Stable current generator for charging batteries and its use in the repair and design of electronic equipment. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

 Comments on the article

The considered stable current generator (GST) is well suited for charging batteries (up to 12 V).

The value of the charging current can be set within 0 ... 10 A. However, this GTS was made not so much for charging batteries, but for other purposes. Powerful HTS allows you to quickly evaluate almost any contact connections by the value of the contact resistance (contacts of relays, switches, etc.). Using a DC millivoltmeter, such as an 830 or 890 series multimeter, you can easily measure resistance down to 0,001 ohms. Having a powerful HTS and a millivoltmeter, we actually purchased a milliohmmeter, and this opens up wide opportunities for a radio amateur.

Being engaged in the repair of radio-electronic means (RES), we are forced to check the serviceability of many components. The design of the RES requires the verification of all radio components without exception (both used and new).

In amateur radio conditions, the process of checking components is, as a rule, very superficial. And how much can you learn about the parameters of a powerful diode or transistor when using a digital multimeter? "Ringing" with a current of several milliamps a powerful diode of 10 ... 30 A, one can only reveal its worthlessness.

The results will be better if a pointer meter is used, for example, М41070/1. The latter provides a current value in the measured circuit of more than 50 mA (subrange 300 Ohm). And at the limit of 300 kOhm, defects in diodes and transistors (current leakage) are easily detected. But not all defects can be detected when checking semiconductor devices with low-voltage resistance meters.

Therefore, meters were made [1, 2]. The meter [1] allows you to quickly evaluate the Uke.max value of transistors, and the portable version of such a meter [2] is designed to operate on battery power (it is not tied to a 220 V network, which is valuable in the radio market). The same meters also evaluated the values ​​of the reverse voltages of the tested diodes.

The search for defective capacitors was convenient and fast. In addition, the meter [2] has a voltage range from 0 to 3000 V. The latter circumstance makes it possible to test insulation, for example, between the windings of a network transformer. In my practice, there were cases when it was even possible to find the place of an insulation defect between the I and II windings of the mains transformer of the power supply. No ohmmeters that were at hand (0 ... 200 MΩ) did not record insulation violations, and the transformer had already begun to "beat with current". In the dark (at a voltage of more than 2,5 kW), the place of the defect was very clearly visible, since the spark jumped in a specific place and created a characteristic crackle. Thus, it was possible to avoid winding rewinding by eliminating the insulation breakdown and filling it with glue.

The most important thing is that radio amateurs who repeated the meters [1, 2] were satisfied with the capabilities of these devices.

When it comes to choosing the best power diodes available, this GTS comes in handy. Diodes with the lowest forward voltage (Upr) heat up less and last longer.

It is very important to use such instances in low-voltage rectifiers, where the value of Upr determines the efficiency of the circuit. I had to observe how intensively the diodes begin to heat up, when the current through them exceeds 7 ... out of service. The current through these diodes should not exceed 10 A (current load factor is 242). However, the practice of using such diodes has shown that they can work for a long time and without fail even at currents of 247 A or more. If the current exceeds 203 A, then the selection of specimens with the lowest Upr value is especially relevant.

It is worth replacing ordinary silicon diodes D242 with diodes with a Schottky barrier, for example, KD2998V, as you realize the advantage of the latter (a small Upr value allows the use of small-sized radiators even at a current of 10 A).

Unfortunately, the prices for diodes are high, and for diode bridges they are excessively high (it may pay off in repairs, and designing at reseller prices ruins a radio amateur). It is cheaper to bridge several diodes, although it is inconvenient with several heatsinks. The parameters of foreign diodes and bridges are clearly overestimated, as evidenced by their replacement in the circuits.

To select diodes with a minimum value of Upr, the diode under test is connected to the output of the GTS (as shown by the dotted line in Fig. 1). This is how diodes of types KD202, KD203, D242D246, D214, D215, D231, KD2997, KD2998, KD2999, etc. were chosen. direct current values.Among a large number (or package) of the same type of diodes, there were almost always instances in which Upr was 25-1,5 times greater than the rest.These instances overheat, for example, in a bridge rectifier (their heating is significantly exceeds the heating of the rest of the diodes.) Upr was measured at a current not less than the operating current of this diode in a particular design.

About measuring small resistance values ​​(milliohmmeter mode)

You will need a millivoltmeter with a limit of 200 or 2000 mV. Resistor R9 (Fig. 1) sets the current through the measured resistance (Rn) 1 A. Now for every millivolt of the voltage drop across the resistance Rn corresponds to a milliohm of this resistance. When a higher measurement accuracy of Rn is required, go to the subrange of 10 A (switch SA2 is pressed) and set the current through Rn to 10 A. Now each milliohm of resistance corresponds to 10 mV.

(click to enlarge)

With such a current value (10 A), almost any detachable connections "ring" perfectly. Depending on the transient resistance, it "settles" on them, from units of millivolts (contact of excellent quality) to tens and hundreds of millivolts (these are already defective contacts). Measurement of low resistances at a current of ≥10 A allows you to quickly identify many defects that are hidden for continuity by multimeters.

An exclusive check (in numbers!) of almost any installation wires is provided. They take a piece of mounting wire several tens of centimeters long and connect it to the GTS. According to the voltage drop across it, its suitability for certain purposes is determined. As long as a person is dealing with structures where the current value does not exceed 1 ... 3 A, then he does not need to measure milliohms. But in designs with currents greater than 10 A, much changes. "Chinese" wires began to appear on the markets (a thick layer of insulation with a small cross section of copper wires). Domestic wires of the same diameter (in terms of insulation) have a per unit resistance two or more times less than "Chinese" ones. In order not to disable the millivoltmeter when Rn is turned off, for the duration of the measurement, the device leads are shunted with a KD2998 diode (any other one with a current ≥10 A is also suitable), as shown in Fig. 1.

GST is of particular value when checking second-hand detachable connections and relay contacts. Contacts that require cleaning or replacement are immediately detected. Here are just a few examples. Widespread toggle switches of types TV, TP, MT, PT, etc. Over time, their contact resistance increases from 3 ... 5 mOhm to 0,1 ... 0,5 Ohm and even more! It makes sense to apply appropriate inscriptions to the switch body, which should determine the purpose (application) of the switch. Often, cleaning the relay contacts gave a good result: usually, the contact resistance decreases by 2-10 times (depending on the wear of the contacts).

A decrease in contact resistance was also achieved by optimal clamping of the contacts. Remember that poor contact causes accelerated destruction of the contact surfaces.

About sore

People buy ordinary mains (220 V) plugs, sockets and switches that overheat when loaded with more than 1 kW. Although encouraging 6 A is written on the cases of these products, the inscriptions do not guarantee the proper quality of the connections. You can, of course, check such products by connecting them for 30 ... 60 minutes with a load of 1 kW (waiting for possible heating in a defective connection). And you can use the GTS to measure the contact resistance. The question is very relevant, because bad contacts in the load of the 220 V electrical network often lead to a fire. And the quality of modern household power plugs, sockets and switches is only declining (saving materials, poor assembly, lack of reliable spring contacts).

About GTS circuitry

The GST is made on the op-amp DA1 and a powerful field-effect transistor VT7, which provides the required current in the load. Since at direct current (our case) the field-effect transistor does not consume current in the gate circuit, the op-amp operates virtually without load, which increases the reliability of the entire HTS. The OU controls the conductivity of the field effect transistor, which determines the current in the load Rn. GST has two subranges of current regulation. In the position of the SA2 switch shown in the diagram, we have 0 ... 2 A. The second subrange is up to 10 A. The current sensor (resistor R16) is used both for the GTS circuit and as an ammeter shunt. The reference voltage source is assembled on a precision Zener diode VD9 type D818E and a current generator, which, in turn, is assembled on transistors VT1-VT4 (borrowed from [3]).

This scheme is undeservedly forgotten by radio amateurs. It has greater parameter stability than single-transistor GTS circuits. The stability of the output current of the HTS in the circuit Rn is almost completely determined by the stability of the voltage at the non-inverting input of the op-amp, i.e. ION stability. The stability of the readings of the PA1 ammeter depends on the stability of the elements R16-R18.

Details

Instead of OU KR140UD708, K140UD7 was also installed. Field effect transistor IR.Z46 (KP741A, B), IR.Z44 (KP723A), IR.Z45 (KP723B), IR.Z40 (KP723V), IR.540 (KP746A), IR.541 (KP746B), IR.542 ( KP746V), IR.P150 (KP747A), etc.

The field effect transistor was chosen for reasons of maximum reliability and simplicity of design. In the absence of a field effect transistor, it is quite possible to replace it with two transistors, as shown in Fig. 2.

However, the KT827A transistor here operates in modes close to the limit (when the current in the load is 10 A). It is advantageous to replace KT827A with two transistors. This is what radio amateurs did, repeating the GTS scheme (Fig. 1) and not having field-effect transistors (Fig. 3).

Transistor VT7 must be equipped with a good heat sink with a surface of at least 2000 cm2. Transistors VT1, VT2 types KT3107, KT361 with any letter indices. Transistors VT3, VT4 types KT3102, KT315 with any letter indices. KT502, KT503 are well suited here. Transistor VT5 type KT815, KT817; transistor VT6 type KT814, KT816.

About Rectifier Diodes

Any powerful diodes with a current of more than 10 A will do. If powerful diodes still could not be purchased (it is simply unrealistic to buy them on the periphery), then they use the old and time-tested scheme (Fig. 4) of the operation of two diode bridges for one common load (parallel mode).

The circuit in Fig. 5 has the same purpose as the circuit in Fig. 4, but the resistors are connected in such a way that all 8 diodes are placed on three heatsinks, just like the diodes of a conventional bridge. However, here the number of resistors is already 8 (instead of 4 in Fig. 4). For the circuit in Fig. 1, the resistances of resistors R1-R4 (Fig. 4) and R1R8 (Fig. 5) should not exceed 0,1 Ohm (their range is 0,03 ... 0,1 Ohm, but they must be the same). In the circuit of Fig. 4, bridges KTs402, KTs405 (R1-R4 are equal to 0,5 ... 1 Ohm) and other diodes (for KTs402, 405 the sum of currents does not exceed 2 A) are also operated.

Wirewound resistors were made from non-deficient nichrome wire with a diameter of more than 1,5 mm. There will be no claims to the stability of the R16 resistor if it is done properly (at a current of 10 A, 10 W of power is dissipated on it). Nichrome in TCS is 30 times worse than constantan, 3 times worse than manganin, but 26 times more stable than copper. To catch up with the stability of manganin, you need to reduce the temperature (power across the resistor). 4 nichrome resistors connected in parallel solve this problem. After all, manganin or constantan shunts on the periphery are scarce. In addition, the maximum operating temperature of manganin is less than 100°C, while that of nichrome is 900°C.

Shunts prepared in the above way will be practically "eternal" (2,5 W of power on each will not cause much heat).

Resistors R7, R8 and R17, R18 are made up of resistors of the C2-13 type, since the stability of their resistance determines the stability of the GTS output current and, accordingly, the ammeter readings. All other resistors of the MLT type, except for the wire R9 type PP2-12.

Electrolytic capacitors C8-C10 are widely available type K50-35 or K50-6. It is impossible to reduce their total capacitance, since ripples will penetrate into the load (Rn) and errors will appear in the operation of the HTS (at a current value close to 10 A). In addition, the insufficient capacitance of the rectifier will not allow to obtain an output current of 10 A (with the specified value of the alternating voltage II of the winding of the network transformer).

If the GTS will not be used as a 12-volt battery charger, then the voltage of the winding II should be reduced. It is possible to check diodes, various contact connections even at a winding voltage II of several volts. In practice, this voltage was reduced to 6 V (at a load of 10 A). The basic version of this HTS contained a transformer, the winding II of which at a current of 10 A should give at least 10,25 V. volt batteries.

A little "know-how" is that it is better to check powerful contact (detachable) connections at a current that is significantly higher than the passport value. For example, 6 A is indicated on the plug, which means that the reliability of the connection must be checked at a current of 10 ... 20 A. In this case, a substandard plug-in connection immediately betrays itself. And there are many such new substandard plugs, sockets and switches on the market!

About transformer T1

The first (basic) version of the HTS was assembled on a rather small-sized transformer with a power of only 160 VA. The inscription on it: "TBS30,16U3 R160 VA 50-60 Hz. GOST.5.1360-72". It uses ShL-iron. In terms of volume, it is smaller than the TS-180, and it works silently, which cannot be said about the TS-180. The secondary windings are rewound. Winding II contains 45 turns of PEV-1,4 mm in two wires. The open circuit voltage is 11,5 V. Under a load of 10 A, the output voltage is at least 10,25 V, but if Schottky diodes (KD2998, 2991) are installed in the diode bridge.

For silicon D242, 243, the voltage in winding II was increased by 2,5 V. If the diodes in the circuits in Fig. 4 and Fig. 5 are matched in pairs, then the resistors R1-R4 (Fig. 4) and R1-R8 (Fig. 5) can be removed (shorted). In practice, this was done only with parallel diodes with a Upr spread of no more than 5%. Winding III T1 contains 78 turns of double wire PELSHO-0,41. The tap from winding II for a current of 20 A (not shown in the diagram) was made from 28 turns.

You can also use the transformer TC-180-2. Windings 9-10 and 9'-10' were connected in series. According to specifications, they have 6,4 V and a load current of 4,7 A. They contain 23 turns of D1,55 mm wire. At a current of 10 A, they cannot be operated, but for a short time it is possible. Windings 5-6, 5'-6' and 11-12, 11'-12' were used as winding III, connecting them in series (5-6 with winding 11-12 and 5'-6' with winding 11'-12 '). Windings 11-12 give 6,4 V each, only 11'-12' is designed for a current of 0,3 A, and 11-12 - for 1,5 A. At a current of 10 A, the "hottest" windings 9-10 ( after a few minutes), but since they are located in the uppermost layer, their cooling is best. For additional heat removal, the outer layer of paper (together with the label) was removed on each TC-180 reel.

When the HTS was made only for the continuity of low-resistance connections, the bridge rectifier was replaced by a full-wave circuit with a midpoint (Fig. 6). Here, just as in the diagrams of Fig. 4 and Fig. 5, 2 pcs were installed. D242A in parallel.

For all the diodes, one radiator is needed here. The main thing in this situation (in relation to the TS-180) is that now the rated current from the windings is no longer 4,7 A, but more than 7 A. According to [4], we have a current gain of 1,4 times relative to one winding 9-10.

A small digression

The enamel wire is now truly gilded: for 1 kg you need to lay out up to 5 USD. For this money it is really possible to buy 2-4 pieces. transformers TS-180, in which the wires are not less.

All other variants of the HTS were carried out mainly on a more powerful basis (rewound TS-270-1 or toroidal transformers), i.e. the secondary windings were rewound. If enameled wire is not available, then almost any solid, stranded copper or aluminum wire can be used. The main thing is that the required section is typed. The reference point is simple - a copper core with a diameter of 2 mm for a current of not more than 10 A.

Very useful information on network transformers [5].

About wire resistors (except R16). All of them can be copper, i.e. in practice, pieces of copper wire D0,4 ... 0,6 mm were used. The latter, with a length of 1 m, gives a resistance of 0,058 Ohm, with a length of 120 cm - 0,07 Ohm. The passage of current (due to the TCS of copper) causes an increase in resistance to 0,092 ohms. Thus, a piece of enameled wire D0,6 mm and a length of 50 ... 100 cm is more than enough for these rectifier circuits. The length of the segment should not be embarrassing, since the wire is easily placed on a frame with a diameter of more than 1 cm.

In the scheme of Fig. 6, it is advantageous to use "tablets" - KD213, KD2997, 2999. It is convenient to place two "tablets" on one radiator just for cases such as KD213. Wherever possible (in terms of voltage), it makes sense to use diodes with a Schottky barrier. When buying KD2998, be sure to check it for the value of Robr. Remember that overheating is the death of all radio components. As the temperature rises, pn junctions degrade, and the number of failures increases. There is no need to focus on the manufacturer, whose main task is to minimize the consumption of materials and components, but you need to create a margin of reliability and strength yourself, where possible.

The location of the elements and the drawing of the printed circuit board are shown in Fig. 7, 8.

References:

1. Zyzyuk A.G. Selection of transistors for powerful UMZCH//Radioamator. - 2001. No. 6. - p.7.
2. Zyzyuk A.G. Portable version of the meter Uke.max//Electric. - 2002. No. 8. - p.8.
3. Bipolar stable current generator//Radio. - 1981. - No. 4. - P.61.
4. Sheikina T.S. Operation of power supply installations of transmission systems. - M.: Radio and communication, 1982.
5. Power transformers of the TC type//Elektrik. - 2003. - No. 11. - P.20.
6. Zyzyuk A.G. About transformers // Radioamator. - 1998. - No. 2. - P.37.

Author: A.G. Zyzyuk

See other articles Section Chargers, batteries, galvanic cells.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Energy saving according to the flamingo way 03.06.2017 Young-Hui Chang and Lena H. Ting, biologists from Georgia Tech University and Emory University (USA), show that flamingos (Phoenicopteridae) require minimal physical effort to support their body on one leg . Only this allows pink birds to spend on one leg not only a long day, but also an equally long night. "For starters, we showed that dead flamingos can continue to stand, passively supporting their body weight with no muscle effort at all," the authors explained. Interestingly, dead birds cannot stand on two legs - such a position still requires muscle effort. Then the researchers took up the study of living birds. They placed the flamingo on a super-sensitive platform capable of picking up the slightest imbalance. They were able to show in this way that the smallest muscular movements of birds allowed them to maintain balance, while the body swayed slightly. While the flamingos were awake, feeding, these body movements were quite strong, but as soon as they fell asleep, the swaying decreased seven times. This happened precisely when the birds stood on one leg. Thus, flamingos take an extremely stable position in a dream. The researchers did not specifically measure the amount of energy expended by the birds to maintain balance while standing on one leg, but all evidence indicates that this position requires significantly less energy expenditure.

Other interesting news:

▪ Vacuum hard drives

▪ Peanut vs copper

▪ Optimal time for jogging

▪ Single Board PC LattePanda 3 Delta

▪ Dell Latitude 2100 Education Netbook

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site for those who like to travel - tips for tourists. Article selection

▪ article Copper forehead. Popular expression

▪ What is the brightest star in the night sky? Detailed answer

▪ Article Nursing Assistant Nurse. Job description

▪ article Manual stick electrode welding. Encyclopedia of radio electronics and electrical engineering

▪ article Scheme, pinout (pinout) of the Alcatel One Touch cable. 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