Current source to compensate for self-discharge of the battery. Encyclopedia of radio electronics and electrical engineering

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

 Comments on the article

Since the self-discharge of chemical current sources is an inevitable matter, attention has always been paid to its compensation in amateur radio literature. The scheme of the automatic set-top box, which, after a simple refinement of any existing charger, can be used for this purpose, is given in [1]. There is a second option - the use for this purpose of a low-power current source (IT), permanently connected to the battery during its long-term storage. Such devices were even produced by the industry. As a base (Fig. 1) in the first version (Fig. 2) IT, a circuit of a recharger of the type UP-N12-0,05-UHL3.1 was used, which in December 1992 was released by Zakarpatmash Production Association in the city of Zakarpatmash. Uzhgorod. Since during the experiments with the circuit there was only an operating manual, in addition to the parameters given in it for the power consumption (5,5 W in short circuit mode) of IT in short circuit mode (short circuit), and the value of the short circuit current of 250 mA, other design data on the device was not.

Based on these data, an approximate calculation of the power transformer was carried out. The value of the input voltage was determined: 5,5 W / 0,25 A \u22d 24 V. Of the transformers available at hand, the step-down transformer (PT) for a 25-volt 2.940.005-watt soldering iron from an electric soldering kit 3TU, produced by the Vinnitsa plant, turned out to be the most suitable " Lighthouse", the diagram of which is shown in Fig. 24. This transformer provides voltages of 28 and 25 V on two regular sockets of the SGZ type, has a fairly low "idle" current (100 mA). The problem of electrical safety is also structurally solved: the primary and secondary windings are located in separate sections of the frame. The resistance of the primary winding is approximately XNUMX ohms.

The device (Fig. 1) is an IT with high internal resistance, made on a powerful transistor VT1.

(click to enlarge)

The constancy of the output current parameters is ensured by supplying a stabilized voltage from the reference voltage source (ION) to the VT1 base, and therefore its output current is practically independent of the load in the collector circuit. With simple circuitry, IT has good temperature stability [2]. High parameters are obtained due to the use of an LED as an ION, which acts as a stabistor. As a result of mutual compensation of the positive temperature coefficient h_21э(+2 mV / deg) of a bipolar transistor and a negative temperature coefficient of voltage drop change from LED temperature, it was possible to obtain the stability of the charge current parameters from temperature, which is essential for a long period of operation of the device.

A certain disadvantage of the schemes in Fig. 1 and Fig. 2 is the possibility of erroneous connection of the battery to the IT in the opposite polarity, with all the ensuing consequences. In [3], this shortcoming is eliminated, but the IT scheme is somewhat complicated. A simpler circuit solution compared to [3] is used in the second version of the IT circuit shown in Fig.4. Unlike the circuits in Fig. 1 and Fig. 2, instead of the resistor R2, a transistor switch is used here, controlled by the voltage from the battery being charged, similarly [1]. Due to the fact that the LED indication should unambiguously determine the state of the device at the moment, more attention is paid to the circuit in Fig. 4 compared to [3]. A two-color LED indicator has been introduced into the circuit, which clearly indicates one or another polarity of the battery connection to the IT. The introduction of a transistor switch makes it possible to completely eliminate the discharge of the battery through the IT with an inverse connection, as well as to eliminate the short circuit mode, since when XS1 and XS2 are closed, the control voltage in the required polarity is not supplied to the VT2 base, it is closed, and the possible battery discharge circuit is interrupted.

The polarity indicator for connecting the battery to the IT consists of two LEDs: VD5 type AJ1307A and VD6 type AL307V red and green, respectively. His work is clear. Schematically, the LEDs in the indicator, in addition to signaling, perform the function of self-protection: a diode that glows protects against the effects of reverse voltage (Uobr.max = 4 V); C. Instead of two LEDs of a different glow color, you can use a two-color LED. The value of the battery discharge current through the LED indicator when the 1,6 V mains voltage is off is determined by resistor R1,8. For this design, it is equal to 220mA. Variants of possible states of LED indicators are given in the table.

To reduce useless losses in the 220 V mains connection indication circuits, the VD8 diode is connected to the FET winding with an alternating voltage of 4 V (T1, Fig. 3). Diode VD8 is also protected from reverse voltage using a silicon diode VD7 connected in the opposite direction.

There was no data on the used radiator in [4]. In the first version of the real design, a powerful silicon transistor KT803 was used, which, as follows from the reference book [5], dissipates power without a heatsink of 5 W.

Since the most difficult mode for VT1 (Fig. 2) is the short circuit mode (as possible), it was in this mode (200 mA) that the operation of the circuit was tested. Power dissipated in this mode on the regulating transistor: Р=240,2=4,8 (W). During the experiments, the transistor VT1 heated up significantly, so it was installed on an additional radiator (plate) made of duralumin with dimensions of 46x85x1,5 mm. The plate itself was mounted on the top cover of the PT housing on three threaded posts 12 mm high.

The physical meaning of a larger short-circuit current than the self-discharge compensation current (TCS) during IT operation on a battery (as a chemical current source), in a certain simplification, can be represented as the subtraction of the battery voltage from the supply voltage at constant internal resistances of IT, battery and other conditions. After finalizing the circuit in Fig. 2 with a transistor switch (Fig. 4), the thermal regime of VT1 improved significantly (P = 24 V0,06A = 1,44 W), however, the design of the plate radiator with VT1 installed on it was left for reasons of maintaining the mounting volume.

(click to enlarge)

The elements of the rectifier and IT are mounted between the plate and the upper plane of the PT case by a hinged method. Four holes with a diameter of 5 mm are drilled in the plate, in which the LEDs are installed. The LEDs and the plate are mutually fixed with a molecular adhesive. Connecting IT to the battery is carried out using the SSH5 connector and a flexible two-wire line with clamps of the appropriate design. As XS1 and XS2 (Fig. 2 and Fig. 4), free sockets XS2.4 and XS2.5 PT (Fig. 3) were used, in which additional petals were installed. As a result of this refinement, the PT has fully retained its original functions.

Details. It is desirable to use silicon transistors in IT for a power of 20 W and more, preferably in a metal case, with a voltage of 1) eq of at least 50 V. Resistor R1 type MLT1, R2 MLT-0,5. Transformer T1 (Fig. 3) can be made independently, for example, on a magnetic circuit Ш16x24 (S = 3,84 cm2) from the ULF output transformer of a tube color TV. Transformer steel, from which its magnetic circuit was made, has low watt losses at a frequency of 50 Hz, which is important for T1 with the expected long-term operation.

The calculation of the number of turns T1 was carried out according to the recommendations [6] according to the formula 50/S (taking into account the use of high-quality magnetic cores, the empirical number is reduced to 50). From where N \u50d 2 / S (cm50) \u3,84d 13 / 220 \u13d 2870 (turns / V). Number of turns of the primary winding 13x24=1,2, secondary 370x13x 4=1,2 + 63x20x0,8=XNUMX (the number of turns of the secondary winding is increased by XNUMX%). Winding wire diameter is calculated by the formula: d=XNUMX(l)^0,5. For the primary winding, for reasons of reducing the active resistance, a diameter of 0,15 mm was adopted. For example, for the secondary winding at a short circuit current of 0,2 A d=0,8(0,2)^0,5=0,36 (mm). The "idling" current of two manufactured transformers, calculated according to the above formulas and assembled on the mentioned magnetic circuits, was about 5 mA.

Setting up the scheme (Fig. 2). Disconnect the VD2 LED (Fig. 2) from the transistor and connect it directly to the rectifier bridge. Connect to the open circuit VD2 (point A) an avometer, connected by an ammeter. Instead of resistor R2, a 4,7 kΩ potentiometer is connected, turned on by a rheostat and set to maximum resistance. By changing the resistance of the potentiometer, set the current through VD2 10 mA. Connect VD2 to the transistor. Instead of the emitter resistor R1, a wire-wound potentiometer 47 ... 100 ohms is installed, turned on by a rheostat and set to maximum resistance. Connect to XS1 and XS2 an avometer, turned on by an ammeter to the maximum measurement limit. By changing the resistance of the potentiometer, the short circuit current is set to 200 mA. The TCR value of the battery, recommended [3], with the connected (preliminarily charged) battery should be 45 mA.

Note Due to the shunting of the E-B transition of the transistor VT1 ION, the VD2 LED (Fig. 1 and Fig. 2) without load (in the absence of a battery connection or a short circuit in the output) should not light.

Setting up the scheme (Fig. 4). Connect a charged battery with a voltage of 14,5 V to the IT output. Replace the resistor R4 with a 470 kΩ potentiometer, turned on by the rheostat and set to maximum resistance. Set the potentiometer current through the milliammeter 10 mA. Setting the output current of the IT fig. 4 is similar to setting the output current of the IT fig. 2, but should only be carried out with the battery connected in the appropriate polarity. The value of the output current IT fig. 4 should be equal to the sum of the TCS of the battery plus the current passing through the battery connection indicator, i.e. 45+15=60 (mA).

References:

1. Elkin S.A. Charger-powered device with extended operational capabilities//Electrician. - 2000. - No. 4. P.46.
2. Editorial translation "LED-thermocompensator"//Radio.- 1978.-№4.-S.61. 3. Chayi L. Battery life saver//Radio hobby. - 2003. - No. 4. - C.59.
3. Operation manual UA2.940.017RE PO "Zakarpatmash".
4. Tereshchuk PM and others. Semiconductor receiving-amplifying devices. Handbook of the radio amateur. - K .: Naukova Dumka, 1981.- S. 125.
5. Polyakov V. Reduction of the stray field of the transformer // Rodio. - 1983. - No. 7. - C.28.

Author: S.A. Elkin

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 diamond diode 22.05.2006 British scientists have made a transistor from amorphous carbon. Semiconductors based on an amorphous substance, such as amorphous silicon, promise to revolutionize electronics by making huge, cheap, flat-panel monitors. After all, such a microcircuit does not need to be placed on a piece of a single crystal, which means that its size is practically unlimited. Unfortunately, electrons move too slowly through a grid of disordered atoms, and the gigahertz speeds required for good displays are beyond their strength. However, as it should be, in addition to the direct path, a roundabout one also leads to the cherished goal. It's called a "resonant tunnel diode". Such a microcircuit consists of nanometer-thick layers in which quantum phenomena begin to play an important role. For example, electrons can move between layers due to the tunnel effect. In a three-layer structure, such movements can be controlled by changing the composition and thickness of the layers and obtain regions with negative resistance. This effect has been repeatedly observed in crystalline microcircuits based on gallium arsenide, and physicists from the University of Surrey (Great Britain) under the guidance of Professor Ravi Silva managed to achieve it on an amorphous structure. In their experiments, they did not use silicon, but diamond-like films of carbon. Until recently, this material was exotic, but now scientists in many laboratories have learned how to work with it. Moreover, diamond-like coatings can be deposited at room temperature on flexible and cheap plastic substrates. By themselves, the layers of such a coating are distinguished by chemical and mechanical resistance.

Other interesting news:

▪ A concussion-surviving brain ages faster

▪ Controlling lightning with a laser beam

▪ Ion microscope

▪ Samsung Display Prototypes

▪ Voice chat on Facebook

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the Electrician website. Article selection

▪ article And I have at least a drop of honey. Popular expression

▪ article Where and when did the football commentator make a full radio broadcast, although he could not see anything on the field because of the fog? Detailed answer

▪ article Machine wash operator. Standard instruction on labor protection

▪ article Another version of a vertical directional antenna. Encyclopedia of radio electronics and electrical engineering

▪ article Miniature triac voltage regulator. 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