Encyclopedia of radio electronics and electrical engineering / Civil radio communications

 Comments on the article

There are times when transceivers fail due to improper connection to the power supply or a sudden increase in voltage. The proposed device will help protect the equipment in these cases.

The statistics of transceiver equipment repairs show that up to 30% of failures are caused by power failures. Typical emergencies include excess supply voltage (overvoltage) and non-observance of its polarity (polarity reversal). Some users manage to create a combination of these situations in some mysteriously incomprehensible way. It should be emphasized that the vulnerability of the radio station increases dramatically if a non-standard (including home-made) fuse and a power source with an unreasonably large current margin are used.

In such cases, the internal protection of the transceiver turns out to be ineffective and the consequences of accidents become very serious, and sometimes even catastrophic. The inevitable mass failure of expensive and scarce components makes the restoration of a "killed" transceiver unprofitable. In case of accidents, various semiconductor devices are primarily damaged - diodes, transistors, integrated circuits. Their characteristics may change, breakdown or breakage of transitions, thermomechanical destruction of the case may occur. Resistors, winding products, backlight lamps fail. Swelling or explosion of oxide capacitors, delamination and burnout of printed conductors, charring of board sections, deformation of thermoplastic parts can occur. The entire collection of failures is taken from practice.

Emergencies occur under the following circumstances: inept actions of a novice user, accidental error or negligence of a trained operator, intentional harm by an unauthorized person, technical malfunction of the power supply system. Unfortunately, no owner of a radio station is immune from such risks. Therefore, the idea arose to develop a device for reliable protection of the transceiver in emergency situations.

The device blocks the power supply of the radio station when an abnormal voltage is received in the range from -50 to +50 V. It also has other useful properties, for example, it does not create a voltage drop in the transceiver power circuit, and also does not require the mandatory use of a fuse. As for the speed of protection, it is not worse than 2 ms and depends on the nature of the emergency.

The scheme of the protection device is shown in fig. one.

When a voltage of positive polarity with a level of less than 10 V arrives at the input of the device, a current flows through the VD1R1K1VT1 circuit, but it is not enough to operate relay K1. At an input voltage of 10 ... 15 V, the relay is activated and supplies power to the transceiver.

If during operation the voltage exceeds 15 V, then the zener diode VD2 will begin to conduct current, which will open the thyristor VS1. The voltage at the anode of the thyristor will drop, the transistor VT1 will close and the winding of the relay K1 will be de-energized. Since it is not shunted by anything, the release of the relay contacts will occur in a minimum time (actually 0,5 ... 2 ms). As a result, the transceiver will be disconnected from the increased voltage source. The Zener diode VD3, the use of which is optional, cuts off the short surge that is possible at a very high rate of voltage rise.

In the event that an emergency high voltage arrives at the input of the device abruptly from the zero level, then it will not reach the transceiver at all, since the electronic "latch" VD2VS1VT1 will react several orders of magnitude faster than the K1 relay has time to operate. In the event of a polarity reversal, the negative polarity voltage will also not be supplied to the transceiver, since the relay will not work due to the VD1 diode, which will be closed by reverse voltage.

After the emergency operation of the protection, the return to the initial state is carried out by briefly removing the input voltage.

Two versions of the design of the device were made. In the first one, the details of the device are mounted inside the K1 relay case, which is used as the KUTs-1 relay (passport RA.362.900) from domestic color TVs. It has a winding resistance of 560 Ohm and operates at a voltage of about 5 V. The overall dimensions of the device (45x45x15mm) allow it to be placed inside the transceiver or outside on the cover.

Another option is also very convenient - in a plastic cylindrical container from photographic film. The container has a diameter of 30 and a length of 50 mm. The finished product is filled with epoxy compound and installed in the break of the transceiver's power cord (similar to an impulse noise filter). Here, a more compact relay RES47 (passport RF4.500.409) with a winding resistance of 175 ohms is used. In this case, the resistor R1 must have a resistance of 110 ohms. Any other relays that operate at a voltage of 5 ... 6 V and are capable of switching a current of at least 3 A are also suitable (for example, TTI's TRC series relays).

Transistor VT1 can be replaced by current keys of the KR1014, KR1064 series with indexes A, B or their analogues ZVN2120, VN2410. Instead of the VD1 diode, any other one with a forward current of at least 0,3 A and a reverse voltage of at least 400 V, for example, KD209A, is suitable. Zener diode VD2 can be replaced with D814 or KS515A. Thyristor VS1 can be with indices E-I, and it is desirable to use specimens selected for maximum sensitivity.

The adjustment of the device begins with the selection of the resistor R1, achieving the operation of the relay at an input voltage of 9,5 ... 10 V. Then, slowly and smoothly increasing the voltage, make sure that the relay releases at 14,5 ... 15 V. If necessary, then the cutoff voltage can be changed by selecting the zener diode VD2.

The author tested the ALAN-78 PLUS CB transceiver equipped with the proposed protection device. The test procedure simulated a series of the most dangerous accidents, namely a combination of polarity reversal and overvoltage. In addition, a factor aggravating the accident was deliberately introduced - instead of a regular fuse with a nominal value of 2 A, a thick wire jumper was installed. Under normal conditions, such, one might say, "lawlessness" guarantees extensive and irreversible destruction of the electronic elements of any transceiver.

During the tests, the device was repeatedly connected to current sources (PS-30, B5-48, B5-71 power supplies, OSM-220/36 V transformer), which had the following parameters: -13,8 V (32 A); +16 V(10A);-16V(10A); + 30 V (10 A); -30 V (10 A); -36 V (50 Hz, 5 A); +50 V (2 A); -50 V (2 A). Each test voltage was applied to the transceiver automatically using a software device operating according to the cyclogram shown in the table.

An extended test mode made it possible to simulate emergency situations of various durations and, along the way, to check the stability of protection against transients. If each fact of applying abnormal voltage to the transceiver is considered as an emergency situation, then it is easy to calculate that their total number was 688. Nevertheless, such a crushing effect did not cause any harm to the radio station. With the control supply of the rated voltage (+13,2 V), the device turned on and showed full performance. This test result testifies to the reliability of the device and allows it to be classified as "fool-proof".

If the device is somewhat more complicated, it can provide additional protection for the current consumption and against an emergency increase in the RF voltage at the collector of the output transistor of the transmitter. Such an increase is possible with a mismatch of the antenna-feeder path or excitation of the output stage.

The scheme of this option is shown in Fig. 2.

Current protection (overload and short circuit) is carried out using the SF1 reed switch with the L1 coil located on it. When the current consumed by the transceiver increases above the set value, the electromagnetic field of the coil becomes sufficient to close the magnetically controlled contact.

Since the reed switch is connected in parallel to the VD2 zener diode, an emergency shutdown of the device occurs similar to the situation with overvoltage. Elements VT2, C1, R4, VD4 form a zone of temporary insensitivity of protection to the inrush current that occurs at the moment the transceiver is turned on. For the radio station ALAN-78PLUS, this time is 22 ms and can be adjusted by selecting the capacitor C1.

When working with the device (Fig. 2), you must first turn on the transceiver, and then the SA1 toggle switch.

Setting the current protection to a level of 2 ... 3 A is reduced to selecting the number of turns of the L1 coil, consisting of 4-8 turns of PEL 0,5 wire (roughly) and moving it along the reed switch (finely) followed by fixing with hot melt adhesive.

With a mismatched load (for example, a break in the antenna-feeder path), the RF voltage at the collector of the output transistor of the transmitter increases, which is fraught with a breakdown of its transitions. However, in this case, the zener diode VD5 begins to conduct current, which opens the transistor VT3. The positive voltage from the collector of the transistor is supplied to the control electrode of the thyristor VS1. The device then shuts down in the same way as other emergencies.

Resistor R7 is selected in such a way that the transceiver turns off when the transmitter is operating on the antenna equivalent of 150 ohms, which corresponds to SWR-3.

The emitter junction of the transistor VT2 (see Fig. 2) must be shunted with a resistor with a resistance of about 10 kOhm.

Author: A.Sokolov, Moscow

See other articles Section Civil radio communications.

Read and write useful comments on this article.

<< Back

<< Back

Latest news of science and technology, new electronics:

A New Way to Control and Manipulate Optical Signals 05.05.2024

The modern world of science and technology is developing rapidly, and every day new methods and technologies appear that open up new prospects for us in various fields. One such innovation is the development by German scientists of a new way to control optical signals, which could lead to significant progress in the field of photonics. Recent research has allowed German scientists to create a tunable waveplate inside a fused silica waveguide. This method, based on the use of a liquid crystal layer, allows one to effectively change the polarization of light passing through a waveguide. This technological breakthrough opens up new prospects for the development of compact and efficient photonic devices capable of processing large volumes of data. The electro-optical control of polarization provided by the new method could provide the basis for a new class of integrated photonic devices. This opens up great opportunities for ... >>

Primium Seneca keyboard 05.05.2024

Keyboards are an integral part of our daily computer work. However, one of the main problems that users face is noise, especially in the case of premium models. But with the new Seneca keyboard from Norbauer & Co, that may change. Seneca is not just a keyboard, it is the result of five years of development work to create the ideal device. Every aspect of this keyboard, from acoustic properties to mechanical characteristics, has been carefully considered and balanced. One of the key features of Seneca is its silent stabilizers, which solve the noise problem common to many keyboards. In addition, the keyboard supports various key widths, making it convenient for any user. Although Seneca is not yet available for purchase, it is scheduled for release in late summer. Norbauer & Co's Seneca represents new standards in keyboard design. Her ... >>

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Random news from the Archive Mosquitoes will stop attacking people 13.06.2013 For the first time, scientists have managed to create genetically modified mosquitoes that react differently than their "natural" relatives to human odors and to the repellent diethyltoluamide (DEET). Scientists from the Howard Hughes Medical Institute announced their discovery. Researchers have not only genetically altered mosquitoes, but also learned why these insects are drawn to people. But most importantly, scientists plan to "wean" mosquitoes to choose people as a priority victim and thereby minimize human infection with diseases such as yellow fever and dengue fever. The orco gene, which was deleted from flies 10 years ago, helped to deal with the olfactory addictions of mosquitoes, and the flies lost their olfactory abilities. In the case of yellow fever mosquitoes (Aedes aegypti), scientists acted rather at random, and were pleasantly surprised when they learned that after the removal of this gene, mosquitoes also stopped reaching out to humans, preferring the laboratory guinea pig. Next, the team tested how mosquitoes with orco mutations reacted to the repellant. To do this, a repellent (diethyltoluamide) was applied to one hand of a person, and the other was left untreated. Mosquitoes with a modified gene landed on both hands equally often, without smelling the repellent. However, when they were already landing on the arm, they quickly flew away from the part of the body that was covered with the repellent. This proves that mosquitoes have two different mechanisms for odor perception. One gene is responsible for the perception of smells that are in the air, and the other comes into action as soon as the insect touches the skin, and makes a decision whether to bite or not. The new insights from the Howard Hughes Medical Institute will help scientists understand how insects react to current insect repellents, as well as what the next generation of repellents should be like. And it cannot be ruled out that soon it will be enough to apply a special repellent to the skin and boldly go to the habitats of the yellow fever mosquito without fear of contracting yellow fever or dengue fever. In addition, the evening on the shore of a summer lake will become much more pleasant.

Other interesting news:

▪ Icebreakers must sail backwards

▪ Innovative lidar Velodyne VLS-128

▪ Dark matter can heat planets from the inside

▪ Supermassive black hole discovered

▪ Security Robot

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Power supply. Article selection

▪ article Aesopian language. Popular expression

▪ article How did Coca-Cola appear? Detailed answer

▪ article Storekeeper. Job description

▪ article AF power amplifier (80 watts). Encyclopedia of radio electronics and electrical engineering

▪ article Cigarettes from nowhere. Focus Secret

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