It took one day to develop this power supply, it was implemented on the same day, and the whole process was filmed on a video camera. A few words about the scheme. This is a stabilized power supply with adjustable output voltage and current limiting. Schematic features allow you to drop the minimum output voltage limit to 0.6 Volts, and the minimum output current in the region of 10mA.
Despite the simplicity of the design, even good laboratory power supplies with a cost of 5-6 thousand rubles are inferior to this power supply! The maximum output current of the circuit is 14Amps, the maximum output voltage is up to 40 Volts - no longer worth it.
Pretty smooth current limiting and voltage regulation. The block also has a fixed protection against short circuits, by the way - the current protection can also be set (almost all industrial designs are deprived of this function), for example, if you need the protection to work at currents up to 1 Ampere - then you just need to adjust this current using operating current setting regulator. The maximum current is 14Amps, but this is not the limit.
As a current sensor, I used several 5 watt 0.39 Ohm resistors connected in parallel, but their value can be changed based on the desired protection current, for example - if you are planning a power supply with a maximum current of not more than 1 Ampere, then the value of this resistor is around 1 Ohm at power 3W.
In case of short circuits, the voltage drop across the current sensor is sufficient to trigger the BD140 transistor. When it opens, the lower transistor, BD139, also fires, through the open junction of which power is supplied to the relay winding, as a result, the relay is activated and the working contact opens (at the circuit output). The circuit can stay in this state for any amount of time. Along with the protection, the protection indicator is also activated. In order to remove the block from protection, you need to press and lower the button S2 according to the scheme.
Protection relay with a 24 Volt coil with a permissible current of 16-20 Amperes or more.
The power switches in my case are my favorite KT8101 installed on the heat sink (there is no need to further isolate the transistors, since the key collectors are common). You can replace transistors with 2SC5200 - a complete imported analogue or with KT819 with the GM index (iron), if desired, you can also use - KT803, KT808, KT805 (in iron cases), but the maximum output current will be no more than 8-10 Amperes. If the block is needed with a current of not more than 5 amperes, then one of the power transistors can be removed.
Low-power transistors of the BD139 type can be replaced with a complete analogue - KT815G, (you can also use KT817, 805), BD140 - with KT816G (you can also use KT814).
Low-power transistors do not need to be installed on heat sinks.
In fact, only the control (adjustment) and protection scheme (working unit) is presented. As a power supply, I used modified computer power supplies (connected in series), but you can use any network transformer with a power of 300-400 watts, in a secondary winding of 30-40 Volts, a winding current of 10-15 Amperes - this is ideal, but transformers and less power.
Diode bridge - any, with a current of at least 15 amperes, the voltage is not important. You can use ready-made bridges, they cost no more than 100 rubles.
Over 10 of these power supplies were assembled and sold in 2 months - no complaints. I assembled exactly such a PSU for myself, and as soon as I didn’t torment him - indestructible, powerful and very convenient for any business.
If there are those who want to become the owner of such a PSU, then I can make it to order, contact me at
Best regards - AKA KASYAN
Many different laboratory power supplies are presented on the Internet on radio engineering sites, though mostly simple designs. The same scheme is characterized by a rather high complexity, which is justified by the quality, reliability and versatility of the PSU. Introducing a completely homemade power supply with a bipolar 2 x 30 V, with adjustable current up to 5 A and a digital LED A / V meter.
In fact, these are two identical power supplies in one housing, which significantly increases the functionality and capabilities of the device, allowing you to combine channel powers up to 10 Amperes. At the same time, this is not a typical balanced power supply, although it is possible to connect serial outputs here for higher voltage or pseudo-symmetry, treating the common connection as ground.
Schemes of laboratory power supply modules
All power board circuits were designed from scratch, and all PCBs are self-developed. The first "Z" module is a diode bridge, voltage filtering, negative voltage generation to power the opamps, 34 VDC positive voltage supply for the opamps, powered by a separate auxiliary transformer, a relay used to switch the main transformer windings controlled from another printed circuit board, and a 5 V 1 A power supply for power meters.
The "Z" modules of both units were designed to be nearly symmetrical (to better fit into the PSU case). Thanks to this, the ARK connectors were placed on the same side to connect the wires and the heatsink for the bridge rectifier, and the boards were placed symmetrically as shown in the pictures.
An 8-amp diode bridge is used here. The main transformers have dual secondary windings, each 14 volts and a current of just over 5 amps. The power supply was rated for 5 amps, but it turned out that at full 30 volts, you don't get the full 5 amps. However, there are no problems with a 5 amp load at a lower voltage (up to 25 V).
The second module is an extended 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 current limiting amplifier U3 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 inverted input U4. Due to this, the output voltage depends on the setting of the potentiometer 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 get a stable source for driving the LM3914 circuits that form the LED line.
The visualization circuitry is especially useful when multi-turn potentiometers are used for adjustment. It is remarkable that with the help of such a potentiometer one can easily set the voltage with an accuracy of three decimal places. Each LED in the line corresponds to a current of 0.25A, so if the current limit is below 250mA, the line is not displayed.
The way the ruler is displayed can be changed from dot to ruler, but a point is selected here to avoid being affected by too many light points and reduce power consumption.
The next module is the winding switching system and the fan control system that are installed on the heatsinks of older processors.
Power supply of circuits from independent windings of the auxiliary transformer. Here m / s LM358 op-amps are used, which contain two operational amplifiers inside. A BD135 transistor was used as a temperature sensor. After exceeding 55C, the fans turn on, and after cooling down to about 50C, they automatically turn off. The winding switching system responds 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 there is a voltmeter and an ammeter on one board for each power supply.
From the very beginning, the idea was to visualize the parameters of the power supplies 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 the cooling system on one Atmega MK, even for both power supplies at once. It's a matter of choice. Using a microcontroller will come out 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 mains 220V (primary). A TS90/11 was used for this purpose.
As a secondary winding, 2 x 26 V AC are wound to power the operational amplifiers, 2 x 8 V AC to power the indicators and 2 x 13 V AC to power the temperature control. In total, six independent windings were created.
Housing and assembly costs
The entire PSU is housed in a case that was also designed from scratch. It was made to order. It is known that at home it is difficult to make a decent box (especially a metal one).
The aluminum front panel used to mount all indicators and additional elements was milled according to the design.
Of course, this is not a low-budget implementation, given the purchase of two powerful toroidal transformers and the execution of the case to order. Want simpler and cheaper -.
The rest can be estimated based on prices in online stores. Of course, some elements were obtained from our own stocks, but these too will need to be bought, creating a power supply from scratch. The total cost came out at the level of 10,000 rubles.
Assembling and configuring the LBP
- Assembling and testing a module with a bridge rectifier, filtering and relay, connecting to a transformer and activating a relay from an independent source to test the output voltages.
- Execution of the module for switching windings and controlling the cooling of radiators. The launch of this module will make it easier to configure the future power supply. To do this, you need another power source to supply a regulated voltage to the input of the system responsible for controlling the relay.
- The temperature part of the circuit can be tuned by temperature simulation. For this purpose, a heat gun was used, which gently heated the radiator with a sensor (BD135). The temperature was measured using a sensor included in the multimeter (at that time there were no ready-made accurate temperature meters). In both cases, the setting is reduced to the selection of PR201 and PR202 or PR301 and PR302, respectively.
- Then we start the power supply by adjusting RV1 in such a way as to get 0 V at the output, which is useful when setting the current limit. The limitation itself depends on the values of the resistors R18, R7, R17.
- The regulation of A / V indicators is reduced to setting the reference voltages between pins 35 and 36 of the ICL microcircuits. The voltage and current meters used an external reference source. In the case of temperature meters, such accuracy is not needed, and the decimal display is still somewhat exaggerated. The transmission of temperature readings is carried out by one rectifier diode (there are three of them in the diagram). It has to do with the PCB design. It has two jumpers.
- Directly at the output terminals, a voltage divider and a 0.01 ohm / 5 W resistor are connected to the voltmeter, on which the voltage drop is used to measure the load current.
An additional element of the power supplies is a circuit that allows you to turn on only one power supply without the need for a second channel, despite the fact that the auxiliary transformer feeds 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 the 220 V network. All circuits in good quality can
Every novice radio amateur needs a laboratory power supply. To do it correctly, 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
Today we will assemble a laboratory power supply with our own hands. We will understand the device of the block, select the correct components, learn how to properly solder, assemble elements on printed circuit boards.
This is a high-quality laboratory (and not only) power supply with adjustable variable voltage from 0 to 30 volts. The circuit also includes an electronic output current limiter that effectively regulates the 2mA output current out of the circuit's maximum current (3A). This characteristic makes this power supply indispensable in the laboratory, as it makes it possible to regulate power, limit the maximum current that the connected device can consume, without fear of damage to it if something goes wrong.
There is also a visual indication that this limiter is active (LED) so you can see if your circuit is exceeding its limits.
The circuit diagram of the laboratory power supply is shown below:
Specifications of the laboratory power supply
Input voltage: ……………. 24 V-AC;
Input current: ……………. 3 A (max.);
Output voltage: …………. 0-30 V - adjustable;
Output current: …………. 2 mA -3 A - adjustable;
Output voltage ripple: …. 0.01% max.
Peculiarities
- Small size, easy to make, simple structure.
— The output voltage is easily adjustable.
- Output current limitation with visual indication.
- Protection against overload and incorrect connection.
Principle of operation
To begin with, the laboratory power supply uses a transformer with a secondary winding of 24V / 3A, which is connected through input terminals 1 and 2 (the quality of the output signal is proportional to the quality of the transformer). The AC voltage from the secondary winding of the transformer is rectified by a diode bridge formed by diodes D1-D4. The ripple of the rectified DC voltage at the output of the diode bridge is smoothed by a filter formed by the resistor R1 and the capacitor C1. The circuit has some features that make this power supply different from other blocks in this class.
Instead of using feedback to control the output voltage, our circuit uses an op-amp to provide the required voltage for stable operation. This voltage drops at the output of U1. The circuit works thanks to the Zener diode D8 - 5.6 V, which operates here at zero current temperature coefficient. The voltage at the output of U1 drops across the diode D8 turning it on. When this happens, the circuit stabilizes and the voltage of the diode (5.6) drops across resistor R5.
The current that flows through the opera. the amplifier changes slightly, which means that the same current will flow through the resistors R5, R6, and since both resistors have the same voltage value, the total voltage will be summed up as if they were connected in series. Thus, the voltage obtained at the output of operas. amplifier will be equal to 11.2 volts. Chain with operas. amplifier U2 has a constant gain of approximately 3, according to the formula A = (R11 + R12) / R11 increases the voltage of 11.2 volts to approximately 33 volts. Trimmer RV1 and resistor R10 are used to set the output voltage so that it does not drop to 0 volts, regardless of the magnitude of other components in the circuit.
Another very important characteristic of the circuit is the ability to obtain the maximum output current that can be obtained from the p.s.u. To make this possible, the voltage is dropped across a resistor (R7) which is connected in series with the load. The IC responsible for this circuit function is U3. An inverted signal to input U3 equal to 0 volts is fed through R21. At the same time, without changing the signal of the same IC, any voltage value can be set by means of P2. Assume that the voltage for a given output is a few volts, P2 is set so that IC has a 1 volt signal at the input. If the load is amplified the output voltage will be constant and having R7 connected in series with the output will have little effect due to its low magnitude and due to its position outside the control loop feedback loop. As long as the load and output voltage are constant, the circuit works stably. If the load is increased so that the voltage across R7 is greater than 1 volt, U3 is turned on and stabilizes at its original settings. U3 works without changing the signal to U2 via D9. Thus, the voltage across R7 is constant and does not increase above a given value (1 volt in our example) reducing the output voltage of the circuit. It is within the power of the device to keep the output signal constant and accurate, which makes it possible to obtain 2 mA at the output.
Capacitor C8 makes the circuit more stable. Q3 is needed to drive the LED whenever you use the limiter indicator. To make this possible for U2 (changing the output voltage down to 0 volts) it is necessary to provide a negative connection, which is done through the circuit C2 and C3. The same negative relationship is used for U3. Negative voltage is supplied by stabilizing through R3 and D7.
To avoid uncontrolled situations, there is a kind of protection circuit built around Q1. The IC has internal protection and cannot be damaged.U1 - reference voltage source, U2 - voltage regulator, U3 - current regulator.
The design of the power supply.
First of all, let's look at the basics in building electronic circuits on printed circuit boards - the basis of any laboratory power supply. The board is made of thin insulating material covered with a thin conductive layer of copper, which is formed in such a way that circuit elements can be connected with conductors as shown in the circuit diagram. It is necessary to properly design the printed circuit board to avoid incorrect operation of the device. To protect the board from oxidation in the future and keep it in excellent condition, it must be coated with a special varnish that protects against oxidation and facilitates soldering.
Soldering elements into a board is the only way to assemble a high-quality laboratory power supply, and the success of your work will depend on how you do it. This one is not very difficult if you follow a few rules and then you won't have any problems. The power of the soldering iron you are using should not exceed 25 watts. The sting should be thin and clean throughout the work. There is a wet sponge for this and you can clean the hot tip from time to time to remove any residue that builds up on it.
- DO NOT try to file or sand a dirty or worn tip. If it cannot be cleaned, replace it. There are many different soldering irons on the market, and you can also buy a good flux to get a good connection when soldering.
- DO NOT use flux if you are using solder that already contains flux. A large amount of flux is one of the main causes of chain failure. If, however, you must use additional flux, as when tinning copper wires, you must clean the work surface after finishing work.
In order to solder the element correctly, you must do the following:
- Clean the leads of the elements with sandpaper (preferably with a small grain).
— Bend component leads at the correct distance from the package exit for easy placement on the board.
- You can find elements whose leads are thicker than the holes in the board. In this case, you need to expand the holes a little, but do not make them too large - this will make soldering difficult.
- It is necessary to insert the element so that its leads protrude slightly from the surface of the board.
- When the solder melts, it will spread evenly over the entire area around the hole (this can be achieved with the correct temperature of the soldering iron).
- Soldering of one element should be no more than 5 seconds. Remove excess solder and wait for the solder on the board to cool naturally (without blowing on it). If everything is done correctly, the surface should have a bright metallic tint, the edges should be smooth. If the solder looks dull, cracked, or shaped like a drop, it's called dry soldering. You must remove it and do everything again. But be careful not to overheat the tracks or they will lag the board and break easily.
- When you are soldering the sensitive element, it is necessary to hold it with metal tweezers or tongs, which will absorb excess heat so as not to burn the element.
- When you are done with your work, trim off the excess from the element leads and you can clean the board with alcohol to remove any flux residue.
Before starting the assembly of the power supply, it is necessary to find all the elements and divide them into groups. First install the sockets for the ICs and the pins for the external connections and solder them in place. Then resistors. Be sure to place R7 at a certain distance from the PCB, as it gets very hot, especially when a large current is flowing, and this can damage it. This is also recommended for R1. then place the capacitors paying attention to the polarity of the electrolytic and finally solder the diodes and transistors, but be careful not to overheat them and solder them as shown in the diagram.
Install the power transistor in the heatsink. To do this, follow the diagram and remember to use an insulator (mica) between the body of the transistor and the heatsink and a special cleaning fiber to isolate the screws from the heatsink.
Connect an insulated wire to each pin, be careful to make a good quality connection as there is a lot of current flowing here, especially between the emitter and collector of the transistor.
Also, when assembling the power supply, it would be nice to figure out where which element will be in order to calculate the length of the wires that will be between the PCB and the potentiometers, the power transistor, and for the input and output connections.
Connect the potentiometers, LED and power transistor and connect two pairs of ends for input and output connections. Make sure from the diagram that you are doing everything correctly, try not to confuse anything, since there are 15 external connections in the chain and if you make a mistake, it will be difficult to find it later. It would also be nice to use wires of different colors.
The printed circuit board of the laboratory power supply, below is a link to download the signet in .lay format:
The layout of the elements on the power supply board:
Connection diagram of variable resistors (potentiometers) for regulating the output current and voltage, as well as connecting the contacts of the power transistor of the power supply:
Designation of the outputs of transistors and operational amplifier:
Terminal designation on the diagram:
- 1 and 2 to the transformer.
— 3 (+) and 4 (-) DC OUT.
- 5, 10 and 12 on P1.
- 6, 11 and 13 on P2.
- 7 (E), 8 (B), 9 (E) to transistor Q4.
- LED must be installed on the outside of the board.
When all external connections are made it is necessary to check the board and clean it to remove solder residue. Make sure there is no connection between adjacent tracks that could cause a short circuit, and if all is well, connect the transformer. And connect a voltmeter.
DO NOT TOUCH ANY PART OF THE CIRCUIT WHILE IT IS LIVE.
The voltmeter should show a voltage between 0 and 30 volts, depending on which position P1 is in. Turning P2 counterclockwise should turn on the LED, indicating that our limiter is working.
List of elements.
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 trimmer
P1, P2 = 10KOhm linear potentiometer
C1 = 3300uF/50V electrolytic
C2, C3 = 47uF/50V electrolytic
C4 = 100nF polyester
C5 = 200nF polyester
C6 = 100pF ceramic
C7 = 10uF/50V electrolytic
C8 = 330pF ceramic
C9 = 100pF ceramic
D1, D2, D3, D4 = 1N5402,3,4 diode 2A - RAX GI837U
D5, D6 = 1N4148
D7, D8 = 5.6V zener
D9, D10 = 1N4148
D11 = 1N4001 diode 1A
Q1 = BC548, NPN transistor or BC547
Q2 = 2N2219 NPN transistor - (Replace with KT961A- everything is working)
Q3 = BC557, PNP transistor or BC327
Q4 = 2N3055 NPN power transistor ( replace with KT 827A)
U1, U2, U3 = TL081, op. amplifier
D12 = LED diode
As a result, I independently assembled a laboratory power supply, but in practice I encountered what I consider necessary to correct. Well, first of all, it's a power transistor. Q4=2N3055 it needs to be deleted and forgotten as a matter of urgency. I don’t know about other devices, but it doesn’t fit in this adjustable power supply. The fact is that this type of transistor fails instantly in the event of a short circuit and a current of 3 amperes does not draw at all !!! I didn't know what was the matter until I changed it to our native Soviet KT 827 A. After installing it on the radiator, I didn’t know grief and never returned to this issue.
As for the rest of the circuitry and details, there are no difficulties. With the exception of the transformer - I had to wind it. Well, this is purely because of greed, half a bucket of them is in the corner - do not buy it =))
Well, in order not to break the good old tradition, I post the result of my work for the general court 🙂 I had to shaman with the column, but in general it turned out not bad:
The front panel itself - I moved the potentiometers to the left side; on the right side, an ammeter and a voltmeter + a red LED were placed to indicate the current limit.
The next photo is a rear view. Here I wanted to show how to mount a cooler with a radiator from the motherboard. A power transistor perched on this radiator from the back.
Here it is, the power transistor KT 827 A. Mounted on the back wall. I had to drill holes for the legs, lubricate all the contact parts with heat-conducting paste and fasten them to the nuts.
Here they are .... the insides! Actually everything is in a pile!
Slightly larger on the inside
Front panel on the other side
Closer, here you can see how the power transistor and transformer are mounted.
Power supply board on top; here I cheated and packed low-power transistors from the bottom of the board. You can't see them here, so don't be surprised if you don't find them.
Here is the transformer. I rewound it to 25 volts of TVS-250 output voltage. Rough, sour, not aesthetically pleasing, but everything works like clockwork =) I did not use the second part. Leave room for creativity.
Somehow like this. A little creativity and patience. The block has been working great for 2 years now. To write this article, I had to disassemble it and reassemble it. It's just awful! But all for you, dear readers!
Designs from our readers!
For radio amateurs, and indeed a modern person, an indispensable thing in the house is the 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 you to pursue your hobby without restrictions. Just about how to make an adjustable type of power supply with your own hands, our article will tell.
What you need to know
A power supply with current and voltage regulation in a modern home is a necessary thing. 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 a similar device with your own hands.
But ready-made PSUs are expensive enough to buy them for specific needs. Therefore, today very often converters for voltage and current are made by hand.
Note! 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 purposes.
Professionals can easily make a powerful power supply, while beginners and hobbyists can start with a simple type of device. In this case, the scheme, depending on the complexity, can be used very different.
What to Consider
The regulated power supply is a universal converter that can be used to connect any household or computing equipment. Without it, no home appliance will be able to function normally.
Such a PSU 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 instrument.
In addition, this type of power supply must have protection for high and low current. Otherwise, any abnormal situation may cause the converter and the electrical device connected to it to simply burn out. This result can also be caused by incorrect soldering of the 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 simple type of converter is the 0-15V PSU. It has protection against exceeding the current in the connected load. The diagram for its assembly is located below.
Simple Assembly Diagram
This is, so to speak, a universal assembly type. The scheme here is available for understanding to any person who at least once held a soldering iron in his 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 the current indicator (at 0.05 and 1A);
- wide range for output voltages;
- high stability in the operation of the converter.
Diode bridge
In this situation, the transformer will provide a voltage in the range of 3V more than the maximum required voltage for the output. It follows from this that a power supply capable of regulating voltage up to 20V needs a transformer of at least 23V.
Note! The diode bridge should be selected based on the maximum current indicator, which will be limited by the available protection.
A 4700 microfarad filter capacitor will allow equipment that is sensitive to power interference not to give a background. This will require a compensation stabilizer with a ripple suppression ratio of more than 1000.
Now that we have dealt with the main aspects of the assembly, we need to pay attention to the requirements.
Instrument 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 specifications look like this:
- regulated stabilized output for 3-24 V. In this case, the current load must be at least 2 A;
- unregulated 12/24V output. This assumes a large current load.
To fulfill the first requirement, you should use an integral stabilizer in your work. 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 decided on the requirements that your stand-alone regulated type power supply must meet, and a suitable circuit has been selected, you can begin the assembly itself. But first of all, let's stock up on the details 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 the 10000uF 50V model;
- microcircuit for the stabilizer;
- strapping;
- details of the circuit (in our case, the circuit that is indicated above).
After that, according to the scheme, we assemble an adjustable power supply with our own hands in strict accordance with all the recommendations. The sequence of actions must be followed.
Ready PSU
The following parts are used to assemble the PSU:
- germanium transistors (mostly). If you want to replace them with more modern silicon elements, then the lower MP37 must remain germanium. MP36, MP37, MP38 transistors are used here;
- a current-limiting assembly is assembled on the transistor. It provides monitoring of the voltage drop across the resistor.
- zener diode D814. It determines the adjustment of the maximum output voltage. On himself, he takes half of the output voltage;
Note! Since the D814 zener diode takes exactly half the output voltage, it should be chosen to create a 0-25V output voltage of about 13 V.
- the lower limit in the assembled power supply has a voltage indicator of only 0.05 V. This indicator is rare for more complex converter assembly circuits;
- pointer indicators display current and voltage indicators.
Assembly Parts
To accommodate all parts, you must select a steel case. He will be able to shield the transformer and the power supply board. As a result, you will avoid the occurrence of various kinds 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 the home laboratory. Also, such a device can be used to assess the performance of a car generator.
Conclusion
Using simple schemes for assembling an adjustable type of power supply, you can fill your hand and later make more complex models with your own hands. You should not take on overwork, because in the end you may not get the desired result, and the home-made converter will work inefficiently, 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 output you will get an excellent power supply with voltage regulation for your home laboratory or other everyday situations.
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