Oscilloscope from the tablet with your own hands

Technologies do not stand still, and keeping up with them is not always easy. There are new items in which I would like to understand in more detail. Especially this applies to a variety of electronic designers, allowing you to assemble almost any simple device step-by-step. Now, among them, there are Arduino boards with their clones, and Chinese microprocessor computers, and ready-made solutions coming with software on board.

However, to work with all of the above spectrum of interesting novelties, as well as for repairing digital equipment, an expensive high-precision tool is required. Among such equipment - and an oscilloscope that allows you to read the frequency readings and conduct diagnostics. Often its cost is quite high, and novice experimenters can not afford such an expensive purchase. Here comes to the rescue solution that appeared on many amateur forums almost immediately after the appearance of tablets on the Android system. Its essence is to make an oscilloscope from a tablet with minimum expenses without introducing any modifications or modifications to its gadget, and also eliminating the risks of its damage.

What is an oscilloscope?

Oscilloscope - as an instrument for measuring and monitoring frequency fluctuations in the electrical network - is known since the middle of the last century. These devices are completed by all training and professional laboratories, since it is possible to detect some faults or to fine-tune the equipment only with its help. It can display information both on the screen and on the paper tape. The readings allow you to see the waveform, calculate its frequency and intensity, and as a result, determine the source of its appearance. Modern oscilloscopes allow you to draw three-dimensional color frequency graphics. Today we will stop on a simple variant of a standard two-channel oscilloscope and realize it with the help of a prefix to a smartphone or tablet and the corresponding software.

The easiest way to create a pocket oscilloscope

If the measured frequency is in the range audible by the human ear frequencies, and the signal level does not exceed the standard microphone, then you can assemble the oscilloscope from the tablet to the Android with your hands without any additional modules. To do this, it is enough to disassemble any headset, on which a microphone must be present. If there is no suitable headset, then you need to buy a 3.5 mm audio plug with four contacts. Before soldering the probes, check the pinout of your gadget connector, because there are two types. Styli should be connected to pins that correspond to the connection of the microphone on your device.

Then download from the Market software that can measure the frequency at the microphone input and draw a graph based on the received signal. There are many such options. Therefore, if desired, will be out of what to choose. As mentioned before, the tablet did not have to be reworked. The oscilloscope will be ready immediately after the calibration of the application.

Pros and cons of the above scheme

The advantages of this solution clearly include simplicity and cheap assembly. The old headset or one new connector is almost worthless, and the time will only take a few minutes.

But this scheme has a number of significant drawbacks, namely:

• A small range of measured frequencies (depending on the quality of the audio path of the gadget ranges from 30 Hz to 15 kHz).
• The lack of protection of the tablet or smartphone (if you accidentally connect the probes to areas of the circuit with increased voltage, you can at best burn the chip responsible for processing the audio signal on your gadget, and at worst - completely disable your smartphone or tablet).
• On very cheap devices there is a significant error in measuring the signal, reaching 10-15 percent. This figure is not allowed for fine-tuning the equipment.

Realization of protection, screening of a signal and reduction of an error

In order to partially protect your device from possible failure, as well as stabilize the signal and expand the range of input voltages, you can use a simple oscilloscope circuit for a tablet that has long been successfully used to build devices for a computer. It uses cheap components, including stabilizers KS119A and two resistors for 10 and 100 kOhm. The zener diodes and the first resistor are connected in parallel, and the second, more powerful, resistor is used at the input of the circuit to expand the maximum possible voltage range. As a result, a large amount of interference disappears, and the voltage rises to 12 V.

Of course, it should be taken into account that the oscilloscope from the tablet works primarily with sound pulses. Therefore, it is necessary to take care of the qualitative screening of both the circuit itself and the probes. If desired, detailed instructions on how to assemble this scheme can be found in one of the thematic forums.

Software

To work with this scheme, you need a program that can draw graphics based on the incoming audio signal. Find it in the "Market" is not difficult, there are many options. Almost all of them require additional calibration, so you can achieve the maximum possible accuracy, and make a professional oscilloscope from the tablet. Otherwise, these programs perform essentially the same task, so the final choice depends on the required functionality and ease of use.

Homemade set-top box with Bluetooth-module

If a wider frequency range is required, then the above option will not be limited. Here a new version comes to the rescue - a separate gadget, which is a prefix with an analog-to-digital converter, which provides signal transmission in digital form. Audio audit of a smartphone or tablet in this case is no longer involved, which means it is possible to achieve a higher accuracy of measurements. In fact, at this stage they are only a portable display, and all information is already collected by a separate device.

Collect the oscilloscope from the tablet on the "Android" with a wireless module you can most. The network has an example where a similar device was implemented in 2010 with the help of a two-channel analog-to-digital converter created on the basis of the PIC33FJ16GS504 microcontroller, and the LMX9838 Bluetooth module served as the signal transmitter. The device turned out to be quite functional, but difficult to assemble, so for beginners it will be a daunting task. But, if you want, to find a similar project on the same amateur forums is not a problem.

Ready-made options for consoles with Bluetooth

Engineers do not doze, and, besides handicrafts, in stores there are more and more consoles that perform the function of an oscilloscope and transmit a signal through a Bluetooth channel to a smartphone or tablet. Oscilloscope-attachment to the tablet, connected via Bluetooth, often has the following main characteristics:

• Limit of measured frequency: 1 MHz.
• Voltage on the dipstick: up to 10 V.
• Range: about 10 m.

These characteristics are quite enough for domestic use, and yet in professional activity, sometimes there are cases when this range is sorely lacking, and it is simply unrealistic to realize a larger one with a slow Bluetooth protocol. What is the solution in this situation?

Oscilloscopes-consoles with data transfer over Wi-Fi

This variant of data transfer significantly expands the capabilities of the measuring device. Now the market of oscilloscopes with this kind of information exchange between the prefix and the tablet is gaining momentum because of its relevance. Such oscilloscopes are practically not inferior to the professional ones, since they transmit the measured information to the tablet without delay, which immediately displays it in a graphical form on the screen.

Control is carried out through simple, intuitive menus that copy the tuning elements of conventional laboratory devices. In addition, this equipment allows you to record or broadcast in real time all that is happening on the screen, which can be an indispensable help if you need to ask for advice from a more experienced master who is located elsewhere.

The characteristics of the oscilloscope for repairing tablets in the form of a set-top box with a Wi-Fi connection grow several times, in comparison with the previous versions. Such oscilloscopes have a measuring range up to 50 MHz, and they can be modified by means of various adapters. Often, they have batteries for autonomous power supply, in order to maximally relieve the workplace of unnecessary wires.

Homemade variants of modern waveform prefixes

Of course, the forums are experiencing a surge of various ideas, with which enthusiasts try to realize their old dream - to build an oscilloscope from a tablet on an Android with a Wi-Fi channel. Some models are successful, others are not. Here it is up to you to decide whether to try, too, happiness and save a few dollars by collecting the device yourself, or to purchase a ready-made version. If you are not confident in your abilities, then it's better not to take risks, so that you do not regret the money wasted.

Otherwise - welcome to one of the communities of radio amateurs, in which you will be able to give effective advice. Perhaps later, according to your scheme, newbies will collect their first oscilloscope in life.

Software for consoles

Often, along with purchased oscilloscopes-prefixes comes a disk with a program that can be installed on your tablet or smartphone. If there is no such a disc, then carefully study the instructions to the device - most likely, it has the names of programs that are compatible with the prefix and located in the application store.

Also, some of these devices can work not only with devices running the operating system "Android", but also with more expensive "apple" devices. In this case, the program will be uniquely located in the AppStore, because another version of the installation is not provided. After making an oscilloscope from the tablet, do not forget to check the accuracy of the readings and, if necessary, calibrate the instrument.

USB Oscilloscopes

If you do not have a portable device like a tablet, but there is a laptop or computer, do not get upset. Of these, you can also make a wonderful measuring device. The simplest option is to connect probes to the microphone input of the computer in the same way as described at the beginning of the article.

However, given its limitations, this option is not suitable for everyone. In this case, a USB oscilloscope can be used, which will provide the same characteristics as the prefix with signal transmission over Wi-Fi. It should be noted that such devices sometimes work with some tablets that support the technology of connecting external devices OTG. Of course, the YSB oscilloscope is also trying to do it yourself, and quite successfully. At least, this particular article is devoted to a large number of topics on the forums.