Technology does not stand still, and keeping up with them is not always easy. There are new items that I would like to understand in more detail. This is especially true of a variety of electronic kits that allow you to assemble almost any simple device step by step. Now they include Arduino boards with their clones, and Chinese microprocessor computers, and ready-made solutions that already come with software on board.
However, to work with all of the above range of interesting new products, as well as to repair digital equipment, an expensive high-precision tool is required. Among such equipment is an oscilloscope that allows you to read frequency readings and carry out diagnostics. Often, its cost is quite high, and novice experimenters cannot afford such an expensive purchase. Here a solution comes to the rescue, which appeared on many amateur radio forums almost immediately after the appearance of tablets on the Android system. Its essence is to make an oscilloscope from a tablet at minimal cost, without adding to yourgadget no modifications or modifications, as well as eliminating the risk of damage.
What is an oscilloscope
Oscilloscope - as a device for measuring and tracking frequency fluctuations in an electrical network - has been known since the middle of the last century. All educational and professional laboratories are equipped with these devices, since it is possible to detect some malfunctions or fine-tune the equipment only with its help. It can display information both on the screen and on paper tape. The readings allow you to see the shape of the signal, calculate its frequency and intensity, and as a result determine the source of its occurrence. Modern oscilloscopes allow you to draw three-dimensional color frequency graphs. Today we will focus on a simple version of a standard two-channel oscilloscope and implement it using 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 of frequencies audible to the human ear, and the signal level does not exceed the standard microphone level, then you can assemble an oscilloscope from an Android tablet with your own hands without any additional modules. To do this, it is enough to disassemble any headset, which must have a microphone. If there is no suitable headset, then you will need to buy a 3.5 mm audio plug with four pins. Before soldering the probes, verify the pinout of your connectorgadget, because there are two types of them. The probes must be connected to the pins corresponding to the microphone connection on your device.
Next, you should download software from the "Market" that can measure the frequency at the microphone input and draw a graph based on the received signal. There are quite a few such options. Therefore, if desired, there will be plenty to choose from. As mentioned earlier, no modification of the tablet was required. The oscilloscope will be ready as soon as the application is calibrated.
Pros and cons of the above scheme
The advantages of such a solution can definitely include the simplicity and low cost of assembly. An old headset or one new jack costs next to nothing and only takes a few minutes.
But this scheme has a number of significant drawbacks, namely:
- Small range of measured frequencies (depending on the quality of the audio path of the gadget, it ranges from 30 Hz to 15 kHz).
- Lack of protection for your tablet or smartphone (if you accidentally connect the probes to sections 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 signal measurement, reaching 10-15 percent. For fine-tuning equipment, such a figure is not allowed.
Implement protection, signal shielding and error reduction
To orderin order to partially protect your device from possible failure, as well as to stabilize the signal and expand the input voltage range, you can use a simple oscilloscope circuit for a tablet, which has been successfully used for assembling devices for a computer for a long time. It uses cheap components, including KS119A zener diodes and two 10 and 100 kOhm resistors. 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 in order 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 borne in mind that the oscilloscope from the tablet works primarily with sound pulses. Therefore, it is worth taking care of high-quality shielding of both the circuit itself and the probes. If you wish, detailed instructions for assembling this circuit can be found on one of the thematic forums.
Software
To work with such a scheme, you need a program that can draw graphs based on the incoming audio signal. Finding it in the "Market" is easy, there are many options. Almost all of them require additional calibration, so you can achieve the highest possible accuracy, and make a professional oscilloscope from a tablet. Otherwise, these programs perform essentially the same task, so the final choice depends on the required functionality and ease of use.
Homemadeset-top box with Bluetooth module
If a wider frequency range is required, then the above option will not be limited. Here a new option comes to the rescue - a separate gadget, which is a set-top box with an analog-to-digital converter that provides signal transmission in digital form. In this case, the audio path of a smartphone or tablet is no longer involved, which means that higher measurement accuracy can be achieved. In fact, at this stage they are only a portable display, and all information is collected by a separate device.
You can assemble an oscilloscope from an Android tablet with a wireless module yourself. There is an example on the network when a similar device was implemented back in 2010 using a two-channel analog-to-digital converter created on the basis of the PIC33FJ16GS504 microcontroller, and the LMX9838 Bluetooth module served as a signal transmitter. The device turned out to be quite functional, but difficult to assemble, so for beginners it will be an impossible task to make it. But, if you wish, finding a similar project on the same amateur radio forums is not a problem.
Ready options for set-top boxes with Bluetooth
Engineers are not asleep, and, in addition to handicrafts, more and more set-top boxes appear in stores that perform the function of an oscilloscope and transmit a signal via Bluetooth to a smartphone or tablet. An oscilloscope attached to a tablet connected via Bluetooth often has the following mainSpecifications:
- Measured frequency limit: 1MHz.
- Probe voltage: up to 10 V.
- Range: about 10m.
These characteristics are quite enough for domestic use, and yet in professional activities sometimes there are cases when this range is sorely lacking, and it is simply unrealistic to implement a larger one with the slow Bluetooth protocol. What is the way out in this situation?
Wi-Fi STBs
This data transmission option significantly expands the capabilities of the measuring device. Now the market for oscilloscopes with this type of information exchange between the set-top box and the tablet is gaining momentum due to its demand. Such oscilloscopes are almost as good as professional oscilloscopes, because without delay they transmit the measured information to the tablet, which immediately displays it as a graph on the screen.
Management is through simple, intuitive menus that replicate the tuning elements of conventional laboratory devices. In addition, such equipment allows you to record or broadcast in real time everything that happens on the screen, which can be an indispensable tool if you need to ask for advice from a more experienced master 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 compared to the previous versions. Such oscilloscopes have a measurement range of up to 50 MHz, while they can be modifiedthrough various adapters. Often, they are equipped with batteries for autonomous power supply, in order to unload the workplace from unnecessary wires as much as possible.
Homemade versions of modern oscilloscope attachments
Of course, there is a surge of various ideas on the forums, with the help of which enthusiasts are trying to fulfill their old dream - to independently assemble an oscilloscope from an Android tablet with a Wi-Fi channel. Some models are successful, others are not. Here it remains for you to decide whether to try your luck too and save a few dollars by assembling the device yourself, or to purchase a ready-made version. If you are not confident in your abilities, then it is better not to take risks, so that later you will not regret the wasted funds.
Otherwise, welcome to one of the ham radio communities where you can get good advice. Perhaps later, it is according to your scheme that beginners will assemble their first oscilloscope in their life.
Set-top box software
Often, along with purchased oscilloscopes, set-top boxes come with a disk with a program that you can install on your tablet or smartphone. If there is no such disc in the kit, then carefully study the instructions for the device - most likely, it contains the names of programs compatible with the set-top box and located in the application store.
Also, some of these devices can work not only withdevices running the operating system "Android", but also with more expensive "apple" devices. In this case, the program will definitely be in the AppStore, since there is no other installation option. Having made an oscilloscope from a tablet, do not forget to check the accuracy of the readings and, if necessary, calibrate the device.
USB Oscilloscopes
If you don't have a portable device like a tablet, but you do have a laptop or computer, don't worry. They also make excellent measuring instruments. The easiest option would be to connect the 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 for everyone. In this case, a USB oscilloscope can be used, which will provide the same performance as a set-top box with signal transmission over Wi-Fi. It is worth noting that such devices sometimes work with some tablets that support the technology for connecting external OTG devices. Of course, they also try to make a USB oscilloscope on their own, and quite successfully. At least, a large number of topics on the forums are devoted to this craft.
