A power regulator for a soldering iron is a device that allows you to control the soldering process. The quality of this process can be significantly increased if the main parameters are taken under control. A soldering iron is a necessary tool in the household for a person who likes to do everything with his own hands.

The main characteristic of soldering is the maximum temperature at the tip of the soldering iron. The power regulator for the soldering iron ensures that it changes in the desired mode. This allows not only to improve the quality of the metal connection, but also to increase the service life of the device itself.

What is a regulator for?

Soldering of metals is carried out due to the fact that the molten solder fills the space between the workpieces to be joined and partially penetrates into their material. The strength of the connecting seam largely depends on the quality of the melt, i.e. on its heating temperature. If the soldering iron tip has insufficient temperature, then it is necessary to increase the heating time, which can destroy the material of the parts and lead to premature failure of the device itself. Excessive heating of the filler metal leads to the formation of thermal decomposition products, which significantly reduces the quality of the weld.

The temperature of the working area of ​​the soldering iron tip and the time it takes to set it depend on the power of the heating element. A smooth change in voltage allows you to choose the optimal mode of operation of the heater. Therefore, the main task that the power regulator for the soldering iron must solve is to set the required electrical voltage and maintain it during the soldering process.

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The simplest schemes

The simplest power regulator circuit for a soldering iron is shown in Fig. 1. This scheme has been known for more than 30 years and has shown itself perfectly at home. It allows you to solder parts with power control in the range of 50-100%.

Such an elementary circuit is assembled at the output ends of the variable resistor R1 and is connected by four soldering points. The positive terminal of the capacitor C1, the leg of the resistor R2 and the control electrode of the thyristor VD2 are soldered together. The thyristor case acts as an anode, so it should be isolated. The whole circuit is small and fits into a case from an unnecessary power supply of any device.

A hole with a diameter of 10 mm is drilled on the case wall, in which a variable resistor is fixed with its threaded leg. As a load, you can use any light bulb with a power of 20-40 watts. The cartridge with the light bulb is fixed in the housing, and the top of the light bulb is brought out into the hole so that the operation of the device can be controlled by its glow.

Parts that should be used in the recommended circuit: diode 1N4007 (any similar one for a current of 1 A and a voltage of up to 600 V can be used); thyristor KU101G; electrolytic capacitor with a capacity of 4.7 microfarads for a voltage of 100 V; resistor 27-33 kOhm with power up to 0.5 W; variable resistor SP-1 with a resistance of up to 47 kOhm. The soldering iron power regulator with such a circuit proved to be reliable with EPSN type soldering irons.

A simple but more modern circuit can be based on the replacement of a thyristor and a diode with a triac, and a neon lamp of the MH3 or MH4 type can also be used as a load. The following parts are recommended: triac KU208G; electrolytic capacitor 0.1 uF; variable resistor up to 220 kOhm; two resistors with a resistance of 1 kOhm and 300 Ohm.

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Design improvement

The power regulator, assembled on the basis of the simplest circuit, makes it possible to maintain the soldering mode, but does not guarantee the complete stability of the process. There are a number of fairly simple designs that allow for stable maintenance and regulation of the temperature at the soldering iron tip.

The electrical part of the device can be divided into a power section and a control circuit. The power function is determined by the thyristor VS1. The voltage from the electrical network (220 V) is supplied to the control circuit from the anode of this thyristor.

The operation of the power thyristor is controlled on the basis of transistors VT1 and VT2. The power supply of the control system is provided by a parametric stabilizer, which includes the resistance R5 (to eliminate excess voltage) and the zener diode VD1 (to limit the increase in voltage). Variable resistor R2 provides manual voltage control at the output of the device.

The assembly of the regulator from the installation of the power section of the circuit occurs as follows. The legs of the diode VD2 are soldered to the conclusions of the thyristor. The R6 resistance legs are connected to the control electrode and the thyristor cathode, and one R5 resistance leg is connected to the thyristor anode, the second leg is connected to the VD1 zener diode cathode. The control electrode is connected to the control unit by connecting to the emitter of the transistor VT1.

The basis of the control unit is silicon transistors KT315 and KT361. With their help, the magnitude of the voltage created on the control electrode of the thyristor is set. The thyristor passes current only if an unlocking voltage is applied to its control electrode, and its value determines the strength of the transmitted current.

The entire circuit of the regulator has a small-sized design and can easily be placed in the case of a surface-mounted socket. A plastic housing should be selected to simplify drilling holes. It is advisable to assemble the power part and the control unit on different panels, and then connect them with three wires. The best option is to assemble panels on textolite coated with foil, but in practice all connections can be made with thin wires and panels can be assembled on any insulating plate (even on thick cardboard).

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Do-it-yourself power regulator assembly

The device is assembled inside the socket housing. The output ends are connected to the socket contacts, which will make it possible to connect the soldering iron by simply inserting its plug into the socket sockets. In the case, first, a variable resistor should be fixed, and its threaded part should be brought out through the drilled hole. Then a thyristor with a mounted power unit should be placed in the housing. Finally, a control panel is installed in any free space. From below the socket is closed by a cover. A cord with a plug is connected to the input of the power unit, which is led out of the socket housing for connection to the electrical network.

Before connecting the soldering iron, the power regulator should be checked. To do this, a voltmeter or multimeter is connected to the outputs of the device (to the socket). A voltage of 220 V is applied to the input of the device. By smoothly rotating the knob of the variable resistor, observe the change in the reading of the device. If the voltage at the output of the regulator increases smoothly, then the device is assembled correctly. The practice of using the device shows that the optimal value of the output voltage is 150 V. This value should be fixed with a red mark indicating the position of the variable resistor knob. It is advisable to note several voltage values.

The basis was an article in the magazine Radio No. 10 for 2014. When this article caught my eye, I liked the idea and the ease of implementation. But I myself use small-sized low-voltage soldering irons.

A direct circuit for low-voltage soldering irons cannot be used due to the low resistance of the soldering iron heater and, as a result, the significant current of the measuring circuit. I decided to redo the layout.

The resulting circuit is suitable for any soldering iron with a supply voltage of up to 30V. The heater of which has a positive TCR (hot has more resistance). The best result will give a ceramic heater. For example, you can start a soldering iron from a soldering station with a burned out thermal sensor. But soldering irons with a nichrome heater also work.

Since the ratings in the circuit depend on the resistance and TCS of the heater, before implementing it, you need to select and check the soldering iron. Measure the resistance of the heater in cold and hot condition.

And also I recommend to check the reaction to the mechanical load. One of my soldering irons turned out to be a catch. Measure the resistance of the cold heater, turn it on briefly and re-measure. After warming up, measuring the resistance, press on the tip and lightly tap, simulating work with a soldering iron, watch for resistance jumps. My soldering iron ended up behaving as if it had a carbon microphone rather than a heater. As a result, when trying to work, a slightly stronger pressing led to a shutdown due to an increase in the resistance of the heater.

As a result, I redid the assembled circuit for an EPSN soldering iron with a heater resistance of 6 ohms. The EPSN soldering iron is the worst option for this circuit, the low TCR of the heater and the large thermal inertia of the design make thermal stabilization sluggish. But nevertheless, the heating time of the soldering iron was reduced by 2 times without overheating, relative to voltage heating, which gives approximately the same temperature. And with prolonged tinning or soldering, the temperature drop is less.

Consider the algorithm of work.

1. At the initial time at input 6 U1.2, the voltage is close to 0, it is compared with the voltage from the divider R4, R5. Voltage appears at the output of U1.2. (The PIC resistor R6 increases the hysteresis U1.2 for protection interference.)

2. From the output of U1.2, the voltage through the resistor R8 opens the transistor Q1. (Resistor R13 is needed to ensure Q1 is closed if the op-amp cannot output a voltage equal to the negative supply voltage)

3. The measuring current flows through the soldering iron heater RN, diode VD3, resistor R9 and transistor Q1. (the power of the resistor R9 and the current of the transistor Q1 are selected based on the magnitude of the measuring current, while the voltage drop on the soldering iron should be chosen around 3 V, this is a compromise between the measurement accuracy and the power dissipated by R9. If the power dissipated is too large, then you can increase the resistance R9 , but the accuracy of temperature stabilization will decrease).

4. At input 3 U1.1, when the measuring current flows, a voltage appears, depending on the ratio of the resistances R9 and RN, as well as the voltage drop across VD3 and Q1, which is compared with the voltage from the divider R1, R2, R3.

5. If the voltage at input 3 of the amplifier U1.1 exceeds the voltage at input 2 (cold soldering iron low resistance RN). Voltage will appear at output 1 of U1.1.

6. The voltage from output 1 U1.1 through a discharged capacitor C2 and diode VD1 supplies input 6 U1.2, eventually closing Q1 and disconnecting R9 from the measuring circuit. (Diode VD1 is required if the op amp does not allow negative input voltage.)

7. The voltage from output 1 U1.1 through the resistor R12 charges the capacitor C3 and the gate capacitance of the transistor Q2. And when the threshold voltage is reached, the transistor Q2 opens including the soldering iron, while the diode VD3 closes, disconnecting the resistance of the soldering iron heater RN from the measuring circuit. (Resistor R14 is necessary for guaranteed closing of Q2 if the operational amplifier cannot output a voltage equal to the negative supply voltage, and also at a higher supply voltage of the circuit at the gate of the transistor, the voltage does not exceed 12 V.)

8. Resistor R9 and heater resistance RN are disconnected from the measuring circuit. The voltage across capacitor C1 is maintained by resistor R7, compensating for possible leakage through transistor Q1 and diode VD3. Its resistance must significantly exceed the resistance of the soldering iron heater RN, so as not to introduce errors in the measurement. In this case, the capacitor C3 was required for RN to be disconnected from the measuring circuit after R9 was disconnected, otherwise the circuit would not latch into the heating position.

9. The voltage from output 1 U1.1 charges the capacitor C2 through the resistor R10. When the voltage at input 6 U1.2 reaches half the supply voltage, transistor Q1 will open and a new measurement cycle will begin. The charging time is selected depending on the thermal inertia of the soldering iron i.e. its size, for a miniature soldering iron 0.5s for EPSN 5s. It is not worth making the cycle too short, since only the heater temperature will begin to stabilize. The ratings indicated in the diagram give a cycle time of approximately 0.5 s.

10. Capacitor C1 will be discharged through the open transistor Q1 and resistor R9. After the voltage at input 3 U1.1 drops below input 2 U1.1, a low voltage will appear at the output.

11. Low voltage from output 1 U1.1 through diode VD2 will discharge capacitor C2. And also through the resistor R12 chain, the capacitor C3 will close the transistor Q2.

12. When the transistor Q2 is closed, the VD3 diode will open and current will flow through the measuring circuit RN, VD3, R9, Q1. And the charging of the capacitor C1 will begin. If the soldering iron is heated above the set temperature and the resistance RN has increased enough that the voltage at input 3 U1.1 does not exceed the voltage from the divider R1, R2, R3 at input 2 U1.1, then output 1 U1.1 will remain low voltage. This state will last until the soldering iron cools down below the temperature set by resistor R2, then the cycle of work will be repeated starting from the first point.

Choice of components.

1. Operational amplifier I used LM358 with it the circuit can work up to 30V voltage. But you can, for example, use TL 072 or NJM 4558, etc.

2. Transistor Q1. The choice depends on the magnitude of the measuring current. If the current is about 100 mA, then you can use transistors in a miniature package, for example, in the SOT-23 2N2222 or BC-817 package. more e.g. D 882, D1802 etc.

3. Resistor R9. The hottest part in the circuit dissipates almost the entire measuring current on it, the power of the resistor can be approximately considered (U ^ 2) / R9. The resistance of the resistor is selected so that the voltage drop during the measurement on the soldering iron is about 3V.

4. Diode VD3. It is desirable to use a Schottky diode with a current margin to reduce the voltage drop.

5. Transistor Q2. Any power N MOSFET. I used a 32N03 taken from an old motherboard.

6. Resistor R1, R2, R3. The total resistance of the resistors can be from units of kilo-ohms to hundreds of kilo-ohms, which allows you to select the resistances R1, R3 of the divider, under the variable resistor R2 available. It is difficult to accurately calculate the value of the divider resistors, since there is a transistor Q1 and a diode VD3 in the measuring circuit, it is difficult to take into account the exact voltage drop across them.

Approximate resistance ratio:
For cold soldering iron R1/(R2+R3)≈ RNhol/ R9
For the maximum heated R1/R2≈ RNhort/ R9

7. Since the change in resistance to stabilize the temperature is much less than an ohm. Then high-quality connectors should be used to connect the soldering iron, and even better, directly solder the soldering iron cable to the board.

8. All diodes, transistors and capacitors must be rated for at least 1.5 times the supply voltage.

The circuit, due to the presence of the VD3 diode in the measuring circuit, has little sensitivity to changes in temperature and supply voltage.After manufacturing, the idea came up how to reduce these effects.Need to be replaced Q1 on N MOSFET with low on-resistance and add another diode similar to VD3. Additionally, both diodes can be connected with a piece of aluminum for thermal contact.

Execution.

I made the circuit as much as possible using SMD mounting components. Resistors and ceramic capacitors type size 0805.Electrolytes in B.Chip LM358 in the package SOP-8. Diode ST34 in SMC package. Transistor Q1 can be mounted in any of SOT-23, TO-252 or SOT-223 packages. Transistor Q2 can be in TO-252 packages or TO-263. Resistor R2 VSP4-1. Resistor R9 like the hottest itemit is better to place it outside the board, only for soldering irons with a power of less than 10W it is possible as R9 unsolder 3 resistors 2512.

The board is made of two-sided textolite. On one side, copper is not etched and is used underground on the board, the holes into which the jumpers are soldered are designated as holes with metallization, the remaining holes on the side of solid copper are countersinked with a larger diameter drill. For the board, you need to print it in a mirror image.

A bit of theory. Or why high frequency control is not always good.

If you ask what frequency of control is better. Most likely the answer will be the higher the better, i.e. the more accurate.

I will try to explain how I understand this question.

If we take the option when the sensor is at the tip of the sting, then this answer is correct.

But in our case, the sensor is the heater, although in many soldering stations the sensor is not located in the tip, but next to the heater. In such cases, this answer will not be correct.

Let's start with the accuracy of holding the temperature.

When the soldering iron lies on a stand and they begin to compare temperature controllers, which circuit holds the temperature more accurately, and we are often talking about numbers of one degree or less. But is temperature accuracy so important at this moment? Indeed, in fact, it is more important to maintain the temperature at the time of soldering, that is, how much the soldering iron can maintain the temperature with intensive power take-off from the tip.

Imagine a simplified model of a soldering iron. The heater to which power is supplied and the tip from which there is a small power take-off into the air when the soldering iron is on a stand or a large one during soldering. Both of these elements have a thermal inertia or heat capacity, as a rule, a heater has a significantly lower heat capacity. But between the heater and the tip there is a thermal contact that has its own thermal resistance, which means that in order to transfer some power from the heater to the tip, you must have a temperature difference. The thermal resistance between the heater and the tip may vary depending on the design. In Chinese soldering stations, heat transfer generally occurs through an air gap, and as a result, a soldering iron with a power of half a hundred watts and, according to the indicator, holding the temperature to a degree cannot solder the pad on the board. If the temperature sensor is in the sting, then you can simply increase the temperature of the heater. But we have a sensor and a heater as one unit, and with an increase in power take-off from the tip at the time of soldering, the temperature of the tip will drop, because due to thermal resistance, a temperature drop is needed to transfer power.

This problem cannot be completely solved, but it can be minimized as much as possible. And the lower heat capacity of the heater relative to the sting will allow this to be done. And so we have a contradiction in order to transfer power to the sting, it is necessary to increase the temperature of the heater to maintain the temperature of the sting, but we do not know the temperature of the sting because we measure the temperature at the heater.

The control option implemented in this scheme allows us to resolve this dilemma in a simple way. Although you can try to come up with more optimal control models, the complexity of the scheme will increase.

And so in the circuit, energy is supplied to the heater for a fixed time and it is long enough for the heater to have time to warm up significantly above the stabilization temperature. A significant temperature difference appears between the heater and the sting and the heat power is transferred to the sting. After turning off the heating, the heater and the tip begin to cool down. The heater cools down by transferring power to the tip, and the tip cools down by transferring power to the external environment. But due to the lower heat capacity, the heater will have time to cool down before the temperature of the tip changes significantly, and also during heating, the temperature on the tip will not have time to change much. Re-switching on will occur when the heater temperature drops to the stabilization temperature, and since power is transferred mainly to the tip, the heater temperature at this moment will differ slightly from the temperature of the tip. And the stabilization accuracy will be the higher the lower the heat capacity of the heater and the lower the thermal resistance between the heater and the tip.

If the duration of the heating cycle is too low (high control frequency), then the heater will not experience overheating moments when there is an effective transfer of power to the tip. And as a result, at the time of soldering, there will be a strong drop in the temperature of the tip.

If the heating time is too long, the heat capacity of the tip will not be enough to smooth out temperature fluctuations to an acceptable value, and the second danger is that if the thermal resistance between the heater and the tip is high at high heater power, then the heater can be heated above the temperatures allowed for its operation, which will lead to its breakdown.

As a result, it seems to me that it is necessary to select the time setting elements C2 R10 so that when measuring the temperature at the end of the sting, slight temperature fluctuations are visible. Taking into account the accuracy of the indication of the tester and the inertia of the sensor, noticeable fluctuations of one or several degrees will not lead to fluctuations in the actual temperature of more than a dozen degrees, and such temperature instability is more than sufficient for an amateur radio soldering iron.

Here's what ended up happening

Since the soldering iron that I initially counted on turned out to be unsuitable, I converted it into a version for an EPSN soldering iron with a 6 ohm heater. Without overheating, I worked from 14v, I applied 19v to the circuit, so that there would be a margin for regulation.

Modified under option with VD3 installation and replacing Q1 with a MOSFET. I did not remake the board, I just installed new parts.

The sensitivity of the circuit to changes in the supply voltage has not completely disappeared. Such sensitivity will not be noticeable on soldering irons with a ceramic tip, and for nichrome it becomes noticeable when the supply voltage changes by more than 10%.

LUT fee

The wiring is not quite according to the board layout. Instead of resistors, I soldered the VD5 diode, cut the track to the transistor and drilled a hole for the wire from the resistor R9.

An LED and a resistor go to the front panel. The board will be attached to a variable resistor, since it is not large and mechanical loads are not expected.

Finally, the circuit acquired the following form; I indicate the resulting denominations for any other soldering iron, which must be selected as I wrote above. The resistance of the soldering iron heater is of course not exactly 6 ohms. Transistor Q1 had to be taken because the power case did not just change, although they both can be the same. Resistor R9 even PEV-10 heats up sensitively. Capacitor C6 does not particularly affect the operation and I removed it. On the board, I also soldered the ceramics parallel to C1, but normally without it.

P.S. It is interesting if someone collects for a soldering iron with a ceramic heater, there is nothing to check for yourself yet.Write if you need additional materials or explanations.

In order to get high-quality and beautiful soldering, you need to choose the right soldering iron power and provide a certain temperature of its tip, depending on the brand of solder used. I offer several schemes for home-made thyristor temperature controllers for heating the soldering iron, which will successfully replace many industrial ones that are incomparable in price and complexity.

Attention, the following thyristor circuits of temperature controllers are not galvanically isolated from the electric network and touching the current-carrying elements of the circuit is life-threatening!

To adjust the temperature of the soldering iron tip, soldering stations are used in which the optimum temperature of the soldering tip is maintained in manual or automatic mode. The availability of a soldering station for the home craftsman is limited by the high price. For myself, I solved the issue of temperature control by developing and manufacturing a regulator with manual smooth temperature control. The circuit can be modified to automatically maintain the temperature, but I don’t see the point in this, and practice has shown that manual adjustment is quite enough, since the mains voltage is stable and the room temperature too.

Classic thyristor regulator circuit

The classic thyristor circuit of the soldering iron power regulator did not meet one of my main requirements, the absence of radiating interference into the mains and the air. And for a radio amateur, such interference makes it impossible to fully engage in what you love. If the circuit is supplemented with a filter, then the design will turn out to be cumbersome. But for many applications, such a thyristor regulator circuit can be successfully used, for example, to adjust the brightness of incandescent lamps and heating appliances with a power of 20-60 watts. That's why I decided to present this scheme.

In order to understand how the circuit works, I will dwell in more detail on the principle of operation of the thyristor. A thyristor is a semiconductor device that is either open or closed. to open it, you need to apply a positive voltage of 2-5 V to the control electrode, depending on the type of thyristor, relative to the cathode (k is indicated in the diagram). After the thyristor has opened (the resistance between the anode and cathode will become 0), it is not possible to close it through the control electrode. The thyristor will be open until the voltage between its anode and cathode (marked a and k in the diagram) becomes close to zero. It's that simple.

The circuit of the classical regulator works as follows. The AC mains voltage is supplied through the load (an incandescent bulb or a soldering iron winding) to a rectifier bridge circuit made on VD1-VD4 diodes. The diode bridge converts the AC voltage into a DC voltage that changes according to a sinusoidal law (diagram 1). When the middle terminal of the resistor R1 is in the leftmost position, its resistance is 0, and when the voltage in the network begins to increase, the capacitor C1 begins to charge. When C1 is charged to a voltage of 2-5 V, current will flow through R2 to the control electrode VS1. The thyristor will open, short-circuit the diode bridge and the maximum current will flow through the load (upper diagram).

When you turn the knob of the variable resistor R1, its resistance will increase, the charge current of the capacitor C1 will decrease and it will take more time for the voltage across it to reach 2-5 V, so the thyristor will not open immediately, but after some time. The larger the value of R1, the longer the charge time for C1, the thyristor will open later and the power received by the load will be proportionally less. Thus, by rotating the knob of the variable resistor, the heating temperature of the soldering iron or the brightness of the incandescent light bulb is controlled.

Above is a classic thyristor controller circuit made on a KU202N thyristor. Since more current is needed to control this thyristor (according to the passport 100 mA, the real one is about 20 mA), the values ​​​​of the resistors R1 and R2 are reduced, and R3 is excluded, and the value of the electrolytic capacitor is increased. When repeating the circuit, it may be necessary to increase the value of the capacitor C1 to 20 microfarads.

The simplest thyristor regulator circuit

Here is another of the simplest thyristor power controller circuits, a simplified version of the classic controller. The number of parts is kept to a minimum. Instead of four diodes VD1-VD4, one VD1 is used. Its principle of operation is the same as that of the classical scheme. The schemes differ only in that the adjustment in this temperature controller circuit occurs only according to the positive period of the network, and the negative period passes through VD1 without changes, so the power can only be adjusted in the range from 50 to 100%. To adjust the heating temperature of the soldering tip, more is not required. If the VD1 diode is excluded, then the power adjustment range will be from 0 to 50%.

If a dinistor, for example KN102A, is added to the circuit break from R1 and R2, then the electrolytic capacitor C1 can be replaced with an ordinary one with a capacity of 0.1 mF. Thyristors for the above circuits are suitable, KU103V, KU201K (L), KU202K (L, M, N), designed for a forward voltage of more than 300 V. Diodes are also almost any, designed for a reverse voltage of at least 300 V.

The above circuits of thyristor power controllers can be successfully used to control the brightness of the glow of lamps in which incandescent bulbs are installed. It will not work to regulate the brightness of the glow of lamps in which energy-saving or LED bulbs are installed, since electronic circuits are mounted in such bulbs, and the regulator will simply disrupt their normal operation. The bulbs will shine at full power or flash and this may even lead to premature failure.

The circuits can be used for regulation with a supply voltage of 36 V or 24 V AC. It is only necessary to reduce the resistor values ​​​​by an order of magnitude and use a thyristor that matches the load. So a soldering iron with a power of 40 W at a voltage of 36 V will consume a current of 1.1 A.

Thyristor regulator circuit does not emit interference

The main difference between the circuit of the presented soldering iron power regulator and those presented above is the complete absence of radio interference in the electrical network, since all transients occur at a time when the voltage in the supply network is zero.

Starting to develop a temperature controller for a soldering iron, I proceeded from the following considerations. The scheme should be simple, easily repeatable, components should be cheap and available, high reliability, minimal dimensions, efficiency close to 100%, no radiating interference, the possibility of modernization.

The temperature controller circuit works as follows. The AC voltage from the mains is rectified by a diode bridge VD1-VD4. From a sinusoidal signal, a constant voltage is obtained, varying in amplitude as half a sinusoid with a frequency of 100 Hz (diagram 1). Further, the current passes through the limiting resistor R1 to the zener diode VD6, where the voltage is limited in amplitude to 9 V, and has a different shape (diagram 2). The resulting pulses charge the electrolytic capacitor C1 through the VD5 diode, creating a supply voltage of about 9 V for the DD1 and DD2 microcircuits. R2 performs a protective function, limiting the maximum possible voltage on VD5 and VD6 to 22 V, and ensures the formation of a clock pulse for the operation of the circuit. With R1, the generated signal is fed to the 5th and 6th outputs of the 2OR-NOT element of the logical digital microcircuit DD1.1, which inverts the incoming signal and converts it into short rectangular pulses (diagram 3). From the 4th output of DD1, the pulses are fed to the 8th output of the D trigger DD2.1, operating in the RS trigger mode. DD2.1, like DD1.1, also performs the function of inverting and signal conditioning (diagram 4).

Please note that the signals in diagram 2 and 4 are almost the same, and it seemed that it was possible to apply a signal from R1 directly to pin 5 of DD2.1. But studies have shown that in the signal after R1 there is a lot of interference coming from the mains, and without double shaping, the circuit did not work stably. And it is not advisable to install additional LC filters when there are free logic elements.

On the DD2.2 trigger, a soldering iron temperature controller control circuit is assembled and it works as follows. Rectangular pulses arrive at pin 3 DD2.2 from pin 13 DD2.1, which with a positive edge overwrite at pin 1 DD2.2 the level that is currently present at the D input of the microcircuit (pin 5). At pin 2, the signal is the opposite level. Consider the work of DD2.2 in detail. Let's say on pin 2, a logical unit. Through the resistors R4, R5, the capacitor C2 is charged to the supply voltage. Upon receipt of the first pulse with a positive drop, 0 will appear at pin 2 and capacitor C2 will quickly discharge through diode VD7. The next positive drop at pin 3 will set a logical unit at pin 2 and capacitor C2 will start charging through resistors R4, R5.

The charge time is determined by the time constant R5 and C2. The larger R5, the longer it will take C2 to charge. Until C2 is charged to half the supply voltage at pin 5 there will be a logical zero and positive pulse drops at input 3 will not change the logic level at pin 2. As soon as the capacitor is charged, the process will repeat.

Thus, only the number of pulses from the supply network specified by resistor R5 will pass to the outputs of DD2.2, and most importantly, these pulses will fluctuate during the transition of the voltage in the supply network through zero. Hence the absence of interference from the operation of the temperature controller.

From pin 1 of the DD2.2 microcircuit, pulses are fed to the DD1.2 inverter, which serves to eliminate the influence of the thyristor VS1 on the operation of DD2.2. Resistor R6 limits the control current of thyristor VS1. When a positive potential is applied to the control electrode VS1, the thyristor opens and voltage is applied to the soldering iron. The regulator allows you to adjust the power of the soldering iron from 50 to 99%. Although the resistor R5 is variable, the adjustment due to the operation of DD2.2 heating the soldering iron is carried out in steps. With R5 equal to zero, 50% of the power is supplied (diagram 5), when turning through a certain angle it is already 66% (diagram 6), then already 75% (diagram 7). Thus, the closer to the rated power of the soldering iron, the smoother the adjustment works, which makes it easy to adjust the temperature of the soldering tip. For example, a 40W soldering iron can be set to 20W to 40W.

The design and details of the temperature controller

All parts of the thyristor temperature controller are placed on a fiberglass printed circuit board. Since the circuit does not have a galvanic isolation from the electrical network, the board is placed in a small plastic case of the former adapter with an electrical plug. A plastic handle is put on the axis of the variable resistor R5. Around the handle on the body of the regulator, for the convenience of adjusting the degree of heating of the soldering iron, a scale with conditional numbers is applied.

The cord from the soldering iron is soldered directly to the PCB. You can make the connection of the soldering iron detachable, then it will be possible to connect other soldering irons to the temperature controller. Surprisingly, the current drawn by the temperature controller control circuit does not exceed 2 mA. This is less than the consumption of the LED in the lighting circuit of the light switches. Therefore, special measures to ensure the temperature regime of the device are not required.

Chips DD1 and DD2 any 176 or 561 series. The Soviet thyristor KU103V can be replaced, for example, with a modern thyristor MCR100-6 or MCR100-8, designed for a switching current of up to 0.8 A. In this case, it will be possible to control the heating of a soldering iron with a power of up to 150 W. Diodes VD1-VD4 are any, designed for a reverse voltage of at least 300 V and a current of at least 0.5 A. IN4007 is perfect (Uob \u003d 1000 V, I \u003d 1 A). Diodes VD5 and VD7 any pulse. Any low-power zener diode VD6 for a stabilization voltage of about 9 V. Capacitors of any type. Any resistors, R1 with a power of 0.5 W.

The power regulator does not need to be adjusted. With serviceable parts and without installation errors, it will work immediately.

The circuit was developed many years ago, when computers, and even more so laser printers, did not exist in nature, and therefore I made a printed circuit board drawing using old-fashioned technology on chart paper with a grid pitch of 2.5 mm. Then the drawing was glued with Moment glue to thick paper, and the paper itself to foil-coated fiberglass. Next, holes were drilled on a home-made drilling machine and the paths of future conductors and contact pads for soldering parts were drawn by hand.

The drawing of the thyristor temperature controller has been preserved. Here is his photo. Initially, the VD1-VD4 rectifier diode bridge was made on the KTs407 microassembly, but after the microassembly was torn twice, it was replaced with four KD209 diodes.

How to reduce the level of interference from thyristor regulators

To reduce interference emitted by thyristor power controllers into the electrical network, ferrite filters are used, which are a ferrite ring with wound turns of wire. Such ferrite filters can be found in all switching power supplies for computers, TVs and other products. An efficient, interference-suppressing ferrite filter can be retrofitted to any thyristor controller. It is enough to pass the wire for connecting to the electrical network through the ferrite ring.

It is necessary to install a ferrite filter as close as possible to the source of interference, that is, to the place where the thyristor is installed. The ferrite filter can be placed both inside the instrument housing and on its outer side. The more turns, the better the ferrite filter will suppress interference, but it is enough and just to pass the mains wire through the ring.

The ferrite ring can be taken from the interface wires of computer equipment, monitors, printers, scanners. If you pay attention to the wire connecting the computer system unit to the monitor or printer, you will notice a cylindrical thickening of the insulation on the wire. This location contains a ferrite high-frequency noise filter.

It is enough to cut the plastic insulation with a knife and remove the ferrite ring. Surely you or your friends will find an unnecessary interface cable from an inkjet printer or an old kinescope monitor.

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.

There are many models of soldering irons in stores - from cheap Chinese to expensive ones, with a built-in temperature controller, even soldering stations are sold.

Another thing is whether the same station is needed if such work needs to be done once a year, or even less often? It's easier to buy an inexpensive soldering iron. And someone at home has preserved simple but reliable Soviet instruments. A soldering iron that is not equipped with additional functionality heats to the fullest while the plug is in the network. And when turned off, it cools down quickly. An overheated soldering iron can ruin the work: it becomes impossible for them to solder something firmly, the flux evaporates quickly, the tip oxidizes and the solder rolls off it. An insufficiently heated tool can completely ruin the parts - due to the fact that the solder does not melt well, the soldering iron can be overexposed close to the parts.

To make work more comfortable, you can assemble a power regulator with your own hands, which will limit the voltage and thereby prevent the soldering iron tip from overheating.

Do-it-yourself soldering iron regulators. Overview of mounting methods

Depending on the type and set of radio components, power regulators for a soldering iron can be of different sizes, with different functionality. It is possible to assemble both a small simple device in which heating is stopped and resumed by pressing a button, or an overall one with a digital indicator and program control.

Possible types of mounting in the housing: plug, socket, station

Depending on the power and tasks, the regulator can be placed in several types of housing. The simplest and most comfortable is a fork. To do this, you can use a cell phone charger or any adapter case. It remains only to find a handle and place it in the wall of the case. If the body of the soldering iron allows (there is enough space), you can place the board with the parts in it.

Another type of housing for simple regulators is a socket. It can be either single or a tee-extension. In the latter, you can very conveniently put a pen with a scale.

There can also be several mounting options for a regulator with a voltage indicator. It all depends on the ingenuity of the radio amateur and imagination. This can be either an obvious option - an extension cord with an indicator mounted there, or original solutions.

You can even assemble a semblance of a soldering station, install a soldering iron stand on it (you can buy it separately). When installing, you must not forget about the safety rules. Parts must be insulated - for example, with heat shrink tubing.

Circuit options depending on the power limiter

The power regulator can be assembled according to different schemes. Basically, the differences are in the semiconductor part, the device that will regulate the current supply. It can be a thyristor or triac. To more accurately control the operation of a thyristor or triac, a microcontroller can be added to the circuit.

You can make a simple regulator with a diode and a switch - in order to leave the soldering iron in working condition for some (possibly long) time, preventing it from cooling down or overheating. The remaining regulators make it possible to set the temperature of the soldering iron tip more smoothly - for various needs. The assembly of the device according to any of the schemes is carried out in a similar way. The photos and videos show examples of how you can assemble a power regulator for a soldering iron with your own hands. Based on them, you can make a device with the variations you personally need and according to your own scheme.

Thyristor- a kind of electronic key. Passes current in only one direction. Unlike a diode, a thyristor has 3 outputs - a control electrode, an anode and a cathode. The thyristor opens by applying a pulse to the electrode. It closes when the direction changes or the current flowing through it stops.

Or a triac - a type of thyristor, only unlike this device, it is bilateral, it conducts current in both directions. It is, in fact, two thyristors connected together.

Triac, or triac. The main parts, the principle of operation and the method of display on the diagrams. A1 and A2 - power electrodes, G - control gate

The power regulator circuit for a soldering iron - depending on its capabilities - includes the following redo parts.

Resistor- serves to convert voltage to current and vice versa. Capacitor- the main role of this device is that it ceases to conduct current as soon as it is discharged. And it starts to conduct again - as the charge reaches the desired value. In regulator circuits, the capacitor is used to turn off the thyristor. Diode A semiconductor is an element that passes current in the forward direction and does not pass in the reverse direction. Diode subspecies - zener diode- used in devices for voltage stabilization. microcontroller- a microcircuit, with the help of which the electronic control of the device is provided. There are varying degrees of difficulty.

Circuit with switch and diode

This type of regulator is the easiest to assemble, with the fewest parts. It can be collected without a fee, by weight. The switch (button) closes the circuit - all the voltage is applied to the soldering iron, opens it - the voltage drops, the tip temperature too. At the same time, the soldering iron remains heated - this method is good for standby mode. A rectifier diode rated for a current of 1 ampere is suitable.

Assembly of a two-stage regulator on weight

1. Prepare parts and tools: a diode (1N4007), a switch with a button, a cable with a plug (it can be a soldering iron cable or an extension cable - if there is a fear of ruining the soldering iron), wires, flux, solder, soldering iron, knife.
2. Strip and then tin the wires.
3. Tin the diode. Solder the wires to the diode. Remove the excess ends of the diode. Put on heat shrink tubing, heat it up. You can also use an electrical insulating tube - cambric. Prepare a cable with a plug in the place where it will be more convenient to mount the switch. Cut the insulation, cut one of the wires inside. Leave part of the insulation and the second wire intact. Strip the ends of the cut wire.
4. Place the diode inside the switch: minus the diode - to the plug, plus - to the switch.
5. Twist the ends of the cut wire and the wires connected to the diode. The diode must be inside the gap. Wires can be soldered. Connect to the terminals, tighten the screws. Assemble the switch.

Regulator with switch and diode - step by step and clearly

thyristor regulator

Regulator with power limiter - thyristor - allows you to smoothly set the temperature of the soldering iron from 50 to 100%. In order to expand this scale (from zero to 100%), a diode bridge must be added to the circuit. The assembly of regulators on both the thyristor and the triac performs in a similar way. The method can be applied to any device of this type.

Assembling a thyristor (triac) regulator on a printed circuit board

1. Make a wiring diagram - outline the convenient location of all the parts on the board. If the board is purchased, the wiring diagram is included.
2. Prepare parts and tools: a printed circuit board (you need to make it in advance according to the diagram or buy it), radio components - see the specification for the diagram, wire cutters, a knife, wires, flux, solder, a soldering iron.
3. Place the parts on the board according to the wiring diagram.
4. Bite off the excess ends of the parts with wire cutters.
5. Lubricate with flux and solder every detail - first resistors with capacitors, then diodes, transistors, thyristor (triac), dinistor.
6. Prepare the body for assembly.
7. Strip, tin the wires, solder to the board according to the wiring diagram, install the board into the case. Insulate the wire connections.
8. Check the regulator - connect to an incandescent lamp.
9. Assemble the device.

Scheme with a low-power thyristor

The thyristor of small power is inexpensive, takes up little space. Its feature is in increased sensitivity. To control it, a variable resistor and a capacitor are used. Suitable for devices up to 40W.

Specification

Scheme with a powerful thyristor

The thyristor is controlled by two transistors. The power level is controlled by resistor R2. The regulator, assembled according to this scheme, is designed for loads up to 100 watts.

Specification

Name	Designation	Type/Nominal
Capacitor	C1	0.1uF
Transistor	VT1	KT315B
Transistor	VT2	KT361B
Resistor	R1	3.3 kOhm
variable resistor	R2	100 kOhm
Resistor	R3	2.2 kOhm
Resistor	R4	2.2 kOhm
Resistor	R5	30 kOhm
Resistor	R6	100 kOhm
Thyristor	VS1	KU202N
zener diode	VD1	D814V
rectifier diode	VD2	1N4004 or KD105V

Assembling a thyristor regulator according to the above diagram in a case - clearly

Assembly and testing of the thyristor regulator (review of parts, installation features)

Scheme with a thyristor and a diode bridge

Such a device allows you to adjust the power from zero to 100%. The scheme uses a minimum of details.

Specification

The regulator on the triac

Triac regulator circuit with a small number of radio components. Allows you to adjust the power from zero to 100%. The capacitor and resistor will ensure accurate operation of the triac - it will open even at low power.

Assembling the triac regulator according to the above diagram step by step

Triac regulator with diode bridge

The scheme of such a regulator is not very complicated. In this case, the load power can be varied in a fairly large range. With a power of more than 60 W, it is better to put the triac on the radiator. At lower power, cooling is not needed. The assembly method is the same as in the case of a conventional triac regulator.

ResistorR31 kOhm ResistorR41 kOhm ResistorR5100 ohm ResistorR647 ohm ResistorR71 MΩ ResistorR8430 kOhm ResistorR975 ohm VS1BT136-600E zener diodeVD21N4733A (5.1v) DiodeVD11N4007 microcontrollerDD1PIC 16F628 IndicatorHG1ALS333B

Before installation, the assembled regulator can be checked with a multimeter. You need to check only with a connected soldering iron i.e. under load. We rotate the knob of the resistor - the voltage changes smoothly.

In the regulators, assembled according to some of the schemes given here, there will already be indicator lights. They can be used to determine if the device is working. For the rest, the easiest test is to connect an incandescent bulb to the power regulator. Changing the brightness will clearly reflect the level of the applied voltage.

Regulators where the LED is in series with a resistor (as in the low-power thyristor circuit) can be adjusted. If the indicator is off, you need to choose the value of the resistor - take it with a lower resistance until the brightness is acceptable. Too high brightness cannot be achieved - the indicator will burn out.

As a rule, adjustment with a properly assembled circuit is not required. With the power of a conventional soldering iron (up to 100 W, average power - 40 W), none of the regulators assembled according to the above schemes requires additional cooling. If the soldering iron is very powerful (from 100 W), then the thyristor or triac must be installed on the radiator to avoid overheating.

You can assemble the power regulator for the soldering iron with your own hands, focusing on your own capabilities and needs. There are many variants of regulator circuits with various power limiters and different controls. Here are some of the simpler ones. A small overview of the cases in which parts can be mounted will help you choose the format of the device.