After connecting the device to the network, a certain voltage appears on resistor R2, which is transmitted to transistor VT2. Then, the current flows further, as a result of which the VD7 LED begins to burn intensely.

A story about a homemade device

Charging from USB port

You can make a charger for nickel-cadmium batteries based on a regular USB port. At the same time, they will be charged with a current of approximately 100 mA. The scheme, in this case, will be as follows:

At the moment, there are quite a lot of different chargers sold in stores, but their cost can be quite high. Considering that the main point of various homemade products is precisely saving cash, then self-assembly is even more advisable in this case.

This circuit can be modified by adding an additional circuit to charge a pair of AA batteries. Here's what we ended up with:

To make it more clear, here are the components that were used during the assembly process:

It is clear that we cannot do without basic tools, so before starting assembly you need to make sure that you have everything you need:

• soldering iron;
• solder;
• flux;
• tester;
• tweezers;
• various screwdrivers and knife.

Read also: Review of chargers for AA batteries

Interesting material about making it yourself, we recommend viewing it

A tester is necessary to check the performance of our radio components. To do this, you need to compare their resistance, and then check it with the nominal value.

For assembly we will also need a case and a battery compartment. The latter can be taken from the children's Tetris simulator, and the body can be made from a regular plastic case (6.5cm/4.5cm/2cm).

We attach the battery compartment to the case using screws. The board from the Dandy console, which needs to be cut out, is perfect as a basis for the circuit. We remove all unnecessary components, leaving only the power socket. The next step is to solder all the parts based on our diagram.

The power cord for the device can be taken from a regular computer mouse cord with a USB input, as well as part of the power cord with a plug. When soldering, polarity must be strictly observed, i.e. solder plus to plus, etc. We connect the cord to USB, checking the voltage supplied to the plug. The tester should show 5V.

Among the many schemes for assembling chargers for Krona batteries, I found one that was relatively simple and affordable. By the way, the 9-volt battery, known in Russia and the CIS countries as “Krona,” has a 6F22 standard.

The battery consists of 7 4A nickel-metal hydride batteries connected in series. The recommended charging current is no more than 20-30 mA.

The charger is made by redesigning the charger for mobile phones made in China.

There are 2 types of inexpensive chargers originating from China. They are pulsed, and both are based on self-oscillator circuits capable of delivering 5 V output.

The first type is the most common. It does not have control of the output voltage, but by selecting a zener diode, which is located in such circuits in the input circuit near the 1N4148 diode, you can obtain the desired voltage. Usually there are two types - 4.7 and 5.1 V.

To charge the Krona you need a voltage of about 10-11 V. This can be achieved by replacing the zener diode with one that has the appropriate voltage. It is also recommended to change the capacitor, which is located at the charging output. As a rule, it is 10 V. You need to install a 16-25 V capacitor with a capacity of 47-220 μF.

The second type of such circuits has control of the output voltage, implemented by installing an optocoupler and a zener diode.

Take a look at the principle of redesigning the second circuit.

It is necessary to remove all components located after the transformer, and leave only the unit that controls the output voltage. This unit consists of an optocoupler, a pair of resistors and a zener diode.

It is necessary to replace the diode rectifier, since manufacturers claim a charging current of 500 mA, and the maximum diode current is no more than 200 mA, although the peak current is about 450 mA. It's dangerous! In general, you need to install the FR107 diode. Thus, charging will produce the required voltage.

The next thing to do is to assemble a current stabilization unit, using the LM317 microcircuit as a basis. In general, you can get by with one quenching resistor instead of assembling a stabilization unit.

But in this example, preference is given to reliable stabilization, because the Krona battery is not the cheapest.

Resistor R1 affects the stabilization current. The calculation program can be downloaded in the Attached files at the end of the article.

The operating principle of this circuit is as follows:

When the Krona is connected, the LED lights up.

A voltage drop is created across resistor R2. Gradually, the current in the circuit decreases, and the voltage that allows the LED to light suddenly becomes insufficient. It simply goes out.

This occurs at the end of the charging process when the battery voltage becomes equal to the charger voltage. The charging process stops and the current drops to almost zero.

The LM317 chip does not need to be installed on a radiator, unlike the one, because the charge current is very tiny.

All that remains is to attach the battery connector to the case, which can be made from a non-working battery.

If you use DC-DC converter, then you get a charger for the Krona via a USB port. like this.

Attached files: .

Soldering the plug to the shielded audio cable Universal protection for batteries

It is worth saying that such a battery is called “Krona” only in the countries of the former USSR. The name comes from regular battery the same standard size produced at that time.
It is recommended to charge these batteries with a current of no more than 20-30mA, otherwise we will significantly shorten their life.

The circuit is simple and based on a Chinese charger for mobile phones. Cheap chargers come in 2 types, but both options are pulsed and are implemented using a self-oscillator circuit with an output voltage of 5V.
The first variety is the most popular. There is no control of the output voltage, but it can be changed by selecting a zener diode installed in the input circuit near the 1N4148 diode. Usually the nominal value is 4.7V or 5.1V, but charging 6F22 requires 10 -11V, so we’ll replace it with another one with the required value. The output should also be replaced electrolytic capacitor, because it is rated for 10V. We set it to 16-25V, with a capacity of 47 to 220 µF.

The second type provides control of the output voltage through an optocoupler and a zener diode. The zener diode can be regular or adjustable, like the TL431. My sample has the usual 4.7V.
Let's consider the principle of alteration of the 2nd type. First, we remove everything that is located after the transformer, except for the output voltage control unit. Those. we leave the zener diode, optocoupler and a couple of resistors. I also replaced the rectifier diode, because The Chinese stated an output current of 500mA, but installed a diode with a maximum current of 200mA (according to the datasheet), and soldered in FR107. I replaced the output electrolyte with a higher voltage one and selected a 10V zener diode. As a result, at the output we have the desired voltage of about 10.5V.
After checking the converted charger, we assemble a current stabilization unit based on LM317. In principle, for such low currents you can do without a microcircuit and simply install a quenching resistor. But I preferred good stabilization; after all, this battery is not such a cheap product.

The stabilizer circuit is the same as for the converted screwdriver charger.
The stabilization current depends on R1. The calculation program for LM317 is here. The HL1 LED will light up when the load is connected, because there is a voltage drop across R2. As the charge progresses, the current drops and at some point the voltage drop across R2 will become insufficient for HL1 to glow. This will happen at the end of the charging process, when the battery voltage equals the output voltage charger. Those. We practically have automatic shutdown.

Due to the minuscule current, LM317 is not required to be installed on a radiator. To complete the design, all that remains is to attach a connector to the output, which can be taken by disassembling the unusable “Krona” and installing everything in a suitable housing.
And another very simple option!

Instructions

Familiarize yourself with the pinout of the Krona battery. The battery itself or an accumulator of this type, as well as the power supply that replaces it, has a large terminal - negative, and a small terminal - positive. For the charger, as well as for any device powered by the Krona, everything is the other way around: the small terminal is negative, the large terminal is positive.

Make sure that the battery you have is actually a rechargeable battery.

Determine the charging current battery. To do this, divide its capacity, expressed in milliamp-hours, by 10. You get the charging current in milliamps. For example, for a battery with a capacity of 125 mAh, the charging current is 12.5 mA.

As a power source for the charger, use any power supply whose output voltage is about 15 V, and the maximum permissible current consumption does not exceed the charging current of the battery.

Check out the pinout of the LM317T stabilizer. If you put it with the front side with the markings facing you, and the terminals down, then there will be an adjustment terminal on the left, an output in the middle, and an input on the right. Install the microcircuit on a heat sink, which is isolated from any other current-carrying parts of the charger, since it is electrically connected to the output of the stabilizer.

The LM317T chip is a voltage stabilizer. To use it for other purposes - as a current stabilizer - connect a load resistor between its output and the control output. Calculate its resistance using Ohm's law, taking into account that the voltage at the output of the stabilizer is 1.25 V. To do this, substitute the charging current, expressed in milliamps, into the following formula:
R=1.25/I
The resistance will be in kilo-ohms. For example, for a charging current of 12.5 mA, the calculation would look like this:
I=12.5 mA=0.0125A

R=1.25/0.0125=100 Ohm

Calculate the power of the resistor in watts by multiplying the voltage drop across it, equal to 1.25 V, by the charging current, also previously converted to amperes. Round the result up to the nearest standard value.

Connect the plus of the power source to the plus of the battery, the minus of the battery to the input of the stabilizer, the adjusting terminal of the stabilizer to the minus of the power source. Between the input and the adjusting terminal of the stabilizer, connect an electrolytic capacitor of 100 μF, 25 V plus to the input. Shunt it with a ceramic one of any capacity.

Turn on the power supply and leave the battery to charge for 15 hours.

Video on the topic

Krona batteries appeared in the Soviet Union, but still remain in demand. This battery is indispensable for devices with high energy consumption, as it produces a much higher current compared to other batteries.

Characteristics of Krona batteries

The batteries are of types AA, AAA, C, D, they are cylindrical in shape and differ only in size. In contrast, the Krona battery has a standard size of PP3 and is a parallelepiped. Salt batteries are characterized by their fragility and cannot be used in high-tech devices. The maximum they are designed for is a watch or other simple device. Batteries are also distinguished by their electrochemical system. Alkaline and lithium batteries have better performance.

Krona mini-batteries are quite different high performance, they have an output voltage of around nine (in comparison, a lithium or alkaline AA battery “produces” only 1.5 volts). The Krona battery consists of six one-and-a-half-volt batteries connected in series in one chain (the output is nine volts.) The batteries can have a current of up to 1200 mAh, the standard power is 625 mAh. The capacity of Krona batteries will vary depending on the types chemical elements. Nickel-cadmium cells have a capacity of 50 mAh, nickel-metal hydride batteries are an order of magnitude more powerful (175-300 mAh). Largest capacity have lithium-ion cells, their power is 350-700 mAh. Standard size batteries "Krona" - 48.5x26.5x17.5 mm. These batteries are used in children's toys and control panels; they can be found in navigators and shockers.

How to charge a Krona battery

In the Soviet Union, carbon-manganese batteries of this size were produced, as well as alkaline ones, which had a higher price and were called “Korundum”. The batteries were produced from rectangular biscuits; for their manufacture, a metal body made of tinned tin, a bottom made of plastic or genitax, and a contact pad were used. Simple disposable Krona batteries allowed small quantity recharging, although this was not recommended by the manufacturer. However, due to the shortage of these nutrients, many books and magazines published

I present to your attention something useful for owners of devices that contain Krona batteries.

Especially for Spirit deeprus k711 and other visitors of the music while away the time on the pages in search of reviews of goodies.

The worst thing about batteries is that they manage to run out at the most inopportune moment, it’s especially infuriating when in the evening (in the midst of activity) your multimeter sits down and there’s nowhere to buy a battery. I decided to solve this problem)))

I liked one thing about her and we’ll talk about it today.


For $24 we get
2 lithium batteries
Charger
Useless cord (50 cm long and someone else's plug)

Specifications(specified by the manufacturer)
Zu
Mains voltage 100V-240V 50-60Hz
Output voltage 8.4V
Charge current 260ma
(stated charge time 2-3 hours)
Maximum chargeable battery capacity up to 600mAh
Protection and self-shutdown device

Battery
Nominal voltage 7.4V
Charging voltage 8.4V +- 0.15V
Nominal capacity 500mAh
Weight< 36g

The charger is made of white plastic and is designed specifically for batteries from the kit (more precisely, for two lithium cells connected in series). Mechanical protection is provided against improper installation of the battery. Charging other types of batteries is prohibited.

The charger is small in size 85x62x25, the weight of the charger is 60g. For comparison, its popularly known colleague nitecore I4 (if a fortunate combination of circumstances, I4 can be bought for $16)

The charger is connected with a standard cord. Operation is indicated by two two-color LEDs. When turned on, the segments light up green, if there is a battery on charge, then the corresponding segment lights up red, if the battery is charged, then the color lights up green (everything is intuitive).

On the back it says “Do Not Disassemble Charger” - DNDC))) I’ll probably break this rule)

The internals “roughly speaking, so to speak”, I would especially like to note the electrical

When SMD resistor soldered directly to the leg of the SMD component and classic flux residues. For your own peace of mind, “finish before use.”

Let's consider batteries

Thanks to the plastic case, the weight is small (the standard crown has about 35g). It tastes like a regular “crown”)) The voltage on a freshly charged battery is ~ 8.412V (We conclude that the charger has a problem with overcharging, I think that this is not critical but a little unpleasant)

The battery says:
Capacity 500mAh
Protection voltage 5V (somehow small for lithium 5/2 = 2.5V)
Maximum discharge current 500ma
(remember the first two numbers)

We perform an autopsy
Opening it revealed the presence of a circuit in the battery, most of the volume is occupied by lithium components. (no batteries were observed flying around the room, but for emergency situations there are holes in the case (red dot on the top of the battery in the head photo))

The battery consists of two cells connected in series, the voltage on the cells is equal to the voltage on the battery from this output circuit to turn off when the minimum voltage value is reached.

Opening the battery was more satisfying than opening the charger. Some inscriptions were applied to the lithium cells, but the search did not yield results and it was decided to conduct a performance test.

Sweet time)))

The test “stand” is assembled using an LM317 integrated stabilizer connected in current stabilization mode and a digital multimeter
A contact group was made from an old crown with a simple wave of a knife and a soldering iron. The “stand” ensures battery discharge DC, digital multimeter records voltage readings and sends data to PC.

After running the test we have the following results:

Let's remember the numbers that I asked you to remember
1 The shutdown voltage is not 5V but 6V.
2 The declared capacity is close to that determined during testing.

Conclusions:

The culprit of the review is suitable for people who often change crown-type batteries; good capacity will allow your devices to work longer. It is necessary to focus on the fact that the reviewed batteries do not produce 9V, but in most cases this is not critical, but the contents of the charger are critical. When purchasing, keep in mind that the battery needs to work (receive a load) if your device is capable of working for several years from a simple “crown” then there is no point in switching to lithium.

Considering the battery capacity, I think the price is justified and I recommend this kit for purchase.