A quartz resonator is an electronic device built on the piezoelectric effect, as well as mechanical resonance. It is used by radio stations, where it sets the carrier frequency, in hours and timers, fixing an interval of 1 second in them.
The device is a source that provides high-precision harmonic oscillations. It has, when compared with analogues, greater work efficiency, stable parameters.
The first samples of modern devices appeared on radio stations in 1920-1930. as elements with stable operation, capable of setting the carrier frequency. They:
A little later, quartz resonators became an integral part of timers and clocks. Electronic components with a natural resonant frequency of 32768 Hz, which in a binary 15-bit counter sets a time interval of 1 second.
Devices are used today in:
Devices are manufactured with different cases. They are divided into output, used in bulk mounting, and SMD, used in surface mounting.
Their work depends on the reliability of the switching circuit, which affects:
Surpasses previously existing analogues, which makes the device indispensable in many electronic circuits and explains the scope of the device. This is confirmed by the fact that in the first decade since the invention in the United States (not counting other countries) more than 100 thousand pieces of devices have been produced.
Among the positive properties of quartz resonators, which explain the popularity and demand for devices:
Quartz resonators also have disadvantages:
The device works on the basis of the piezoelectric effect, which manifests itself on a quartz plate, and at low temperature. The element is cut out of a single quartz crystal, observing the specified angle. The latter determines the electrochemical parameters of the resonator.
The plates are coated on both sides with a layer of silver (platinum, nickel, gold are suitable). Then they are firmly fixed in the housing, which is sealed. The device is an oscillatory system that has its own resonant frequency.
When the electrodes are subjected to an alternating voltage, the quartz plate, which has a piezoelectric property, bends, contracts, shifts (depending on the type of processing of the crystal). At the same time, a counter-EMF appears in it, as happens in an inductor located in an oscillatory circuit.
When a voltage is applied with a frequency coinciding with the natural vibrations of the plate, then resonance is observed in the device. Simultaneously:
The energy that is needed to maintain oscillations is low in the case of equal frequencies.
The device is designated similarly to a capacitor. Difference: a rectangle is placed between the vertical segments - a symbol of a plate made of quartz crystal. The sides of the rectangle and the capacitor plate are separated by a gap. Nearby on the diagram there may be a letter designation of the device - QX.
Problems with small appliances arise if they receive a strong blow. This happens when devices containing resonators in the design fall. The latter fail and require replacement according to the same parameters.
Checking the resonator for performance requires a tester. It is assembled according to a circuit based on a KT3102 transistor, 5 capacitors and 2 resistors (the device is similar to a quartz oscillator assembled on a transistor).
The device must be connected to the base of the transistor and the negative pole in the connected connections, connections, protecting by installing a protective capacitor. The power supply of the switching circuit is constant - 9V. Plus, they connect to the input of the transistor, to its output - through a capacitor - a frequency meter, which fixes the frequency parameters of the resonator.
The scheme is used when setting up the oscillation circuit. When the resonator is in good condition, when connected, it produces oscillations that lead to the appearance of an alternating voltage at the emitter of the transistor. Moreover, the voltage frequency coincides with a similar characteristic of the resonator.
The device is faulty if the frequency meter does not detect the occurrence of a frequency or determines the presence of a frequency, but it is either much different from the nominal value, or it changes greatly when the case is heated with a soldering iron.
The reason for the creation of this device was a considerable number of accumulated quartz resonators, both purchased and soldered from different boards, and many did not have any designations. Traveling through the endless expanses of the Internet and trying to collect and launch various ones, it was decided to come up with something of my own. After many experiments with different generators, both on different digital logics and on transistors, I chose the 74HC4060, though it was also not possible to eliminate self-oscillations, but as it turned out, this does not interfere with the operation of the device.
The device is based on two CD74HC4060 generators (the 74HC4060 was not in the store, but judging by the datasheet they are even “cooler”), one operates at a low frequency, the second at a high one. The lowest frequencies I had were watch quartz, and the highest frequency was non-harmonic quartz at 30 MHz. Due to their tendency to self-excitation, it was decided to switch generators simply by switching the supply voltage, as indicated by the corresponding LEDs. After the generators, I installed a repeater on the logic. Perhaps instead of resistors R6 and R7 it is better to install capacitors (I did not check it myself).
As it turned out, not only quartz is launched in the device, but also all sorts of filters with two or more legs, which were successfully connected to the appropriate connectors. One "two-legged" ceramic-like capacitor started at 4 MHz, which was then successfully used instead of a quartz resonator.
The pictures show that two types of connectors are used to check radio components. The first one is made from parts of the panels - for output parts, and the second one is a board fragment glued and soldered to the tracks through the corresponding holes - for SMD quartz resonators. To display information, a simplified frequency meter was used on the PIC16F628 or PIC16F628A microcontroller, which automatically switches the measurement limit, that is, the frequency on the indicator will be either in kHz or in MHz.
Part of the board is assembled on lead parts, and part on SMD. The board is designed for the Winstar single-line LCD indicator WH1601A (this is the one with the contacts on the top left), contacts 15 and 16, which are used for illumination, are not separated, but whoever needs it can add tracks and details for himself. I didn’t dim the backlight because I used an indicator without backlight from some phone on the same controller, but first there was Winstar. In addition to WH1601A, you can use WH1602B - two-line, but the second line will not be used. Instead of a transistor, that in the circuit you can apply any of the same conductivity, preferably with a larger h21. The board has two power inputs, one from mini USB, the other through the bridge and 7805. There is also a place for a stabilizer in another case.
When setting with the S1 button, turn on the low-frequency mode (the VD1 LED will light up) and by plugging a 32768 Hz quartz resonator into the appropriate connector (preferably from the computer motherboard) with a tuning capacitor C11, set the frequency of 32768 Hz on the indicator. Resistor R8 sets the maximum sensitivity. All files - boards, firmware, datasheets for the radio elements used and more, download in the archive. Project author - nefedot.
Discuss the article DEVICE FOR CHECKING THE FREQUENCY OF QUARTZ
Quartz resonators, like most other radio components, it is desirable to check for performance before using them in amateur radio practice. One of the simplest schemes for such a probe was published in a Czech amateur radio magazine. The probe circuit is extremely simple to repeat, therefore it is of interest to a wide range of radio amateurs.
Quartz resonators are among the simplest radio components, but radio amateurs have practically no instruments to test them before use. This sometimes leads to misunderstandings. Outwardly, the quartz resonator may not have any damage, but it does not work in the circuit. There can be many reasons for this. In particular, one of them is the fall of the resonator due to careless handling. The simple design described in will help to perform an initial check of quartz resonators even before they are used.
The tested quartz resonator is connected to contacts K2 (Fig. 1). A wide-range generator is made on transistor T1. It is designed to test quartz, the operating frequency of which is in the range of 1 ... 50 MHz. Having slightly changed the parameters of some radio components of the circuit, in particular. C2 and SZ. you can check other quartzes.
In the event that the quartz resonator is operational. on the emitter of the transistor T1 there is a high-frequency alternating voltage. It is rectified by diodes D1, D2, smoothed out by capacitor C5 and fed to the base of the key transistor T2, unlocking it. At the same time, the LED LD1 lights up.
I would like to say right away that check the quartz resonator with a multimeter will not work. To check a quartz resonator with an oscilloscope, you need to connect the probe to one of the quartz leads, and the earth crocodile to the other, but this method does not always give a positive result., below is why.
One of the main reasons for the failure of a quartz resonator is a banal fall, so if the TV remote control, car alarm key fob stops working, then the first thing to do is to check it. It is not always possible to check the generation on the board because the oscilloscope probe has a certain capacitance, which is usually about 100pF, that is, when connecting the oscilloscope probe, we connect a 100pF capacitor. Since the capacitance ratings in the circuits of quartz oscillators are tens and hundreds of picofarads, less often nanofarads, the connection of such a capacitance introduces a significant error in the calculated parameters of the circuit and, accordingly, can lead to generation failure. The capacitance of the probe can be reduced to 20pF by setting the divider to 10, but this does not always help.
Based on the above, we can conclude that to check the quartz resonator, a circuit is needed, when connected to which the oscilloscope probe will not break the generation, that is, the circuit should not feel the capacitance of the probe. The choice fell on the Clapp generator on transistors, and in order not to break the generation, an emitter follower is connected to the output.
I did not find a quartz resonator for a frequency above 32MHz, but even this result can be considered excellent.
Obviously, for a novice radio amateur, the method is preferable without using an expensive oscilloscope, so the circuit for checking quartz using an LED is shown below. The maximum frequency of the quartz that I was able to check using this circuit is 14MHz, the next denomination that I had was 32MHz, but the generator did not start with it, but from 14MHz to 32MHz there is a large gap, most likely up to 20MHz will work.
A resonator is a system capable of oscillatory movements with a maximum amplitude under certain conditions. Quartz resonator - a plate of quartz, usually in the form of a parallelepiped, acts like this when an alternating current is applied (the frequency is different for different plates). The working frequency of this part is determined by its thickness. The dependence is inverse here. The thinnest plates have the highest frequency (not exceeding 50 MHz).
In rare cases, you can achieve a frequency of 200 MHz. This is only valid when operating at an overtone (a non-fundamental frequency that is higher than the fundamental). Special filters are able to suppress the fundamental frequency of the quartz plate and highlight the overtone multiple of it.
Only odd harmonics (another name for overtones) are suitable for work. In addition, when using them, the frequency readings increase at lower amplitudes. Usually, a ninefold decrease in wave height becomes the maximum. Further, it becomes difficult to detect changes.
Quartz is a dielectric. In combination with a pair of metal electrodes, it turns into a capacitor, but its capacity is small and there is no point in measuring it. In the diagram, this part is displayed as a crystalline rectangle between the capacitor plates. A quartz plate, like other elastic bodies, is characterized by the presence of its own resonant frequency, which depends on its size. Plates of small thickness have a higher resonant frequency. As a result: it is only necessary to choose a plate with parameters such that the frequency of mechanical vibrations would coincide with the frequency of the alternating voltage applied to the plate. Quartz plate, suitable only when using alternating current, since direct current can only provoke a single compression or expansion.
As a result, it is obvious that quartz is a very simple resonant system (with all the properties inherent in oscillatory circuits), but this does not at all reduce the quality of its work.
The quartz resonator is even more efficient. His quality factor is 10 5 - 10 7 . Quartz resonators increase the overall life of the capacitor due to their thermal stability, durability and manufacturability. Ease of use is added by the small size of the parts. But the most important advantage is the ability to provide a stable frequency.
Among the minuses are only the narrowness of the range of attunement of the available frequency with the frequency of external elements.
In any case, quartz resonators are very popular and are used in watches, numerous radio electronics and other devices. In some countries, quartz plates are installed directly on the sidewalks, and people produce energy just by walking back and forth.
The functions of the quartz resonator are provided by the piezoelectric effect. This phenomenon provokes the appearance of an electric charge if there is a mechanical deformation of some types of crystals (natural quartz and tourmaline are included here). The force of the charge in this case is directly dependent on the force of deformation. This is called the direct piezoelectric effect. The essence of the inverse piezoelectric effect is that if an electric field is applied to the crystal, it will deform.
There are several simple methods for checking the condition of quartz in a movement. Here are a couple of them:
In general, a reliable check of quartz resonators can only be carried out when they are replaced. Yes, and to suspect a breakdown of the resonator in the mechanism is only in the most extreme case. Although portable electronics subject to frequent drops, this does not apply.
