How to make a voltage regulator for a soldering iron. Soldering iron with temperature control. Description of the power boost controller circuit

16.01.2022

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 needed to ensure Q2 is closed if the operational amplifier cannot output a voltage equal to the negative supply voltage, and also with 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 most 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 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 kind of 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 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.

When working with an electric soldering iron, the temperature of its tip must remain constant, which is a guarantee of obtaining a high-quality solder joint.

However, in real conditions, this indicator is constantly changing, leading to cooling or overheating of the heating element and the need to install a special power regulator for the soldering iron in the power circuits.

Fluctuations in the temperature of the tip of the soldering device can be explained by the following objective reasons:

instability of the input supply voltage;
large heat losses when soldering volumetric (massive) parts and conductors;
significant fluctuations in ambient temperature.

To compensate for the impact of these factors, the industry has mastered the production of a number of devices that have a special dimmer for the soldering iron, which maintains the temperature of the tip within the specified limits.

However, if you want to save money on arranging a home soldering station, the power regulator may well be made by yourself. This will require knowledge of the basics of electronics and the utmost care when studying the instructions below.

The principle of operation of the soldering station controller

There are many schemes for home-made soldering iron heating controllers that are part of a home-operated station. But they all work on the same principle, which is to control the amount of power delivered to the load.

Common options for home-made electronic regulators may differ in the following ways:

type of electronic circuit;
an element used to change the power delivered to the load;
number of adjustment steps and other parameters.

Regardless of the version, any home-made soldering station controller is a conventional electronic switch that limits or increases the useful power in the heating coil of the load.

As a result, the main element of the regulator in the station or outside it is a powerful supply unit, which provides the possibility of varying the tip temperature within strictly specified limits.

A sample of the classic one with an adjustable power supply built into it is shown in the photo.

Controlled Diode Converters

Each of the possible versions of the devices differs in its circuit and control element. There is a scheme of power regulators on thyristors, triacs and other options.

Thyristor devices

According to their circuit design, most of the known control units are made according to a thyristor circuit controlled from a voltage specially formed for this purpose.

A two-mode controller circuit on a low power thyristor is shown in the photo.

Through such a device, it is possible to control soldering irons, the power of which does not exceed 40 watts. Despite the small dimensions and the absence of a ventilation module, the converter practically does not heat up in any permissible operating mode.

Such a device can operate in two modes, one of which corresponds to the standby state. In this situation, the handle of the variable resistor R4 is set to the far right position according to the diagram, and the thyristor VS2 is completely closed.

Power is supplied to the soldering iron through a chain with a VD4 diode, on which the voltage drops to about 110 volts.

In the second mode of operation, the voltage regulator (R4) is removed from the far right position; moreover, in its middle position, the thyristor VS2 opens slightly and begins to pass alternating current.

The transition to this state is accompanied by the ignition of the VD6 indicator, which is triggered at an output supply voltage of about 150 volts.

By further turning the R4 knob, it will be possible to smoothly increase the output power, raising its output level to the maximum value (220 volts).

Triac converters

Another way to organize the control of a soldering iron involves the use of an electronic circuit built on a triac and also designed for a low power load.

This circuit works on the principle of reducing the effective voltage value on the semiconductor rectifier, to which the payload (soldering iron) is connected.

The state of the control triac depends on the position of the “engine” of the variable resistor R1, which changes the potential at its control input. With a fully open semiconductor device, the power supplied to the soldering iron is approximately halved.

The simplest control option

The simplest voltage regulator, which is a "truncated" version of the two circuits discussed above, involves mechanical power control in the soldering iron.

Such a power regulator is in demand in conditions where long breaks in work are expected and it makes no sense to keep the soldering iron on all the time.

In the open position of the switch, a small amplitude voltage (approximately 110 volts) is supplied to it, which provides a low tip heating temperature.

To bring the device into working condition, it is enough to turn on the S1 toggle switch, after which the soldering iron tip quickly heats up to the required temperature, and it will be possible to continue soldering.

Such a thermostat for a soldering iron allows you to reduce the temperature of the tip to a minimum value in the intervals between soldering. This feature provides a slowdown in oxidative processes in the tip material and significantly extends its service life.

On the microcontroller

In the event that the performer is completely confident in his abilities, he can take on the manufacture of a heat stabilizer for a soldering iron running on a microcontroller.

This version of the power regulator is made in the form of a full-fledged soldering station, which has two working outputs with voltages of 12 and 220 volts.

The first of them has a fixed value and is intended to power miniature low-current soldering irons. This part of the device is assembled according to the usual transformer circuit, which, due to its simplicity, can be ignored.

At the second output of a do-it-yourself regulator for a soldering iron, an alternating voltage operates, the amplitude of which can vary in the range from 0 to 220 volts.

The diagram of this part of the regulator, combined with a PIC16F628A type controller and a digital output voltage indicator, is also shown in the photo.

For the safe operation of equipment with two different output voltages, a home-made regulator must have sockets that are different in design (incompatible with each other).

Such forethought eliminates the possibility of error when connecting soldering irons designed for different voltages.

The power part of such a circuit is made on a VT 136 600 triac, and the power in the load is adjusted by means of a push-button switch with ten positions.

By switching the push-button regulator, you can change the power level in the load, indicated by numbers from 0 to 9 (these values are displayed on the display of the indicator built into the device).

As an example of such a regulator, assembled according to the scheme with the SMT32 controller, a station designed for connecting soldering irons with T12 tips can be considered.

This industrial design of the device that controls the heating mode of the soldering iron connected to it is able to regulate the temperature of the tip in the range from 9 to 99 degrees.

With it, it is also possible to automatically switch to standby mode, in which the temperature of the soldering iron tip drops to the value set by the instruction. Moreover, the duration of this state can be adjusted in the range from 1 to 60 minutes.

We add to this that this device also provides a mode for smoothly reducing the temperature of the sting during the same adjustable period of time (1-60 minutes).

At the end of the review of power regulators for soldering devices, we note that their manufacture at home is not something completely inaccessible to the average user.

If you have some experience with electronic circuits and after carefully studying the material presented here, anyone can cope with this task quite independently.

A typical problem when working with a soldering iron is burning the tip. This is due to its high heat. During operation, soldering operations require unequal power, so you have to use soldering irons with different power. To protect the device from overheating and the rate of change in power, it is best to use a temperature-controlled soldering iron. This will allow you to change the operating parameters in a matter of seconds and extend the life of the device.

Origin story

A soldering iron is a tool designed to transfer heat to a material in contact with it. Its direct purpose is to create an integral connection by melting solder.

Before the beginning of the 20th century, there were two types of soldering tools: gas and copper. In 1921, German inventor Ernst Sachs invented and registered a patent for a soldering iron, which was heated by electric current. In 1941, Karl Weller patented a transformer-shaped tool that resembles a pistol in shape. Passing current through its tip, it quickly heated up.

Twenty years later, the same inventor suggested using a thermocouple in a soldering iron to control the heating temperature. The design included two metal plates pressed together with different thermal expansion. Since the mid-60s, due to the development of semiconductor technology, soldering tools began to be produced with a pulsed and induction type of work.

Types of soldering irons

The main difference between soldering devices is their maximum power, on which the heating temperature also depends. In addition, electric soldering irons are divided according to the value of the voltage supplying them. They are produced both for an AC voltage of 220 volts, and for its constant value of various sizes. Separation of soldering irons also occurs according to the type and principle of operation.

According to the principle of work there are:

nichrome;
ceramic;
impulse;
induction;
hot air;
infrared;
gas;
open type.

In appearance, they are rod and hammer. The former are designed for spot heating, and the latter for heating a certain area.

Principle of operation

Most devices are based on the conversion of electrical energy into thermal energy. For this, a heating element is located in the inside of the device. But some types of device are simply heated on fire or use an ignited directional gas flow.

Nichrome devices use a wire helix through which current is passed. The spiral is located on the dielectric. When heated, the spiral transfers heat to the copper sting. The heating temperature is regulated by a temperature sensor, which, when a certain heating value is reached, disconnects the spiral from the electric line, and when it cools down, reconnects it to it. The temperature sensor is nothing more than a thermocouple.

Ceramic soldering irons use rods as heaters. Adjustment in them is most often carried out by lowering the voltage applied to the ceramic rods.

Induction equipment works due to the inductor. The sting is covered with a ferromagnet. With the help of a coil, a magnetic field is induced and currents appear in the conductor, leading to heating of the tip. During operation, there comes a moment that the sting loses its magnetic properties, the heating stops, and when it cools down, the properties return and the heating is restored.

The operation of pulsed soldering irons is based on the use of a high-frequency transformer. The secondary winding of the transformer has several turns made of thick wire, the ends of which are the heaters. The frequency converter increases the frequency of the input signal, which is reduced by the transformer. Heating is controlled by power control.

A hot air soldering iron, or, as it is called, a hot air gun, uses hot air during operation, which heats up when passing through a spiral made of nichrome. The temperature in it can be regulated both by reducing the voltage applied to the wire, and by changing the air flow.

One of the types of soldering irons are devices that use infrared radiation. Their work is based on the process of heating by radiation with a wavelength of up to 10 microns. For regulation, a complex control unit is used that changes both the wavelength and its intensity.

Gas burners are conventional burners that use nozzles of different diameters instead of a sting. Temperature control is almost impossible, except for changing the intensity of the gas output using a damper.

Understanding the principle of operation of the soldering iron, you can not only repair it yourself, but also modify its design, for example, make it adjustable.

Devices for adjustment

The price of soldering irons with temperature control is several times higher than the price of ordinary devices. Therefore, in some cases it makes sense to buy a good ordinary soldering iron, and make the regulator yourself. In this way, soldering equipment is controlled by two control methods:

power;
temperature.

Temperature control allows you to achieve more accurate readings, but it is easier to implement power control. In this case, the regulator can be made independent and various devices can be connected to it.

Universal Stabilizer

A soldering iron with a thermostat can be made using a factory-made dimmer or designed by analogy on its own. A dimmer is a regulator that changes the power supplied to the soldering iron. In a 220 volt network, a variable current with a sinusoidal shape flows. If this signal is cut off, then an already distorted sinusoid will be supplied to the soldering iron, which means that the power value will also change. To do this, before the load, a device is included in the gap, which passes the current only at the moment the signal reaches a certain value.

Dimmers are distinguished by the principle of operation. They may be:

analog;
impulse;
combined.

The dimmer circuit is implemented using various radio components: thyristors, triacs, specialized circuits. The simplest dimmer model comes with a mechanical knob. The principle of operation of the model is based on the change in resistance in the circuit. In fact, this is the same rheostat. Dimmers on triacs cut off the leading edge of the input voltage. The controllers use a complex electronic voltage reduction circuit in their work.

It is easier to make a dimmer on your own using a thyristor for this. The circuit does not need scarce parts, and it is assembled by a simple hinged installation.

The operation of the device is based on the ability to open the thyristor at times when a signal is applied to its control output. The input current, acting on the capacitor through a chain of resistors, charges it. In this case, the dinistor opens and passes through itself for a short time the current supplied to the control of the thyristor. The capacitor is discharged and the thyristor closes. At the next cycle, everything repeats. By changing the resistance of the circuit, the duration of the charge of the capacitor is regulated, and hence the time of the open state of the thyristor. Thus, the time is set during which the soldering iron is connected to the 220 volt network.

Simple thermostat

Using the TL431 Zener diode as the basis, you can assemble a simple thermostat with your own hands. Such a circuit consists of inexpensive radio components and practically does not need to be tuned.

The zener diode VD2 TL431 is connected according to the comparator circuit with one input. The value of the required voltage is determined by a divider assembled on resistors R1-R3. As R3, a thermistor is used, the property of which is to reduce the resistance when heated. Using R1, the temperature value is set at which the device turns off the soldering iron from power.

When a signal value exceeding 2.5 volts is reached on the zener diode, it breaks through, and power is supplied through it to the switching relay K1. The relay sends a signal to the control output of the triac and the soldering iron turns on. When heated, the resistance of the temperature sensor R3 decreases. The voltage on the TL431 drops below the compared one and the triac power supply circuit breaks.

For a soldering tool with a power of up to 200 W, the triac can be used without a heatsink. RES55A with an operating voltage of 12 volts is suitable as a relay.

Power boost

It happens that there is a need not only to reduce the power of soldering equipment, but vice versa, to increase it. The meaning of the idea is that you can use the voltage that occurs on the network capacitor, the value of which is 310 volts. This is due to the fact that the mains voltage has an amplitude value greater than its effective value by 1.41 times. From this voltage, pulses of rectangular amplitude are formed.

By changing the duty cycle, you can control the effective value of the pulse signal from zero to 1.41 of the effective value of the input voltage. Thus, the heating power of the soldering iron will vary from zero to twice the rated power.

The input part is a standard assembled rectifier. The output unit is made on a field-effect transistor VT1 IRF840 and is able to switch a soldering iron with a power of 65 watts. The operation of the transistor is controlled by a microcircuit with pulse-width modulation DD1. Capacitor C2 is in the corrective chain and sets the generation frequency. The microcircuit is powered by radio components R5, VD4, C3. Diode VD5 is used to protect the transistor.

Soldering Station

A soldering station is, in principle, the same adjustable soldering iron. Its difference from it is in the presence of a convenient indication and additional devices that help facilitate the soldering process. Usually, an electric soldering iron and a hair dryer are connected to such equipment. If you have experience as a radio amateur, you can try to assemble a soldering station circuit with your own hands. It is based on the microcontroller (MK) ATMEGA328.

Such an MK is programmed on a programmer, Adruino or a home-made device is suitable for this. An indicator is connected to the microcontroller, which is used as a liquid crystal display LCD1602. Station control is simple, for this a variable resistance of 10 kOhm is used. Turning the first one sets the temperature of the soldering iron, the second - the hair dryer, and the third one can reduce or increase the air flow of the hair dryer.

A field-effect transistor operating in a key mode, together with a triac, is installed on a radiator through a dielectric gasket. LEDs are used with low current consumption, no more than 20 mA. The soldering iron and hair dryer connected to the station must have a built-in thermocouple, the signal from which is processed by the MK. The recommended soldering iron power is 40 W, and the hair dryer is no more than 600 W.

The power supply will need 24 volts with a current of at least two amperes. For power, you can use a ready-made adapter from a monoblock or laptop. In addition to stabilized voltage, it contains various types of protection. And you can do it yourself analog type. This will require a transformer with a secondary winding rated for 18-20 volts, and a rectifier bridge with a capacitor.

After assembling the circuit, it is adjusted. All operations consist in adjusting the temperature. First of all, the temperature on the soldering iron is set. For example, we set 300 degrees on the indicator. Then, pressing the thermometer to the tip, with the help of an adjustable resistor, the temperature is set corresponding to the actual readings. The temperature of the hair dryer is calibrated in the same way.

All radioelements are conveniently purchased in Chinese online stores. Such a device, excluding a homemade case, will cost about one hundred US dollars with all accessories. Firmware for the device can be downloaded here: http://x-shoker.ru/lay/pajalnaja_stancija.rar.

Of course, it will be difficult for a novice radio amateur to assemble a digital temperature controller with his own hands. Therefore, you can purchase ready-made temperature stabilization modules. They are boards with soldered connectors and radio components. You only need to buy a case or make it yourself.

Thus, using a soldering iron heating stabilizer, it is easy to achieve its versatility. In this case, the temperature change range is achieved in the range from 0 to 140 percent.

I am sure that every radio amateur has encountered the problem of falling tracks on the getinax and loose tin. The reason for this is an overheated or insufficiently heated soldering iron tip. How to solve this problem? Yes, it’s very simple, or rather a very simple device, the assembly of which will be possible even for a beginner radio amateur. The circuit diagram of the regulator was once published in a magazine Radio:

About the principle of operation: this scheme makes it possible to adjust the power of the soldering iron or lamp from 50 to 100%. In the lower position of the potentiometer, the thyristor VS1 is closed, and the load is powered through VD2, that is, the voltage is reduced by half. When the potentiometer is rotated, the control circuit begins to open the thyristor and a gradual increase in voltage occurs.

You can take a print. There are two resistors P5 on the board - do not be alarmed, there was simply no required value. If desired, the signet can be miniaturized, I have it sweeping out of principle - in transformerless and power circuits I always breed in a big way - it's safer.

The scheme for the year was used very often and did not have a single failure.

Attention! The soldering iron regulator has a transformerless power supply of 220 V. Follow the safety rules and test the circuit only through a light bulb!

Many soldering irons are sold without a power regulator. When connected to the network, the temperature rises to the maximum and remains in this state. To adjust it, you need to disconnect the device from the power source. In such soldering irons, the flux instantly evaporates, oxides are formed and the tip is in a constantly polluted state. It has to be cleaned frequently. Soldering large components requires high temperatures, while small parts can be burned. To avoid such problems, power regulators are made.

How to make a reliable power regulator for a soldering iron with your own hands

The power controls help control how hot the soldering iron is.

Connecting a ready-made heating power controller

If you do not have the opportunity or desire to mess with the manufacture of the board and electronic components, then you can buy a ready-made power regulator in a radio store or order it on the Internet. The regulator is also called a dimmer. Depending on the power, the device costs 100-200 rubles. You may need to modify it a little after purchase. Dimmers up to 1000 W are usually sold without a cooling radiator.

Power regulator without heatsink

And devices from 1000 to 2000 W with a small heatsink.

Power regulator with small heatsink

And only the more powerful ones are sold with larger heatsinks. But in fact, a dimmer from 500 W should have a small cooling radiator, and from 1500 W large aluminum plates are already installed.

Chinese power regulator with a large heatsink

Keep this in mind when connecting the device. If necessary, install a powerful cooling radiator.

Improved power regulator

For correct connection of the device to the circuit, look at the reverse side of the printed circuit board. The IN and OUT terminals are indicated there. The input is connected to a power outlet, and the output to a soldering iron.

Designation of input and output terminals on the board

The controller is mounted in different ways. To implement them, you do not need special knowledge, and from the tools you only need a knife, a drill and a screwdriver. For example, you can include a dimmer in a soldering iron power cord. This is the easiest option.

Cut the soldering iron cable into two pieces.
Connect both wires to the board terminals. Screw the segment with the fork to the entrance.
Choose a plastic case that is suitable in size, make two holes in it and install the regulator there.

Another easy way: you can install the regulator and socket on a wooden stand.

Not only a soldering iron can be connected to such a regulator. Now consider a more complex, but compact version.

Take a large plug from an unnecessary power supply.
Remove the existing board with electronic components from it.
Drill holes for the dimmer knob and two terminals for the input plug. Terminals are sold in the radio shop.
If your regulator has indicator lights, make holes for them too.
Install the dimmer and terminals into the plug housing.
Take a portable outlet and plug it in. Insert a plug with a regulator into it.

This device, like the previous one, allows you to connect different devices.

Homemade two-stage temperature controller

The simplest power regulator is a two-stage one. It allows you to switch between two values: the maximum and half of the maximum.

Two stage power regulator

When the circuit is open, current flows through diode VD1. The output voltage is 110 V. When the circuit is closed with switch S1, the current bypasses the diode, since it is connected in parallel and the output voltage is 220 V. Select the diode according to the power of your soldering iron. The output power of the regulator is calculated by the formula: P = I * 220, where I is the diode current. For example, for a diode with a current of 0.3 A, the power is calculated as follows: 0.3 * 220 \u003d 66 W.

Since our block consists of only two elements, it can be placed in the body of the soldering iron using surface mounting.

Solder the parts of the microcircuit in parallel to each other directly using the legs of the elements themselves and the wires.
Connect to chain.
Fill everything with epoxy, which serves as an insulator and protection against displacement.
Make a hole in the handle for the button.

If the case is very small, then use the switch for the lamp. Mount it in the soldering iron cord and insert a diode parallel to the switch.

Light switch

On triac (with indicator)

Consider a simple triac regulator circuit and make a printed circuit board for it.

Triac power regulator

PCB manufacturing

Since the circuit is very simple, it makes no sense to install a computer program for processing electrical circuits because of it alone. Moreover, special paper is needed for printing. And not everyone has a laser printer. Therefore, let's go by the simplest way of manufacturing a printed circuit board.

Take a piece of textolite. Cut off the required size for the chip. Sand the surface and degrease.
Take a marker for laser discs and draw a diagram on the textolite. In order not to be mistaken, first draw with a pencil.
Next, let's start etching. You can buy ferric chloride, but after it the sink is poorly washed. If you accidentally drip on clothes, stains will remain that cannot be completely removed. Therefore, we will use a safe and cheap method. Prepare a plastic container for the solution. Pour in 100 ml of hydrogen peroxide. Add half a tablespoon of salt and a sachet of citric acid to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. Copper should be all etched. This takes about an hour.
Rinse the board under a stream of well water. Dry. Drill holes.
Wipe the board with an alcohol - rosin flux or a regular solution of rosin in isopropyl alcohol. Take some solder and tin the tracks.

To apply the scheme to the textolite, you can make it even easier. Draw a diagram on paper. Glue it with adhesive tape to the cut out textolite and drill holes. And only after that draw the circuit with a marker on the board and poison it.

Mounting

Prepare all the necessary components for installation:

solder coil;
pins in the board;
triac bta16;
100nF capacitor;
2 kΩ fixed resistor;
dinistor db3;
variable resistor with a linear dependence of 500 kOhm.

Proceed with the installation of the board.

Bite off four pins and solder them to the board.
Install the dinistor and all other parts except for the variable resistor. Solder the triac last.
Take a needle and a brush. Clean the gaps between the tracks to remove possible short circuits.
Take an aluminum radiator to cool the triac. Drill a hole in it. The triac with a free end with a hole will be fixed to an aluminum radiator for cooling.
Clean the area where the element is attached with fine sandpaper. Take the KPT-8 heat-conducting paste and apply a small amount of paste on the radiator.
Secure the triac with a screw and nut.
Gently bend the board so that the triac takes a vertical position with respect to it. To keep the design compact.
Since all parts of our device are under mains voltage, we will use a handle made of insulating material for adjustment. It is very important. Metal holders are life-threatening here. Put the plastic handle on the variable resistor.
With a piece of wire, connect the extreme and middle terminals of the resistor.
Now solder two wires to the extreme conclusions. Connect the opposite ends of the wires to the corresponding terminals on the board.
Take an outlet. Remove the top cover. Connect two wires.
Solder one wire from the socket to the board.
And connect the second to the wire of a two-core network cable with a plug. The power cord has one free core. Solder it to the corresponding pin on the PCB.

In fact, it turns out that the regulator is connected in series to the load power circuit.

Scheme of connecting the regulator to the circuit

If you want to install an LED indicator in the power regulator, then use a different scheme.

Power Regulator Circuit with LED Indicator

Diodes added here:

VD 1 - diode 1N4148;
VD 2 - LED (operation indication).

The triac circuit is too bulky to be included in a soldering iron handle, as is the case with a two-stage regulator, so it must be connected externally.

Installation of the structure in a separate housing

All elements of this device are under mains voltage, so you can not use a metal case.

Take a plastic box. Outline how the board with the radiator will be placed in it and on which side to connect the power cord. Drill three holes. The two extreme ones are needed to mount the socket, and the middle one is for the radiator. The head of the screw to which the radiator will be attached must be hidden under the socket for electrical safety reasons. The radiator has contact with the circuit, and it has direct contact with the network.
Make another hole on the side of the case for the network cable.
Install the radiator mounting screw. Put the washer on the reverse side. Screw on the radiator.
Drill an appropriately sized hole for the potentiometer, that is, for the knob of the variable resistor. Insert the part into the body and secure with a regular nut.
Lay the socket on the case and drill two holes for the wires.
Fix the socket with two M3 nuts. Insert the wires into the holes and tighten the cover with a screw.
Route the wires inside the case. Solder one of them to the board.
The other is to the core of the network cable, which is first inserted into the plastic case of the regulator.
Insulate the joint with electrical tape.
Connect the free wire of the cord to the board.
Close the case with a cap and tighten with screws.

The power regulator is connected to the network, and the soldering iron is connected to the regulator outlet.

Video: installation of a regulator circuit on a triac and assembly in a housing

On thyristor

The power regulator can be made on the bt169d thyristor.

Thyristor power regulator

Circuit components:

VS1 - thyristor BT169D;
VD1 - diode 1N4007;
R1 - 220k resistor;
R3 - 1k resistor;
R4 - 30k resistor;
R5 - resistor 470E;
C1 - capacitor 0.1mkF.

Resistors R4 and R5 are voltage dividers. They reduce the signal, since the bt169d thyristor is low-power and very sensitive. The circuit is assembled in the same way as a regulator on a triac. Since the thyristor is weak, it will not overheat. Therefore, a cooling radiator is not needed. Such a circuit can be mounted in a small box without an outlet and connected in series with the soldering iron wire.

Power regulator in a small package

Scheme on a powerful thyristor

If in the previous circuit we replace the thyristor bt169d with a more powerful ku202n and remove the resistor R5, then the output power of the regulator will increase. Such a regulator is assembled with a thyristor radiator.

Scheme on a powerful thyristor

On the microcontroller with indication

A simple power regulator with light indication can be made on a microcontroller.

Regulator circuit on the ATmega851 microcontroller

Prepare the following components to assemble it:

Using the S3 and S4 buttons, the power and brightness of the LED will change. The circuit is assembled similarly to the previous ones.

If you want the instrument to show the percentage of output power instead of a simple LED, then use a different circuit and appropriate components, including a numeric indicator.

Regulator circuit on the PIC16F1823 microcontroller

The circuit can be mounted in a socket.

The regulator on the microcontroller in the socket

Checking and adjusting the thermostat block circuit

Before connecting the unit to the instrument, test it.

Take the assembled circuit.
Connect it to the mains cable.
Connect a 220 lamp to the board and a triac or thyristor. Depending on your schema.
Plug the power cord into a socket.
Turn the variable resistor knob. The lamp should change the degree of incandescence.

The circuit with the microcontroller is checked in the same way. Only the digital indicator will still show the percentage of output power.

To adjust the circuit, change the resistors. The more resistance, the less power.

Often you have to repair or modify various devices using a soldering iron. The operation of these devices depends on the quality of soldering. If you purchased a soldering iron without a power regulator, be sure to install it. With constant overheating, not only electronic components will suffer, but also your soldering iron.