How to make a home laboratory with your own hands. Laboratory power supply: a master class on how to make a simple device with your own hands. Block in final form

Laboratory work involves the application of theory in practice - its meaning lies in the experiment, the study of a phenomenon, method or program. To do laboratory work means to perform a certain set of tasks aimed at mastering the scientific methodology of practical research.

Structure of the laboratory work

The laboratory is built according to the following principle:

1. Theoretical substantiation of the workshop.
2. Actually a workshop: conducting an experiment or research to obtain factual data.
3. Analysis of the data obtained and conclusions on the work done.

It is necessary to carefully prepare for laboratory work by studying the recommended manuals, instructions and guidelines. The degree of readiness is controlled by the teacher, and before conducting the workshop, it is necessary to obtain permission to perform the laboratory.

In the course of work it is required:

• demonstrate theoretical knowledge on the topic;
• strictly adhere to the established order of work;
• impeccably follow all the recommendations of the teacher;
• describe step by step all the practical actions and the resulting results.

A laboratory workshop at a university differs from a school one primarily in the presence of a scientific approach. After completing the work, it is necessary to write a report, which is an independent analysis of the study. And in many universities, the requirements for a report on laboratory work are similar to the requirements for writing a scientific article.

Lab report

The lab report structure includes the following elements:

1. Introduction: the formulation of the task of the workshop.
2. The main part: theoretical information, a brief description of the experience, calculations, research methodology and analysis of the results. It is also necessary to indicate what equipment or software was used during the work.
3. Conclusion: general conclusions.

A mandatory element of the report is also a list of literature used to prepare for the laboratory.

If necessary, the report may include applications that clearly show the progress and results of the laboratory (graphs, tables, program listing).

Rules for writing a report on laboratory work

The finished report is submitted for protection to the teacher in charge of the laboratory. On the basis of the report, the teacher assesses not only the level of the student's theoretical knowledge and his professional training, but also the ability for scientific thinking.

Report writing algorithm:

1. We formulate the purpose of the work according to the task received.
2. We describe the essence of the phenomenon, program or method to be investigated.
3. We list the equipment necessary for work. If a special installation is used, we draw its diagram.
4. We record all measurement data and task conditions in the report.
5. We describe in detail the course of the study, citing all the calculation methods, formulas, calculations, and so on. Each step of the study should be analyzed and conclusions drawn.
6. We present the results of the work, summarize.

Remember: if the laboratory work is not credited, you will not be allowed to take the exam!

Assistance in performing laboratory work

You do not know how to do a lab work flawlessly, or for some reason you cannot write a lab report yourself? Contact Dip24 specialists for help. And do not worry about the deadlines - we work around the clock and do laboratory work to order of any complexity quickly and accurately.

Step-by-step instructions for creating a laboratory power supply - a diagram, the 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 a network. In most cases, it converts the alternating current of the network into direct current. Every radio amateur has such a device, and today we will look at how to create it with our own hands, what is needed for this and what nuances are important to consider during installation.

Advantages of the laboratory power supply

First, we note the features of the PSU, which we are going to manufacture:

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

Laboratory power supply - circuit

Diagram of a laboratory power supply

Now let's take a look at the diagram. It has been on the web for a long time. Let's talk separately about some of the nuances.

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

• See also how to do

Designation of circles in the diagram:

• 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 the transistor Q4.

An alternating voltage of 24 V is supplied to inputs 1 and 2 from the mains transformer. The transformer must be dimensional so that it can easily deliver up to 3 A to the load (you can buy it or wind it).

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

Chips U1, U2, U3 are operational amplifiers. Their pinouts, when viewed from above:

On the eighth output, “NC” is written - this means that it does not need to be connected to either the minus or the plus of the power supply. In the circuit, conclusions 1 and 5 also do not cling anywhere.

• See also step-by-step instructions for creating

Transistor Q1 brand BC547 or BC548. Below is its pinout:

Pinout diagram for transistor Q1

Transistor Q2 is better to take the Soviet KT961A. But do not forget to put it on the radiator

Transistor Q3 brand BC557 or BC327:

Transistor Q4 exclusively KT827!

Here is his pinout:

Q4 transistor pinout diagram

The variable resistors in this circuit are confusing. They are labeled here as follows:

Scheme for input of variable resistors

We label them like this:

Here is also a list of components:

• 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 kΩ 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 = 56kΩ 1/4W
• R14 = 1.5 kOhm 1/4W
• R15, R16 = 1 kΩ 1/4W
• R17 = 33 ohm 1/4W
• R22 = 3.9 kOhm 1/4W
• RV1 = 100K multi-turn trimmer
• P1, P2 = 10KOhm linear potentiometer
• C1 = 3300uF/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 = 5.6V zener diodes
• 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 are preparing the case for the PSU.

We make a printed circuit board using LUT:

PCB diagram for laboratory power supply

Etching it:

Rinse off toner:

Learn something about building a foundation. It doesn't mean you have to get a degree, but what good is it that your lab comes crashing down on you, especially if it takes your house with it?

Build under the house.

Decide which way to enter. Hidden door, fake cabinet back, floor trapdoor, classic bookcase door, steps or ladder? Stairs take up the least space from your basement, but are very hard to get equipment and furniture down. Steps, on the other hand, can take up a lot of space, but a pantry under such a ladder can come in handy. Consider making two exits.

Learn basement building techniques. Be sure to pay attention to the drain and the problem of water penetration, as well as building materials. Remember that a huge truck that pumps large amounts of concrete can be replaced with slow-drying concrete and stamina, because you have to mix and lay it yourself. Laziness is not an option when it comes to cement.

Obtain the necessary materials slowly and without suspicion, preferably from cities or places within a 2-4 hour drive from you. Gather them in a hidden location, possibly rented, if possible, under a pseudonymous warehouse in a nearby town.

Make sure you have somewhere to put the excavated earth. This is not a video game. The dug up earth will not disappear by itself! Large piles of earth in the backyard will definitely arouse suspicion. Although, if you start redoing the garden in parallel and spend some time landscaping it with this land, this will remove the questions. More work, but more secrecy. Another idea is to make a hanging garden, with levels on retaining walls (see "How to Build a Retaining Stone Wall").

Support earthen walls. The ground settles all the time, so make sure it's secured as you dig! This is especially important in rainy areas or during the rainy season. You can't reinforce the walls too much!

Provide a support structure if you are tunneling to make the lab larger than the hole you originally dug. This is related to props, but even more important. A mistake here could mean your death. dig a tunnel not recommended if you are not an experienced tunnel builder who has designed durable tunnels such as metro systems.

Make sure your walls are strong enough to hold the ground, support the structure from above and each other from falling inward. Embedded beams between walls can help contain outside pressure if you sacrifice some space for safety.

Pour the floor in the same way as in any basement, providing drainage for groundwater.

Bring electricity to your laboratory. Make a series of branches from several lines in rooms (for new wiring) or from the least used line in the house (for old wiring). Learn about how your home is wired before working on it. There are many books on this subject. If your lab's needs are too large for this kind of wiring, have a qualified electrician install a new line. Say it's for a high-powered laser printer, an electric water heater without a tank, a new dryer, or a power tool, depending on where the wiring will lead, and then branch off from it.

Consider plumbing. During construction, you may come across your house's internal plumbing system as you excavate. If so, then you're in luck. You can very easily branch off a pipe to get a source of water. If you also found a sewer pipe, that's fine too, but if you're below it, you'll need to store and pump sewage into it. The waste tank will take up the valuable space you dug under the floor, and the pump will take the energy. If your experiments don't require water, you might not want to think about plumbing.

Every novice radio amateur needs a laboratory power supply. To do it right, you need to choose the right scheme, and this usually causes a lot of problems.

Types and features of power supplies

There are two types of power supplies:

• Pulse;
• Linear.

A pulse-type block can generate interference that will affect the tuning of receivers and other transmitters. A linear type power supply may not be able to deliver the required power.

How to make a laboratory power supply correctly, from which it will be possible to charge the battery, and power sensitive circuit boards? If you take a simple linear-type power supply for 1.3-30 V, and a current capacity of not more than 5 A, you will get a good voltage and current stabilizer.

Let's use the classic scheme for assembling a power supply with our own hands. It is designed on LM317 stabilizers, which regulate the voltage in the range of 1.3-37V. Their work is combined with KT818 transistors. These are powerful radio components that are capable of passing a large current. The protective function of the circuit is provided by LM301 stabilizers.

This scheme has been developed for a long time, and periodically modernized. Several diode bridges appeared on it, and the measuring head received a non-standard switching method. The transistor MJ4502 was replaced by a less powerful analogue - KT818. There are also filter capacitors.

Do-it-yourself block installation

At the next assembly, the block diagram received a new interpretation. The capacitance of the output-type capacitors has increased, and several diodes have been added for protection.

The KT818 type transistor was an unsuitable element in this circuit. It overheated a lot, and often led to a breakdown. They found a replacement for him with a more profitable option TIP36C, in the circuit he has a parallel connection.

Step by step setup

A do-it-yourself laboratory power supply made with your own hands needs to be turned on step by step. The initial start-up takes place with the LM301 and transistors disabled. Next, the function regulating the voltage through the P3 regulator is checked.

If the voltage is regulated well, then transistors are included in the circuit. Their work will then be good when several resistances R7, R8 begin to balance the emitter circuit. We need such resistors so that their resistance is at the lowest possible level. In this case, the current should be enough, otherwise in T1 and T2 its values ​​\u200b\u200bwill differ.

This adjustment step allows you to connect a load to the output end of the power supply. You should try to avoid a short circuit, otherwise the transistors will immediately burn out, followed by the LM317 stabilizer.

The next step is to mount the LM301. First, you need to make sure that there is -6V on the op-amp in pin 4. If +6V is present on it, then there may be an incorrect connection of the BR2 diode bridge.

Also, the connection of capacitor C2 may be incorrect. After inspecting and correcting installation defects, it is possible to supply power to the 7th leg of the LM301. This can be done from the output of the power supply.

At the last stages, P1 is configured so that it can operate at the maximum operating current of the PSU. A laboratory power supply with voltage regulation is not so difficult to adjust. In this case, it is better to once again double-check the installation of parts than to get a short circuit with the subsequent replacement of elements.

Basic radio elements

To assemble a powerful laboratory power supply with your own hands, you need to purchase the appropriate components:

• A transformer is required for power;
• Several transistors;
• Stabilizers;
• Operational amplifier;
• Several types of diodes;
• Electrolytic capacitors - no more than 50V;
• Resistors of different types;
• Resistor P1;
• Fuse.

The rating of each radio component must be compared with the diagram.

Block in final form

For transistors, it is necessary to choose a suitable heatsink that can dissipate heat. Moreover, a fan is mounted inside to cool the diode bridge. Another one is installed on an external radiator, which will blow the transistors.

For the internal filling, it is desirable to choose a high-quality case, since the thing turned out to be serious. All elements should be well fixed. In the photo of the laboratory power supply, you can see that digital devices have come to replace the pointer voltmeters.

Photo of the laboratory power supply

HOW TO ORGANIZE YOUR HOME

LABORATORY

G. BALUEV

LABORATORY DESK. First of all, for the experiments it is necessary to have a permanent place where you can work and where all the equipment, utensils and reagents will be stored. How to make the simplest laboratory table is clear from Figure 1. The hinged door of the cabinet can be hooked during operation, and the rest of the time it can be locked (especially if there are younger children in the family). If the table is long enough, the locker can be made not the entire length of the table, but if there is not enough space - on the side of the table, as a continuation of its cover, it is good to make a shelf.

In order to protect the surface of the table from damage, it must be covered with a piece of linoleum, plastic or wood treated as follows: first soak with a solution of tannin, then with an 8-10% solution of iron sulfate and, when the table dries, rub it several times with raw linseed oil. Such a surface is easy to clean with soap and is not afraid of acids and alkalis.

Take a small shelf in the cabinet for bottles with acids and alkali solutions; put a piece of window glass on this shelf. In a drawer, if its dimensions allow, you can store filter paper, corks, glass rods, clips and other small things in addition to a work journal. But we must remember that it is impossible, for example, to store glass together with metal. If it is difficult to

Lay in the drawer of the partition, you can use a variety of boxes.

Close to the "laboratory" there is a water tap - very good. And if it is not there, you need to put a bottle of water on top of the cabinet and make a siphon for it, as shown in Figure 2. You can use a clothespin as a clamp.

Under the table you need to put two buckets (preferably plastic) - one for dry garbage, the other for collecting liquids. After finishing the work, empty the buckets: pour the liquids into the sewer (but not into the plumbing sink), throw the dry waste also in the appropriate place.

Crockery and equipment can be purchased in stores, but it is much more interesting to do everything that you can do yourself. Your heating source will be an alcohol stove. It is not difficult to make it (Fig. 3). Remember that only denatured alcohol should be poured into it; gasoline, kerosene or other flammable liquids cannot be used in an alcohol lamp. If there is an electrical outlet near the table, make a heating device from an electric lamp (Fig. 4). It is very handy when you only need to slightly heat the substance or when working with flammable liquids. Make the cone in which the lamp is fixed from tin or from a flower pot.

All reagents should be stored in glass jars and bottles with stoppers or lids.