Charger for nickel-cadmium batteries. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Charger for nickel-cadmium batteries. Encyclopedia of radio electronics and electrical engineering

Free technical library

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

Comments on the article

At present, miniature MP3 players are very popular, especially among young people, as well as electronic cameras that are powered by a voltage source of 1,2 ... 1,5 V. The use of galvanic disposable cells is hardly justified here - the current consumption is high, and even with prolonged continuous operation. Ordinary cells of the "AAA" type have to be changed several times a day in this mode, which is quite expensive, but the battery can save you a lot of nerves and money.

In order for the battery to serve for a long time, it is necessary to ensure its optimal mode, both charging and discharging.

Nickel-cadmium batteries are characterized by the so-called "memory effect". Consisting in the fact that if you charge an incompletely discharged battery, then during further discharge it will give only part of the energy, starting from the level from which charging began. Therefore, before starting charging, it is advisable to discharge the battery to a voltage of less than 1 V. And only after that start charging. The figure shows a diagram of a charger - an attachment to a laboratory power source that measures the voltage on the battery, discharges the battery to 1 V before charging and charges it to 1,4 V. The charger itself consists of a current stabilizer at A1. The value of the charging current can be set to 60mA, 80mA or 120mA with switch S2.

(click to enlarge)

The charger is turned on and off using transistors VT3 and VT4. To start charging to the VT3 base, you need to apply a logical zero. And to stop charging - one (through resistor R14).

The discharge circuit is made on a transistor key on VT5 and VT6, connected according to the circuit of a composite transistor. The discharge load is resistor R16.

The voltage on the battery (G1) is measured by the meter on the A1 polycomparator chip. LEDs HL1-HL6 indicate the voltage on the battery, and the cascades on VT1 and VT2 form logic levels for supplying information about the voltage on the battery to a simple control logic circuit on two RS-flip-flops made on the elements of the K561LE5 microcircuit. Now consider the operation of the scheme as a whole. When the battery is connected, the A1 chip measures the voltage on it. The measurement result can be seen on a display of six LEDs. The measurement is made without load. To find out the voltage under load, you need to press the "Start" button S1. In this case, the RS flip-flop D1.3-D1.4 is set to a state with a logical unit at the output D1.4. The transistor key VT5-VT6 opens and loads the battery with resistor R16. If at the same time the voltage on the battery drops to 1 V and one of the diodes VD1-VD3 opens below, which leads to the opening of the transistor VT2. A logical unit voltage appears on its emitter, which, after some time (R8-C2), switches the RS flip-flop D1.3-D1.4 to the opposite state.

The load (R16) from the battery is disconnected. At the same time, the unit that occurred at the output of D1.3 sets the trigger D1.1-D1.2 to a state with a logical zero at the output of D1.2. This causes the charger to turn on. A2 (VT4 opens). Battery charging starts.

If the loaded battery voltage is greater than 1V, it will be held under load until the voltage across it is 1V or less. And only after that the charging will start.

Charging will continue until the voltage on the battery reaches 1,4 V. After that, the transistor VT1 will open and the voltage of the logical unit level will be set on its collector RS-trigger D1.1-D1.2 will switch to a state with a unit at the output D1.2 .XNUMX and battery charging will stop.

The disadvantage of this scheme is that only one battery can be charged at the same time. Batteries cannot be charged. Even if you make a switchable divider at the input of the A1 microcircuit, the charger will not be able to work well with the battery, since it is impossible to determine how discharged one or the other battery included in it is by the total battery voltage. Therefore, if you need to charge several batteries at the same time, you need to make an appropriate number of such circuits.

The K561LE5 chip can be replaced by a domestic analogue K176LE5 or any foreign analogue. The LM3914 chip can be replaced with some kind of analogue, but subject to a linear indication (not logarithmic) using the running point method. Or assemble a comparator circuit on operational amplifiers.

The adjustment consists in setting the charging current by selecting the resistances R10-R12 and calibrating the voltage meter by adjusting the resistor R2.

Another point - when the HL6 LED is off, the voltage across R4 should be zero. If this is not the case, you need to include a diode of the KD1 type in the emitter circuit VT522, in the forward direction. The same applies to the transistor VT2 (the voltage on its collector should be zero when the LEDs HL1, HL2, HL3 are off).

Author: Zamkov V.S.

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:

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 ... >>

The threat of space debris to the Earth's magnetic field 01.05.2024

More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>

Solidification of bulk substances 30.04.2024

There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>

Random news from the Archive

Video on e-books with color ink 28.11.2020

E-readers with E Ink displays have led to a new and extremely convenient class of reading devices in any environment, day or night. The only thing they were unable to do was video playback. The E Ink screen refreshes too slowly. With color, too, it does not add up yet, but video is clearly not the strong point of this technology. The Chinese promise to fix this, and the old Philips research helps them in this.

South China Normal University (SCNU) announced the progress in the development of color reflective displays with the ability to show video. Back in 2012, a group for the development of "paper" displays was created as part of the university, led by former Philips engineers. Later, the team began working with a local company, Shenzhen Guohua Optoelectronics Ltd, which is likely to commercialize the development.

To date, the efforts of E Ink and other companies that have tried to create an alternative technology for reflective displays in terms of color reproduction and video playback have not led to anything sensible, and two of the most promising technologies - Mirasol and Liquavista - have completely sunk into oblivion. Or not? The most striking thing about the new development of the Chinese is that it is the electrowetting technology brought to mind, which the Dutch Liquavista tried to exploit. However, there is nothing to be surprised here. Liquavista and new Chinese achievements are based on the same developments of Philips researchers.

Liquavista went out of business in 2013. China picked up the banner that fell from its hands and now promises to release a commercial product in 2021. These can be portable devices for reading and watching videos that can work for weeks on autonomous power, like regular e-readers on E Ink. But unlike book readers, video on them is played at a high frame rate.

At the moment, the developers show two color reflective displays and two monochrome ones, in particular, a 5,8-inch color screen. It is reported to show bright colors in sunlight with good levels of contrast and reflection. The display uses three standard printing colors - cyan, magenta and yellow - to generate color, therefore, as stated, the image quality approaches print. Of the other declared characteristics, you can voice the contrast level - 10:1 (about the same as black and white E Inks) and 40% reflectivity, which is also close to the performance of conventional E Inks.

Other interesting news:

▪ Light of extraterrestrial cities

▪ Reconstructed the navel of the earth

▪ glasses with music

▪ Police drones will arm

▪ Mouse Logitech G502 X

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Standard instructions for labor protection (TOI). Selection of articles

▪ article Logistics. Lecture notes

▪ article Why is a crow considered a harmful bird? Detailed answer

▪ article Kopeck pea. Legends, cultivation, methods of application

▪ article Multiband directional antennas. Encyclopedia of radio electronics and electrical engineering

▪ article Hybrid linear power amplifier. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

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