Homemade voltage regulator for a soldering iron. To help the home handyman: temperature controller diagram for a soldering iron

In amateur radio practice it is impossible to do without a soldering iron. He is always at his workplace and must be ready. Most simple and common soldering irons have a fixed power, and therefore a fixed tip heating temperature, which is not always justified. Of course, if you turn it on for a short time to quickly solder something, you can do without a temperature controller.

Why do you need a soldering iron tip temperature regulator?

The most common soldering iron produced by industry has a power of 40 watts. This power is quite enough for soldering large, heat-intensive parts that require heating to the melting temperature of the solder.

But using a soldering iron of such power, for example, when installing radio components, is extremely inconvenient. Tin constantly rolls off from an overheated tip, making the soldering area unstable. In addition, the tip very quickly becomes covered with scale and it has to be cleaned off, and so-called craters are formed on the working surface of the copper tip, which can be removed with a file. The length of such a sting will decrease very quickly.

Using tip temperature controller The soldering iron is always ready, its temperature will be optimal for a specific job, you will never overheat the radio components. If you need to be away for a short time, then it is enough to reduce the voltage on the soldering iron, and not turn it off from the network, as before. Upon returning to the workplace, just add the voltage regulator, and the warm soldering iron will quickly reach the desired temperature.

Temperature controller circuit for a soldering iron

Below is a simple diagram of a power regulator:

I used this circuit for my regulator about 20 years ago, I still use this soldering iron. Of course, some parts, such as transistors, a neon light bulb, can be replaced with modern ones.

Device details:

Transistors; KT 315G, MP 25 can be replaced with KT 361B
Thyristor; KU 202N
Zener diode; D 814B or with the letter B
Diode;KD 202Zh
Fixed resistors: MLT-3k, 2k-2 pcs, 30k, 100 ohm, 470k
Variable resistor; 100k
Capacitor; 0.1 µF

As you can see, device diagram very simple. Even a beginner can repeat it.

Making a simple soldering iron temperature controller with your own hands

The presented device is built according to the so-called half-wave power regulator. That is, with the thyristor VS 1 fully open, which is controlled by transistors VT 1 and VT 2, one half-wave of the mains voltage passes through the diode VD 1, and the other half-wave through the thyristor. If you turn the slider of the variable resistor R 2 in the opposite direction, then the thyristor VS 1 will close, and the load will have one half-wave that will pass through the diode VD 1:

Therefore, it is impossible to reduce the voltage below 110 volts with this regulator. As practice shows, this is not necessary, since at minimum voltage the temperature of the tip is so low that the tin barely melts.

The part ratings presented in the diagram are selected to work together with high-power soldering irons. If you do not need this, then the power elements, thyristor and diode can be replaced with less powerful ones. If you do not have a two-watt resistor R 5 with a nominal value of 30 kilo ohms, then it can be made up of two series-connected resistors of 15 kilo ohms, like mine:

This device does not require configuration. When assembled correctly and from serviceable parts, it starts working immediately.

Attention! Be careful. This temperature controller does not have galvanic isolation from the network. Secondary circuits have high potential.

All that remains is to choose the appropriate housing size. Place the soldering iron socket:

It is not necessary to take the fuse out; for example, I have it soldered into the break in the power cord. But the variable resistor needs to be installed in a convenient place and, of course, the scale must be calibrated, for example, in volts:

The resulting regulator is very reliable, which has been tested by time, and it will serve you for many years, and the soldering iron will thank you.

In order to obtain high-quality and beautiful soldering, it is necessary to correctly select the power of the soldering iron and ensure a certain temperature of its tip, depending on the brand of solder used. I offer several circuits of homemade thyristor temperature controllers for soldering iron heating, 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 electrical network and touching the current-carrying elements of the circuit is dangerous to life!

To adjust the temperature of the soldering iron tip, soldering stations are used, in which the optimal temperature of the soldering iron tip is maintained in manual or automatic mode. The availability of a soldering station for a home craftsman is limited by its high price. For myself, I solved the issue of temperature regulation by developing and manufacturing a regulator with manual, stepless 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 sufficient, since the voltage in the network is stable and the temperature in the room is also stable.

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 power supply network and the airwaves. But for a radio amateur, such interference makes it impossible to fully engage in what he loves. If the circuit is supplemented with a filter, the design will turn out to be bulky. But for many use cases, such a thyristor regulator circuit can be successfully used, for example, to adjust the brightness of incandescent lamps and heating devices with a power of 20-60 W. That's why I decided to present this diagram.

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 (indicated by k in the diagram). After the thyristor has opened (the resistance between the anode and cathode becomes 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 (indicated a and k in the diagram) becomes close to zero. It's that simple.

The classical regulator circuit works as follows. AC mains voltage is supplied through the load (incandescent light bulb or soldering iron winding) to a rectifier bridge circuit made using diodes VD1-VD4. The diode bridge converts alternating voltage into direct voltage, varying according to a sinusoidal law (diagram 1). When the middle terminal of resistor R1 is in the extreme left position, its resistance is 0 and when the voltage in the network begins to increase, 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 (top diagram).

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

Above is a classic circuit of a thyristor regulator made on a KU202N thyristor. Since controlling this thyristor requires a larger current (according to the passport 100 mA, the real one is about 20 mA), the values of resistors R1 and R2 are reduced, R3 is eliminated, and the size of the electrolytic capacitor is increased. When repeating the circuit, it may be necessary to increase the value of capacitor C1 to 20 μF.

The simplest thyristor regulator circuit

If you add a dinistor, for example KN102A, to the open circuit 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 regulators can be successfully used to regulate the brightness of lamps in which incandescent light bulbs are installed. It will not be possible to adjust the brightness of lamps that have energy-saving or LED bulbs installed, since such bulbs have electronic circuits built in, and the regulator will simply disrupt their normal operation. The light bulbs will shine at full power or flicker and this may even lead to their premature failure.

The circuits can be used for adjustment with a supply voltage of 36 V or 24 V AC. You only need 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 circuit of the regulator 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 into the electrical network, since all transient processes occur at a time when the voltage in the supply network is zero.

When starting to develop a temperature controller for a soldering iron, I proceeded from the following considerations. The circuit must be simple, easily repeatable, components must be cheap and available, high reliability, minimal dimensions, efficiency close to 100%, no radiated interference, and the possibility of upgrading.

The temperature controller circuit works as follows. The AC voltage from the supply network is rectified by the 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). Next, 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 diode VD5, creating a supply voltage of about 9 V for microcircuits DD1 and DD2. 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. From R1, the generated signal is supplied to the 5th and 6th pins 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 pin 4 of DD1, pulses are sent to pin 8 of D trigger DD2.1, operating in RS trigger mode. DD2.1, like DD1.1, performs the function of inverting and signal generation (Diagram 4).

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

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

Thus, only the number of pulses specified by resistor R5 from the supply network will pass to the outputs of DD2.2, and most importantly, changes in these pulses will occur during the voltage transition 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 supplied 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 resistor R5 is variable, adjustment due to the operation of DD2.2 heating the soldering iron is carried out in steps. When R5 is equal to zero, 50% of the power is supplied (diagram 5), when turning at a certain angle it is already 66% (diagram 6), then 75% (diagram 7). Thus, the closer to the design power of the soldering iron, the smoother the adjustment works, which makes it easy to adjust the temperature of the soldering iron tip. For example, a 40 W soldering iron can be configured to run from 20 to 40 W.

Temperature controller design and details

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

The cord coming from the soldering iron is soldered directly to the printed circuit board. 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 consumed by the temperature controller control circuit does not exceed 2 mA. This is less than what the LED in the lighting circuit of the light switches consumes. Therefore, no special measures are required to ensure the temperature conditions of the device.

Microcircuits DD1 and DD2 are 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 (Uob = 1000 V, I = 1 A) is perfect. Any pulse diodes VD5 and VD7. Any low-power zener diode VD6 with 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. If the parts are in good condition and there are no installation errors, it will work immediately.

The circuit was developed many years ago, when computers and especially laser printers did not exist in nature, and therefore I made a drawing of the printed circuit board using old-fashioned technology on chart paper with a grid pitch of 2.5 mm. Then the drawing was glued with Moment glue onto thick paper, and the paper itself was glued to foil fiberglass. Next, holes were drilled on a homemade 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 rectifier diode bridge VD1-VD4 was made on a 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 the interference emitted by thyristor power regulators 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, televisions and other products. An effective, noise-suppressing ferrite filter can be retrofitted to any thyristor regulator. It is enough to pass the wire connecting to the electrical network through the ferrite ring.

The ferrite filter must be installed as close as possible to the source of interference, that is, to the installation site of the thyristor. The ferrite filter can be placed both inside the device body and on its outside. The more turns, the better the ferrite filter will suppress interference, but simply threading the power cable through the ring is sufficient.

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 insulation on the wire. In this place there is a ferrite filter for high-frequency interference.

It is enough to cut the plastic insulation with a knife and remove the ferrite ring. Surely you or someone you know has an unnecessary interface cable from an inkjet printer or an old CRT monitor.

In order for soldering to be beautiful and of high quality, it is necessary to correctly select the power of the soldering iron and ensure the temperature of the tip. This all depends on the brand of solder. For your choice, I provide several circuits of thyristor regulators for regulating the temperature of a soldering iron, which can be made at home. They are simple and can easily replace industrial analogues; moreover, the price and complexity will differ.

Carefully! Touching the elements of the thyristor circuit can lead to life-threatening injury!

To regulate the temperature of the soldering iron tip, soldering stations are used, which maintain the set temperature in automatic and manual modes. The availability of a soldering station is limited by the size of your wallet. I solved this problem by making a manual temperature controller that has smooth adjustment. The circuit can be easily modified to automatically maintain a given temperature mode. But I concluded that manual adjustment is sufficient, since the room temperature and network current are stable.

Classic thyristor regulator circuit

The classic regulator circuit was bad in that it had radiating interference emitted into the air and the network. For radio amateurs, this interference interferes with their work. If you modify the circuit to include a filter, the size of the structure will increase significantly. But this circuit can also be used in other cases, for example, if it is necessary to adjust the brightness of incandescent lamps or heating devices whose power is 20-60 W. Therefore I present this diagram.

To understand how this works, consider the operating principle of a thyristor. A thyristor is a semiconductor device of a closed or open type. To open it, a voltage of 2-5 V is applied to the control electrode. It depends on the selected thyristor, relative to the cathode (letter k in the diagram). The thyristor opened, and a voltage equal to zero formed between the cathode and anode. It cannot be closed through the electrode. It will remain open until the cathode (k) and anode (a) voltage values are close to zero. This is the principle. The circuit works as follows: through the load (soldering iron winding or incandescent lamp), voltage is supplied to the rectifier diode bridge, made of diodes VD1-VD4. It serves to convert alternating current into direct current, which varies according to a sinusoidal law (1 diagram). In the extreme left position, the resistance of the middle terminal of the resistor is 0. As the voltage increases, capacitor C1 is charged. When the voltage of C1 is 2-5 V, current will flow to VS1 through R2. In this case, the thyristor will open, the diode bridge will short-circuit, and the maximum current will pass through the load (diagram above). If you turn the knob of resistor R1, the resistance will increase, and capacitor C1 will take longer to charge. Therefore, the opening of the resistor will not occur immediately. The more powerful R1, the longer it will take to charge C1. By rotating the knob to the right or left, you can adjust the heating temperature of the soldering iron tip.

The photo above shows a regulator circuit assembled on a KU202N thyristor. To control this thyristor (the data sheet indicates a current of 100 mA, in reality it is 20 mA), it is necessary to reduce the values of resistors R1, R2, R3, eliminate the capacitor, and increase the capacitance. Capacitance C1 must be increased to 20 μF.

The simplest thyristor regulator circuit

Here is another version of the diagram, only simplified, with a minimum of details. 4 diodes are replaced by one VD1. The difference between this scheme is that the adjustment occurs when the network period is positive. The negative period, passing through the VD1 diode, remains unchanged, the power can be adjusted from 50% to 100%. If we exclude VD1 from the circuit, the power can be adjusted in the range from 0% to 50%.

If you use a KN102A dinistor in the gap between R1 and R2, you will have to replace C1 with a capacitor with a capacity of 0.1 μF. The following thyristor ratings are suitable for this circuit: KU201L (K), KU202K (N, M, L), KU103V, with a voltage of more than 300 V. Any diodes whose reverse voltage is not less than 300 V.

The above-mentioned circuits are successfully suitable for adjusting incandescent lamps in lamps. It will not be possible to regulate LED and energy-saving lamps, as they have electronic control circuits. This will cause the lamp to flicker or run at full power, which will eventually damage it.

If you want to use regulators to operate on a 24.36 V network, you will have to reduce the resistor values and replace the thyristor with an appropriate one. If the power of the soldering iron is 40 W, the mains voltage is 36 V, it will consume 1.1 A.

Thyristor circuit of the regulator does not emit interference

This circuit differs from the previous one in the complete absence of studied radio interference, since the processes take place at the moment when the mains voltage is equal to 0. When starting to create the regulator, I proceeded from the following considerations: the components should have a low price, high reliability, small dimensions, the circuit itself should be simple, easily repeatable, efficiency should be close to 100%, and there should be no interference. The circuit must be upgradeable.

The operating principle of the circuit is as follows. VD1-VD4 rectify the mains voltage. The resulting DC voltage varies in amplitude equal to half a sinusoid with a frequency of 100 Hz (1 diagram). The current passing through R1 to VD6 - a zener diode, 9V (diagram 2) has a different shape. Through VD5, pulses charge C1, creating 9 V voltage for microcircuits DD1, DD2. R2 is used for protection. It serves to limit the voltage supplied to VD5, VD6 to 22 V and generates a clock pulse for the operation of the circuit. R1 transmits the signal to the 5, 6 pins of element 2 or a non-logical digital microcircuit DD1.1, which in turn inverts the signal and converts it into a short rectangular pulse (diagram 3). The pulse comes from the 4th pin of DD1 and comes to pin D No. 8 of the DD2.1 trigger, which operates in RS mode. The operating principle of DD2.1 is the same as DD1.1 (4 diagram). Having examined diagrams No. 2 and 4, we can conclude that there is practically no difference. It turns out that from R1 you can send a signal to pin No. 5 of DD2.1. But this is not true, R1 has a lot of interference. You will have to install a filter, which is not advisable. Without double circuit formation there will be no stable operation.

The controller control circuit is based on a DD2.2 trigger; it works according to the following principle. From pin No. 13 of the DD2.1 trigger, pulses are sent to pin 3 of DD2.2, the level of which is rewritten at pin No. 1 of DD2.2, which at this stage are located at the D input of the microcircuit (pin 5). The opposite signal level is on pin 2. I propose to consider the operating principle of DD2.2. Let's assume that at pin 2 there is a logical one. C2 is charged to the required voltage through R4, R5. When the first pulse appears with a positive drop on pin 2, 0 is formed, C2 is discharged through VD7. The subsequent drop on pin 3 will set a logical one on pin 2, C2 will begin to accumulate capacitance through R4, R5. Charging time depends on R5. The larger it is, the longer it will take to charge C2. Until capacitor C2 accumulates 1/2 capacitance, pin 5 will be 0. The pulse drop at input 3 will not affect the change in logic level at pin 2. When the capacitor is fully charged, the process will repeat. The number of pulses specified by resistor R5 will be sent to DD2.2. The pulse drop will occur only at those moments when the mains voltage passes through 0. That is why there is no interference on this regulator. Pulses are sent from pin 1 of DD2.2 to DD1.2. DD1.2 eliminates the influence of VS1 (thyristor) on DD2.2. R6 is set to limit the control current of VS1. Voltage is supplied to the soldering iron by opening the thyristor. This occurs due to the fact that the thyristor receives a positive potential from the control electrode VS1. This regulator allows you to adjust the power in the range of 50-99%. Although resistor R5 is variable, due to the included DD2.2, the soldering iron is adjusted in a stepwise manner. When R5 = 0, 50% power is supplied (diagram 5), if turned to a certain angle, it will be 66% (diagram 6), then 75% (diagram 7). The closer to the calculated power of the soldering iron, the smoother the operation of the regulator. Let's say you have a 40 W soldering iron, its power can be adjusted in the region of 20-40 W.

Temperature controller design and details

The regulator parts are located on a fiberglass printed circuit board. The board is placed in a plastic case from a former adapter with an electrical plug. A plastic handle is placed on the axis of resistor R5. On the regulator body there are marks with numbers that allow you to understand which temperature mode is selected.

The soldering iron cord is soldered to the board. The connection of the soldering iron to the regulator can be made detachable to be able to connect other objects. The circuit consumes a current not exceeding 2mA. This is even less than the consumption of the LED in the switch illumination. Special measures to ensure the operating mode of the device are not required.

At a voltage of 300 V and a current of 0.5 A, DD1, DD2 and 176 or 561 series microcircuits are used; any diodes VD1-VD4. VD5, VD7 - pulse, any; VD6 is a low-power zener diode with a voltage of 9 V. Any capacitors, a resistor too. The power of R1 should be 0.5 W. No additional adjustment of the controller is required. If the parts are in good condition and no errors occurred during connection, it will work immediately.

The scheme was developed a long time ago, when there were no laser printers and computers. For this reason, the printed circuit board was manufactured using the old-fashioned method, using chart paper with a grid pitch of 2.5 mm. Next, the drawing was glued with “Moment” onto the paper more tightly, and the paper itself onto foil fiberglass. Why the holes were drilled, the traces of conductors and contact pads were drawn manually.

I still have a drawing of the regulator. Shown in the photo. Initially, a diode bridge with a rating of KTs407 (VD1-VD4) was used. They were torn a couple of times and had to be replaced with 4 KD209 type diodes.

How to reduce the level of interference from thyristor power regulators

To reduce the noise emitted by the thyristor regulator, ferrite filters are used. They are a ferrite ring with a winding. These filters are found in switching power supplies for televisions, computers and other products. Any thyristor regulator can be equipped with a filter that will effectively suppress interference. To do this, you need to pass a network wire through the ferrite ring.

The ferrite filter should be installed near sources that emit interference, directly at the location where the thyristor is installed. The filter can be located both outside the housing and inside. The greater the number of turns, the better the filter will suppress interference, but it is enough to thread the wire going to the outlet through the ring.

The ring can be removed from the interface wires of computer peripherals, printers, monitors, scanners. If you look at the wire that connects the monitor or printer to the system unit, you will notice a cylindrical thickening on it. It is in this place that a ferrite filter is located, which serves to protect against high-frequency interference.

We take a knife, cut the insulation and remove the ferrite ring. Surely your friends or you have an old interface cable for a CRT monitor or inkjet printer lying around.

In order for the soldering to be of high quality, you need to assemble the soldering iron power regulator with your own hands. Below we will list such devices that are assembled using thyristors. In some of them, the power of the soldering iron is controlled without galvanic isolation from the electrical network, so all live parts must be carefully insulated.

A simple thyristor regulator

This is the simplest option. It uses a minimum number of parts. Instead of a conventional diode bridge, only one diode is used. Temperature regulation occurs only during the positive half-wave of the current, and during the negative period the voltage passes through the mentioned diode without changes. Therefore, in this case, adjusting the power of the soldering iron with your own hands can be done in the range from 50 to 100%. If you remove the diode, it will shift to the range of 0-49%. If a dinistor (KN102A) is inserted into the break in the resistance chain, then the electrolyte can be replaced with a regular capacitor with a capacity of 0.1 microfarad.

To make such a power regulator, you need to use thyristors such as KU103V, KU201L, KU202M, which operate at a forward voltage of more than 350 V. Any diodes can be used for a reverse potential difference of at least 400 volts.

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The classic version of the thyristor device

It gives radio interference to the network and requires the installation of a filter. But it can be successfully used to change the brightness of incandescent lamps or change the temperature of heating elements with a power of 20 to 40 W.

This device works according to the following principle:

the device is powered through a device whose temperature or brightness must be changed;
then the current passes to the diode bridge;
it converts alternating current into direct current;
through a variable resistor and a filter of two resistances and a capacitor it reaches the control terminal of the thyristor, which opens and passes the maximum current value through the light bulb or soldering iron;
if you turn the variable resistor knob, this process will occur with a delay, which depends on the discharge time of the capacitor;
The temperature level to which the soldering iron tip heats up depends on this.

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Soldering iron power regulator without radio interference

The difference between this option and the previous one is the absence of interference into the electrical network. It operates during the period when the supply voltage passes through the zero point. It is not difficult to make such a soldering iron regulator with your own hands, and its efficiency reaches 98%. Amenable to subsequent modernization.

The device works like this: the mains voltage is smoothed by a diode bridge, and the constant component has the form of a sinusoid, which pulsates with a frequency of 100 Hz.

Having passed through the resistance and the zener diode, the current has a maximum voltage amplitude of 8.9 V. Its shape changes and becomes pulsed, and it charges the capacitor.

The microcircuits receive the necessary power, and resistances are needed to reduce the voltage amplitude of about 20-21 V and provide a clock signal for the LSI and individual 2OR-NOT logic cells, which all convert into rectangular pulses. At other pins of the microcircuits, inversion and formation of a pulse clock occur so that the thyristor cannot influence the logic. When a positive signal passes to the control terminal of the thyristor, it opens and soldering can be done.

This one has a range of 49-98%, allowing you to tune the instrument from 21 to 39 Watts.

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Internal installation of the device and its other parts

All the parts from which the regulator is assembled are located on a printed circuit board, which is made of fiberglass. This device does not contain galvanic isolation and is directly connected to the mains supply, so it is better to install the device in a box made of any insulating material, such as plastic. It should be no larger than the adapter. You will also need an electrical cord and plug.

A handle made of any insulating material, for example, textolite or plastic, must be put on the axis of the variable resistor. Around it, on the body of the soldering iron power regulator, marks are applied with the corresponding numbers, which will show the degree of heating of the tip.

The cord connecting the regulator to the soldering iron is soldered directly to the board. Instead, you can install connectors on the case and then you can connect several soldering irons. The current consumed by the device described above is quite small. It is equal to 2 mA, which is less than what the LED in a backlit switch takes. Therefore, you don’t have to use any effort to ensure the temperature regime.

After assembly, the device does not require adjustment. If there are no errors in installation and all parts are in working order, then the power regulator should work immediately after plugging in the power supply.

If the device described above seems difficult to manufacture, then a simpler one can be made, but additional filters will have to be installed to reduce radio interference. They are made from ferrite rings on which turns of copper wire are wound.

You can use similar elements removed from computer power supplies, printers, televisions and other similar equipment.

The filter is installed in front of the regulator input, between the device and the power cord.

It should be installed as close as possible to the thyristor, which is the source of radio interference. The filter can also be placed in or on the inside of the housing. The more turns are wound on it, the more reliably the network is protected from interference. In the simplest case, you can wrap 2-3 wires of the power cord around the ring. You can remove ferrite cores from computers, junk printers, old monitors or scanners. The PC system unit is connected to them with a cord that has a thickening. A ferrite filter is mounted in it.

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In order to obtain high-quality and beautiful soldering, it is necessary to maintain a certain temperature of the soldering iron tip, depending on the brand of solder used. I offer a homemade soldering iron heating temperature controller, which can successfully replace many industrial ones that are incomparable in price and complexity.

The main difference between the circuit of the presented soldering iron temperature controller and many existing ones is its simplicity and complete absence of radiated radio interference into the electrical network, since all transient processes occur at a time when the voltage in the supply network is zero.

Electrical circuit diagrams of soldering iron temperature controllers

Attention, the temperature controller circuits below are not galvanically isolated from the electrical network and touching the current-carrying elements of the circuit is dangerous to life!

Classic thyristor regulator circuit

The classic thyristor circuit of the soldering iron temperature controller did not meet one of my main requirements, the absence of radiating interference into the power supply network and the airwaves. But for a radio amateur, such interference makes it impossible to fully engage in what he loves. If the circuit is supplemented with a filter, the design will turn out to be bulky. But for many use cases, such a thyristor regulator circuit can be successfully used, for example, to adjust the brightness of incandescent lamps and heating devices with a power of 20-60 W. That's why I decided to present this diagram.

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 2-5V to the control electrode, depending on the type of thyristor, relative to the cathode (indicated by k in the diagram). After the thyristor has opened (the resistance between the anode and cathode becomes 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 (indicated a and k in the diagram) becomes close to zero. It's that simple.

The classical regulator circuit works as follows. The mains voltage is supplied through a load (incandescent light bulb or soldering iron winding) to a rectifier bridge circuit made using diodes VD1-VD4. The diode bridge converts alternating voltage into direct voltage, varying according to a sinusoidal law (diagram 1). When the middle terminal of resistor R1 is in the extreme left position, its resistance is 0 and when the voltage in the network begins to increase, capacitor C1 begins to charge. When C1 is charged to a voltage of 2-5V, 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 (top diagram). When you turn the knob of the variable resistor R1, its resistance will increase, the charge current of capacitor C1 will decrease and it will take more time for the voltage on it to reach 2-5V, so the thyristor will not open immediately, but after some time. The greater the value of R1, the longer the charging time of C1 will be, the thyristor will open later and the power received by the load will be proportionally less. Thus, by rotating the variable resistor knob, you control the heating temperature of the soldering iron or the brightness of the incandescent light bulb.

The simplest thyristor regulator circuit

Here is another very simple circuit of a thyristor power regulator, a simplified version of the classic regulator. The number of parts is kept to a minimum. Instead of four diodes VD1-VD4, one VD1 is used. Its operating principle is the same as the classical circuit. The circuits differ only in that the adjustment in this temperature controller circuit occurs only over 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 iron tip, no more is required. If diode VD1 is excluded, the power adjustment range will be from 0 to 50%.

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

The circuits can be used for adjustment with a supply voltage of 36V or 24V AC. You just need 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 watts at a voltage of 36V will consume a current of 1.1A.

Thyristor circuit of the regulator does not emit interference

Since I was not satisfied with the regulators that emitted interference, and there was no suitable ready-made temperature controller circuit for the soldering iron, I had to start developing it myself. The temperature controller has been in trouble-free service for more than 5 years.

The temperature controller circuit works as follows. The voltage from the supply network is rectified by the 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). Next, 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 diode VD5, creating a supply voltage of about 9V for the microcircuits DD1 and DD2. R2 performs a protective function, limiting the maximum possible voltage on VD5 and VD6 to 22V, and ensures the formation of a clock pulse for the operation of the circuit. From R1, the generated signal is supplied to the 5th and 6th pins 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 pin 4 of DD1, pulses are sent to pin 8 of D trigger DD2.1, operating in RS trigger mode. DD2.1, like DD1.1, performs the function of inverting and signal generation (Diagram 4). Please note that the signals in diagram 2 and 4 are almost the same, and it seemed that the signal from R1 could be applied directly to pin 5 of DD2.1. But studies have shown that the signal after R1 contains a lot of interference coming from the supply network, and without double shaping the circuit did not work stably. And installing additional LC filters when there are free logic elements is not advisable.

The DD2.2 trigger is used to assemble a control circuit for the soldering iron temperature controller and it works as follows. Pin 3 of DD2.2 receives rectangular pulses from pin 13 of DD2.1, which with a positive edge overwrite at pin 1 of DD2.2 the level that is currently present at the D input of the microcircuit (pin 5). At pin 2 there is a signal of the opposite level. Let's consider the operation of DD2.2 in detail. Let's say at pin 2, logical one. Through resistors R4, R5, capacitor C2 will be charged to the supply voltage. When the first pulse with a positive drop arrives, 0 will appear at pin 2 and capacitor C2 will quickly discharge through the diode VD7. The next positive drop at pin 3 will set a logical one at pin 2 and through resistors R4, R5, capacitor C2 will begin to charge. The charging time is determined by the time constant R5 and C2. The greater the value of R5, the longer it will take for C2 to charge. Until C2 is charged to half the supply voltage, there will be a logical zero at pin 5 and positive pulse drops at input 3 will not change the logical level at pin 2. As soon as the capacitor is charged, the process will repeat.

All parts of the temperature controller are located on the printed circuit board. Since the circuit does not have galvanic isolation from the power supply, the board is placed in a small plastic box, which also serves as a plug. The rod of the variable resistor R5 is fitted with a plastic handle.

The cord coming from the soldering iron is soldered directly to the printed circuit board. 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 consumed by the temperature controller control circuit does not exceed 2 mA. This is less than what the LED in the lighting circuit of the light switches consumes. Therefore, no special measures are required to ensure the temperature conditions of the device.
Microcircuits DD1 and DD2 are any 176 or 561 series. Diodes VD1-VD4 are any, designed for a reverse voltage of at least 300V and a current of at least 0.5A. VD5 and VD7 any pulse. Zener diode VD6 is any low-power one with a stabilization voltage of about 9V. Capacitors of any type. Any resistors, R1 with a power of 0.5 W. There is no need to adjust the temperature controller. If the parts are in good condition and there are no installation errors, it will work immediately.

Mobile soldering iron

Even people who are familiar with a soldering iron are often stopped by the inability to solder wires due to the lack of electrical connection. If the soldering site is not far away and it is possible to extend an extension cord, then it is not always safe to work with a soldering iron powered from a 220-volt electrical network in rooms with high humidity and temperature, with conductive floors. To be able to solder anywhere and safely, I offer a simple version of a stand-alone soldering iron.

Powering the soldering iron from the computer's UPS battery

By connecting the soldering iron to the battery using the method below, you will not be tied to the electrical network and will be able to solder wherever needed without extension cords in compliance with the requirements of the rules for safe work.
It is clear that in order to solder autonomously, you need a larger capacity battery. I immediately remember the automobile one. But it is very heavy, from 12 kg. However, there are other battery sizes, for example, those used in uninterruptible power supplies (UPS) for computer equipment. Weighing only 1.7 kg, they have a capacity of 7 Ah and produce a voltage of 12 V. Such a battery can be easily transported.

In order to make an ordinary soldering iron mobile, you need to take a plate of plywood, drill 2 holes in it with a diameter equal to the thickness of the soldering iron support wire and glue the plate to the battery. When bending the support, the width of the place where the soldering iron is installed should be made slightly smaller than the diameter of the tube with the heater of the soldering iron. Then the soldering iron will be inserted with tension and fixed. It will be convenient to store and transport.

For soldering wires with a diameter of up to 1 mm, a soldering iron designed to operate at a voltage of 12 volts and a power of 15 watts or more is suitable. The time of continuous operation from a freshly charged soldering iron battery will be more than 5 hours. If you plan to solder wires of larger diameter, then you need to take a soldering iron with a power of 30 - 40 watts. Then the continuous operation time will be at least 2 hours.

Batteries are quite suitable for powering a soldering iron, since they can no longer ensure the normal operation of uninterruptible power supplies due to the loss of their capacity over time. After all, to power a computer you need at least 250 watts of power. Even if the battery capacity has decreased to 1 A*hour, it will still provide operation of a 30-watt soldering iron for 15 minutes. This time is quite enough to complete the work of soldering several conductors.

In case of a one-time need to perform soldering, you can temporarily remove the battery from the uninterruptible power supply and return it to its place after soldering.

All that remains is to install connectors on the ends of the soldering iron wire by pressing or soldering, put them on the battery terminals and the mobile soldering iron is ready for use. Chapter.