Soldering iron boost controller. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Ham Radio Technologies

 Comments on the article

The device brought to the attention of readers is designed to control the power of soldering irons and other heating devices with a power of up to 100 watts. It can also be used to power lighting fixtures with incandescent lamps of the same power at reduced mains voltage.

A distinctive feature of the device is its ability to regulate the power transmitted to the load, not only in the direction of its decrease, but also in the direction of increase relative to the nominal value. The control interval is very wide - from 1 to 180% of the rated power of the connected load.

As you know, the amplitude value of the sinusoidal mains voltage is 1,41 times greater than the effective one. Due to this, by connecting a rectifier with a smoothing filter to the network, you can get a constant voltage of about 310 V. It is easy to form rectangular pulses of this amplitude from it, and by changing their duty cycle, you can adjust the effective value of the impulse voltage from zero to 1,41 of the effective value of the initial sinusoidal voltage. The thermal power of a soldering iron or other heating device fed with such a voltage will vary from zero to twice the rated power.

A description of the device operating according to the principle described above was published earlier in the article by S. Lusta "Boost voltage regulator" ("Radio", 2006, No. 5, p. 39). The regulator proposed in it is simple and compact, but it has some disadvantages. There is no indication of the set power level, it is regulated by turning the knob of the variable resistor. In addition, certain rules must be observed when connecting the device to the network, otherwise it may be damaged.

I bring to the attention of readers a regulator assembled on a microcontroller. It has push-button control and digital indication of installed power. Three operating modes, selected by pressing the corresponding buttons, allow you to quickly heat up the soldering iron even at low mains voltage, and then maintain its operating temperature. The power set for each operating mode can also be changed by pressing the buttons. The set value is automatically stored in the non-volatile memory of the microcontroller. Soldering irons up to 100 W, as well as lighting devices with incandescent lamps, can be connected to the regulator.

The power regulator circuit is shown in fig. 1. Its basis is the PIC16F628 (DD1) microcontroller, which has a PWM module that generates programmatically variable duty cycle rectangular pulses at the RB3 output. The repetition rate of these pulses when the microcontroller is operating from the built-in RC generator is about 360 Hz. Their duty cycle (the reciprocal of the duty cycle) is proportional to the set value of the output power.

Rice. 1. Scheme of the soldering iron power regulator (click to enlarge)

The pulses are fed to the emitting diode of the optocoupler U1, which is necessary for galvanic isolation of the power and low-voltage parts of the device. From the collector of the phototransistor of the optocoupler, the control pulses are fed to the gate of the field-effect transistor VT3, which switches the load. The Zener diode VD6, connected between the gate and the source of the transistor, limits the amplitude of the control pulses to a safe value.

The pulse shaper is powered by a mains voltage rectifier on a VD5 diode bridge with a smoothing capacitor C4. To limit the charging current of this capacitor at the moment the device is connected to the network, a thermistor RK1 is used. The L1C1C2 filter prevents the penetration of interference from the device into the mains.

A four-digit seven-element LED indicator HG4 is connected to the outputs RB7-RB2 of the microcontroller through a code converter DD1, in which only three digits are used. The common anodes of the discharge elements are connected to the emitters of transistors VT1, VT2, VT4.

LEDs are connected to the outputs RA3, RA6, RA7 of the microcontroller, which show the selected operating mode. Control buttons are connected to RBO-RB2 inputs.

The digital part of the device is powered by a voltage regulator on the DA1 chip. Its output voltage is 5 V at a load current of up to 0,4 A.

The device uses MLT resistors and imported oxide capacitors. KT503D transistors can be replaced with devices of the same series with any letter index, the 2SK2761 transistor can be replaced with IRF830 or KP707V2. PC817 optocoupler - on PC 120. Instead of the FYL-3014UGC LED, you can use any green one, and instead of the FYL-3014src - red glow. Buttons - any small-sized.

The CA56-21SRWA indicator can be replaced with a BQ-M51DRD or three single-digit seven-element indicators with a common anode can be used, for example, ALS324B or ALS3ZZB2. The cathodes of the same-name elements of such indicators are combined and connected to the corresponding outputs of the code converter through resistors R9-R15.

As C1, C2 it is necessary to use imported capacitors designed for operation in AC circuits. In extreme cases, you can use capacitors K73-17 for a constant voltage of 630 V. The inductor L1 and thermistor RK1 are from the IBM PC power supply.

All parts of the device, with the exception of the power supply (consisting of a transformer T1, diodes VD1-VD4, microcircuit DA1, capacitors C3, C5, C6), are mounted on a printed circuit board, the drawing of which is shown in fig. 2.

Rice. 2. PCB drawing

The HG1 indicator is installed on the edge of the board perpendicular to its surface, its outputs are connected to the corresponding contact pads with segments of a thin mounting wire.

The power supply is mounted on a separate printed circuit board, the drawing of which is not given. It can use any small-sized step-down transformer with a voltage on the secondary winding of 7 ... 10 V at a load current of 0,4 A. Some unified transformers of the TPP series are suitable, for example, TPP220-127 / 220-50.

To obtain the required voltage, in this transformer it is necessary to connect in series all the secondary windings, with the exception of one with a voltage of 2,5 V. In addition, terminals 3 and 7 of the primary windings should be connected, and a voltage of 220 V should be applied to terminals 2 and 9. The DA1 stabilizer must be equipped with a heat sink with an area of ​​​​5 ... 7 cm² from aluminum sheet.

To power the regulator, you can also use a ready-made transformer or switching power supply that provides a stabilized voltage of 5 V at a load current of at least 0,4 A. For example, a switching power supply from a faulty DVD player.

The appearance of the regulator is shown in fig. 3. It is assembled in a PC CD-ROM drive case. The front panel contains the HG1 indicator, control buttons and LEDs. Holders for a soldering iron are fixed on the top cover, and an XS1 socket is installed on the back wall for connecting it.

Rice. 3. Appearance of the soldering iron power regulator

After assembling, it is necessary to supply voltage to the regulator and make sure that its digital part is working properly. After that, you should check the amplitude and shape of the pulses at the gate of the transistor VT3 with an oscilloscope. Their amplitude should be at least 10 V, and the shape should be close to rectangular. If this is not the case, it is necessary to select the resistor R8. I draw the attention of readers that during the execution of the operations described above, the common wire of the oscilloscope must be connected to the source of the transistor VT3, which has a galvanic connection with the mains. When working with an oscilloscope connected in this way, care must be taken to avoid electrical shock.

When operating the device, it must be remembered that through it it is impossible to power electrical appliances containing inductive elements (transformers, chokes, electric motors), as well as any electronic components. When supplying power to the load that exceeds the rated power, remember that this leads to a sharp reduction in its resource, and more serious troubles are possible. Strictly observe fire safety rules and do not leave heaters turned on unattended.

The microcontroller program can be downloaded from ftp://ftp.radio.ru/pub/2014/01/power.zip.

Author: A. Abramovich

See other articles Section Ham Radio Technologies.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive Self-healing glass 15.12.2017 A group of Japanese researchers created a special glass that has the ability to self-heal if its integrity is violated. During the development of a new type of adhesive type, a material was created that can be easily restored after a breakdown. Researchers at the University of Tokyo, in the course of their experiments to create a special adhesive agent, managed to make a material that resembles ordinary glass in all characteristics. The main feature of the created novelty is that if the parts of the glass formed from its breaking are applied to each other along the junction where the split occurred, then they will rejoin each other. Scientists argue that the former strength of this material in case of violation of its integrity can be easily restored by holding the broken parts in contact with each other for several hours. The scientists called this invention "polythiourea", and according to their assurances, the new material can soon replace the usual fragile glass, which is thrown away immediately after losing its integrity.

Other interesting news:

▪ Nitroglycerin May Cause Migraines and Abnormal Cardiovascular Reactions

▪ Europe's largest dinosaur

▪ 1 Tbps or higher wireless data antenna

▪ Cosmic rays - a threat to the colonists of Mars

▪ The retina does not change with age

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Visual illusions. Article selection

▪ article Keep in a black body. Popular expression

▪ article What keeps a duck afloat? Detailed answer

▪ article Barman. Standard instruction on labor protection

▪ Mustard article. Simple recipes and tips

▪ article Resistors. PHILIPS code marking. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024