The electronic circuit of the soldering iron temperature controller. Temperature controller for soldering iron. Power regulator with information display

For a decent quality of soldering work, a home craftsman, and even more so a radio amateur, will need a simple and convenient temperature controller for the soldering tip. For the first time, I saw a device diagram in the Young Technician magazine of the early 80s, and having collected several copies, I still use it.

To assemble the device you will need:
-diode 1N4007 or any other, with a permissible current of 1A and a voltage of 400 - 600V.
- thyristor KU101G.
- electrolytic capacitor 4.7 microfarads with an operating voltage of 50 - 100V.
-resistance 27 - 33 kilo-ohms with a permissible power of 0.25 - 0.5 watts.
- variable resistor 30 or 47 kilo-ohm SP-1, with a linear characteristic.

For simplicity and clarity, I drew the placement and interconnection of parts.

Before assembly, it is necessary to isolate and mold the leads of the parts. We put on insulating tubes 20 mm long on the conclusions of the thyristor, and 5 mm on the leads of the diode and resistor. For clarity, you can use colored PVC insulation, removed from suitable wires, or heat shrink. Trying not to damage the insulation, we bend the conductors, guided by the drawing and photographs.

All parts are mounted on the terminals of a variable resistor, connected to the circuit with four solder points. We put the conductors of the components into the holes on the terminals of the variable resistor, trim everything and solder it. We shorten the conclusions of the radioelements. The positive terminal of the capacitor, the control electrode of the thyristor, the resistance terminal, are connected together and fixed by soldering. The thyristor case is an anode, for safety, we isolate it.

To give the design a finished look, it is convenient to use the case from the power supply with a power plug.

We drill a hole with a diameter of 10 mm on the upper edge of the case. We insert the threaded part of the variable resistor into the hole and fix it with a nut.

To connect the load, I used two connectors with holes for pins with a diameter of 4 mm. On the case we mark the centers of the holes, with a distance between them of 19 mm. In drilled holes with a diameter of 10 mm. insert connectors, fix with nuts. We connect the plug on the case, the output connectors and the assembled circuit, the soldering points can be protected with heat shrink. For a variable resistor, it is necessary to choose a handle made of insulating material of such a shape and size as to cover the axis and nut. We assemble the case, securely fix the regulator knob.

We check the regulator by connecting an incandescent lamp of 20 - 40 watts as a load. Turning the knob, we are convinced of a smooth change in the brightness of the lamp, from half the brightness to full heat.

When working with soft solders (for example, POS-61), soldering iron EPSN 25, 75% of the power is sufficient (the position of the regulator knob is approximately in the middle of the stroke). Important: on all elements of the circuit there is a supply voltage of 220 volts! Electrical safety measures must be followed.

Recently had to repair a lot of small things. However, it was not always convenient to do this with the available soldering iron EPSN-25.
An inexpensive Chinese soldering iron with temperature control from 200 to 450 degrees was ordered and received.

The soldering iron comes with a set of five pieces of tips for performing various types of work (replicas of the Hakko 900 series).
The declared power of the soldering iron is 60 watts. A little upset by the length of the wire - 1.38 meters. As for me, the wire is a bit short, but everything is individual here and depends on the organization of the workplace and the location of the sockets.
Before switching on, having disassembled the soldering iron, he examined its inner world. The soldering is decent, the circuit of the triac regulator (normal dimmer), there is an indicator LED (it only reports on the supply of mains voltage).

There is no thermal sensor, but its presence for such money was not expected. The heating element is declared as ceramic - there is a characteristic step. However, the network has a photo of such a broken heater. And despite the step, there was nichrome wire inside. So, I can not say that there is a ceramic heater. Its resistance is 592 ohms.

It would seem that everything is not bad, but the first results were very puzzling. The soldering iron's first exposure to rosin resulted in a Hollywood smoke cloud and rosin cracking throughout its depth. The adjustment didn't help much. The soldering iron was put aside until the arrival of the wattmeter and thermometer. At first I tried to take temperature measurements with an immersion kitchen thermometer, but the limit of its measurement was 300 degrees and inertia forced me to refuse his services.

It took about 20 minutes for the whole procedure of examining the appearance and the inner world, turning it on, summoning magic smoke, and getting out of the stupor. IT IS BURNED!!!

Since the parcels arrived with a difference of three weeks, as they arrived, first measurements of the power consumption were made, and then the temperature. The photos were taken both at home and in the “house in the village”, so the surrounding background in the photo, although different, is made by hand and the same soldering iron appears on them.
SO:

Upon arrival of the wattmeter, I decided to measure the power consumed by the soldering iron and it turned out that it consumes the declared 60 W only at the moment of switching on (it is very difficult to capture it with a camera). At the same time, the temperature controller is brought to the maximum position. I didn’t install the sting - at least there are a lot of them in the set, but still.
The wattmeter reading quickly drops to 40 watts and then drops to 30.1 watts.

Then let the soldering iron cool down, brought the regulator to a minimum and measured the consumption again.
At the minimum, the start of consumption also starts from the region of 60 watts, but sharply decreases to 25.2 and finally stabilizes at 20.6 watts.

Pay attention - heating occurs in the second half of the heater where the sting is located.

But we solder not with power consumption, but with a tip with a certain temperature, and before the arrival of the thermometer, the soldering iron again went to the bench.
Upon arrival of the thermometer, I took measurements in the same positions of the regulator - maximum and minimum.
The maximum temperature reached 587 degrees!!! (I was slipped a burner???)

The minimum is 276 degrees.

I finalized the adjustment circuit by adding another capacitor in parallel to the existing capacitor with a total capacity of 47 nanoFarads * 400 Volts.

Since everything is already clear with the power consumption, that is, it is not critical, I only took temperature measurements at the maximum and minimum and already assembled - with a sting:

At the maximum it turned out:

At the minimum:

Which borders on the heating level of the EPSN-25 soldering iron familiar to me.

There is information on the network that the heating element can be unsoldered from the board and pushed forward slightly - this supposedly should increase the heat transfer to the soldering tip.

I tried it, but I didn’t notice a significant difference - the soldering iron didn’t suffer from underheating anyway. In addition, one should not forget about the linear expansion of materials as a result of heating, and with such a modification, the assembled heater rests against a cold tip, and when heated, due to linear expansion, the heater may be destroyed. Indirectly, this is evidenced by the fact that after these tests, the nut that fixes the sting turned out to be quite loose. Therefore, he refused this modification and returned the heater to its original state.
For practical testing of the stings, I chose the most massive (replica 900M-K) sting. Why him? Mass determines the heat capacity, and therefore it will cool more slowly. By the way, all the tips are tinned from the factory and are not magnetic. Those. it’s even difficult to call it a replica - a pathetic likeness. Later, the most massive tip, used at the beginning of testing, was put under the needle file and it can be assumed that the tips are made of copper. However, their weight is confusing, for those made of copper they are quite light, although this is my subjective opinion not based on chemical analysis)).

I didn’t experiment with all the stings, but out of habit I chose a replica 900M-T-3C (round with a bevel). I got used to this form of sting using EPSN-25.
But even here a fiasco awaited - even after the soldering iron was finalized, the sting was burned at minimum power. The rest did not even begin to install - they will burn. The price of the whole set speaks for itself.
Since there was nothing to lose, I remembered the needle file and ruthlessly sharpened the T3C sting using the usual technology. I thought everything was in a bucket, but it turned out that in this form the sting is excellent friends with tin and soldering has acquired a new meaning)). I can't say how long it will last, but so far I'm happy with the result.
EVENTUALLY:
1. A thing for enthusiasts - it is unlikely to be used without refinement;
2. The stings from the set are rubbish;
3. Buying new stings - a lottery) because there are a lot of fakes;
4. The tactile sensations from using the soldering iron are the most positive - it lies like a glove in the hand, thanks to the rubber lining, the grip is confidently fixed and there is no slipping of the hand, heating the upper part of the handle after an hour of use at a temperature of around 250 degrees (drained donors) in the "absent" range up to "not significant";
5. Not a large extension of the working surface of the tip from the handle of the soldering iron is a definite plus;
6. Fast heating, low solder consumption, undoubted convenience of soldering SMD components, the ability to change tips for different types of work.

Yes, this is not a professional tool for working every day for 8 hours, but for most radio amateurs who fill their hands, that's it (taking into account the above).
Another quality that I cannot attribute to shortcomings, but thanks to which there is a difference from using a conventional low-power soldering iron with an ordinary tip - rosin does not linger on the tips of a new soldering iron. Those. by the time you bring it to the board, the sting is already dry. This is due to the small size of the tips from the kit and, as a result, a small surface area.
I got out of the situation with the help of flux Amtech RMA-223. The soldering is perfect. The worst results were shown by the alcohol-rosin mixture.
Given that you need to get used to each tool, I can say that after the experience gained and the adjustments made, I am generally satisfied with the soldering iron. Let everyone decide for themselves.

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When working with a soldering iron, it often becomes necessary to adjust its power. This is necessary when choosing the optimal temperature of the soldering iron tip, since at too low a temperature the solder does not melt well, and at too high a temperature, the tip overheats and destroys it, and the soldering is of poor quality.

In addition, an amateur often has to perform various soldering jobs that require different soldering iron power.

To control the power, a large number of different schemes are used. Examples are:

with a variable resistor;
with resistor and diode;
with a microcircuit and a field effect transistor;
with thyristor.

The simplest power regulator for a soldering iron is a circuit with variable resistor. In this embodiment, a variable resistor is connected in series with the soldering iron. The disadvantage of this scheme is that a lot of power is dissipated on the element, which goes into heat. In addition, a high power variable resistor is a rather scarce element.

More complex is the method using resistor and rectifying diode. This scheme has three modes of operation. In maximum mode, the soldering iron is connected directly to the network. In operating mode, a resistor is connected in series with the tool, which determines the optimal operating mode. When turned on in standby mode, the soldering iron is powered through a diode, which cuts off one half-cycle of the AC mains. As a result, the power of the soldering iron is halved.

Using microchips and field effect transistor soldering iron power adjustment is provided not only to the smaller, but also to the larger side. At the same time, a rectifier bridge is involved in the circuit, at the output of which the voltage can reach 300 V. In series with, a powerful field-effect transistor of the KP707V2 type is included in the package.

In addition to the temperature controller, the soldering tool itself is assembled from improvised parts. It's not hard to learn. It is only necessary to find all the constituent elements and follow a certain assembly order.

One of the most common tools for household work related to electricity is. Everyone knows how to use it, but there are some nuances in the operation of different types of such screwdrivers.

The power of the soldering iron is controlled pulse-width method. To do this, pulses with an average frequency of 30 kHz are applied to the gate, generated using a multivibrator assembled on a K561LA7 microcircuit. By changing the generation frequency, you can adjust the voltage on the soldering iron from ten to 300 V. As a result, the current of the tool and the temperature of its heating change.

The most common option used to adjust the power of a soldering iron is a circuit using thyristor. It consists of a small number of non-deficient elements, which makes it possible to design such a regulator in very small dimensions.
Next, consider the circuit of the triac power controller for the soldering iron in more detail.

Features of the most optimal controller - with a thyristor

The composition of a typical thyristor circuit includes the elements shown in the table.

The power diode VD2 and the thyristor VS1 in the circuit are connected in series with the load - a soldering iron. The voltage of one half-cycle is directly supplied to the load. The second half-cycle is controlled by a thyristor, the electrode of which receives a control signal.

On transistors VT1, VT2, capacitor C1, resistors R1, R2, a sawtooth voltage circuit is implemented, which is applied to the control electrode of the thyristor. Depending on the position of the resistance value of the adjusting resistor R2, the thyristor opening time changes for the passage of the second half-cycle of the alternating voltage. As a result of this, there is a change in the average voltage over the period, and, consequently, the power.

Resistor R5 dampens the excess voltage, and the zener diode VD1 is designed to provide power to the control circuit. The rest of the components are designed to ensure the modes of operation of the structural elements. To read the characteristics of such devices is.

Do-it-yourself device design

As follows from the consideration of the circuit, it consists of a power section, which should be carried out using surface mounting, and a control circuit on a printed circuit board.

Creation printed circuit board includes making a board drawing. For this, in domestic conditions, the so-called LUT is usually used, which means laser-ironing technology. The PCB manufacturing method includes the following steps:

creating a drawing;
transferring the pattern to the board blank;
etching;
cleaning;
drilling holes;
tinning of conductors.

Sprint Layout is the most commonly used program for creating a board image. After receiving a drawing with a laser printer, it is transferred to a foil getinax using a heated iron. Then the excess foil is etched with ferric chloride and the pattern is cleaned. Holes are drilled in the right places, and the conductors are tinned. The elements of the control circuit are placed on the board and they are desoldered (there are certain recommendations -).

Assembly power unit the circuit includes connecting resistors R5, R6 and diode VD2 to the thyristor.

Last build step– placement of the power section and the control circuit board in the housing. The order of placement in the housing depends on its type.

In the case of installation of open wiring, so as not to be distracted by additional purchases in the store, you can make. The difference between such devices is only in the functional component - the lighting switching circuit.

You can read more about the features of pass-through switches in. In addition, other types of switches are gaining more and more popularity in modern lighting control systems - for example,.

Since the dimensions of the elements are small and there are not many of them, then, for example, a plastic socket can be used as a housing. The largest place there is occupied by a variable adjustment resistor and a powerful thyristor. Nevertheless, as experience shows, all elements of the circuit, together with the printed circuit board, fit into such a case.

Checking and adjusting the circuit

To check the circuit, a soldering iron and a multimeter are connected to its output. By turning the knob of the regulator, it is necessary to check the smoothness of the change in the output voltage.

An additional element of the regulator can be an LED.
By turning on the LED at the output of the regulator, you can visually determine the increase and decrease in the output voltage by the brightness of the glow. In this case, a limiting resistor must be installed in series with the light source.

conclusions:

In the process of working with a soldering iron, it is often necessary to adjust its power.
There are numerous schemes for adjusting the power of a soldering iron with a resistor, transistor, thyristor.
The power control circuit of the soldering iron with a thyristor is simple, has small dimensions and can be easily assembled by hand.

Video with tips for assembling a soldering iron temperature controller with your own hands

To perform various electrical work, assembling electronic circuits, a tool such as an electric soldering iron is very often used. Its simplest form, which can be purchased at any hardware store, has, as a rule, an elementary design.

It includes a heating element, a sting, a handle, often wooden, and a power cable or cord. In some versions, the soldering iron can be equipped with several interchangeable tips.

The power of such a soldering iron is fixed, most often 40 or 60 watts. But it is more convenient to use a tool with the ability to adjust the power. Such models are also produced, although they are more expensive.

To perform soldering work, tools with different parameters are required. At the same time, it is not advisable to have several soldering irons with different power and, accordingly, with different tip heating temperatures.

When mounting components on a board, the temperature of the tip is required to warm up the leads and melt the solder. Increased temperatures can lead to the combustion of individual elements, peeling of conductive tracks from the board, damage to the insulation of the wires.

At the same time, the use of a soldering iron with a lower power, and therefore with a lower tip heating temperature, which makes it possible to reach the set value, forces an increase in the exposure time to the parts and solder.

As a result, components fail from prolonged heating, and the insulation may crack over time due to the loss of mechanical properties.

Conclusion: when soldering, if heating of large areas and massive parts is required, it is necessary to increase not the temperature, but the power of the soldering iron, reducing the contact time of the tip with the outputs of the part to the minimum possible.

In this case, the solder must melt and provide reliable contact with the part, which in this mode will not undergo overheating.

Heat management

To heat a massive part to the desired temperature, the same massive soldering iron tip is needed so that the heating rate is higher than the heat removal rate of the part.

A tool that can simultaneously cope with the above tasks is a fairly powerful soldering iron with temperature control.

That is, the maximum power of the soldering iron should be sufficient to heat large leads, and the temperature should be regulated within certain limits and selected in accordance with the working conditions.

Then the massive tip will have greater thermal inertia and heat the part to the required degree, without the risk of overheating.

There are several ways to adjust the soldering iron temperature:

maximum-minimum heating (simple switch);
dimmer adjustment;
the use of control microcircuits in the handle of the device;
external control unit;
use of a hair dryer.

Using a soldering iron with adjustment, in addition to the advantages described above, you can significantly save on electricity consumption with large amounts of work performed, extend the life of the device, due to its shorter operating time at maximum power, and reduce the amount of harmful substances released during high temperature soldering.

Switches and dimmers

The simplest temperature adjustment is used in soldering irons with a switch that allows only two positions, and, accordingly, two temperature values.

At the minimum value, the soldering iron, mounted on a stand, simply keeps the tip warm, and when you press a key or button, the tip heats up to the maximum temperature at which soldering is performed.

Obviously, of the advantages described above, such a soldering iron has only the ability to save electricity. The main task of adjustment - the production of high-quality and safe installation of components - remains impossible.

The second type of soldering iron with adjustment is dimmable. Their design involves the inclusion of a dimmer in the gap of the power cable - a device that limits the power consumption of the soldering iron.

In this case, it really becomes possible to adjust the temperature of the sting, but this is done due to the voltage drop in the dimmer.

Accordingly, there can be no question of any efficiency of such a scheme. But the price of such devices is quite low and can play a decisive role in the choice.

Control units

The next type of soldering irons are already more complex devices with a power supply, in which regulation takes place using a block of semiconductors and microcircuits. Such a unit is compact and can be located in the body of the soldering iron handle, which is very convenient.

The regulator can also be located on the handle. At a fairly modest price, this is a completely acceptable option that allows you to produce high-quality soldering.

Another type of soldering iron with adjustment are tools with an external power supply. Due to the presence of these blocks, it is possible to operate the device on a rectified direct current with stable voltage values.

Such a power supply also serves as a soldering iron temperature stabilizer, which will remain unchanged no matter how much the mains voltage changes. Many radio components are demanding precisely for this soldering mode.

The disadvantage of the models can be considered bulky, low mobility, but if we take into account that high-quality installation can only be done in an equipped workshop, and not “on the knee”, as they say in such cases, then you can turn a blind eye to this.

The most precise adjustment and adjustment can only be achieved with the help of a hairdryer, which preheats the board or solder to help a conventional soldering iron.

DIY temperature controller

If you have sufficient knowledge, skills and suitable materials, you can turn an ordinary 60-watt soldering iron into a device in which it will be possible to adjust the temperature of the tip, and a full and high-quality installation of radio components will be ensured.

To do this, you will need a little fine-tuning of the tool. To do this, you can use the adjustment circuits assembled on the available radio components of domestic production.

To assemble the simplest temperature controller, you can use a circuit with a variable resistor from the SP-1 series, a KU101G thyristor, any diode rated for a current of at least 1 A.

The circuit is assembled directly on the case of a variable resistor, without making a board. To accommodate the device, you can use a case from any power supply of suitable sizes. The result is a device in which a standard soldering iron is powered from the mains through a voltage regulator located in the plug.

Such a temperature controller can be used when working with a soldering iron with low power up to 60 watts.

To adjust the temperature when using a soldering iron of greater power, a more complicated device is used.

It is also assembled on parts and components of domestic production. This circuit is assembled on a board and placed in a suitably sized case.

Adjustment is carried out by a variable resistor R2 in the range from 50% to 100% of the power of the connected device. The circuit will withstand loads up to 300 watts. This will be more than enough for using a household soldering iron.

Since the soldering process is associated with the melting of solder, it is always necessary to maintain the optimum heating temperature. The following factors are taken into account:

Solder melting temperature (from 150 to 320 degrees);
Heat resistance of elements on which soldering is performed. Many radio components simply fail during prolonged heating, and the wire insulation loses its properties;
Scattering area of contacts. When connecting massive elements, it is necessary to have a margin for temperature and power.

If you are just soldering wires, it is enough to know the power of the soldering iron and the approximate melting point of the solder. The criterion is simple - fast or slow heating.

But when installing printed circuit boards or repairing electrical appliances, an incorrectly selected soldering iron temperature can result in the purchase of expensive radio components that will be damaged by high temperatures.

Soldering iron temperature for soldering - how to choose

If the installation is not associated with specific radio components that are sensitive to overheating, the degree of heating of the tip should be 10 degrees higher than the melting point of the solder. And not the starting point of the melt - namely, the temperature of a stable presence in the liquid state;
If you plan to connect contacts with a large area and mass, it is not the amount of heating that increases, but the power of the soldering iron. A low-power device with a high temperature will still not cope with dissipation. The mass of the part is compensated by the corresponding size of the working tip. And for its warming up, power is required, not degrees;
The passport of radio components usually indicates the maximum allowable value of case heating. This also applies to the soldering temperature. Again, opt for power over higher degrees. We must try to keep the contact time between the sting and the part to be minimal. The solder should melt, and the body should not be overheated.

Electric soldering irons with temperature control are produced for various working conditions.

It does not matter the design, the regulator can be built into the housing or made as a separate unit. The main thing is that you know how hot the tip of the tool is.

Benefits of Adjusting the Temperature of the Soldering Iron

Energy saving;
Extending the life of the electrical appliance;
At elevated temperatures, the sting becomes covered with scale, you are constantly distracted by cleaning it. At the same time, the thickness of the metal decreases - accordingly, wear occurs faster;
You will not damage radio components that are sensitive to overheating;
On the circuit board, there will be no delamination of current-carrying tracks due to overheating;
When changing the solder, the soldering quality will remain at the same level;
Less smoke from overheated flux;
You do not need to change the soldering iron when performing different types of work - just change the temperature;