Three-phase and single-phase thyristor power regulator - operating principle, circuits. DIY voltage regulator circuit Thyristor power regulator operating principle
The temperature of the soldering iron tip depends on many factors.
- Input network voltage, which is not always stable;
- Heat dissipation in massive wires or contacts on which soldering is performed;
- Ambient air temperatures.
For high-quality work, it is necessary to maintain the thermal power of the soldering iron at a certain level. There is a large selection of electrical appliances with a temperature controller on sale, but the cost of such devices is quite high.
Soldering stations are even more advanced. Such complexes contain a powerful power supply, with which you can control temperature and power over a wide range.
The price matches the functionality.
What should you do if you already have a soldering iron and don’t want to buy a new one with a regulator? The answer is simple - if you know how to use a soldering iron, you can make an addition to it.
DIY soldering iron regulator
This topic has long been mastered by radio amateurs, who are more interested in a high-quality soldering tool than anyone else. We offer you several popular solutions with electrical diagrams and assembly procedures.
Two-stage power regulator
This circuit works on devices powered by an alternating voltage network of 220 volts. A diode and a switch are connected in parallel to each other into the open circuit of one of the supply conductors. When the switch contacts are closed, the soldering iron is powered in standard mode.
When opened, current flows through the diode. If you are familiar with the principle of alternating current flow, the operation of the device will be clear. The diode, passing current in only one direction, cuts off every second half-cycle, reducing the voltage by half. Accordingly, the power of the soldering iron is reduced by half.
Basically, this power mode is used during long pauses during work. The soldering iron is in standby mode and the tip is not very cool. To bring the temperature to 100%, turn on the toggle switch - and after a few seconds you can continue soldering. When the heating decreases, the copper tip oxidizes less, extending the service life of the device.
IMPORTANT! The test is performed under load, that is, with a soldering iron connected.
When rotating resistor R2, the voltage at the input to the soldering iron should change smoothly. The circuit is placed in the body of the overhead socket, which makes the design very convenient.
IMPORTANT! It is necessary to reliably insulate the components with heat-shrinkable tubing to prevent short circuits in the housing - socket.
The bottom of the socket is covered with a suitable cover. The ideal option is not just an overhead socket, but a sealed street socket. In this case, the first option was chosen.
It turns out to be a kind of extension cord with a power regulator. It is very convenient to use, there are no unnecessary devices on the soldering iron, and the control knob is always at hand.
1. Resistor 4.7 kOhm mlt-0.5 (even 0.25 watt will do).
2. A variable resistor 500kOhm-1mOhm, with 500kOhm it will regulate quite smoothly, but only in the range of 220V-120V. With 1 mOhm - it will regulate more tightly, that is, it will regulate with a gap of 5-10 volts, but the range will increase, it is possible to regulate from 220 to 60 volts! It is advisable to install the resistor with a built-in switch (although you can do without it by simply installing a jumper).
3. Dinistor DB3. You can get one from economical LSD lamps. (Can be replaced with domestic KH102).
4. Diode FR104 or 1N4007, such diodes are found in almost any imported radio equipment.
5. Current-efficient LEDs.
6. Triac BT136-600B or BT138-600.
7. Screw terminal blocks. (you can do without them by simply soldering the wires to the board).
8. Small radiator (up to 0.5 kW it is not needed).
9. Film capacitor 400 volt, from 0.1 microfarad to 0.47 microfarad.
AC voltage regulator circuit:
Let's start assembling the device. First, let's etch and tin the board. The printed circuit board - its drawing in LAY, is in the archive. A more compact version presented by a friend sergei - .
Then we solder the capacitor. The photo shows the capacitor from the tinning side, because my example of the capacitor had too short legs.
We solder the dinistor. The dinistor has no polarity, so we insert it as you wish. We solder the diode, resistor, LED, jumper and screw terminal block. It looks something like this:
And in the end, the last stage is to install a radiator on the triac.
And here is a photo of the finished device already in the case.
It should be noted that this device will cope most effectively with resistive loads - lamps, heaters, etc. Inductive current consumers can also be connected, but if its value is too small, the reliability of the adjustment will decrease.
The circuit of this homemade thyristor regulator does not contain any scarce parts. When using the rectifier diodes indicated in the diagram, the device can withstand a load of up to 5A (about 1 kW), taking into account the presence of radiators.
To increase the power of the connected device, you need to use other diodes or diode assemblies designed for the current you need.
The thyristor also needs to be replaced, because KU202 is designed for a maximum current of up to 10A. Among the more powerful ones, domestic thyristors of the T122, T132, T142 and other similar series are recommended.
There are not so many parts; in principle, mounted mounting is acceptable, but on a printed circuit board the design will look more beautiful and more convenient. Drawing of the board in LAY format. The D814G zener diode can be changed to any one with a voltage of 12-15V.
Once assembled, the simplest voltage regulator on one transistor was intended for a specific power supply and a specific consumer; of course, there was no need to connect it anywhere else, but as always, there comes a moment when we stop doing the right thing. The consequence of this is troubles and thoughts about how to live and be further and the decision to restore what was created earlier or continue to create.
Scheme number 1
There was a stabilized switching power supply that gave an output voltage of 17 volts and a current of 500 milliamps. A periodic change in voltage was required in the range of 11 - 13 volts. And the well-known one on one transistor coped with this perfectly. I added only an indication LED and a limiting resistor to it. By the way, the LED here is not only a “firefly” signaling the presence of output voltage. With the correct value of the limiting resistor, even a small change in the output voltage is reflected in the brightness of the LED, which provides additional information about its increase or decrease. The output voltage could be changed from 1.3 to 16 volts.
KT829, a powerful low-frequency silicon compound transistor, was installed on a powerful metal radiator and it seemed that, if necessary, it could easily withstand a heavy load, but a short circuit occurred in the consumer circuit and it burned out. The transistor has a high gain and is used in low-frequency amplifiers - you can really see its place there and not in voltage regulators.
On the left are removed electronic components, on the right are prepared for replacement. The difference in quantity is two items, but in terms of the quality of the circuits, the former and the one that was decided to be collected, it is incomparable. This begs the question - “Is it worth assembling a scheme with limited capabilities when there is a more advanced option “for the same money”, in the literal and figurative sense of this saying?”
Scheme number 2
The new circuit also has a three-pin electrical connection. component (but this is no longer a transistor) constant and variable resistors, an LED with its own limiter. Only two electrolytic capacitors have been added. Typically, typical diagrams indicate the minimum values of C1 and C2 (C1=0.1 µF and C2=1 µF) which are necessary for stable operation of the stabilizer. In practice, capacitance values range from tens to hundreds of microfarads. The containers should be located as close to the chip as possible. For large capacities, the condition C1>>C2 is required. If the capacitance of the capacitor at the output exceeds the capacitance of the capacitor at the input, then a situation arises in which the output voltage exceeds the input, which leads to damage to the stabilizer microcircuit. To exclude it, install a protective diode VD1.
This scheme has completely different possibilities. Input voltage is from 5 to 40 volts, output voltage is 1.2 - 37 volts. Yes, there is an input-output voltage drop of approximately 3.5 volts, but there are no roses without thorns. But the KR142EN12A microcircuit, called a linear adjustable voltage stabilizer, has good protection against excess load current and short-term protection against short circuits at the output. Its operating temperature is up to + 70 degrees Celsius, works with an external voltage divider. Output load current is up to 1 A during long-term operation and 1.5 A during short-term operation. The maximum permissible power when operating without a heat sink is 1 W, if the microcircuit is installed on a radiator of sufficient size (100 cm2) then P max. = 10 W.
What happened
The updated installation process itself took no more time than the previous one. In this case, what was obtained was not a simple voltage regulator that is connected to a stabilized voltage power supply; the assembled circuit, when connected even to a network step-down transformer with a rectifier at the output, itself provides the necessary stabilized voltage. Naturally, the output voltage of the transformer must correspond to the permissible parameters of the input voltage of the KR142EN12A microcircuit. Instead, you can use an imported analogue integral stabilizer. Author Babay iz Barnaula.
Discuss the article TWO SIMPLE VOLTAGE REGULATORS
Thyristor power regulators are used both in everyday life (in analog soldering stations, electric heating devices, etc.) and in production (for example, to start powerful power plants). In household appliances, as a rule, single-phase regulators are installed; in industrial installations, three-phase ones are more often used.
These devices are electronic circuits that operate on the principle of phase control to control the power in the load (more on this method will be discussed below).
Operating principle of phase control
The principle of regulation of this type is that the pulse that opens the thyristor has a certain phase. That is, the further it is located from the end of the half-cycle, the greater the amplitude will be the voltage supplied to the load. In the figure below we see the reverse process, when the pulses arrive almost at the end of the half-cycle.
The graph shows the time when the thyristor is closed t1 (phase of the control signal), as you can see, it opens almost at the end of the half-cycle of the sinusoid, as a result, the voltage amplitude is minimal, and therefore, the power in the load connected to the device will be insignificant (close to the minimum). Consider the case presented in the following graph.
Here we see that the pulse that opens the thyristor occurs in the middle of the half-cycle, that is, the regulator will output half the maximum possible power. Operating at close to maximum power is shown in the following graph.
As can be seen from the graph, the pulse occurs at the beginning of the sinusoidal half-cycle. The time when the thyristor is in the closed state (t3) is insignificant, so in this case the power in the load approaches the maximum.
Note that three-phase power regulators work on the same principle, but they control the voltage amplitude not in one, but in three phases at once.
This control method is easy to implement and allows you to accurately change the voltage amplitude in the range from 2 to 98 percent of the nominal value. Thanks to this, smooth control of the power of electrical installations becomes possible. The main disadvantage of devices of this type is the creation of a high level of interference in the electrical network.
An alternative to reduce noise is to switch the thyristors when the AC voltage sine wave passes through zero. The operation of such a power regulator can be clearly seen in the following graph.
Designations:
- A – graph of half-waves of alternating voltage;
- B – thyristor operation at 50% of maximum power;
- C – graph displaying the operation of the thyristor at 66%;
- D – 75% of maximum.
As can be seen from the graph, the thyristor “cuts off” half-waves, not parts of them, which minimizes the level of interference. The disadvantage of this implementation is the impossibility of smooth regulation, but for loads with high inertia (for example, various heating elements), this criterion is not the main one.
Video: Testing a thyristor power regulator
Simple power regulator circuit
You can adjust the power of the soldering iron using analog or digital soldering stations for this purpose. The latter are quite expensive, and it is not easy to assemble them without experience. While analog devices (which are essentially power regulators) are not difficult to make with your own hands.
Here is a simple diagram of a device using thyristors, thanks to which you can regulate the power of the soldering iron.
Radioelements indicated in the diagram:
- VD – KD209 (or similar in characteristics)
- VS-KU203V or its equivalent;
- R 1 – resistance with a nominal value of 15 kOhm;
- R 2 – variable resistor 30 kOhm;
- C – electrolytic type capacitance with a nominal value of 4.7 μF and a voltage of 50 V or more;
- R n – load (in our case it is a soldering iron).
This device regulates only the positive half-cycle, so the minimum power of the soldering iron will be half the rated one. The thyristor is controlled through a circuit that includes two resistances and a capacitance. The charging time of the capacitor (it is regulated by resistance R2) affects the duration of the “opening” of the thyristor. Below is the operating schedule of the device.
Explanation of the picture:
- graph A – shows a sinusoid of alternating voltage supplied to the load Rn (soldering iron) with a resistance R2 close to 0 kOhm;
- graph B – displays the amplitude of the sinusoid of the voltage supplied to the soldering iron with a resistance R2 equal to 15 kOhm;
- graph C, as can be seen from it, at the maximum resistance R2 (30 kOhm), the operating time of the thyristor (t 2) becomes minimal, that is, the soldering iron operates with approximately 50% of the nominal power.
The circuit diagram of the device is quite simple, so even those who are not very well versed in circuit design can assemble it themselves. It is necessary to warn that when this device operates, a voltage dangerous to human life is present in its circuit, therefore all its elements must be reliably insulated.
As already described above, devices operating on the principle of phase regulation are a source of strong interference in the electrical network. There are two options for getting out of this situation:
Regulator operating without interference
Below is a diagram of a power regulator that does not create interference, since it does not “cut off” half-waves, but “cuts off” a certain amount of them. We discussed the principle of operation of such a device in the section “The principle of operation of phase control,” namely, switching the thyristor through zero.
Just like in the previous scheme, power adjustment occurs in the range from 50 percent to a value close to the maximum.
List of radioelements used in the device, as well as options for replacing them:
Thyristor VS – KU103V;
Diodes:
VD 1 -VD 4 – KD209 (in principle, you can use any analogs that allow a reverse voltage of more than 300V and a current of more than 0.5A); VD 5 and VD 7 – KD521 (any pulse-type diode can be installed); VD 6 – KC191 (you can use an analogue with a stabilization voltage of 9V)
Capacitors:
C 1 – electrolytic type with a capacity of 100 μF, designed for a voltage of at least 16 V; C 2 – 33H; C 3 – 1 µF.
Resistors:
R 1 and R 5 – 120 kOhm; R 2 -R 4 – 12 kOhm; R 6 – 1 kOhm.
Chips:
DD1 – K176 LE5 (or LA7); DD2 –K176TM2. Alternatively, 561 series logic can be used;
R n – soldering iron connected as a load.
If no errors were made when assembling the thyristor power regulator, then the device starts working immediately after switching on; no configuration is required for it. Having the ability to measure the temperature of the soldering iron tip, you can make a gradation of the scale for resistor R5.
If the device does not work, we recommend checking the correct wiring of the radio elements (do not forget to disconnect it from the network before doing this).