 | Resistor | 300 Ohm | 1 | 2 W | To notepad | ||
| R6 | Resistor | 39 Ohm | 1 | 2 W | To notepad | ||
| R7 | Resistor | 12 kOhm | 1 | 0.5 W | To notepad | ||
| R8 | Resistor | 18 kOhm | 1 | 0.5 W | |||
There comes a time in the life of every “radio killer” when you need to weld several lithium batteries together - either when repairing a laptop battery that has died from age, or when assembling power for another craft. Soldering "lithium" with a 60-watt soldering iron is inconvenient and scary - you will overheat a little - and you have a smoke grenade in your hands, which is useless to extinguish with water.
Collective experience offers two options - either go to the trash heap in search of an old microwave, tear it apart and get a transformer, or spend a lot of money.
For the sake of several welds a year, I didn’t want to look for a transformer, saw it and rewind it. I wanted to find an ultra-cheap and ultra-simple way to weld batteries electric shock.
A powerful low-voltage DC source available to everyone - this is an ordinary used one. Car battery. I'm willing to bet that you already have it somewhere in your pantry or that your neighbor has it.
I'll give you a hint - best way getting an old battery for free is
wait for frost. Approach the poor guy whose car won’t start - he will soon run to the store for a fresh new battery, and give the old one to you for nothing. In the cold, an old lead battery may not work well, but after charging the house in a warm place it will reach its full capacity.
To weld batteries with current from the battery, we will need to supply current in short pulses in a matter of milliseconds - otherwise we will not get welding, but burning holes in the metal. The cheapest and affordable way switch the current of a 12-volt battery - an electromechanical relay (solenoid).
The problem is that regular 12 volt automotive relays are rated for a maximum of 100 amps, and the currents short circuit when welding many times more. There is a risk that the relay armature will simply weld. And then, in the vastness of Aliexpress, I came across motorcycle starter relays. I thought that if these relays can withstand the starter current, many thousands of times, then they will be suitable for my purposes. What finally convinced me was this video, where the author tests a similar relay:
In some cases, it is more profitable to use spot welding instead of soldering. For example, this method may be useful for repairing batteries consisting of several batteries. Soldering causes excessive heating of the cells, which can lead to cell failure. But spot welding does not heat the elements as much, since it operates 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 energy supply of the installation. Thus, each welding is optimal for a particular case, and as much energy is consumed as necessary, no more and no less. The contact elements here are copper wire, and the energy comes from a regular car battery, or two if higher 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 will be 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 the board 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 entire system? Using a foot switch, of course. It's very simple.
And here is the result of the work:
In some cases, it is more profitable to use spot welding instead of soldering. For example, this method may be useful for repairing batteries consisting of several batteries. Soldering causes excessive heating of the cells, which can lead to cell failure. But spot welding does not heat the elements as much, since it operates 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 energy supply of the installation. Thus, each welding is optimal for a particular case, and as much energy is consumed as necessary, no more and no less. The contact elements here are copper wire, and the energy comes from a regular car battery, or two if higher 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 will be 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 the board 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 entire system? Using a foot switch, of course. It's very simple.
And here is the result of the work:
A time relay timer is a device with which you can adjust the time of exposure to a current or pulse. The time relay timer for spot welding measures the duration of exposure of the welding current to the parts being connected and the frequency of its occurrence. This device is used to automate welding processes, weld production, and create a variety of sheet metal structures. It controls the electrical load in accordance with a given program. The time relay for resistance welding is programmed in strict accordance with the instructions. This process involves setting time intervals between certain actions, as well as the duration of the welding current.
Operating principle
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. To put it simply, it closes and opens contacts. Using a rotation sensor, you can adjust the time intervals in minutes and seconds after which you need to turn welding on or off.
The display is used to display information about the current switching 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
You can find timers on the market with digital or analog programming. The relays used in them are different types, but the most common and inexpensive are electronic devices. Their operating principle is based on a special program that is recorded on a microcontroller. It can be used to adjust the delay or on time.
Currently you can purchase a time relay:
- with shutdown delay;
- with delay on switching on;
- tuned to set time after applying voltage;
- configured for a set time after the pulse is given;
- clock generator.
Accessories for creating a time relay
To create a time relay timer for spot welding you will need the following parts:
- Arduino Uno board for programming;
- prototyping board or Sensor shield – facilitates the connection of installed sensors with the board;
- female-to-female wires;
- a display that can display a minimum of two lines with 16 characters per row;
- relay that switches the load;
- rotation angle sensor equipped with a button;
- power supply to ensure the device is supplied with electric current (during testing, it can be powered via a USB cable).
Features of creating a time relay timer for spot welding on an arduino board
To make it, you must strictly follow the diagram.
At the same time, it would be better to replace the frequently used arduino uno board with an arduino pro mini since it has a significantly smaller size, costs less and is much easier to solder the wires.
After collecting everyone components To make a timer for resistance 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 select a suitable case and assemble all the elements in it. It will provide the device with decent appearance, protection from accidental impacts and mechanical influences.
To complete, it is necessary to install the switch. It will be needed if the welding owner decides to leave it unattended for a long time in order to prevent fire or damage to property in the event of emergency situations. With its help, leaving the premises, any user will be able to special effort turn off the device.
“Pay attention!
The timer for resistance welding on 561 is a more advanced device, as it is created on a new modern microcontroller. It allows you to measure time more accurately and set the frequency of turning the device on and off.”
The timer for resistance welding on the 555 is not so perfect and has reduced 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 company staff. In addition, we propose to consider the design of this device. It will help you understand the principle of operation of the device, what needs to be soldered and where.
Conclusion
The timer for spot welding on Arduino 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 site. In addition, the spot welding timer is easy to maintain. It works even in severe frost, and is practically unaffected by negative manifestations of the natural environment.
You can assemble the device yourself or turn to professionals. The last option is more preferable, as it guarantees the final result. The company will test the device elements, identify problems, fix them, thus restoring its functionality.
