Frequency divider circuit 10 for an oscilloscope. How to make a digital oscilloscope from a computer with your own hands? Wideband frequency using a separate gadget

An oscilloscope is a tool that almost every radio amateur has. But for beginners it is too expensive.

The problem of high cost is easily solved: there are many options for making an oscilloscope.

The computer is perfect for such a modification, and its functionality and appearance will not be affected in any way.

Device and purpose

The circuit diagram of an oscilloscope is difficult for a novice radio amateur to understand, so it should not be considered as a whole, but first broken down into separate blocks:

Each block represents a separate microcircuit or board.

The signal from the device under test is supplied through the Y input to the input divider, which sets the sensitivity of the measuring circuit. After passing preamp and the delay line it goes to the final amplifier, which controls the vertical deflection of the indicator beam. The higher the signal level, the more the beam is deflected. This is how the vertical deflection channel is designed.

The second channel is horizontal deflection, needed to synchronize the beam with the signal. It allows you to keep the beam in the place specified by the settings.

Without synchronization, the beam will float off the screen.

Synchronization happens three types: from an external source, from the network and from the signal being studied. If the signal has a constant frequency, then it is better to use synchronization from it. The external source is usually a laboratory signal generator. Instead, a smartphone with a special application installed on it is suitable for these purposes, which modulates the pulse signal and outputs it to the headphone jack.

Oscilloscopes are used in the repair, design and configuration of various electronic devices. This includes car system diagnostics, troubleshooting V household appliances and much more.

The oscilloscope measures:

• Signal level.
• Its shape.
• Pulse rise rate.
• Amplitude.

It also allows you to sweep a signal down to thousandths of a second and view it in great detail.

Most oscilloscopes have a built-in frequency counter.

Oscilloscope connected via USB

There are many manufacturing options homemade USB oscilloscopes, but not all of them are accessible to beginners. The most simple option It will be assembled from ready-made components. They are sold in radio stores. A cheaper option would be to buy these radio components in Chinese online stores, but you need to remember that components purchased in China may arrive in a faulty condition, and money for them is not always returned. After assembly, you should get a small set-top box that connects to a PC.

This version of the oscilloscope has the highest accuracy. If the problem arises of which oscilloscope to choose for repairing laptops and other complex equipment, it is better to opt for it.

For production you will need:

• Board with separated tracks.
• Processor CY7C68013A.
• AD9288−40BRSZ analog-to-digital converter chip.
• Capacitors, resistors, chokes and transistors. The values ​​of these elements are indicated on the circuit diagram.
• Soldering gun for sealing SMD components.
• Wire in varnish insulation with a cross-section of 0.1 mm².
• Toroidal core for winding a transformer.
• A piece of fiberglass.
• Soldering iron with a grounded tip.
• Solder.
• Flux.
• Solder paste.
• Memory chip EEPROM flash 24LC64.
• Frame.
• USB connector.
• Socket for connecting probes.
• Relay TX-4.5 or other, with a control voltage of no more than 3.3 V.
• 2 AD8065 operational amplifiers.
• DC-DC converter.

You need to collect according to this scheme:

Usually for making printed circuit boards Radio amateurs use the etching method. But you won’t be able to make a double-sided printed circuit board with complex layout in this way yourself, so you need to order it in advance from a factory that produces such boards.

To do this, you need to send a drawing of the board to the factory, according to which it will be manufactured. The same factory makes boards of different quality. It depends on the options selected when placing your order.

In order to get a good payment in the end, you need to indicate in the order the following conditions:

• The thickness of fiberglass is at least 1.5 mm.
• The thickness of copper foil is at least 1 OZ.
• Through metallization of holes.
• Tinning of contact pads with lead-containing solder.

After receiving the finished board and purchasing all the radio components, you can begin assembling the oscilloscope.

The first to assemble is a DC-DC converter that produces voltages of +5 and -5 volts.

It needs to be assembled on a separate board and connected to the main one. using shielded cable.

Solder the microcircuits to the main board carefully, without overheating them. The temperature of the soldering iron should not be higher than three hundred degrees, otherwise the soldered parts will fail.

After installing all components, assemble the device into a suitable-sized housing and connect it to computer USB cable. Close jumper JP1.

You need to install and launch the Cypress Suite program on your PC, go to the EZ Console tab and click on LG EEPROM. In the window that appears, select the firmware file and press Enter. Wait for the message Done to appear, indicating the successful completion of the process. If the message Error appears instead, it means that an error occurred at some stage. You need to restart the flasher and try again.

After flashing the firmware, your self-made digital oscilloscope will be completely ready for use.

Self-powered option

At home, radio amateurs usually use stationary devices. But sometimes a situation arises when you need to repair something located far from home. In this case, you will need a portable, self-powered oscilloscope.

Before starting assembly, prepare the following components:

• Unnecessary bluetooth headphones or audio module.
• Android tablet or smartphone.
• Lithium-ion battery size 18650.
• Holder for him.
• Charge controller.
• Jack 2.1 x 5.5 mm.
• Connector for connecting test leads.
• The probes themselves.
• Switch.
• Plastic shoe sponge box.
• Shielded wire with a cross section of 0.1 mm².
• Tact button.
• Hot melt adhesive.

Needs to be disassembled wireless headset and remove the control board from it. Unsolder the microphone, power button and battery from it. Set the board aside.

Instead of Bluetooth headphones, you can use a Bluetooth audio module.

Use a knife to scrape off the remaining sponge from the box and clean it well using detergents. Wait until it dries and cut out holes for the button, switch and connectors.

Solder the wires to the sockets, holder, button and switch. Place them in place and secure with hot glue.

The wires must be connected as follows shown in the diagram:

Explanation of symbols:

1. Holder.
2. Switch.
3. Contacts “BAT + and “BAT -”.
4. Charge controller.
5. Contacts “IN + and “IN -”.
6. Jack 2.1 x 5.5 mm connector.
7. Contacts “OUT+ and “OUT -”.
8. Battery contacts.
9. Control board.
10. Power button contacts.
11. Tact button.
12. Probe socket.
13. Microphone contacts.

Then download the virtual oscilloscope application from the play market and install it on your smartphone. Turn on the Bluetooth module and synchronize it with your smartphone. Connect the probes to the oscilloscope and open its software on your phone.

When you touch the signal source with the probes, a curve showing the signal level will appear on the screen of your Android device. If it doesn't appear, it means a mistake was made somewhere.

You should check the correct connection and serviceability of the internal components. If everything is ok, you need to try to start the oscilloscope again.

Installation in the monitor case

This version of a homemade oscilloscope is easily installed in the housing of a desktop LCD monitor. This solution allows you to save some space on your desktop.

For assembly you will need:

• Computer LCD monitor.
• DC-DC inverter.
• Motherboard from a phone or tablet with HDMI output.
• USB connector.
• A piece of HDMI cable.
• Wire with a cross section of 0.1 mm².
• Tact button.
• 1 kOhm resistor.
• Double sided tape.

Every radio amateur can build an oscilloscope into a monitor with his own hands. First you need to remove it from the monitor back cover and find a place to install motherboard. Once you have decided on the location, next to it you need to cut holes in the case for the button and USB connector.

The second end of the cable must be soldered to the board from the tablet. Before soldering each wire, test it with a multimeter. This will help you avoid confusing the order in which they are connected.

Next step You need to remove the power button and micro USB connector from the tablet board. Solder wires to the clock button and USB socket and secure them in the cut holes.

Then connect all the wires as shown in the figure and solder them:

Place a jumper between the GND and ID contacts in the micro USB connector. This is needed for translation USB port to OTG mode.

You need to glue the inverter and the motherboard from the tablet with double-sided tape, and then snap the monitor cover.

Connect to USB port mouse and press the power button. While the device is booting up, turn on the Bluetooth transmitter. Then you need synchronize it with the receiver. You can open the oscilloscope application and verify the functionality of the assembled device.

Instead of a monitor, an old LCD TV that does not have a Smart TV is also perfect. The tablet's hardware surpasses many Smart TV systems in its capabilities. You should not limit its use to just an oscilloscope.

Manufacturing from an audio card

An oscilloscope assembled from an external audio adapter will cost only 1.5-2 dollars and will take a minimum of time to manufacture. In size it will be no larger than a regular flash drive, and in terms of functionality it will not be inferior to its larger brother.

Required parts:

• USB audio adapter.
• 120 kOhm resistor.
• Mini Jack 3.5 mm plug.
• Test leads.

You need to disassemble the audio adapter; to do this, you need to pry the housing halves open and separate them.

Remove capacitor C6 and solder a resistor in its place. Then install the board back into the case and reassemble it.

You should cut off the standard plug from the probes and solder a mini-jack in its place. Connect the probes to the audio input of the audio adapter.

Then you need to download the corresponding archive and unpack it. Insert the card into the USB connector.

The simplest thing left is to go to Device Manager and in the “Audio, game and video devices” tab, find the connected USB audio adapter. Click on it right click mouse and select “Update Driver”.

Then move the files miniscope.exe, miniscope.ini and miniscope.log from the archive to a separate folder. Run "miniscope.exe".

Before use, the program must be configured. Required settings shown in the screenshots:

If you touch the signal source with the probes, a curve should appear in the oscilloscope window:

So to turn audio adapter for oscilloscope, you need to put in a minimum of effort. But it is worth remembering that the error of such an oscilloscope is 1-3%, which is clearly not enough to work with complex electronics. It is perfect for a beginner radio amateur, but craftsmen and engineers should take a closer look at other, more accurate oscilloscopes.

Recently I already reviewed one construction kit, today is a continuation of a small series of reviews about all sorts of homemade things for beginner radio amateurs.
I’ll say right away that this is certainly not Tectronics, or even DS203, but it’s an interesting thing in its own way, even though it’s essentially a toy.
Usually, before testing, the thing is first disassembled, here you have to assemble it first :)

In my opinion, these are the “eyes” of a radio amateur. This device rarely has high accuracy, unlike a multimeter, but it allows you to see processes in dynamics, i.e. in move".
Sometimes such a second “look” can help more than a day of fiddling with the tester.

Previously, oscilloscopes were tube oscilloscopes, then they were replaced by transistor ones, but the result was still displayed on the CRT screen. Over time, they were replaced by their digital counterparts, small, light, and the logical continuation was the appearance of a designer for assembling such a device.
Several years ago, on some forums, I came across attempts (sometimes successful) to develop a homemade oscilloscope. The constructor is of course simpler than them and weaker in technical specifications, but I can say with confidence that even a schoolchild can assemble it.
This construction set was developed by jyetech. of this device on the manufacturer's website.

Perhaps this review will seem overly detailed to specialists, but the practice of communicating with novice radio amateurs has shown that they perceive information better this way.

In general, I’ll tell you about everything a little below, but for now the standard introduction, unpacking.

They sent the construction set in a regular zip-lock bag, although quite thick.
In my opinion, such a set would really benefit from some nice packaging. Not for the purpose of protection from damage, but for the purpose of external aesthetics. After all, the thing should be pleasant even at the unpacking stage, because it is a construction set.

The package contained:
Instructions
Printed circuit board
Cable for connecting to measured circuits
Two bags of ingredients
Display.

The technical characteristics of the device are very modest, as for me it is more of a training set than a measuring device, although even with the help of this device it is possible to carry out measurements, albeit simple ones.

The kit also includes detailed color instructions on two sheets.
The instructions describe the sequence of assembly, calibration and quick guide by use.
The only negative is that it’s all in English, but the pictures are made clearly, so even in this version most of it will be understandable.
The instructions even indicate the positional positions of the elements and make “checkboxes” where you need to put a tick after completing a certain stage. Very thoughtful.

There is a separate sheet of paper with a list of SMD components.
It is worth noting that there are at least two variants of the device. On the first, only the microcontroller is initially wired, on the second, all SMD components.
The first option is designed for slightly more experienced users.
This is the option that is included in my review; I learned about the existence of the second option later.

The printed circuit board is double-sided, as in the previous review, even the color is the same.
On top there is a mask with the designation of the elements, one part of the elements is fully designated, the second has only a position number according to the diagram.

There are no markings on the reverse side, there is only a designation of jumpers and the name of the device model.
The board is covered with a mask, and the mask is very durable (I had to check it involuntarily), in my opinion, what is needed specifically for beginners, since it is difficult to damage anything during the assembly process.

As I wrote above, the designations of the installed elements are marked on the board, the markings are clear, there are no complaints about this item.

All contacts are tinning, the board is soldered very easily, well, almost easily, more on this nuance in the assembly section :)

As I wrote above, a microcontroller is preinstalled on the board
This is a 32-bit microcontroller based on the ARM 32-bit Cortex™-M3 core.
The maximum operating frequency is 72 MHz, and it also has 2 x 12-bit, 1 μs ADC.

On both sides of the board its model is indicated, DSO138.

Let's return to the list of components.
Small radio components, connectors, etc. Packed in small snap bags.

Pour the contents of a large bag onto the table. Inside there are connectors, stands and electrolytic capacitors. Also in the package there are two more small bags :)

Having opened all the packages, we see quite a lot of radio components. Although, given that this is a digital oscilloscope, I expected more.
It’s nice that the SMD resistors are labeled, although in my opinion, it wouldn’t hurt to label regular resistors as well, or provide a small color-coding guide in the kit.

The display is packed in soft material; as it turned out, it does not slip, so it will not dangle in the bag, and the printed circuit board protects it from damage during transportation.
But still, I think that normal packaging would not hurt.

The device uses a 2.4-inch TFT LCD indicator with LED backlight.
Screen resolution 320x240 pixels.

A small cable is also included. To connect to the oscilloscope, a standard BNC connector is used; at the other end of the cable there is a pair of alligator clips.
The cable is medium soft, the crocodiles are quite large.

Well, here’s a view of the entire set completely unfolded.

Now you can move on to the actual assembly of this constructor, and at the same time try to figure out how difficult it is.

Last time I started the assembly with resistors, as the lowest elements on the board.
If you have SMD components, it is better to start assembly with them.
To do this, I laid out all the SMD components on the attached sheet, indicating their nominal value and position designation on the diagram.

When I was ready to solder, I thought that the elements were in a case that was too small for a beginner; it would have been possible to use resistors of size 1206 instead of 0805. The difference in the space taken up is insignificant, but soldering is easier.
The second thought was - now I’ll lose the resistor and won’t find it. Okay, I’ll open the table and take out a second such resistor, but not everyone has such a choice. In this case, the manufacturer took care of this.
I gave all the resistors (it’s a pity that they weren’t microcircuits) by one more, i.e. in reserve, very prudently, offset.

Next I’ll talk a little about how I solder such components, and how I advise others to do it, but this is just my opinion, of course, everyone can do it in their own way.
Sometimes SMD components are soldered using a special paste, but it is not often that a beginning radio amateur (and even a non-beginner) has it, so I will show you how easier it is to work without it.
We take the component with tweezers and apply it to the installation site.

In general, I often first coat the installation site of the component with flux; this makes soldering easier, but complicates cleaning the board; it can sometimes be difficult to wash the flux out from under the component.
Therefore, in this case I simply used 1mm tubular solder with flux.
Holding the component with tweezers, place a drop of solder on the soldering iron tip and solder one side of the component.
It’s not scary if the soldering turns out to be ugly or not very strong, but at this stage It is enough that the component holds itself.
Then we repeat the operation with the remaining components.
After we have secured all the components in this way (or all components of the same denomination), we can safely solder them as needed; to do this, we turn the board so that the already soldered side is on the left and hold the soldering iron in your right hand (if you are right-handed), and the solder in with the left, we go through all the unsoldered places. If the soldering of the second side is not satisfactory, then rotate the board 180 degrees and similarly solder the other side of the component.
This makes it easier and faster than soldering each component individually.

Here in the photo you can see several installed resistors, but so far soldered only on one side.

Microcircuits in an SMD package are marked in the same way as in a regular one, on the left near the mark (although usually on the bottom left when looking at the marking) there is the first contact, the rest are counted counterclockwise.
The photo shows the location for installing the microcircuit and an example of how it should be installed.

We proceed with microcircuits in a completely similar way to the example with resistors.
We place the microcircuit on the pads, solder any one pin (preferably the outermost one), slightly adjust the position of the microcircuit (if necessary) and solder the remaining contacts.
You can do different things with the stabilizer microcircuit, but I advise you to solder the petal first, and then the contact pads, then the microcircuit will definitely lie flat on the board.
But no one forbids soldering the outermost pin first, and then all the others.

All SMD components are installed and soldered, there are a few resistors left, one of each value, put them in a bag, maybe they will come in handy someday.

Let's move on to installing conventional resistors.
In the last review I talked a little about color coding. This time I would rather advise you to simply measure the resistance of the resistors using a multimeter.
The fact is that the resistors are very small, and with such sizes the color marking is very difficult to read (the smaller the area of ​​​​the painted area, the more difficult it is to determine the color).
Initially, I looked for a list of denominations and positional designations in the instructions, but I couldn’t find them, because I was looking for them in the form of a plate, and after installation it turned out that they were in the pictures, with checkboxes for marking the established positions.
Because of my carelessness, I had to make my own plate, on which I laid out the installed components next to each other.
On the left you can see the resistor separately; when compiling the plate it was superfluous, so I left it at the end.

We proceed with resistors in a similar way as in the previous review; we shape the terminals using tweezers (or a special mandrel) so that the resistor easily falls into place.
Be careful, the positional designations of components on the board can be not only labeled, but also SIGNED, and this can play a cruel joke on you, especially if there are many components in one row on the board.

This is where a small minus of the printed circuit board came out.
The fact is that the holes for the resistors have a very large diameter, and since the installation is relatively tight, I decided to bend the leads, but not too much, and therefore they do not hold very well in such holes.

Due to the fact that the resistors did not hold up very well, I recommend not filling in all the values ​​at once, but installing half or a third, then soldering them and installing the rest.
Don’t be afraid to bite the pins too much, a double-sided board with metallization forgives such things, you can always solder a resistor even on top, which you can’t do with a single-sided printed circuit board.

That's it, the resistors are sealed, let's move on to the capacitors.
I treated them the same way as resistors, laying them out according to the plate.
By the way, I still have one extra resistor left, apparently they put it in by accident.

A few words about labeling.
Such capacitors are marked in the same way as resistors.
The first two digits are the number, the third digit is the number of zeros after the number.
The resulting result is equal to the capacitance in picofarads.
But there are capacitors on this board that do not fall under this marking; these are values ​​of 1, 3 and 22pF.
They are marked simply by indicating the capacitance since the capacitance is less than 100pF, i.e. less than three digits.

First, I solder the small capacitors according to the positional designations (that’s a quest).

With capacitors with a capacity of 100nF, I stepped a little, without adding them to the plate right away, I had to do it later by hand.

I also did not bend the leads of the capacitors completely, but at about 45 degrees, this is quite enough to prevent the component from falling out.
By the way, in this photo you can see that the spots connected to the common contact of the board are made correctly, there is an annular gap to reduce heat transfer, this makes it easier to solder such places.

Somehow I relaxed a little on this board and remembered about the chokes and diodes after soldering the ceramic capacitors, although it would have been better to solder them in front of them.
But this didn’t really change the situation, so let’s move on to them.
The board was supplied with three chokes and two diodes (1N4007 and 1N5815).

Everything is clear with the diodes, the location is labeled, the cathode is marked with a white stripe on the diode itself and on the board, it is very difficult to confuse.
With chokes it can be a little more complicated, they are sometimes also color coded, fortunately in this case all three chokes have the same rating :)

On the board, the chokes are indicated by the letter L and a wavy line.
The photo shows a section of the board with sealed chokes and diodes.

The oscilloscope uses two transistors of different conductivity and two stabilizer microcircuits with different polarities. In this regard, be careful when installing, since the designation 78L05 is very similar to 79L05, but if you put it the other way around, you will most likely go for new ones.
With transistors it is a little simpler, although the board simply shows the conductivity without indicating the type of transistor, but the type of transistor and its position designation can be easily seen from the diagram or component installation map.
The terminals here are noticeably more difficult to mold, since all three terminals need to be molded; it is better not to rush, so as not to break off the terminals.

The conclusions are formed in the same way, this simplifies the task.
The position of the transistors and stabilizers is indicated on the board, but just in case, I took a photo of how they should be installed.

The kit included a powerful (relatively) inductor, which is used in the converter to obtain negative polarity, and a quartz resonator.
They don’t need to draw conclusions.

Now about the quartz resonator, it is made for a frequency of 8 MHz, it also has no polarity, but it is better to put a piece of tape under it, since its body is metal and it lies on the tracks. The board was covered with a protective mask, but I’m somehow used to making some kind of backing in such cases, for safety.
Don’t be surprised that at the beginning I indicated that the processor has a maximum frequency of 72 MHz, and the quartz costs only 8, inside the processor there are both frequency dividers and sometimes multipliers, so the core can easily operate, for example, at a frequency of 8x8 = 64 MHz.
For some reason, the inductor contacts on the board are square and round in shape, although the inductor itself is a non-polar element, so we simply solder it in place; it is better not to bend the leads.

The kit included quite a few electrolytic capacitors, they all have the same capacitance of 100 μF and a voltage of 16 Volts.
They must be soldered with correct polarity, otherwise pyrotechnic effects are possible :)
The long lead of the capacitor is the positive contact. The board has polarity markings both near the corresponding pin and next to the circle marking the position of the capacitor, which is quite convenient.
The positive output is marked. Sometimes they mark it as negative, in which case approximately half of the circle is shaded. And then there is a computer hardware manufacturer like Asus, which shades the positive side, so you always have to be careful.

Little by little we came to a rather rare component, the trimmer capacitor.
This is a capacitor whose capacitance can be changed within small limits, for example 10-30pF, usually the capacitance of these capacitors is small, up to 40-50pF.
In general, this is a non-polar element, i.e. Formally, it doesn’t matter how you solder it, but sometimes it matters how you solder it.
The capacitor contains a screwdriver slot (like the head of a small screw) that has an electrical connection to one of the terminals. SO in this circuit, one terminal of the capacitor is connected to the common conductor of the board, and the second to the remaining elements.
To reduce the influence of the screwdriver on the circuit parameters, it is necessary to solder it so that the pin connected to the slot is connected to the common wire of the board.
The board is marked on how to solder it, and later in the review there will be a photo where you can see this.

Buttons and switches.
Well, it’s hard to do something wrong here, since it’s very difficult to insert them somehow :)
I can only say that the terminals of the switch body must be soldered to the board.
In the case of a switch, this will not only add strength, but will also connect the switch body to the common contact of the board and the switch body will act as a shield from interference.

Connectors.
The most difficult part in terms of soldering. It is difficult not because of the accuracy or small size of the component, but on the contrary, sometimes it is difficult to warm up the soldering area, so for the BNC connector it is better to take a more powerful soldering iron.

In the photo you can see -
Soldering a BNC connector, an additional power connector (the only connector here that can be installed in reverse) and a USB connector.

There was a slight problem with the indicator, or rather with the connectors for connecting it.
They forgot to include a pair double contacts(pins), they are used here to secure the side of the indicator opposite the signal connector.

But after looking at the pinout of the signal connector, I realized that some contacts could easily be bitten off and used instead of the missing ones.
I could open the desk drawer and take out such a connector from there, but it would be uninteresting and to some extent dishonest.

We solder the socket (so-called female) parts of the connectors onto the board.

The board has an output of a built-in 1KHz generator, we will need it later, although these two contacts are connected to each other, we still solder in a jumper, it will be convenient for connecting the “crocodile” signal cable.
It is convenient to use a bitten pin for a jumper electrolytic capacitor, they are long and quite tough.
This jumper is located to the left of the power connector.

There are also a couple of important jumpers on the board.
One of them, called JP3 it must be short-circuited immediately, this is done with a drop of solder.

With the second jumper, it’s a little more complicated.
First you need to connect the multimeter in voltage measurement mode at the test point located above the petal of the stabilizer chip. The second probe is connected to any contact connected to the common contact of the board, for example to a USB connector.
Power is supplied to the board and the voltage at the test point is checked, if everything is in order, then there should be about 3.3 Volts.

After this jumper JP4, located slightly to the left and below the stabilizer, is also connected using a drop of solder.

There are four more jumpers on the back of the board; you don’t need to touch them; these are technological jumpers for diagnosing the board and switching the processor to firmware mode.

Let's return to the display. As I wrote above, I had to bite off several contact pairs in order to use them to replace the missing ones.
But when assembling, I decided not to bite out the outer pairs, but from the middle, as it were, and solder the outer one in place, so it would be more difficult to confuse something during installation.

Although there is a protective film on the display, I would recommend covering the screen with a piece of paper when soldering the connector, in which case drops of flux that boils during soldering will fly off onto the paper and not onto the screen.

That's it, you can apply power and check :)
By the way, one of the diodes that we soldered earlier serves to protect the electronics from incorrect power connections; on the part of the developer, this is a useful step, since the board can be burned with the wrong polarity in a second.
The board indicates a power supply of 9 Volts, but a range of up to 12 Volts is specified.
In the tests, I powered the board from a 12 Volt power supply, but I also tried from two series-connected lithium batteries, the difference was only in a slightly lower brightness of the screen backlight, I think that by using a 5 Volt stabilizer with a low drop and removing the protective diode (or connecting it in parallel with the power supply and installing a fuse), you can quite easily power the board from two lithium batteries.
Alternatively, use a 3.7-5 Volt power converter.

Since the startup of the board was successful, it is better to wash the board before setting it up.
I use acetone, although it is prohibited for sale, but there are small reserves; as an option, we also used toluene, or, in extreme cases, medical alcohol.
But the board must be washed, you don’t need to “bathe” it entirely, just go over it from below with a cotton swab.

At the end, we put the board “on its feet” using the supplied stands; of course, they are a little smaller than necessary and dangle a little, but it’s still more convenient than just putting it on the table, not to mention the fact that the pins of the parts can scratch the table top, and so on. this way nothing gets under the board and shorts out anything underneath it.

The first test is from the built-in generator, for this we connect the crocodile with a red insulator to the jumper near the power connector; there is no need to connect the black wire anywhere.

I almost forgot, a few words about the purpose of switches and buttons.
On the left are three three-position switches.
The top one switches the input operating mode.
Grounded
Operating mode without taking into account the constant component, or AC, or operating mode with a closed input. Well suited for AC current measurements.
Operating mode with the ability to measure direct current, or operating mode with an open input. Allows measurements taking into account the constant voltage component.

The second and third switches allow you to select the scale along the voltage axis.
If 1 Volt is selected, this means that in this mode a swing of one scale cell of the screen will be equal to a voltage of 1 Volt.
At the same time, the middle switch allows you to select the voltage, and the lower multiplier, therefore, using three switches, you can select nine fixed voltage levels from 10 mV to 5 Volts per cell.

On the right are buttons for controlling scan modes and operating modes.
Description of the buttons from top to bottom.
1. When pressed briefly, it turns on the HOLD mode, i.e. recording readings on the display. when long (more than 3 seconds), turns on or off the mode of digital output of signal parameter data, frequency, period, voltage.
2. Button to increase the selected parameter
3. Button to decrease the selected parameter.
4. Button to cycle through operating modes.
Sweep time control, range from 10 µs to 500 sec.
Select the operating mode of the synchronization trigger, Auto, normal and standby.
The mode of capturing the synchronization signal by a trigger, at the front or rear of the signal.
Selecting the voltage level of the synchronization trigger signal capture.
Scrolling the waveform horizontally allows you to view the signal “off the screen”
Setting the vertical position of the oscillogram helps when measuring signal voltages and when the oscillogram does not fit on the screen...
The reset button, simply rebooting the oscilloscope, as it turned out, is sometimes very convenient.
There is a green LED next to the button; it blinks when the oscilloscope has synchronized.

All modes when the device is turned off are remembered and it then turns on in the mode in which it was turned off.

There is also a USB connector on the board, but as I understand it, it is not used in this version; when connected to a computer, it displays that an unknown device has been detected.
There are also contacts for flashing the device.

All modes selected by buttons or switches are duplicated on the oscilloscope screen.

I did not update the software version, since it is the latest one at the moment 113-13801-042

Setting up the device is very simple; the built-in generator helps with this.
Most likely, when you connect to the built-in rectangular pulse generator, you will see the following picture; instead of even rectangles, there will be either a “collapse” of the top/bottom angle, down or up.

This is corrected by rotating the tuning capacitors.
There are two capacitors, in the 0.1 Volt mode we adjust C4, in the 1 Volt mode, respectively, C6. In 10mV mode no adjustment is made.

By adjusting it is necessary to achieve even rectangular pulses on the screen, as shown in the photograph.

I looked at this signal with another oscilloscope, in my opinion it is “smooth” enough to calibrate this oscilloscope.

Although the capacitors are installed correctly, even in this option there is a slight influence from the metal screwdriver, as long as we hold the tip on the adjustable element, the result is the same, as soon as you remove the tip, the result changes slightly.
In this option, either tighten it with small shifts, or use a plastic (dielectric) screwdriver.
I got such a screwdriver with some kind of Hikvision camera.

On one side it has a cross tip, cut off, specifically for such capacitors, on the other it is straight.

Since this oscilloscope is more a device for studying the principles of operation than a truly full-fledged device, I don’t see the point in conducting full testing, although I will show and check the main things.
1. I completely forgot, sometimes when working, a manufacturer’s advertisement appears at the bottom of the screen :)
2. Displays the digital values ​​of the signal parameter, a signal is supplied from the built-in rectangular pulse generator.
3. This is the intrinsic noise of the oscilloscope input; I have seen mentions of this on the Internet, as well as the fact that a new version has a lower noise level.
4. To check that this is really noise from the analog part and not interference, I switched the oscilloscope to the mode with a short-circuited input.

1. Switched the sweep time to 500 seconds per division mode, as for me, well, this is absolutely for extreme sports enthusiasts.
2. The input signal level can be changed from 10mV per cell
3. Up to 5 Volts per cell.
4. Rectangular signal with a frequency of 10 KHz from the generator of the DS203 oscilloscope.

1. Rectangular signal with a frequency of 50 KHz from the generator of the DS203 oscilloscope. It can be seen that at this frequency the signal is already highly distorted. 100KHz doesn't make much sense anymore.
2. Sinusoidal signal with a frequency of 20 KHz from the generator of the DS203 oscilloscope.
3. Triangular signal with a frequency of 20 KHz from the generator of the DS203 oscilloscope.
4. Ramp signal with a frequency of 20 KHz from the generator of the DS203 oscilloscope.

Next, I decided to look a little at how the device behaves when working with a sinusoidal signal supplied from an analog generator and compare it with my DS203
1. Frequency 1KHz
2. Frequency 10KHz

1. Frequency 100KHz, in the designer you cannot select a sweep time less than 10ms, that’s why it’s the only way :(
2. And this is what a sinusoidal signal with a frequency of 20KHz, fed from the DS203, may look like, but in a different input divider mode. Above was a screenshot of such a signal, but given in the position of the divider 1 Volt x 1, here the signal is in the 0.1 Volt x 5 mode.
Below you can see what this signal looks like when fed to the DS203

20KHz signal supplied from an analog generator.

Comparative photo of two oscilloscopes, DSO138 and DS203. Both are connected to an analog sine generator, frequency 20KHz, both oscilloscopes are set to the same operating mode.

Summary.
pros
Interesting educational design
High-quality printed circuit board, durable protective coating.
Even a novice radio amateur can assemble the set.
Well-thought-out packaging, I was pleased with the spare resistors included.
The instructions describe the assembly process well.

Minuses
Low frequency input signal.
They forgot to include a couple of contacts for attaching the indicator.
Simple packaging.

My opinion. Let me say briefly, if I had such a construction set in my childhood, I would probably be very happy, even despite its shortcomings.
Long story short, I was pleasantly surprised by the designer, I consider it a good basis for gaining experience in assembly and commissioning electronic device, and in the experience of working with a very important device for a radio amateur - an oscilloscope. It may be simple, even without memory and with a low frequency, but it is much better than fiddling with audio cards.
Of course, it cannot be considered a serious device, but it is not positioned as such, but as a designer, more than anything.
Why did I order this designer? Yes, it was just interesting, because we all love toys :)

I hope that the review was interesting and useful, I’m looking forward to suggestions regarding testing options :)
Well, as always, additional materials, firmware, instructions, sources, diagram, description -

Regardless of the class of devices, to analyze certain signals, it is necessary to bring the signals under study to the inputs of the devices. It is very rarely possible to bring their sources very close to the inputs of oscilloscopes and analyzers. They are often located at a distance of a fraction of a meter to several meters. This means that special matching devices are needed, connected between the signal sources and the inputs of the oscilloscope and analyzers.
Typically, probes are used for the following important purposes:

• remote connection oscilloscope to the object of study;
• reducing the sensitivity of vertical (sometimes horizontal) deflection channels and studying high-level signals (passive probes);
• decoupling of measuring circuits from oscilloscope units (optical probes);
• high signal attenuation and signal research in high-voltage circuits (high-voltage probes);
• increasing the input resistance and decreasing the input capacitance (compensated dividers and repeater probes);
• correction of the amplitude-frequency response of the probe-oscilloscope system;
• obtaining current oscillograms (current probes);
• selection of antiphase signals and suppression of common mode signals (differential probes);
• increasing the sensitivity of oscilloscopes (active probes);
• special purposes (for example, matching the outputs of wideband signal sources with the 50-Ohm input of an oscilloscope).

It is quite obvious that the role of probes is very important and sometimes is in no way inferior to the importance of the oscilloscopes and analyzers themselves. But, often, the role of probes is underestimated and this is a serious mistake for novice users of these devices. Below are the main types of probes and other accessories for oscilloscopes, spectrum analyzers, signal analyzers, and logic analyzers.

Probes based on compensated divider

The simplest and long-used type of probes are passive probes with a compensated voltage divider - Fig. 5.1. The voltage divider is built on resistors R1 and R2, and R2 can simply be the input resistance of the oscilloscope.

Rice. 5.1. Compensated divider circuit

Divider parameters by DC are calculated using the formulas:

For example, if R2 = 1 MOhm and R1 = 9 MOhm, then it has RВХ = 10 MOhm and KD = 1/10. Thus, the input resistance is increased by 10 times, but the voltage level supplied to the input of the oscilloscope also drops by 10 times.

In the general case (for alternating current) for the divider transmission coefficient, you can write the expression (τ1= R1C1 and τ2= C2R2):

. (5.3)

Thus, if the time constants τ1 and τ2 are equal, the transfer coefficient of the divider ceases to depend on frequency and is equal to its value at direct current. Such a divisor is called compensated. Capacitance C2 is the total capacitance of the cable, mounting, and input capacitance of the oscilloscope. In practice, to achieve the compensation condition, capacitance C1 (or C2) must be adjusted, for example, using a variable capacitor trimmer - trimmer (see Fig. 5.2.). Adjustment is performed with a special plastic screwdriver included in the probe accessory kit. It includes various tips, adapters, colored stickers and other useful little things.

Rice. 5.2. HP-9250 Standard Passive Probe Design Based on a Frequency Compensated Divider

When compensated, there is no distortion of the rectangular pulse (meander), usually created by the calibrator built into the oscilloscope (see Fig. 5.3). When the peak of the pulse decreases, undercompensation is observed, and when it rises, overcompensation is observed. The nature of the oscillograms is also shown in Fig. 3 (taken with a TDS 2024 oscilloscope with a P2200 probe). It is recommended to carry out compensation at maximum large image oscillograms of the corresponding channel.

Rice. 5.3. Oscillograms of Tektronix TDS 2024 oscilloscope calibrator pulses at different degrees of compensation (top to bottom): normal compensation, overcompensation and undercompensation

When working with a multichannel oscilloscope, you should use probes individually for each channel. To do this, they need to be marked (if this has not already been done at the factory) with stickers of different colors, usually corresponding to the colors of the oscillogram lines. If you do not adhere to this rule, then due to the inevitable variation in the input capacitances of each channel, compensation will be inaccurate.

For a 1:10 divider, resistor R1 should be equal to 9R2. This means that the capacitance C1 must be 9 times less than the input capacitance C2. The input capacitance of the divider is determined by the series connection of C1 and C2:

(5.4)

The approximate value is valid for KD»1 and C1«C2. At KD =10, the input capacitance of the divider is almost 10 times less than the input capacitance of the oscilloscope. It should be remembered that C2 includes not only the true input capacitance of the oscilloscope, but also the capacitance of C1 is increased by the amount of the mounting capacitance. Therefore, in fact, the decrease in the input capacitance of the divider compared to the input capacitance of the oscilloscope will not be so noticeable. Nevertheless, this is precisely what explains the significant reduction in distortion of pulse fronts when working with a divider.

Increasing the active component of the input resistance of the divider is not always useful, since it also leads to a change in the load on the device under test and different results are obtained in the absence of a divider and when using it. Therefore, dividers are often designed so that the input impedance of the oscilloscope remains unchanged both when working without a divider and when working with it. In this case, the divider does not increase the input impedance of the oscilloscope, but still reduces the input capacitance.

Increasing the level of the studied signals

The maximum voltage at the oscilloscope input is determined by the product of the number of divisions of its scale grid by the vertical deviation coefficient. For example, if the number of graticule divisions is 10, and the deviation factor is 5 V/div, then the total voltage swing at the input is 50 V. This is often not enough to examine signals even moderately high level- above tens of volts.

Most probes allow you to increase the maximum test voltage at direct current and low frequency from tens of V to 500-600 V. However, high frequencies reactive power (and active power, released at the loss resistance of the probe capacitors) increases sharply and it is necessary to reduce the maximum voltage at the probe input - Fig. 5.4. If you do not take this circumstance into account, you can simply burn the sample!

Rice. 5.4. Dependence of the maximum voltage at the probe input on frequency

The probe's maximum input voltage should never be exceeded at high signal frequencies. This may cause the probe to overheat and fail.

A type of passive probe is high-voltage probe. They typically have a division ratio of 1/100 or 1/1000 and an input impedance of 10 or 100 MΩ. Low-power probe divider resistors can usually withstand voltages of up to 500-600 V without breakdown. Therefore, in high-voltage probes, resistor R1 (and capacitor C1) must be made using series-connected components. This increases the size of the probe's measuring head.

A view of the Tektronix P6015A high-voltage probe is shown in Fig. 5.5. The probe has a well-insulated body with a protruding ring that prevents fingers from slipping into the circuit whose voltage waveform is being recorded. The probe can be used at voltages up to 20 kV at direct current and up to 40 kV at high duty cycle pulses. frequency range An oscilloscope with such a probe is limited to 75 MHz, which is more than enough for measurements in high-voltage circuits.

Rice. 5.5. Appearance Tektronix P6015A High Voltage Probe

When working with high-voltage probes, the greatest possible precautions must be taken. First connect the ground wire, and only then connect the probe needle to the point at which you want to obtain a voltage waveform. It is recommended to secure the probe and generally remove your hands from it when taking measurements.

High-voltage probes are available for both digital and analog oscilloscopes. For example, the HV-P30 probe is available for the unique ACK7000/8000 series wideband analog oscilloscopes with up to 50 MHz bandwidth, 1/100 split ratio, 30 kV peak-to-peak sine wave voltage, and up to 40 kV peak pulse voltage. Probe input impedance 100 MΩ, input capacitance 7 pF, cable length 4 m, BNC output connector. Another probe, the HV-P60, has a 1/2000 division ratio and can be used at maximum voltages up to 60 kV for sine wave and up to 80 kV for pulse signal. The probe's input resistance is 1000 MΩ, input capacitance is 5 pF. The seriousness of these products is eloquently demonstrated by their high price - about 66,000 and 124,000 rubles (according to the Elix company price list).

Probes with frequency response correction

Passive probes are often used to correct the frequency response of oscilloscopes. Sometimes this is a correction designed to expand the frequency band, but more often the inverse problem is solved - narrowing the frequency band to reduce the influence of noise when observing low-level signals and eliminating fast spikes on the edges of pulsed signals.
These probes (P2200) are included with the Tektronix TDS 1000B/2000B series commercial oscilloscopes. Their appearance is shown in Fig. 5.6.

The main parameters of the probes are given in table. 5.1.

Table 5.1. Basic Parameters of P2200 Passive Probes

Rice. 5.6. P2200 Passive Probe with Built-in Filter low frequencies in the voltage division switch position 1/10

From the table 5.1 clearly shows that the use of a probe with a division ratio of 1/1 is advisable only when studying low-frequency devices, when a frequency band of up to 6.5 MHz is sufficient. In all other cases, it is advisable to work with the probe at a division ratio of 1/10. In this case, the input capacitance is reduced from 110 pF to approximately 15 pF, and the frequency band is expanded from 6.5 MHz to 200 MHz. Oscillograms of a square wave with a frequency of 10 MHz, shown in Fig. 5.7, well illustrate the degree of distortion of oscillograms at division ratios of 1/10 and 1/1. In both cases, a standard probe connection with an interlocking tip and a long ground wire (10 cm) with an alligator clip was used. A square wave with a rise time of 5 ns was obtained from a Tektronix AFG 3101 generator.

Rice. 5.7. 10 MHz square wave waveforms using a 200 MHz Tektronix TDS 2024B oscilloscope with P2200 probes at 1/10 (upper waveform) and 1/1 (lower waveform) division ratios.

It is easy to notice that in both cases the oscillograms of the observed signal (and for the AFG 3101 generators at a frequency of 10 MHz it is close to ideal and has smooth peaks without a hint of “ringing”) are greatly distorted. However, the nature of the distortion is different. With a divider position of 1/10, the signal shape is close to a meander and has short-duration fronts, but is distorted by damped oscillations arising due to the inductance of a long grounding wire - Fig. 8. And in the 1/1 divider position, the damped oscillations disappeared, but a significant increase in the time constant of the probe-oscilloscope system was clearly noticeable. As a result, instead of a meander, sawtooth pulses with exponential rise and fall are observed.

Rice. 5.8. Scheme for connecting the probe to the RL load

Probes with built-in correction must be used strictly for their intended purpose, taking into account the strong differences frequency characteristics at different positions of the voltage divider.

Accounting for Probe Parameters

We present typical data of the circuit in Fig. 5.8: internal resistance of the signal source Ri=50 Ohm, load resistance RL>>Ri, input resistance of the probe RP=10 MOhm, input capacitance of the probe CP=15 pF. With such data of circuit elements, it degenerates into a series oscillatory circuit containing resistance R≈Ri, inductance of the ground wire L≈LG (about 100-120 nH) and capacitance C≈CP.

If an ideal voltage drop E is applied to the input of such a circuit, then the time dependence of the voltage at C (and the oscilloscope input) will look like:

(5.5)

Calculations show that this dependence can have a significant overshoot at large L and small R, which is observed in the upper oscillogram in Fig. 5.7. At α/δ=1, this surge is no more than 4% of the amplitude of the difference, which is a completely satisfactory indicator. To do this, the value L=LG must be chosen equal to:

For example, if C=15 pF and R=50 Ohm, then L=19 nH. To reduce L to such a value (from the typical order of 100-120 nH for a ground wire 10 cm long), it is necessary to shorten the ground (possibly signal) wire to a length of less than 2 cm. To do this, remove the nozzle from the probe head and abandon the use of a standard ground wires. The beginning of the probe in this case will be represented by a contact needle and a cylindrical ground strip (Fig. 5.9) with low inductance.

Rice. 5.9. Probe head with tip removed (left) and adapter to coaxial connector (right)

The effectiveness of the measures used to combat ringing is illustrated in Fig. 5.10. It shows waveforms of a 10 MHz square wave when the probe is turned on normally and when the probe is turned on with the tip removed and without the long ground wire. The almost complete elimination of obvious damped oscillatory processes on the lower oscillogram is clearly visible. Small fluctuations at the top are associated with wave processes in the connecting coaxial cable, which in such probes operates without matching at the output, which generates signal reflections.

Rice. 5.10. Oscillograms of a 10-MHz square wave when the probe is turned on normally (upper waveform) and turned on with the nozzle removed and without a long ground wire (lower waveform)

To obtain oscillograms with extremely short rise times and ringing, measures should be taken to minimize the inductance of the measured circuit: removing the probe tip and connecting the probe using a needle and a cylindrical ground insert. All possible measures should be taken to reduce the inductance of the circuit in which the signal is observed.
Important parameters of the probe-oscilloscope system are the system rise time (at the 0.1 and 0.9 levels) and the bandwidth or maximum frequency (at the 3 dB sensitivity roll-off level). If we use the known value of the resonant frequency of the circuit

, (5.7)
then we can express the value of R through the resonant frequency of the circuit, which determines the limiting frequency of the deflection system path:

. (5.8)
It is easy to prove that the time the voltage u(t) reaches the value E of the drop amplitude will be equal to:

. (5.10)

This value is usually taken as the settling time of the probe with optimal transient response. The total rise time of an oscilloscope with a probe can be estimated as:

, (5.11)
where tosc is the rise time of the oscilloscope (when a signal is applied directly to the input of the corresponding channel). The upper limit frequency fmax (which is also the frequency band) is defined as

. (5.12).
For example, an oscilloscope with t0=1 ns has fmax=350 MHz. Sometimes the 0.35 multiplier is increased to 0.4-0.45, since the frequency response of many modern oscilloscopes with fmax>1 GHz differs from the Gaussian one, which is characterized by a 0.35 multiplier.

Do not forget about another important parameter of probes - signal delay time tз. This time is determined, first of all, by the linear delay time (per 1 m of cable length) and the length of the cable. It usually ranges from units to tens of ns. To prevent the delay from affecting the relative position of oscillograms on the screen of a multichannel oscilloscope, you must use probes of the same type with cables of the same length in all channels.

Connecting Probes to Signal Sources

Connecting probes to the desired points of the devices under study can be done using various tips, nozzles, hooks and “micro-crocodiles”, which are often included in the probe accessory kit. However, most often the most precise measurements are performed when connecting using the primary probe needle - see fig. 5.11 or two needles. When developing high-frequency and pulsed devices on a printed circuit board, special contact pads or metallized holes are provided for this purpose.

Rice. 5.11. Connecting the probe to the contact pads of the printed circuit board of the device under test

It is especially important in our time to connect probes to the contact pads of miniature printed circuit boards, hybrid and monolithic integrated circuits)