Do-it-yourself oscilloscope PC attachment. How to make an oscilloscope from a computer. Installing and configuring the program

Quite often in Lately Instead of making, for example, an oscilloscope from a computer, many people prefer to simply buy a digital USB oscilloscope. However, after browsing the market, you can see that budget oscilloscopes actually start at around $250. And more serious equipment even has a price several times higher.

It is for those people who are not satisfied with this cost that it is more relevant to make an oscilloscope from a computer, especially since it allows you to solve a large number of problems.

What should I use?

One of the best options is the Osci program, which has an interface similar to a standard oscilloscope: there is a standard grid on the screen with which you can independently measure the duration or amplitude.

One of the disadvantages of this utility is that it is somewhat unstable. During its operation, the program may sometimes freeze, and in order to reset it later, you will need to use a specialized Task Manager. However, all this is compensated by the fact that the utility has a familiar interface, is quite convenient to use, and is also quite different big amount functions that allow you to make a full-fledged oscilloscope from a computer.

On a note

It’s worth noting right away that these programs include a specialized low-frequency generator, but its use is highly not recommended, since it tries to completely independently regulate the operation of the audio card driver, which can cause irreversible sound muting. If you try to use it, make sure that you have your own restore point or the ability to make a backup operating system. The best option for making an oscilloscope from a computer with your own hands is to download a normal generator, which is located in the “Additional Materials”.

"Vanguard"

"Avangard" is a domestic utility that does not have a standard and familiar measuring grid, and also has a screen that is too large for taking screenshots, but at the same time it provides the ability to use a built-in voltmeter of amplitude values, as well as a frequency meter. This allows you to partially compensate for the disadvantages mentioned above.

Having made such an oscilloscope from a computer with your own hands, you may encounter the following: at low signal levels, both the frequency meter and the voltmeter can greatly distort the results, however, for beginner radio amateurs who are not accustomed to perceiving diagrams in volts or milliseconds per division, this utility will quite acceptable. The other one is her useful function is that you can carry out completely independent calibration of two existing scales of the built-in voltmeter.

How will it be used?

Since the input circuits of the audio card have a specialized isolation capacitor, the computer as an oscilloscope can only be used with a closed input. That is, only the variable component of the signal will be observed on the screen, however, with some skill, using these utilities it will also be possible to measure the level of the constant component. This is quite relevant if, for example, the counting time of a multimeter does not make it possible to record a certain amplitude voltage value on a capacitor, which is charged through a large resistor.

The lower voltage limit is limited by noise and background levels and is approximately 1 mV. The upper limit is limited only by the parameters of the divider and can even reach several hundred volts. The frequency range is directly limited by the capabilities of the audio card itself and for budget devices ranges from approximately 0.1 Hz to 20 kHz.

Of course, in this case we are considering a relatively primitive device. But if you do not have the opportunity, for example, to use a USB oscilloscope (attachment to a computer), then its use is quite optimal.

Such a device can help you repair various audio equipment, and can also be used exclusively for educational purposes, especially if it is supplemented with a virtual low-frequency generator. In addition, an oscilloscope program for a computer will allow you to save a plot to illustrate certain material or for posting on the Internet.

Electrical diagram

If you need a computer attachment (oscilloscope), then making one will be somewhat more difficult. On this moment On the Internet you can find a fairly large number of different circuits for such devices, and to build, for example, a two-channel oscilloscope, you will need to duplicate them. The use of a second channel is often relevant if you need to compare two signals or if a computer attachment (oscilloscope) will also be used with an external synchronization connection.

In the vast majority of cases, the circuits are extremely simple, but in this way you can independently provide a fairly wide range of voltages available for measuring, using a minimum number of radio components. In this case, an attenuator, which is built according to the classical scheme, would require you to use specialized high-ohm resistors, and its input resistance would constantly change if the range is switched. For this reason, you would experience certain limitations in using standard oscilloscope cables, which are designed for an input impedance of no more than 1 mOhm.

We provide security

In order for the linear input of the audio card to be protected from the possibility of accidental contact high voltage, specialized zener diodes can be installed in parallel.

Using resistors you can limit the current of the zener diodes. For example, if you are going to use your computer oscilloscope (generator) to measure a voltage of about 1000 Volts, then in this case you can use two one-watt or one two-watt resistor as a resistor. They differ from each other not only in their power, but also in what voltage in them is the maximum permissible. It is also worth noting the fact that in this case you will also need a capacitor, the maximum permissible value for which is 1000 Volts.

Attention!

Often it is necessary to initially look at the variable component of a relatively small amplitude, which at the same time may differ from a rather large constant component. In this case, on the screen of an oscilloscope with a closed input, there may be a situation where you will not see anything except the alternating voltage component.

Selecting voltage divider resistors

Due to the fact that quite often modern radio amateurs experience certain difficulties in finding precision resistors, it often happens that they have to use standard devices of wide application, which will need to be adjusted with maximum accuracy, since otherwise it is impossible to make an oscilloscope from a computer will come out.

In most cases, high-precision resistors are several times more expensive than conventional ones. Moreover, today they are most often sold in 100 pieces at a time, and therefore their purchase cannot always be called advisable.

Trimmers

In this case, each arm of the divider is made up of two resistors, one of which is constant, while the second is tuning. The disadvantage of this option is its bulkiness, however, the accuracy is limited only by what available parameters the measuring device has.

Selecting resistors

The second option to make a computer act as an oscilloscope is to select pairs of resistors. Accuracy in this case is ensured by using pairs of resistors from two sets with a fairly large spread. The important thing here is to initially make a thorough measurement of all devices, and then select pairs whose sum of resistances is most appropriate for the circuit you are running.

It is worth noting that this particular method was used on an industrial scale in order to adjust the divider resistors for the legendary TL-4 device. Before you make an oscilloscope from a computer with your own hands, you need to study the possible disadvantages of such a device. First of all, we can note the labor intensity, as well as the need to use large quantity resistors. After all, the longer the list of devices you use, the higher the final accuracy of the measurements will be.

Fitting resistors

It is worth noting that adjusting resistors by removing part of the film is sometimes used today even in modern industry, that is, an oscilloscope is often made from a computer (USB or some other) in this way.

However, it is immediately worth noting that if you are going to adjust high-resistance resistors, then in this case the resistive film should in no case be cut through. The thing is that in such devices it is applied to a cylindrical surface in the shape of a spiral, so cutting must be done extremely carefully to prevent the possibility of breaking the chain.

If you are making an oscilloscope from a computer with your own hands, then in order to adjust the resistors at home, you just need to use the simplest “zero” sandpaper.

Initially, from the resistor that has a known lower resistance, you need to carefully remove the protective layer of paint.
After this, you should solder the resistor to the ends, which will be glued to the multimeter. By performing careful movements with sandpaper, the resistance of the resistor is brought to a normal value.
Now that the resistor is finally adjusted, the cut area needs to be covered with an additional layer of specialized protective varnish or glue.

At the moment, this method can be called the simplest and fastest, but at the same time it allows you to get good results, which makes it optimal for doing work at home.

What to consider?

There are several rules that must be followed in any case if you are going to carry out such work:

The computer you use must be reliably grounded.
Under no circumstances should you stick a ground wire into an outlet. It is connected through a specialized line-in connector housing to the housing system unit. In this case, regardless of whether you hit zero or phase, you will not experience a short circuit.

In other words, only a wire connecting to a resistor, which is located in the adapter circuit and has a rating of 1 megohm, can be plugged into the socket. If you try to connect a cable that connects to the case to the network, then in almost all cases this leads to the most unpleasant consequences.

If you will be using an Avangard oscilloscope, then during the calibration process you should select the voltmeter scale “12.5”. After you see the mains voltage on your screen, you will need to enter the value 311 into the calibration window. It is worth noting that the voltmeter should then show you a result of 311 mV or something close to it.

Among other things, do not forget that the voltage waveform in modern electrical networks differs from sinusoidal, since today electrical appliances are produced with switching power supplies. It is for this reason that you will need to focus not just on the visible curve, but also on its sinusoidal continuation.

An oscilloscope is a device that helps you see the dynamics of oscillations. With its help, you can diagnose various breakdowns and obtain the necessary data in radio electronics. Previously, oscilloscopes based on transistor tubes were used. These were very bulky devices that were connected exclusively to a built-in or specially designed screen.

Today, instruments for measuring basic frequency, amplitude characteristics and signal shapes are convenient, portable and more compact devices. They are often performed as a separate console connected to a computer. This maneuver allows you to remove the monitor from the package, significantly reducing the cost of the equipment.

You can see what a classic device looks like by looking at a photo of an oscilloscope in any search engine. You can also mount this device at home using inexpensive radio components and housings from other equipment for a more presentable appearance.

How can I get an oscilloscope?

Equipment can be obtained in several ways and it all depends solely on the amount of money that can be spent on purchasing equipment or parts.

Buy a ready-made device in a specialized store or order it online;
Buy a construction set, for example, sets of radio components and housings, which are sold on Chinese websites, are now widely popular;
Independently assemble a full-fledged portable device;
Mount only the attachment and probe, and organize the connection to a personal computer.

These options are listed in order of lower hardware costs. Buying a ready-made oscilloscope will cost the most, since it is an already delivered and working unit with all the necessary functions and settings, and in case of incorrect operation, you can contact the sales center.

The designer includes a diagram simple oscilloscope with your own hands, and the price is reduced by paying only the cost of radio components. In this category, it is also necessary to distinguish between models that are more expensive and simpler in terms of configuration and functionality.

Assembling the device yourself according to existing diagrams and radio components purchased at different points may not always turn out to be cheaper than purchasing a designer kit, so it is necessary to first evaluate the cost of the undertaking and its justification.

The cheapest way to get an oscilloscope is to solder only the attachment to it. Use a computer monitor for the screen, and programs for capturing and transforming the received signals can be downloaded from various sources.

Oscilloscope Designer: Model DSO138

Chinese manufacturers have always been famous for their ability to create electronics for professional needs with very limited functionality and for fairly little money.

On the one hand, such devices are not able to fully satisfy a number of needs of a person involved in radio electronics on a professional basis, however, for beginners and lovers of such “toys” it will be more than enough.

One of the popular Chinese-made models of the oscilloscope design type is considered to be the DSO138. First of all, this device has a low cost, and it comes with all the necessary parts and instructions, so there should be no questions about how to properly make an oscilloscope with your own hands, using the documentation included in the kit.

Before installation, you need to familiarize yourself with the contents of the package: board, screen, probe, all necessary radio components, assembly instructions and circuit diagram.

The work is made easier by the presence of corresponding markings on almost all the parts and the board itself, which really turns the process into assembling a children's construction set for an adult. The diagrams and instructions clearly show all the necessary data and you can figure it out even without knowing a foreign language.

The output should be a device with the following characteristics:

Input voltage: DC 9V;
Maximum input voltage: 50 Vpp (1:1 probe)
Current consumption 120 mA;
Signal bandwidth: 0-200KHz;
Sensitivity: electronic bias with vertical adjustment option 10mV/div - 5V/Div (1 - 2 - 5);
Discrete frequency: 1 Msps;
Input resistance: 1 MOhm;
Time interval: 10 µs / Div - 50s / Div (1 - 2 - 5);
Measurement accuracy: 12 bits.

Step-by-step instructions for assembling the DSO138 construction set

Should be considered in more detail detailed instructions for the manufacture of an oscilloscope of this brand, because other models are assembled in a similar way.

It is worth noting that in this model the board comes immediately with a soldered 32-bit Cortex™ microcontroller on the M3 core. It operates two 12-bit inputs with a characteristic of 1 μs and operates in a maximum frequency range of up to 72 MHz. Having this device already installed makes the task somewhat easier.

Step 1. It is most convenient to start installation with SMD components. You need to take into account the rules when working with a soldering iron and a board: do not overheat, hold for no longer than 2 seconds, do not connect different parts and tracks together, use solder paste and solder.

Step 2. Solder the capacitors, inductors and resistances: you need to insert the specified part into the space provided for it on the board, cut off the excess length of the leg and solder it on the board. The main thing is not to confuse the polarity of the capacitors and not to close adjacent tracks with a soldering iron or solder.

Step 3. We mount the remaining parts: switches and connectors, buttons, LED, quartz. Particular attention should be paid to the diode and transistor side. Quartz has metal in its structure, so you need to ensure that there is no direct contact of its surface with the board tracks or take care of the dielectric lining.

Step 4. 3 connectors are soldered to the display board. After completing manipulations with the soldering iron, you need to rinse the board with alcohol without auxiliary products - no cotton wool, discs or napkins.

Step 5. Dry the board and check how well the soldering was done. Before connecting the screen, you need to solder two jumpers to the board. The existing bitten-off pins of the parts will be useful for this.

Step 6. To check operation, you need to connect the device to a network with a current of 200 mA and a voltage of 9 V.

The check consists of taking indicators from:

9 V connector;
Test point 3.3 V.

If all parameters correspond to the required values, you need to disconnect the device from the power supply and install the JP4 jumper.

Step 7. You need to insert a display into the 3 available connectors. You need to connect an oscilloscope probe to the input and turn on the power yourself.

The result correct installation and the assembly will appear on the display with its number, firmware type, version and developer’s website. After a few seconds, you will be able to see sine waves and a scale when the probe is turned off.

Computer console

When assembling this simple device, you will need a minimum number of parts, knowledge and skills. The circuit diagram is very simple, except that you will need to make the board yourself to assemble the device.

The size of the attachment for a do-it-yourself oscilloscope will be approximately the size of a matchbox or a little larger, so it is best to use a plastic container or battery box of this size.

Having placed the assembled device with ready-made outputs into it, you can begin organizing work with a computer monitor. To do this, download the Oscilloscope and Soundcard Oscilloscope programs. You can test their work and choose the one you like best.

The connected microphone will also be able to relay to the connected oscillator sound waves, the program will reflect the changes. This set-top box is connected to a microphone or line input and does not require any additional drivers.

DIY oscilloscope photos

Nowadays, the use of various measuring devices based on interaction with personal computer, enough. A significant advantage of their use is the ability to store the obtained values in a sufficiently large volume in the device’s memory, with their subsequent analysis.

Digital USB oscilloscope from computer, which we describe in this article, is one of the options for such amateur radio measuring instruments. It can be used as an oscilloscope and a device for recording electrical signals in RAM and on HDD computer.

The circuit is not complicated and contains a minimum of components, resulting in a very compact device.

Main characteristics of USB oscilloscope:

ADC: 12 bits.
Time base (oscilloscope): 3…10 ms/division.
Time scale (recorder): 1…50 sec/sample.
Sensitivity (without divider): 0.3 Volts/division.
Synchronization: external, internal.
Data recording (format): ASCII, text.
Maximum input resistance: 1 MΩ in parallel with a 30 pF capacitance.

Description of the operation of an oscilloscope from a computer

To exchange data between a USB oscilloscope and a personal computer, the Universal Serial Bus (USB) interface is used. This interface operates on the basis of the FT232BM (DD2) microcircuit from Future Technology Devices. It is an interface converter. The FT232BM chip can operate both in direct BitBang bit control mode (when using the D2XX driver) and in virtual COM port mode (when using the VCP driver).

The AD7495 (DD3) integrated circuit from Analog Devices is used as an ADC. It is nothing more than a 12-bit A/D converter with an internal voltage reference and a serial interface.

The AD7495 chip also contains a frequency synthesizer that determines the speed at which information will be exchanged between the FT232BM and the AD7495. To create the necessary data exchange protocol, USB program The oscilloscope populates the USB output buffer with the individual bit values for the SCLK and CS signals as shown in the following figure:

The measurement of one cycle is determined by a series of nine hundred and sixty successive transformations. The FT232BM chip, with a frequency determined by the built-in frequency synthesizer, sends electrical signals SCLK and CS, in parallel with the transmission of conversion data on the SDATA line. The 1st full conversion period of the FT232BM ADC, which sets the sampling frequency, corresponds to the duration of the period of sending 34 bytes of data issued by the DD2 chip (16 data bits + CS line pulse). Since the speed of data transfer of the FT232BM is determined by the frequency of the internal frequency synthesizer, to modify the sweep values you only need to change the values of the frequency synthesizer of the FT232BM chip.

The data received by the personal computer, after some processing (change of scale, zero adjustment) is displayed on the monitor screen in graphical form.

The signal under study is supplied to connector XS2. The OP747 operational amplifier is designed to match the input signals with the rest USB circuit oscilloscope.

On modules DA1.2 and DA1.3, a circuit is built to shift the bipolar input signal to the positive voltage zone. Since the internal reference voltage of the DD3 chip has a voltage of 2.5 volts, without using dividers, the input voltage coverage is -1.25..+1.25 V.

To be able to study signals with negative polarity, with virtually unipolar power supply from the USB connector (a), a voltage converter DD1 is used, which generates a voltage of negative polarity to power the op-amp OP747. To protect the analog part of the oscilloscope from interference, components R5, L1, L2, C3, C7-C11 are used.

The uScpoe program is designed to display information on a computer monitor screen. Using this program, it becomes possible to visually evaluate the magnitude of the signal under study, as well as its shape in the form of an oscillogram.

The ms/div buttons are used to control the sweep of the oscilloscope. In the program, you can save the oscillogram and data to a file using the corresponding menu items. To virtually turn the oscilloscope on and off, use Power buttons ON/OF. When you disconnect the oscilloscope circuit from the computer, the uScpoe program is automatically switched to OFF mode.

In electrical signal recording mode (recorder), the program creates text file, whose name can be set in the following path: File->Choice data file. the data.txt file is initially generated. The files can then be imported into other applications (Excel, MathCAD) for further processing.

(3.0 Mb, downloaded: 5,421)

On the website http://www.semifluid.com I found a very simple solution for creating a digital computer oscilloscope. The device is based on an eight-bit PIC12F675 processor.

The processor operates at a frequency of 20 MHz. The microcontroller continuously measures the input voltage, converts it, and sends a digital value to the computer's serial port. The serial port baud rate is 115 kBit and, as shown in the following figure, data is scanned and sent at a rate of about 7.5 kHz (134 µs).

Device diagram

The basis of the circuit is the PIC12F675 microcontroller (U2 chip) which works with clock frequency 20 MHz crystal Y1. J1 is a standard power connector for connecting 9-12 V power, which is then stabilized at U1 to 5 V to power the processor.

After U2, a simple TTL level converter is added to the circuit with the RS232 serial port of a personal computer. It is built on the basis of transistor BC337 (Q1) and resistors R1 and R3. Input 5 of the microcontroller leads to switch S1. In its main position (1-2), the device switches to DC oscilloscope mode, which is capable of displaying a 0-5V input signal. In the second position - switch to AC oscilloscope mode. In this position, the maximum voltage is from -2.5 to +2.5 V. I used a 22000nF ceramic capacitor C6 to observe low frequencies without much distortion.

If necessary, you can add an additional input attenuator (splitter), or op-amp.

Software

In the original site mentioned above, a simple control program for Windows is also available. The program is written in Visual Basic.

The program starts immediately and waits for data to appear on serial port COM1. On the left, four sliders used to measure the period and voltage of the signal. Then there are on/off synchronization, fields for scaling or changing sample size values.

Installation

I didn't do it printed circuit board, and mounted everything in a small plastic box with hinged mounting. The case must have holes for the RS232 connector of the switch, input jack, power jack.

Firmware for the processor is at the end of the article. The configuration bits (fuse) must be set as follows during programming:

Photo of my finished prototype

Below you can download the source, firmware and software for windows

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
U1	Linear regulator		1		Search in Chip and Dip	To notepad
U2	MK PIC 8-bit		1	675-I/P	Search in Chip and Dip	To notepad
Q1	Bipolar transistor		1		Search in Chip and Dip	To notepad
C1, C2, C5	Capacitor	0.1 µF	3		Search in Chip and Dip	To notepad
C3, C4	Capacitor	22 pF	2		Search in Chip and Dip	To notepad
C6	Capacitor	22 µF	1		Search in Chip and Dip	To notepad
R1, R3	Resistor		2

Nowadays, there is quite a lot of use of various measuring devices based on interaction with a personal computer. A significant advantage of their use is the ability to store the obtained values in a sufficiently large volume in the device’s memory, with their subsequent analysis.

The circuit is not complicated and contains a minimum of components, resulting in a very compact device.

Main characteristics of USB oscilloscope:

ADC: 12 bits.
Time base (oscilloscope): 3…10 ms/division.
Time scale (recorder): 1…50 sec/sample.
Sensitivity (without divider): 0.3 Volts/division.
Synchronization: external, internal.
Data recording (format): ASCII, text.
Maximum input resistance: 1 MΩ in parallel with a 30 pF capacitance.

Description of the operation of an oscilloscope from a computer

The AD7495 (DD3) integrated circuit from Analog Devices is used as an ADC. It is nothing more than a 12-bit A/D converter with an internal voltage reference and a serial interface.

The AD7495 chip also contains a frequency synthesizer that determines the speed at which information will be exchanged between the FT232BM and the AD7495. To create the required communication protocol, the oscilloscope's USB software populates the USB output buffer with individual bit values for the SCLK and CS signals as shown in the following figure:

The data received by the personal computer, after some processing (change of scale, zero adjustment) is displayed on the monitor screen in graphical form.

The signal under study is supplied to connector XS2. The OP747 operational amplifier is designed to match the input signals with the rest of the oscilloscope's USB circuitry.

To be able to study signals that have negative polarity, with virtually unipolar power supply from the USB connector (a), a voltage converter DD1 is used, which generates a voltage of negative polarity to power the op-amp OP747. To protect the analog part of the oscilloscope from interference, components R5, L1, L2, C3, C7-C11 are used.

The ms/div buttons are used to control the sweep of the oscilloscope. In the program, you can save the oscillogram and data to a file using the corresponding menu items. To virtually turn the oscilloscope on and off, use the Power ON/OF buttons. When you disconnect the oscilloscope circuit from the computer, the uScpoe program is automatically switched to OFF mode.

In electrical signal recording mode (recorder), the program creates a text file, the name of which can be specified in the following path: File->Choice data file. the data.txt file is initially generated. The files can then be imported into other applications (Excel, MathCAD) for further processing.

(3.0 Mb, downloaded: 3,610)

An oscilloscope is a very important instrument that is used in radio engineering laboratories involved in the manufacture and testing of many devices. But they can also be used in ordinary radio workshops. The main task of devices of this type is to detect and correct electronic circuits, debug their operation, and most importantly, to prevent problems in the manufacture of new circuits.

A significant drawback of oscilloscopes is their fairly high price. Therefore, not everyone can buy them. That's why the question arises, ? Although there are many known options for such manufacturing, each method involves one main element - a PC sound card. An adapter is attached to it, thanks to which the levels of the measured signals are coordinated.

Software

This device works thanks to a specific program. It transmits signals to the screen that are visualized. In this way, the measured pulses are converted. The choice of utilities is quite large, but not all of them can work consistently well.

The proven Osci program has gained the most popularity. Thanks to it, the oscilloscope works in normal mode. The program has an interface; a grid is installed on the screen, thanks to which you can measure the signal in length and amplitude. This mesh is special because it provides additional features. By choosing this program, there are a number of positive aspects that other programs cannot guarantee.

Technical data

To build an oscilloscope from a computer, you need to assemble a so-called voltage divider or attenuator. This device allows you to cover a wide range of measured voltages and protect the input port of the sound card from damage. Damage of this level occurs mainly due to high voltage.

Almost all audio cards have an input voltage of no more than 2 volts. An oscilloscope made from a computer is limited in the capabilities of the sound card. If we consider budget cards, then for them this figure remains at the level of 0.1 Hz - 20 kHz.

The voltage at its lower point is 1 mV. Such a low figure is explained by the limitation of background and noise levels. Upper voltage parameters – up to 500 volts. It is limited by the adapter parameters.

Advantages and disadvantages of oscilloscopes

No radio amateur can do without an oscilloscope. Although this device is sold at a fairly high price. But at the same time, it has both advantages and a number of disadvantages.

The main advantage of an oscilloscope created with your own hands from a computer is its low price. That is, you will have to spend very little money on its re-equipment. But there are several disadvantages:
1. High sensitivity. The device responds to even low-level interference. This leads to large errors.
2. Sound signal amplitude up to 2V. Entrance sound card unable to withstand a higher rate. Therefore, the sound card can fail quite quickly. However, this can be avoided.
3. Failure to continuously measure voltage. This, in fact, is not a significant drawback.

Creating an Oscilloscope

Since some oscilloscopes do not allow a signal higher than 2V, and for some it does not exceed 1V, you need to try to eliminate this problem, since such an amplitude is clearly not enough. The solution to the problem lies in increasing the limits that the adapter can handle. A modern program that ensures the operation of an oscilloscope allows one to achieve such measurement limits - 12.5 and 250 Volts.

If a signal whose amplitude is 250 Volts is not needed, then you can make an adapter with two channels. To do this, a protection is installed that controls the operation of the device, that is, it does not allow erroneous switching on if the voltage is quite high.

To reduce the influence of external noise on the oscilloscope from the computer, it is necessary to place the board in a housing made of metal. Afterwards, a common wire is connected to this housing.

The process of setting up the sound card is accompanied by turning off the microphone gain. To do this, the volume on it is set to average or below average. Once all the work is done, you can start measuring the secondary processing pulses of the transformer. If everything is done correctly, then it will be able to display oscillograms of even the most low frequencies. Thanks to installed program it will be possible to easily determine the signal frequency level.

It’s quite easy to make a modern device from a computer. The oscilloscope will produce waveforms that will help in work and experiments carried out in radio engineering and home laboratories.

Below is a project of a USB oscilloscope that you can assemble with your own hands. The capabilities of the USB oscilloscope are minimal, but for many amateur radio tasks it will do just fine. Also, the circuit of this USB oscilloscope can be used as a basis for building more serious circuits. The circuit is based on an Atmel Tiny45 microcontroller.

The oscilloscope has two analog inputs and is powered by a USB interface. One input is activated via a potentiometer, which allows you to reduce the input signal level.

The software for the tiny45 microcontroller is written in C and compiled using V-USB developed by Obdev, which implements HID devices on the microcontroller side.
The circuit does not use external quartz, but uses the USB frequency of 16.5 MHz in software. Naturally, you should not expect 1Gs/s sampling from this scheme.

The oscilloscope operates via USB via HID mode, which does not require the installation of any special drivers. Windows software is written using .NET C#. Using my program source code as a basis, you can expand the software as you need.

The circuit diagram of a USB oscilloscope is very simple!

List of used radioelements:
1 LED (any)
1 LED resistor, 220 to 470 ohms
2 x 68 Ohm resistors for USB D+ & D-lines
1 x 1.5K resistor for USB device detection
2 3.6V Zener diodes for USB level equalization
2 capacitors 100nF and 47uF
2 filter capacitors on analog inputs (from 10nF to 470nF), it is possible without them
1 or 2 potentiometers on analog inputs, to reduce the input voltage level (if necessary)
1 USB port
1 Atmel Tiny45-20 microcontroller.

List of radioelements

Designation	Type	Quantity	Shop	My notepad
R1, R5	Resistor	2	Search in Chip and Dip	To notepad
R2	Resistor	1	Search in Chip and Dip	To notepad
R3	Resistor	1

An oscilloscope is one of the key instruments in any radio engineering laboratory for industrial use, as well as in an ordinary radio workshop. With the help of such a device you can detect malfunctions electronic circuits, as well as debugging their operation when designing new devices. However, the price of this kind of devices is very high, and not every radio amateur can afford to purchase such a thing. This article is devoted to the question of how to make it. There are many ways to make such a device, but the basis is the same everywhere: a PC sound card serves as the board that will receive pulses, and a special adapter is attached to it. It serves to match the levels of the measured signals and the input of the computer audio card.

Oscilloscope on a computer: software

One of the main elements of the mentioned device is a program that visualizes the measured pulses on the monitor. There is a huge selection of such software, but not all utilities work stably. The Osci oscilloscope program from the AudioTester kit is especially popular among radio amateurs. It has an interface that looks similar to a standard analog device; there is a grid on the screen that allows you to measure the duration and amplitude of the signal. It is easy to use and has a number of additional functions, which programs of this type do not have. But every radio amateur will be able to choose the software that he likes best for work.

Technical data

So, in order to make an oscilloscope from a computer, you need to assemble a special attenuator (voltage divider) that can cover the widest possible range of the measured voltage. The second function of such an adapter is to protect the input port of the sound card from damage that can be caused by high voltage levels. For most audio cards, the input voltage is limited to 1-2 volts. An oscilloscope from a computer is limited by the capabilities of the sound card. For budget cards it ranges from 0.1Hz to 20kHz (sinusoidal signal). The lower voltage limit that can be measured is limited by the level of background and noise and is 1 mV, and the upper limit is limited by the adapter parameters and can be several hundred volts.

Voltage divider device

An oscilloscope from a computer is very simple electrical diagram. It contains only two zener diodes and three depend on the virtual oscilloscope scale used. This divider is designed for three different scales, with ratios of 1:1, 1:20 and 1:100. Accordingly, the device will have three inputs, each of which is connected to a resistor. The nominal resistance of the direct input resistor is 1 MΩ. The common wire is connected through the reverse connection of two zener diodes. They are designed to protect the sound card from overvoltage when the switch is in the "direct input" position. Capacitors can be connected in parallel to the resistors; they will equalize the amplitude-frequency component of the device.

Conclusion

This computer-oscilloscope is not elegant, but a simple circuit design will allow you to achieve a wide range of measured voltages. The mentioned device will help in repairing audio equipment or can be used as a training measuring device.