|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Chargers for nickel-cadmium accumulators and batteries. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells The specialized literature substantiates the expediency of charging batteries from a fixed voltage source with current limitation. This mode is convenient in that recharging during, for example, the night guarantees their full charge by the morning, regardless of their initial state, without the danger of overcharging. This section describes several options for such devices for charging nickel-cadmium batteries and batteries. The scheme of the first of the proposed chargers is shown in fig. 113.
Zener diode VD6, operational amplifier DA1.1, transistor VT1 and elements connected directly to them form a highly stable voltage source. Its feature is the supply of the R2VD6 parametric stabilizer with the output voltage of the source, which provides it with high parameters. The divider R17 - R28 generates 12 voltage steps corresponding to the limit when charging single batteries and batteries made up of 2 - 12 nickel-cadmium batteries. The required charging voltage is selected by switch SA2. The operational amplifier (op-amp) DA1.2 together with the transistor VT2 form an accurate repeater of this voltage with a high load capacity. Its output resistance is very small - the voltage change with an increase in the output current from 0 to 350 mA cannot be detected by a four-digit digital voltmeter, i.e. it is less than 1 mV, and the output resistance is accordingly less than 0,003 Ohm. To limit the current at the beginning of charging, a comparison of the voltage drop across the resistor R32 (and the resistors R6 - R16 connected to it in parallel) and the reference voltage taken from the divider R35 - R39 is used. The collector current of the transistor VT2 is equal to the charging current with sufficient accuracy. The exemplary voltage taken from the resistors R3S and R36 is 1,2 V. The comparison of the voltages is carried out by the comparator, its function is performed by the op-amp DA2.2. When the charging current creates a voltage drop of more than 32 V across the resistor R1,2, the op-amp DA2.2 opens the transistor VT3, which, with its collector current, increases the voltage at the inverting input of the op-amp DA1.2, which leads to a decrease in the output voltage of the op-amp and the transition of the entire source to the mode current stabilization. Setting the value of the current limit in the range from 2,5 to 350 mA is carried out by the SA3 switch. The output resistance of the device in the current stabilization mode is equal to the resistance of the resistor R30. The microammeter PA1 with an additional resistor R31 forms a voltmeter for a voltage of 1,2 V, therefore, when the source is operating in the current stabilization mode, its arrow points to the last division of the scale. For the voltmeter, a microammeter for a current of 100 μA was used, so this reading corresponds to a charging current equal to 100% of the value set by switch SA3. If a discharged battery is connected to sockets X1 and X2 of the charger by setting switch SA2 to the position corresponding to their number in it, at first the charging current will be determined by the position of switch SA3. After a few hours, the battery voltage will reach the value set by the SA2 switch, and the device will enter the voltage stabilization mode. The charging current will begin to decrease, which can be monitored by the indication of the PA1 device. When the current decreases to a value of approximately 5% of the value set by the SA3 switch, the comparator on the op-amp DA2.1 switches and the HL2 LED lights up, signaling the end of charging. If the battery (or a single battery) continues to be charged even during the day, nothing will happen to it, since the current at the end of charging is very small. LED HL1 - indicator of device connection to the network. By selecting a capacitor C7, the high-frequency generation of the op-amp DA1.2 is eliminated. What is the role of diodes VD2 - VDS? When charging a single battery, the voltage at the non-inverting input of the op-amp DA1.2 is 1,4 V, and in the mode of closing the output of the charger, its output voltage, which ensures the transfer of the device to the current stabilization mode, should be about 0,6 V relative to the common wire. In order for the op-amp DA1.2 to work normally in such modes, the voltage of its negative power supply must be at least 2 V in absolute value, which is ensured by the voltage drop across the diodes VD3 - VD5. Similarly, for the normal operation of the op-amp DA2.1 with a voltage at the inputs close to the voltage of the positive power supply, the difference between them must be at least 0,6 V - provided by the voltage drop across the diode VD2. A drawing of a printed circuit board made of one-sided foil fiberglass 1,5 mm thick, on which most of the device parts are located, is shown in fig. 114.
The VT2 transistor is equipped with a needle-shaped heat sink with dimensions of 60x45 mm, the height of the needles is 20 mm. Switches SA2 and SA3 together with resistors soldered to them, microammeter RA1, LEDs HL1 and HL2, output sockets X1 and X2 are installed on the front panel of the device, made of fiberglass 1,5 mm thick, and transformer T1, switch SA1, fuse FU1, diode bridge VD1 and capacitors - on the rear duralumin panel of the same thickness. The panels are fastened together with duralumin ties 135 mm long, a printed circuit board is screwed to the same ties. The finished structure is installed in an aluminum case in the form of a section of a rectangular pipe. Network transformer T1 - unified TN-30. But any other similar transformer is applicable, the secondary winding of which provides a voltage of 19 ... 20 V at a current of at least 400 mA. The rectifier bridge VD1, designed for the same output current, can be assembled from four diodes with an operating current of 300 mA, for example, a series. D226. These can be diodes VD2 -VD5. Capacitor C1 is made up of three parallel-connected oxide capacitors K50-29 with a capacity of 1000 microfarads for a nominal voltage of 25 V. Capacitor C2 is K53-1, the rest are KM-5 and. KM-6. The thermocompensated zener diode KS191F (VD6) can be replaced with. D818 with letter indexes. B - E or on KS191 with any letter index. Resistors R3, R5 and R17 - R28 are desirable to use stable, for example, C2-29. The resistances of resistors R17 - R28 can be within 160 Ohm ... 10 kOhm, but always the same value with an accuracy of no worse than 0,3%. The resistances of resistors R6 - R16 do not have to be exact. It is advisable to select them in accordance with the values \u15b\u16bspecified in the diagram from resistors of similar ratings, which will simplify the setup of the device. Each of the resistors R4, R38 consists of several resistors of higher rating and lower power dissipation, which are connected in parallel. Trimmer resistors R19 and RXNUMX - SPZ-XNUMXa. LEDs HL1 and HL2 - any, but preferably a different color of glow. Zener diodes VD7 and VD8 for a stabilization voltage of 5,6 ... 7,5 V. Switches SA2 and SA3 - PG2-5-12P1N or similar other small ones. Microammeter RA1 type M4247 for a current of 100 μA. Using the device for a different current of the full deflection of the arrow, you will have to select not only the limiting resistor R31, but also R32 - to provide a charging current of 2,5 mA at the extreme left (according to the diagram) position of the SA3 switch. Transistors VT1, VT2 can be any medium-power npn silicon structures, and VT3 can be any low-power silicon pn-p structures with a permissible voltage of at least 30 V. Operational amplifiers K140UD20 (DAI, DA2) are replaceable by a double number of K140UD7 op-amps. The use of other types of op amps is determined by the possibility of their operation in the modes mentioned above, but this has not been verified by the author. Briefly about setting up the charger. First, with a trimmer resistor R4, set a voltage of 1 V on the emitter of transistor VT16,8. Having loaded the device with a resistor of 51 ... SA68 in each next position (up in the circuit), the output voltage increases by 7,5 V. Check the absence of high-frequency generation at the output and, if necessary, select capacitor C43. Next, restore the connection of the resistor R43, and set the switch SA2 to position "12". When changing the position of switch SA3, make sure that the output current, measured by a milliammeter connected in series with the load resistor, is limited to the value corresponding to the position of this switch (except 350 mA). Replace the load resistor with a chain of two or three diodes (of the same type as VD2 - VD5) and, setting the SA3 switch to the "100 mA" position, set the same output current with the trimming resistor R38. The arrow of the microammeter should point to the last division of the scale, if this is not the case, select the resistor R31. Now set switch SA2 to position "1" and switch SA3 to position "10 mA". Connect a 3,3 kΩ variable resistor and a milliammeter to the output of the device, then increase the resistance of this resistor from zero. With an output current of approximately 0,5 mA, the HL2 LED should turn on. When setting up the device, remember that its output impedance is sharply asymmetrical - it is small for the outgoing current and large for the incoming one. Therefore, an unloaded device is sensitive to mains noise and measuring the output voltage with a high-resistance voltmeter can give an unexpectedly high result. Charging the battery is easy. You just need to set the switches to the positions corresponding to the number of batteries in it and the maximum charging current, connect the battery to the output with the correct polarity and turn on the power of the device. A sign of the end of charging is the lighting of the HL2 LED. The maximum charging current should be 3.4 times less than the capacity of the battery being charged. What additions or changes can be made to this charger option? First of all, it is necessary to supplement it with an electromagnetic relay K1, as shown in fig. 115, which would turn off the battery or battery after charging is complete. When the HL2 LED is turned on, the relay is activated and breaks the charging circuit with its normally closed contacts. Resistor R44 is necessary for a clear operation of the relay and to ensure a small hysteresis of the comparator at the op amp DA2.1. Relay K1 must be for a voltage of 20 ... 27 V, transistor VT4 - any medium or high power pn-p structure, for example, the KT502, KT814, KT816 series.
But having introduced such an addition into the device, it should be borne in mind that after the start of charging, any switching of its circuits leads to the operation of the relay, so the necessary settings must be made in advance. The device can be used to discharge batteries of seven batteries without fear of overdischarging them. To do this, switch SA2 must be set to position "5", switch SA3 - to the nearest in terms of discharge current, but larger than it, connect a resistor between the output sockets X1 and X2 that provides the necessary discharge current and connect the battery being discharged. Since the battery voltage is greater than that supplied to the non-inverting input of the op-amp DA1.2, the transistor VT2 will be closed, and the battery will be discharged through the resistor. When the battery voltage drops to 7 V, the op amp DA1.2 and the transistor VT1 will switch to voltage stabilization mode, the discharge will stop. The HL2 LED serves as an indicator of the completion of the battery discharge - during the discharge process, it glows, and when it is completed, it goes out. If the device is often supposed to be used to discharge batteries, besides with a different number of batteries, it is advisable to introduce an additional resistor into it, the resistance of which is 40% of the total resistance of resistors R17 - R28, and, of course, a switch. The resistor is connected between the output of the reference voltage source (in the diagram of Fig. 113, the connection point of the emitter of the transistor VT1, resistors R2, R3, capacitor C3) and the fixed contact "12" of the SA2 switch connected to the resistor R17, and in parallel with this resistor - an additional switch. The battery is charged with the contacts of the switch closed, and when they are opened, when the output voltage decreases by 1,4 times (up to 1 V per battery), the battery can be discharged.
Discharging the battery through the resistor occurs with a time-varying current, which can be stabilized by the K142EHI2A chip by turning it on according to the circuit shown in fig. 116. The resistance of the resistor R46 (Ohm) is determined by the formula: R46 \u1250d XNUMX / V, where W is the discharge current (mA). The resistor values, on which the discharge current depends, correspond to the resistances of the resistors R6 - R16 at the same currents as the charging current. The diagram of the second version of the charger is shown in fig. 117. It is much simpler, but it does not have a node for indicating the end of charging. The device uses two KR142EN12A microcircuits. The first of them (DA1) works in the current limiting mode, and the second one acts as a charging voltage stabilizer. Diodes VD2-VD4 are protection elements. Trimmer resistors R25 and R28 precisely set the output voltages at different positions of the switch SA3. Capacitors C2-C4 prevent the possible generation of DAI, DA2 microcircuits. Power transformer T1, diode bridge VD1, capacitor C1, switches SA2 and SA3 can be the same as in the first version of the device. Diodes VD2-VD4 - any low-power silicon. Resistors R13-R24, R26 must be accurate and stable, and their resistances must be within 120 ... 180 Ohms. Before installing microcircuits on the board, it is advisable to check their stabilization voltage. This can be done by connecting the circuit, made according to the scheme of Fig. 116, to a voltage source of 5 ... 15 V, measuring the voltage across the resistor R46 (160 ohms). Use the one of the microcircuits, the stabilization voltage of which is closer to 1,2 V, in the charging current limiting node (DA1). And if it is very different from 1,2 V, the resistance of the resistors R2-R12 will have to be selected when setting up the device. Set up this charger as follows. First, set the switches SA2 and SA3 to positions "350" and "12", respectively, the engine of the tuning resistor R25 to the middle position, after which, with the resistor R27, set the output voltage to 16,8 V. Next, switch the switch SA3 to position "1" and the resistor R25, set the output of the device to 1,4 V. These operations are interconnected, so repeat them several times. Then, connect three silicon diodes connected in series for a current of at least 300 mA and a milliammeter to the output. Set the switches SA2 and SA3 to positions "2,5" and "2" and by selecting the resistor R1 achieve an output current of 2,5 mA. If the stabilization voltage of the DA1 microcircuit is 1,2 V and the resistances of the resistors R2-R12 correspond to those indicated in the diagram, then for other positions of the switches, the charging currents must correspond to those indicated in the diagram. Otherwise, you will have to additionally select resistors R2-R12. The output resistance of the device in the current stabilization mode is much less than that of the design of the first variant, and is equal to the total resistance of the introduced resistors R13-R24 and R25-R28. If the charger according to the diagram in Fig. 117 is intended only for batteries from batteries of the same type, the SA2 switch and resistors R2-R12 can be excluded, and the charging end indicator, assembled according to the scheme of fig. 118, enter. While the total charging current and flowing through the resistors R13-R24 is large enough, it flows mainly through the emitter junction of the transistor VT1. At the same time, the transistor opens and the HL1 LED lights up, indicating the charging process. When the current decreases to a value determined by the resistance of the resistor R29 and the opening voltage of the transistor VT1, this transistor will close and the LED will turn off. It was assembled (with the exception of the SA2 switch and with the addition of an indicator of the end of charging according to the scheme of Fig. 118) a charger for batteries from batteries. TsNK-0,45 (up to six pieces). To limit the output current to 150 mA, a resistor (R1 in Fig. 117) with a resistance of 8,2 ohms was required. In the indicator of the end of charging, with a resistance of resistor R29 of 30 ohms, the decrease in the brightness of the LED began at a charging current of 10 mA, it completely went out at a current of 7 mA.
The device uses a transformer. CCI-220, all six secondary windings of which are connected in series. It is convenient to install jumpers like this: 16-17, 18-11, 12-13, 14-19, 20-21, the voltage on the diode bridge is removed from terminals 15 and 22. The mains voltage is supplied to terminals 2 and 9 of the transformer, between terminals 3 and 7 you also need to install a jumper. All elements of the device, except for the mains transformer with a power switch, fuse, SA3 switch and output sockets, are mounted on a printed circuit board measuring 90 x 50 mm (Fig. 119). The board is designed to install a diode bridge KTs407A (VD1), an oxide capacitor K50-29 (C1) with a capacity of 2200 uF for a nominal voltage of 16 V. Other details are the same as in the design of the first version of the device. Microcircuits DA1 and DA2 are installed on needle heat sinks 45x25 mm in size, the height of the needles is 20 mm.
The mounting plate, with the help of threaded bushings riveted into its corners, together with other parts, is installed in a plastic case with dimensions of 133x100x56 mm. The LED on elongated terminals is brought to the housing cover. Set up the device in this order. Trimmer resistors R25 and R27 are set at the voltage output of 8,4 and 1,4 V at positions "6" and "1" of the SA3 switch, respectively, the output current is 150 mA - by selecting the resistor R1 and the LED extinction threshold - by selecting the resistor R29 V In the event of generation of the DA1 microcircuit between its input terminal 2 and the negative wire of the power circuit, a capacitor C * (several tens or hundreds of nanofarads) is included, indicated in Fig. 119 dashed lines. The printed circuit board of this version of the charger can also become the basis for the device according to the diagram in Fig. 117-it has contacts for connecting the switch SA2 with resistors R2-R12. Each of the microcircuits must be installed on its own radiator of the same dimensions as in the device according to the diagram in Fig. 113.
Fans of listening to music using a player powered by a battery of two TsNK-0,45 batteries are offered a simpler charger (Fig. 120, the circuit differs from Fig. 105 in ratings and the absence of a capacitor connected in parallel to the secondary winding of the transformer) transformer T1 must be designed for a voltage of 8 ... 9 V and a current of at least 160 mA. The microcircuit should be equipped with a small plate heat sink. The output voltage, equal to 2,8 V, is set with a tuning resistor R2, and then, having loaded the device on three diodes connected in series for a current of 300 mA or two discharged batteries, by selecting a resistor R1, the output current is 150 ... 180 mA.
And if there are no KR142EN12A microcircuits? In this case, it is recommended to assemble a charger of a similar purpose according to the scheme of Fig. 121. The basis of such a variant of the charger can be the PM-1 power supply, intended for powering electric motors of toys, any other transformer that lowers the mains voltage to 6 ... 6,3 V, or a network adapter. All parts of the device, except for the mains transformer, are mounted on a printed circuit board, the drawing of which is shown in fig. 122, designed for the installation of oxide capacitors K 50-6 (C1-C3), a tuning resistor SPZ-196 (R5), LEDs on it. AL341A or. AL307B. The LEDs are brought out through the ventilation slots of the casing. Transistor VT1 is equipped with a small plate heat sink made of brass (or aluminum) 0,5 mm thick. The mounting plate is fixed in the housing on two threaded bushings riveted into it. When setting up this device, like the previous one, first set the output voltage to 2,8 V (resistor R5), after which it is loaded with three diodes connected in series for an operating current of 300 mA and by selecting resistor R7, an output current of 150 ... 180 mA is achieved. LED HL2 goes out. The cases of the described chargers must have ventilation holes to provide cooling for the heat sinks of the microcircuits or transistors. Author: Biryukov S.
Machine for thinning flowers in gardens
02.05.2024 Advanced Infrared Microscope
02.05.2024 Air trap for insects
01.05.2024
▪ TEKTRONIX TDS6154C - the world's widest bandwidth oscilloscope ▪ The stylus automatically slides out of the smartphone body ▪ Chip MSA66 powerful three-phase amplifier for working with electric motors
▪ site section Color and music installations. Selection of articles ▪ article Accounting. Lecture notes ▪ article Who saved over 150 people from suicide with simple conversation and tea? Detailed answer ▪ article Blood in the urine (hematuria). Health care ▪ article Ejector power plant. Encyclopedia of radio electronics and electrical engineering
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page