Simple power supply with digital display. Digital laboratory power supply controlled via PC. About PCB
Every self-respecting power supply has a built-in voltmeter and ammeter. In older device models, the indicators were pointer, but progress does not stand still, and now many people want to see a digital display. Many radio amateurs make such indicators based on a microcontroller or using ADC chips, for example KR572PV2, KR572PV5. However, there are other microcircuits that are similar in functionality.
One of the many is the CA3162E microcircuit, it is designed to create an analog value meter with subsequent display of the result on a three-digit digital indicator. This microcircuit is an ADC, with a maximum input voltage of 999 mV and a logic circuit, the latter produces the measurement result in the form of three alternately changing binary-decimal four-bit codes on a parallel output and three outputs for polling the bits of the dynamic indication circuit. But to make a complete device, it is necessary to add a decoder for the operation of the seven-segment indicator and an assembly of three seven-segment indicators, which are included in the matrix for dynamic display. And also, three control keys. Any type of indicator can be used, be it LED, fluorescent, gas-discharge or even liquid crystal, everything will depend on the circuit of the output node on the decoder and keys. This circuit uses an LED indication consisting of three seven-segment indicators with common anodes. They are connected according to a dynamic matrix circuit, in other words, all their segment pins are connected in parallel. And for interrogation, that is, sequential switching, common anode terminals are used.
The figure we see above shows a circuit of a voltmeter that can measure voltage from 0 to 100V. The measured voltage is supplied to a divider assembled on resistors R1-R3, and then further to pins 11-10 of microcircuit D1. Capacitor C3 serves to eliminate noise that interferes with measurements.
Resistor R4 is used to set the device reading to zero in the absence of input voltage. But with resistor R5, you can set the measurement limit so that the measurement result corresponds to the real one, i.e. we can say that it is used to calibrate the device.
The logical part of the CA3162E microcircuit is built according to TTL logic, and the outputs are also with open collectors. At the outputs “1-2-4-8” a binary decimal code is generated, which changes periodically, providing sequential transmission of data on three digits of the measurement result. If a TTL decoder is used, such as KR514ID2, then its inputs are directly connected to these inputs of D1. If a CMOS or MOS logic decoder is used, then its inputs will need to be pulled to positive using resistors. This will need to be done, for example, if a decoder or CD4056 is used instead.
The outputs of the decoder D2, through current-limiting resistors R7-R13, are connected to the segment pins of the LED indicators H1-NC. The same segment pins of all three indicators are connected together. To poll the indicators, it is necessary to use transistor switches VT1-VT3, to the bases of which commands are sent from the outputs H1-NC of the D1 chip. These conclusions are made according to an open collector circuit. Active zero, so p-n-p structure transistors are used.
The circuit of an ammeter is not very different from a voltmeter. Instead of a divider, a shunt is installed here, on a five-watt resistor R2 with a resistance of 0.1 Ohm. Thanks to this shunt, the device can measure current up to 10A (to be absolutely precise, then 0...9.99A). And zeroing and calibration, as in the voltmeter circuit, is carried out by two resistors R4 and R5.
By using other dividers and shunts, you can set other measurement limits. For example, 0...9.99V, 0...999 mA, 0...999V, 0...99.9A, it all depends on the tasks assigned to the manufacture of the device. And in general, based on these circuits, you can make an independent measuring device for measuring voltage and current (in other words, a multimeter). However, it is worth considering that even when using liquid crystal indicators, the device will consume considerable current, since the logical part of the CA3162E is built on TTL logic.
The device is powered by a constant, stabilized voltage of 5V. The power source in which they will be installed must provide for the presence of such a voltage at a current of at least 150 mA.
Setting up the device is not difficult. So, a voltmeter. First, we connect terminals 10 and 11 of D1 to each other, and by turning resistor R4 we set the reading to zero. Next, remove the jumper that closes terminals 11-10 and connect a standard device, for example, a multimeter, to the “load” terminals. By adjusting the voltage at the source output, we use resistor R5 to calibrate the device so that its readings coincide with the readings of the multimeter.
Ammeter. First, without connecting the load, adjust the resistor R5 to set the readings to zero. Now you will need a constant resistor with a resistance of 20 Ohms and a power of at least 5W. We set the voltage on the power supply to 10V and connect this resistor as a load. We twist resistor R5 so that the ammeter shows 0.5 A. Although no one forbids performing calibration using a standard ammeter, it just seemed more convenient to the author to do this with a resistor. Although, of course, the quality of calibration is affected by the error in the resistor resistance.
Arduino monitors the output voltage, current, and, using PWM, kicks the power transistor so that the power supply produces the set values.The power supply can output voltage from 1 to 16 volts, provide a current of 0.1 - 8 amperes (with a normal voltage source), go into protection and limit the current. That is, it can be used to charge batteries, but I didn’t risk it, and I already have one. Another feature of this strange power supply is that it is powered by two voltages. The main voltage must be supported by a voltage boost from a battery or a second power supply. This is necessary for the operational amplifier to operate correctly. I used a 19V 4A laptop power supply as the main one, and a 5V 350mA charger from some phone as additional power.
Assembly.
I decided to start the assembly by soldering the main board with the expectation of hammering in the bolt if it didn’t work, since I had read a lot of comments from crooked people about how everything smokes, explodes and doesn’t work, and besides, I made some changes to the circuit.To make the board, I bought a new laser printer in order to finally master LUT; previously I drew boards with a marker (), which is a hemorrhoid. The board turned out right the second time, because for some reason I mirrored the board the first time, which was not necessary.
Final result:
The test run was encouraging, everything worked as it should 
After a successful launch, I began to hack the body.
I started with the largest one - the cooling system of the power transistor. I took a laptop cooler as a basis and put this thing into the back part. 
I stuck control buttons and light bulbs on the front panel. The hefty knob is an encoder with a built-in button. Used for control and configuration. The green button switches display modes on the display, a slot on the bottom for a USB connector, three lights (from left to right) indicate the presence of voltage at the terminals, activation of overload protection, and current limitation. Connector between terminals for connecting additional devices. I stick a circuit board drill and a plexiglass cutter with nichrome wire in there. 
I put all the guts into the case, connected the wires 
After control switching on and calibration, I closed it with a lid.
Photo of the assembled
The holes are made under the radiator of the lm7805 stabilizer, which gets quite hot. Suction of air through them solved the problem of cooling this part 
At the back there is an exhaust pipe, a red power button and a connector for the network cable. 
The device has some accuracy, the Chinese multimeter agrees with it. Of course, calibrating a home-made maharika using a Chinese multimeter and talking about accuracy is quite ridiculous. Despite this, the device will find a place on my table, since for my purposes it is quite sufficient
Some tests
Interaction with the program. It displays voltage and current in real time in the form of graphs, and with the help of this program you can control the power supply. 
A 12-volt incandescent lamp and an ammeter are connected to the power supply. The internal ammeter after adjustment works tolerably 
Let's measure the voltage at the terminals. Fabulous. 
The firmware includes a watt meter. The same 12-volt light bulb is connected to the block, the base of which says “21W”. Not the worst result. 
I am one hundred percent satisfied with the product, which is why I am writing a review. Maybe some of the readers lack such a power supply.
About the stores:
Chip-nn pleased with the speed of delivery, but the assortment is too small in my opinion. A kind of online store, similar to a radio store in a medium-sized town. Prices are lower, for some things significantly.
Chip-dip... I bought something there that was not in chip-nn, otherwise I wouldn’t have poked my head in. retail is a little expensive, but everything is there.
This power supply is built on a common radio element base and does not contain scarce parts. A special feature of the unit is that the regulated DA4 microcircuit does not require bipolar power. On the DA1 chip, a smooth adjustment of the output current has been introduced in the range of 0 ... 3A (according to the diagram). This limit can be expanded to 5A by recalculating resistor R4. In the author's version, resistor R7 is replaced with a tuning one, because Smooth current adjustment was not required. The current limitation with the set ratings of the parts occurs at a current of 3.2A and the output voltage drops to 0. The current limitation is selected by resistor R7. During current limitation, the HL1 LED turns on, signaling a short circuit in the power supply load or the selected current value by resistor R7 being exceeded. If resistor R7 selects a response threshold of 1.5A, then if this threshold is exceeded, a low voltage (-1.4V) will appear at the output of the microcircuit and 127mV will be established at the base of transistor VT2. The voltage at the output of the power supply becomes equal to » 1 µV, which is normal for most amateur radio applications, and the voltage indication unit will read 00.0 volts. The HL1 LED will light up. During normal operation of the overcurrent unit based on the DA1 microcircuit, the voltage will be "5.5V and the HL1 diode will not light up.
The characteristics of the power supply are as follows:
The output voltage is adjustable from 0 to 30 V.
Output current 4A.
The operation of the DA4 microcircuit has no special features and it operates in single-supply mode. 9V is supplied to leg 7, leg 4 is connected to a common bus. Unlike most microcircuits of the 140UD series... it is very difficult to achieve a zero level at the output of the power supply with this connection. Experimentally, the choice was made on the KR140UD17A microcircuit. With this circuit design, it was possible to obtain a voltage of 156 μV at the output of the power supply, which will be displayed on the indicator as 00.0V.
Capacitor C5 prevents excitation of the power supply.
With serviceable parts and error-free installation, the power supply starts working immediately. Resistor R12 sets the upper level of the output voltage, within 30.03V. The VD5 zener diode is used to stabilize the voltage across the regulating resistor R16 and, if the power supply operates without failures, the zener diode can be dispensed with. If resistor R7 is used as a tuning resistor, then it sets the operating threshold when the maximum current is exceeded.
Transistor VT1 is installed on the radiator. The radiator area is calculated by the formula: S = 10I n* (U in. – U out.), where S is the surface area of the radiator (cm 2); I n – maximum current consumed by the load; U in. – input voltage (V); U out – output voltage (V).
The power supply circuit is shown in Fig. 1, the printed circuit board is shown in Figures 2 and 3.
Resistors R7 and R12 are multi-turn SP5-2. Instead of the RS602 diode assembly, you can use the RS407, RS603 diode assembly, depending on the current consumption, or 242 diodes with any letter index, but they must be placed separately from the printed circuit board. The input voltage on capacitor C1 can vary within 35... 40V without changing the ratings of the parts. Transformer T1 must be designed for a power of at least 100 W, the current of winding II is not less than 5 A at a voltage of 35 ... 40 V. The current of winding III is not less than 1 A. Winding III can be with a tap from the middle, which is connected to the common bus of the unit nutrition. The printed circuit board is provided with a contact pad for this purpose. The size of the power supply circuit board is 110 x 75 mm. Transistor KT825 is composite. It can be replaced with transistors, as shown in Figure 4. 
Transistors can be with letter indices B - G, connected according to a Darlington circuit.
Resistor R4 is a piece of nichrome wire with a diameter of 1 mm and a length of about 7 cm (selected experimentally). Microcircuits DA2, DA3 and DA5 can be replaced with domestic analogues K142EN8A, KR1168EN5 and K142EN5A. If the digital display panel is not used, then instead of the DA2 chip you can use KR1157EN902, and exclude the DA5 chip. Resistor R16 is variable with group A dependence. In the author's version, a variable resistor PPB-3A with a nominal value of 2.2K - 5% is used. 
If you do not place great demands on the protection unit, and it will only be required to protect the power supply from overcurrent and short circuit, then such a unit can be used according to the diagram in Fig. 6, and the printed circuit board can be slightly reworked.
The protection unit is assembled on transistors VT1 and VT2 of different structures, resistors R1 - R3 and capacitor C1. Short circuit current 16mA. Resistor R1 regulates the response threshold of the protective block. During normal operation of the unit, the voltage on the emitter of transistor VT2 is about 7 V and does not affect the operation of the power supply. When the protection is triggered, the voltage at the emitter of transistor VT2 drops to 1.2 V and is supplied through the diode VD4 to the base of transistor VT2 of the power supply. The voltage at the output of the power supply drops to 0 V. The HL1 LED signals that the protection has tripped. During normal operation of the power supply and the protection unit, the LED lights up; when the protection is triggered, it goes out. When using the protection unit in Fig. 6, the DA3 microcircuit and capacitors C3, C5 can be excluded from the circuit.
The digital panel serves to visually monitor the voltage and current of the power supply. It can be used separately from the power supply with other designs, performing the above tasks.
The basis of the Digital Panel is the ICL7135CPL chip - a double integration ADC.
A generator is assembled using elements DD1.1 and DD1.2, resistors R1, R2, and capacitor C1, producing rectangular pulses with a frequency of approximately 120 kHz. The generator frequency can be calculated using the formula F = 0.45/ R2C7.
A voltage inverter is assembled using elements DD1.3 and DD1.4, capacitors C2, C3, diodes VD1, VD2, which converts the output voltage of the generator to negative, which is quite sufficient for the DA2 microcircuit Fig. 6. From the outputs of the DA2 B1 - B8 microcircuit, the signals are supplied to the BCD to seven-segment code converter on the DD1 chip. From the outputs of the DD1 microcircuit (9 – 15), the converted signal is supplied through quenching resistors to the anodes of the indicator segments, which are connected to each other in parallel. From the outputs D1 - D5 of the DA2 microcircuit, control signals are supplied to the bases of transistors VT2 - VT6, which, in turn, amplifying them, are supplied to the cathodes of seven-segment LEDs, forcing each LED to display a certain number. Unlike the K572PV2 microcircuit, which controls a 3 1/2-digit display, the ICL7135CPL microcircuit controls a 4 1/2-digit display. That is, using this microcircuit, you can develop measuring devices that indicate voltage up to 1000.9 volts and current up to 19.999A or 199.99A.
Resistor R16, using the third section of the switch, controls the bit points; in the depressed position, the voltage bit is displayed, in the pressed position, the current bit is displayed. Using this digital panel, you can observe current values from 1 mA to 10 A.
The input voltage and current divider shown in Fig. 6 are assembled using resistors R11 – R15 and a current sensor, resistor R10. The current sensor can be made from three pieces of constantan wire Æ = 1 mm and 50 mm long. The difference in denomination should not exceed 15 - 20%. Resistors R11 and R14 type SP5-2 and SP5-16VA. Switch SB1 type P2K. With known good parts and error-free installation, the digital panel starts working immediately. Resistor R4 on leg 2 of the DA2 microcircuit sets the voltage U ref .=1.00V.
The indicators should show 000.0. The input of the voltage and current divider is connected to the output of the power supply, i.e. directly to the output voltage terminals. Resistors R13 and R15 set roughly the specified output voltage of the power supply, resistor R14 more precisely, then switch SB3 is moved to the pressed position and resistor R11 sets the current value at the output of the power supply, not forgetting to connect the equivalent load and set the current within 1A. After adjustment, check the entire range of voltage and current at the output of the power supply again.
Characteristics of the power supply: Output voltage is adjustable from 0 to 30 volts. Output current 5 amperes. The voltage drop at a current of 1 to 6 amperes is negligible and is not reflected in the output indicators. This power supply contains three main units: an internal power supply unit VD1-VD4, C1-C7, DA1, DA2, an overload and short-circuit protection unit on VS1, R1-R4, VD3 and the main unit - an adjustable voltage stabilizer VT2-VT7, VD4-VD5, R4-R14, C8. Diode HL1 indicates overcurrent or short circuit in the load.The main unit is an adjustable voltage stabilizer of the compensation type. It contains an input differential stage on transistors VT5, VT7, two amplification stages on transistors VT3 and VT2, and a control transistor VT 1. Elements VT4, VT6, VD4, VD5, R5 - R8, R10 form current stabilizers. Capacitor C8 prevents self-excitation of the unit. The output voltage is regulated by resistor R13. The upper voltage limit is set by trimming resistor R14. Construction and details. The power of transformer T1 must be at least 100 - 160 watts, the current of winding II must be at least 4 - 6 amperes. Winding current III is within 1...2 amperes. Transistor VT1 should be installed on finned aluminum radiators with an area of more than 1450 sq.cm. Resistor R4 is selected experimentally, based on the protection operation current.
Resistors R 7 and R 14 are multi-turn SP5-2. Resistor - R13 any variable. Microcircuits DA1 and DA2 can be replaced with similar domestic ones KR142EN5A and KR1162EN5A. Their power allows a stabilized voltage of ± 5 volts to power external loads with a current consumption of up to 1 ampere. This load is a digital panel, which is used for digital indication of voltage and current in power supplies. If you do not use a digital panel, then DA1 and DA2 chips can be replaced with 78L05 and 79L05 chips. Diodes VD3 - VD5 can be replaced with KD522B diodes. The digital panel consists of an input voltage and current divider, a KR572PV2A microcircuit and an indication of four seven-segment LED indicators. Resistor R4 of the digital panel consists of two pieces of constantan wire = 1 mm and 50 mm long. The difference in resistor value should exceed 15 - 20%. Resistors R2 and R6 brand SP5-2 and SP5-16VA. P2K type voltage and current indication mode switch. The KR572PV2A microcircuit is a converter with 3.5 decimal places, operating on the principle of sequential counting with double integration, with automatic zero correction and determination of the polarity of the input signal. For display, imported seven-segment LED indicators KINGBRIGT DA56 - 11 SRWA with a common anode were used. It is advisable to use film capacitors C2 - C4 of type K73-17. Instead of imported seven-segment LEDs, you can use domestic ones with a common anode of the ALS324B type.
All radio components of the device:
VD1 - VD4 - RS600
VD5 - VD8 - KS407A
VD9 - AL307B
VD10 - KD102A
VD11 - 1N4148
VD12 - 1N4148
C1 - 10000 uF x 50 volts
C2 - 100 µF
C3 - 100 µF
C4 - 10 µF
C5 - 10 µF
C6 - 10n
C7 - 10n
C8 - 33n
R1 - 330 Ohm
R2 - 3 kOhm
R3 - 33 Ohm
R4 - 2.4 kOhm
R5 - 150 Ohm
R6 - 2.2 kOhm
R7 - 10 kOhm
R8 - 330 kOhm
R9 - 6.8 kOhm
R10 - 1 kOhm
R11 - 5.1 kOhm
R12 - 5.1 kOhm
R13 - 10 kOhm
R14 - 2.2 kOhm
VT1 - KT827A
VT2 - KT815G
VT3 - KT3107A
VT4 - KT3102A
VT5 - KT315D
VT6 - KT315D
VT7 - KT315D
After turning on the power and error-free installation, if the parts are in working order, the indication segments HG1-HG3 should light up. Using a voltmeter, resistor R2 at pin 36 of the KR572PV2 microcircuit sets the voltage to 1 volt. The power supply is connected to legs (a) and (b). At the output of the power supply, set the voltage to 5...15 volts and select a resistor R 10 (roughly), replacing it, temporarily, with a variable one.
Using resistor R8, a more accurate voltage reading is established. After that, a variable resistor with a power of 10 ... 30 watts is connected to the output of the power supply, the current is set to 1 ampere using the ammeter, and the value on the indicator is set with resistor R 6. The reading should be 1.00. At a current of 500 mA - 0.50, at a current of 50 mA - 0.05. Thus, the indicator can indicate a current of 10 mA, that is, 0.01.
The maximum current indication value is 9.99 amperes. For a larger display capacity, you can use the circuit on the KR572PV6. Contact pads U and I on the printed circuit board of the digital panel are connected using flexible conductors to the points of the corresponding indicators HG 2 and HG 1. The KR572PV2A microcircuit can be replaced with an imported ICL7107CPL microcircuit.
The described power supply unit (PSU) is intended for use in an amateur radio laboratory. The device is assembled only from available parts and does not require specialized microcircuits and imported elements.
Main characteristics of the power supply
The output voltage is adjustable from 0 to 30 V.
Output current 5 A.
The voltage drop at a current of 1...6 A is negligible and is not reflected in the output indicators.
The circuit diagram of the power supply is shown in Fig. 1.
The device contains three main units: an internal power supply unit on VD1, VD2, C1-C7, DAI, DA2, an overload and short circuit (short circuit) protection unit on VS1, R1, R3, R4, VD3, the main unit is an adjustable voltage stabilizer on VT1-VT7, VD4, VD5, R2, R5-R16, C8. A digital panel has been added to the power supply unit, i.e. digital display unit (DCU). The circuit diagram of the BCI is shown in Fig. 2.
The internal network power supply unit is built according to a traditional scheme with a T1 network transformer.
The protection unit has no special features. The current sensor is designed for a current of 3 A, but it can be calculated for a current of 5 A. The power supply was operated for a long time with a current of 5 A. No malfunctions were observed in its operation. LED HL1 indicates overcurrent or short circuit in the load. The main unit is an adjustable voltage stabilizer of the compensation type. It contains an input differential stage on transistors VT5, VT7, two amplification stages on transistors VT3 and VT2 and a control transistor VT1. Elements VT4, VT6, VD4, VD5, R5-R8, R10 form current stabilizers. Capacitor C8 prevents self-excitation of the unit. The amplifier is covered by OOS through resistors R13, R14 so that the voltage at the bases VT5 and VT7 are the same and equal to zero. Since transistors VT5 and VT7 were not selected the same, there is a certain “zero offset” of this stage, which is the minimum voltage of the power supply. Within small limits it can be adjusted using trimming resistor R7. In the author’s version, at the PSU output it reached approximately 47 μV. The output voltage is regulated by resistor R13. The upper voltage limit is set by trimming resistor R14.
Construction and details. The power of transformer T1 must be at least 100... 160 W, the current of winding II must be at least 4...6. A, winding current III is at least 1...2 A. The RS602 diode assembly can be replaced with an RS407 assembly or diodes rated for a current of 10 A. Any of the KTs402 - KTs405 series can be used as a VD2 diode bridge. Transistor VT1 should be installed on a heat sink with an area of at least 1500 cm2. Transistor KT825A is composite. It can be replaced with a pair of transistors, as shown in Fig. 3
These transistors are connected using a Darlington circuit. Resistor R4 is selected experimentally, based on the protection operation current. Resistors R7 and R14 are multi-turn type SP5-2. Resistor R13 is any variable with a linear functional characteristic (A). In the author's version, a variable resistor PPB-ZA of 2.2 kOhm ± 5% is used. Microcircuits DA1 and DA2 can be replaced with similar domestic ones KR142EN5A and KR1162EN5A. Their power allows you to stabilize a voltage of ± 5 V to power external loads with a current consumption of up to 1 A. This load is a digital panel, which is used for digital indication of voltage and current in the power supply. The digital panel consists of an input voltage and current divider, a KR572PV2 microcircuit and an indication unit consisting of three seven-segment LED indicators. Resistor R4 of the digital panel consists of two pieces of constantan wire with a diameter of 1 mm and a length of 50 mm. The difference in resistor value should be no higher than 15...20%. Resistors R2 and R6 type SP5-2 and SP5-16VA. P2K type voltage and current indication mode switch. The KR572PV2 microcircuit is a converter with 3.5 decimal places, operating on the principle of sequential counting with double integration, with automatic zero correction and determination of the polarity of the input signal. For display, imported seven-segment LED indicators KINGBRIGT SA56 -11SRWA with a common anode were used. It is advisable to use film capacitors C4-C6 of the K73-17 type. Resistor R9 type C5-16VA. Instead of imported seven-segment LEDs, you can use domestic ones with a common anode of the ALS324B type.
Setting up. Since the design is located on two printed circuit boards, the power supply unit is configured first, then the BCI. Power unit. If the parts are in working order and there are no installation errors, the device starts working immediately after switching on. Its establishment consists of setting the necessary limits for changes in the output voltage and protection current. The sliders of resistors R7 and R13 should be in the middle position. Using resistor R14 on the voltmeter, a reading of 15 V is achieved. Then the slider of resistor R13 is set to the minimum position and the slider of resistor R7 is set to 0 V. Next, the slider of resistor R13 is moved to the maximum position and the voltage of 30 V is set by resistor R14 on the voltmeter. Resistor R14 can be replaced with a constant one. For this purpose, there is a place on the board - resistor R15. In the author's version this is a 360 Ohm resistor.
Digital voltage and current display panel. After turning on the power, with error-free installation and serviceable parts, the indication segments should light up. Using a voltmeter, resistor R9 at pin 36 of the KR572PV2 microcircuit sets the voltage to 1 V. A power supply is connected to legs (a) and (b). At the output of the power supply unit, set the voltage to 5... 15 V and select resistor R1 (roughly), replacing it with a variable one for a while. Using resistor R2, a more accurate voltage reading is established. After this, a variable resistor with a power of 10...30 W is connected to the output of the power supply, the current is set to 1 A using the ammeter, and the value on the indicator is set with resistor R6. The reading should be 1.00. At a current of 500 mA - 0.50, at a current of 50 mA - 0.05. Thus, the indicator can indicate a current of 10 mA, i.e. 0.01. The maximum current indication value is 9.99 A. For a larger indication, you can use the KR572PV6 circuit.
Radioamator No. 9 2005 p. 24
