Power supply with voltage and current regulation. Simple DIY laboratory power supply Diagram of a simple laboratory power supply

Step-by-step instructions for creating laboratory block power supply - diagram, necessary parts, installation tips, video.

A laboratory power supply is a device that generates the necessary voltage and current for further use when connected to the network. In most cases it converts AC network to permanent. Every radio amateur has such a device, and today we will look at how to create it with your own hands, what you will need for this, and what nuances are important to consider during installation.

Advantages of a laboratory power supply

1. The output voltage is adjustable within 0–30 V.
2. Protection against overload and incorrect connection.
3. Low ripple level (direct current at the output of a laboratory power supply is not much different from DC batteries and accumulators).
4. The ability to set a current limit of up to 3 Amps, after which the power supply will go into protection (a very convenient function).
5. On the power supply, by short circuit (short circuit) the “crocodiles” are set to the maximum permissible current(current limit that you set with a variable resistor using an ammeter). Consequently, overloads are not dangerous, since in this case the LED indicator will work, indicating that the set current level has been exceeded.

Laboratory power supply - diagram

Laboratory power supply diagram

So, the numbers in circles are contacts. You need to solder wires to them that will go to radio elements.

• See also how to do

• 1 and 2 - to the transformer.
• 3 (+) and 4 (-) - DC output.
• 5, 10 and 12 - on P1.
• 6, 11 and 13 - on P2.
• 7 (K), 8 (B), 9 (E) - to transistor Q4.

Diodes D1...D4 are connected into a diode bridge. You can take 1N5401...1N5408, some other diodes, and even ready-made diode bridges that can withstand forward current up to 3 A and higher. We used KD213 tablet diodes.

• See also step by step instructions on creation

Transistor Q1 pinout diagram

Transistor Q4 pinout diagram

Variable resistor input circuit

• R1 = 2.2 kOhm 1W
• R2 = 82 Ohm 1/4W
• R3 = 220 Ohm 1/4W
• R4 = 4.7 kOhm 1/4W
• R5, R6, R13, R20, R21 = 10 kOhm 1/4W
• R7 = 0.47 Ohm 5W
• R8, R11 = 27 kOhm 1/4W
• R9, R19 = 2.2 kOhm 1/4W
• R10 = 270 kOhm 1/4W
• R12, R18 = 56kOhm 1/4W
• R14 = 1.5 kOhm 1/4W
• R15, R16 = 1 kOhm 1/4W
• R17 = 33 Ohm 1/4W
• R22 = 3.9 kOhm 1/4W
• RV1 = 100K multi-turn trimmer resistor
• P1, P2 = 10KOhm linear potentiometer
• C1 = 3300 uF/50V electrolytic
• C2, C3 = 47uF/50V electrolytic
• C4 = 100nF
• C5 = 200nF
• C6 = 100pF ceramic
• C7 = 10uF/50V electrolytic
• C8 = 330pF ceramic
• C9 = 100pF ceramic
• D1, D2, D3, D4 = 1N5401…1N5408
• D5, D6 = 1N4148
• D7, D8 = zener diodes at 5.6V
• D9, D10 = 1N4148
• D11 = 1N4001 diode 1A
• Q1 = BC548 or BC547
• Q2 = KT961A
• Q3 = BC557 or BC327
• Q4 = KT 827A
• U1, U2, U3 = TL081, operational amplifier
• D12 = LED

How to make a laboratory power supply with your own hands - printed circuit board and step-by-step assembly

Now let's look at the step-by-step assembly of a laboratory power supply with our own hands. We have a transformer ready from the amplifier. The voltage at its outputs was about 22 V. We prepare the case for the power supply.

Printed circuit board diagram for laboratory power supply

Many different laboratory power supplies are presented on the Internet on radio engineering sites, although mostly simple designs. This same circuit is characterized by a fairly high complexity, which is justified by the quality, reliability and versatility of the power supply. We present in full homemade block bipolar power supply 2 x 30 V, s adjustable current up to 5 A and digital LED A/V meter.

In fact, these are two identical power supplies in one case, which significantly increases the functionality and capabilities of the device, allowing you to combine channel powers up to 10 Amps. At the same time, this is not a typical symmetrical power supply, although it can be connected to serial outputs for more high voltage or pseudo symmetry, treating the overall compound as a mass.

Diagrams of laboratory power supply modules

All power board circuits were designed from scratch, and all printed circuit boards are also independently developed. The first module “Z” is a diode bridge, voltage filtering, generating negative voltage for power supply operational amplifiers, a 34V DC positive voltage source for the op amps, power from a separate auxiliary transformer, a relay used to switch the main transformer windings controlled from another circuit board, and a 5V 1A power supply for the power meters.

The "Z" modules of both units were designed to be nearly symmetrical (to fit better into the PSU case). Thanks to this, the ARK connectors were placed on one side to connect the wires and heatsink for the bridge rectifier, and the boards, as shown in the pictures, were placed symmetrically.

An 8-amp diode bridge is used here. The main transformers have dual secondary windings, each 14 V and a current of just over 5 A. The power supply was rated for 5 amps, but it turned out that at full voltage 30 V does not produce the full 5 A. However, there is no problem with a 5 amp load at lower voltage (up to 25 V).

The second module is an expanded version of the power supply with operational amplifiers.

Depending on whether the power supply is loaded or in standby mode, the voltage in the region of the amplifier U3, responsible for limiting the current, changes (with the same setting of the potentiometer limits). The circuit compares the voltage across potentiometer P2 with the voltage across resistor R7. Part of this voltage drop is applied to the inverse input of U4. Thanks to this, the output voltage depends on the potentiometer setting and is practically independent of the load. Almost because on a scale from 0 to 5 A the deviation is at the level of 15 mV, which in practice is enough to obtain a stable source for driving the LM3914 circuits that form the LED bar.

The visualization diagram is especially useful when multi-turn potentiometers are used for adjustment. It’s great that with the help of such a potentiometer you can easily set the voltage accurate to the third decimal place. Each LED in the line corresponds to a current of 0.25 A, so if the current limit is below 250 mA, the line is not displayed.
The ruler display method can be changed from dot to ruler, but dot is selected here to avoid the influence of too many light dots and reduce power consumption.

The next module is the winding switching system and fan control system that are installed on the radiators of old processors.

The circuits are powered by independent windings of an auxiliary transformer. Here we use m/s op-amp LM358, which contains two operational amplifiers inside. A BD135 transistor is used as a temperature sensor. After exceeding 55C, the fans turn on, and after cooling to approximately 50C, they automatically turn off. The winding switching system reacts to the voltage value at the direct output terminals of the power supply and has a hysteresis of about 3 V, so the relay will not operate too often.

Measurement of load voltage and current is carried out using ICL7107 chips. The meter boards are double-sided and are designed such that for each power source there is a voltmeter and an ammeter on one board.

From the very beginning, the idea was to visualize power supply parameters on seven-segment LED displays because they are more readable than an LCD display. But nothing prevents you from measuring the temperature of radiators, winding switches and cooling systems on one Atmega MK, even for both power supplies at once. It's a matter of choice. Using a microcontroller will be cheaper, but as already mentioned above, this is a matter of taste.

All auxiliary systems are powered by a transformer that has been rewound by removing all windings except the 220V mains (primary). TS90/11 was used for this purpose.

The secondary winding is wound with 2 x 26 V AC to power the operational amplifiers, 2 x 8 V AC to power the indicators and 2 x 13 V to power the temperature control. A total of six independent windings were created.

Housing and assembly costs

The entire power supply is housed in a housing that was also designed from scratch. It was made to order. It is known that it is difficult to make a decent box (especially a metal one) at home.

The aluminum bezel used to mount all indicators and accessories was milled to fit the design.

Of course, this is not a low-budget implementation, given the purchase of two powerful toroidal transformers and the custom-made housing. If you want something simpler and cheaper - .

The rest can be estimated based on prices in online stores. Of course, some elements were obtained from our own stock, but these too will need to be purchased, creating a power supply from scratch. The total cost was 10,000 rubles.

Assembly and configuration of LBP

1. Assembling and testing a module with a bridge rectifier, filtering and relays, connecting to a transformer and activating a relay from an independent source to check the output voltages.
2. Execution of the module for switching windings and monitoring radiator cooling. Running this module will make it easier to configure the future power supply. This will require a different power source to supply adjustable voltage to the input of the system responsible for controlling the relay.
3. The temperature portion of the circuit can be tuned by simulating the temperature. For this purpose, a heat gun was used, which gently heated a radiator with a sensor (BD135). Temperature was measured using a sensor included in a multimeter (at that time there were no ready-made accurate temperature meters). In both cases, the setup comes down to selecting PR201 and PR202 or PR301 and PR302, respectively.
4. We then run the power supply by adjusting RV1 to produce a 0V output, which is useful for setting current limiting. The limitation itself depends on the values ​​of resistors R18, R7, R17.
5. Regulation of A/V indicators comes down to adjusting the reference voltages between pins 35 and 36 of the ICL microcircuits. Voltage and current meters used an external reference source. In the case of temperature meters, such precision is not needed, and the display with a decimal point is still somewhat exaggerated. Temperature readings are transmitted by one rectifier diode (there are three in the diagram). This is due to the PCB design. There are two jumpers on it.
6. Directly at the output terminals, a voltage divider and a 0.01 Ohm / 5 W resistor are connected to the voltmeter, across which the voltage drop is used to measure the load current.

An additional element of the power supplies is a circuit that allows only one power supply to be turned on without the need for a second channel, despite the fact that the auxiliary transformer powers both channels of the power supply at once. On the same board there is a system for turning the power supply on and off using one low-current button (for each channel of the power supply).

The circuit is powered by an inverter, which in the standby state consumes about 1 mA from a 220 V network. All circuits in good quality you can

So the next device has been assembled, now the question arises: what to power it from? Batteries? Batteries? No! The power supply is what we will talk about.

Its circuit is very simple and reliable, it has short circuit protection, smooth adjustment output voltage.
A rectifier is assembled on the diode bridge and capacitor C2, circuit C1 VD1 R3 stabilizer reference voltage, circuit R4 VT1 VT2 is a current amplifier for power transistor VT3, protection is assembled on transistor VT4 and R2, adjustment is performed with resistor R1.

I took the transformer from an old charger from a screwdriver, at the output I got 16V 2A
Regarding diode bridge(at least 3 amperes), I took it from an old ATX unit as well as electrolytes, a zener diode, and resistors.

I used a 13V zener diode, but the Soviet D814D is also suitable.
The transistors were taken from an old Soviet TV; transistors VT2, VT3 can be replaced with one component, for example KT827.

Resistor R2 is a wirewound with a power of 7 Watts and R1 (variable), I took a nichrome one, for adjustment without jumps, but in its absence you can use a regular one.

It consists of two parts: the first one contains the stabilizer and protection, and the second one contains the power part.
All parts are mounted on the main board (except for power transistors), transistors VT2, VT3 are soldered onto the second board, we attach them to the radiator using thermal paste, there is no need to insulate the housing (collectors). The circuit was repeated many times and does not need adjustment. Photos of two blocks are shown below with a large 2A radiator and a small 0.6A.

Indication
Voltmeter: for it we need a 10k resistor and a 4.7k variable resistor and I took an indicator m68501, but you can use another one. From resistors we will assemble a divider, a 10k resistor will prevent the head from burning out, and with a 4.7k resistor we will set the maximum deviation of the needle.

After the divider is assembled and the indication is working, you need to calibrate it; to do this, open the indicator and glue clean paper onto the old scale and cut it along the contour; it is most convenient to cut the paper with a blade.

When everything is glued and dry, we connect the multimeter in parallel to our indicator, and all this to the power supply, mark 0 and increase the voltage to volts, mark, etc.

Ammeter: for it we take a resistor of 0.27 ohm!!! and variable at 50k, The connection diagram is below, using a 50k resistor we will set the maximum deviation of the arrow.

The graduation is the same, only the connection changes, see below; a 12 V halogen light bulb is ideal as a load.

List of radioelements

For radio amateurs, and in general modern man, an indispensable thing in the house is a power supply unit (PSU), because it has a very useful function - voltage and current regulation.

At the same time, few people know that it is quite possible to make such a device with due diligence and knowledge of radio electronics with your own hands. For any radio amateur who likes to tinker with electronics at home, homemade laboratory power supplies will allow him to practice his hobby without restrictions. Our article will tell you how to make an adjustable power supply with your own hands.

What you need to know

A power supply with current and voltage regulation is a must-have item in a modern home. This device, thanks to its special device, can convert the voltage and current available in the network to the level that a particular electronic device can consume. Here is an approximate scheme of work according to which you can make such a device with your own hands.

But ready-made power supplies are quite expensive to buy for specific needs. Therefore, today very often converters for voltage and current are made by hand.

Pay attention! Homemade laboratory power supplies can have different dimensions, power ratings and other characteristics. It all depends on what kind of converter you need and for what purpose.

Professionals can do it easily powerful block power supply, while for beginners and amateurs a simple type of device is suitable to start with. In this case, depending on the complexity, a very different scheme can be used.

What to consider

The regulated power supply is a universal converter that can be used to connect any household or computing equipment. Without it, not a single home appliance will be able to function normally.
Such a power supply consists of the following components:

• transformer;
• converter;
• indicator (voltmeter and ammeter).
• transistors and other parts necessary to create a high-quality electrical network.

The diagram above shows all the components of the device.
In addition, this type of power supply must have protection for high and low current. Otherwise, any emergency situation may lead to the fact that the converter and the electrical device connected to it simply burn out. This result can also be caused by improper soldering of board components, incorrect connection or installation.
If you are a beginner, then in order to make an adjustable type of power supply with your own hands, it is better to choose a simple assembly option. One of the simple types of converter is a 0-15V power supply. It has protection against excess current in the connected load. The diagram for its assembly is located below.

Simple assembly diagram

This is, so to speak, universal type assemblies. The diagram here is understandable to anyone who has held a soldering iron at least once in their hands. The advantages of this scheme include the following points:

• it consists of simple and affordable parts that can be found either on the radio market or in specialized radio electronics stores;
• simple type of assembly and further configuration;
• here the lower limit for voltage is 0.05 volts;
• dual-range protection for current indicator (at 0.05 and 1A);
• wide range for output voltages;
• high stability in the functioning of the converter.

Diode bridge

In this situation, the transformer will provide a voltage that is 3V higher than the maximum required output voltage. It follows from this that a power supply capable of regulating voltage up to 20V requires a transformer of at least 23 V.

Pay attention! The diode bridge should be selected based on the indicator maximum current, which will be limited by the available protection.

A 4700 µF filter capacitor will allow equipment sensitive to power supply noise to avoid background noise. To do this, you will need a compensation stabilizer with a suppression coefficient for ripples of more than 1000.
Now that we have understood the basic aspects of assembly, we need to pay attention to the requirements.

Device requirements

To create a simple, but at the same time high-quality and powerful power supply with the ability to regulate voltage and current with your own hands, you need to know what requirements exist for this type of converter.
These technical requirements look like this:

• adjustable stabilized output for 3–24 V. In this case, the current load must be at least 2 A;
• unregulated 12/24 V output. This assumes a large current load.

To fulfill the first requirement, you should use an integral stabilizer. In the second case, the output must be made after the diode bridge, so to speak, bypassing the stabilizer.

Let's start assembling

Transformer TS-150–1

Once you have determined the requirements that your permanent regulated power supply must meet, and the appropriate circuit has been selected, you can begin the assembly itself. But first of all, let's stock up on the parts we need.
For assembly you will need:

• powerful transformer. For example, TS-150–1. It is capable of delivering voltages of 12 and 24 V;
• capacitor. You can use a 10000 µF 50 V model;
• chip for stabilizer;
• strapping;
• details of the circuit (in our case, the circuit shown above).

After that, we assemble it with our own hands according to the diagram adjustable block nutrition in strict accordance with all recommendations. The sequence of actions must be followed.

Ready power supply

The following parts are used to assemble the power supply:

• germanium transistors (mostly). If you want to replace them with more modern silicon elements, then the lower MP37 should definitely remain germanium. MP36, MP37, MP38 transistors are used here;
• A current-limiting unit is assembled on the transistor. It provides monitoring of the voltage drop across the resistor.
• Zener diode D814. It determines the regulation of the maximum output voltage. It absorbs half of the output voltage;

Pay attention! Since the D814 zener diode takes exactly half the output voltage, it should be selected to create a 0-25V output voltage of approximately 13V.

• lower limit in assembled block The power supply has a voltage indicator of only 0.05 V. This indicator is rare for more complex converter assembly circuits;
• dial indicators display current and voltage indicators.

Assembly parts

To accommodate all the parts, you must choose a steel case. It will be able to shield the transformer and power supply board. As a result, you will avoid situations of various types of interference for sensitive equipment.

The resulting converter can be safely used to power any household equipment, as well as experiments and tests carried out in a home laboratory. Also, such a device can be used to assess the performance of a car generator.

Conclusion

Using simple circuits to assemble an adjustable type of power supply, you will be able to get your hands on and in the future make more complex models with your own hands. You should not take on backbreaking work, as in the end you may not get the desired result, and a homemade converter will work ineffectively, which can negatively affect both the device itself and the functionality of the electrical equipment connected to it.
If everything is done correctly, then at the end you will get an excellent power supply with voltage regulation for your home laboratory or other everyday situations.

Selecting a street motion sensor to turn on the lights