A device for measuring the frequency of any quartz. NM8016DIY Lab: Frequency meter with crystal tester function. Possible causes of failure

Hesitation is given one of the most important roles V modern world. So, there is even the so-called string theory, which claims that everything around us is just waves. But there are other options for using this knowledge, and one of them is a quartz resonator. It just so happens that any technique periodically fails, and they are no exception. How to make sure that after a negative incident it still works as it should?

Let's say a word about the quartz resonator

A quartz resonator is called an analogue of an oscillatory circuit based on inductance and capacitance. But there is a difference between them in favor of the first. As you know, to characterize the oscillatory circuit, the concept of quality factor is used. In a resonator based on quartz, it reaches very high values ​​- in the range of 10 5 -10 7 . In addition, it is more efficient for the entire circuit when the temperature changes, which affects the longer life of parts such as capacitors. Designation quartz resonators on the diagram is carried out in the form of a vertically located rectangle, which is “clamped” by plates on both sides. Outwardly, in the drawings, they resemble a hybrid of a capacitor and a resistor.

How does a quartz resonator work?

A plate, ring or bar is cut out of a quartz crystal. At least two electrodes are applied to it, which are conductive strips. The plate is fixed and has its own resonant frequency mechanical vibrations. When voltage is applied to the electrodes, due to the piezoelectric effect, compression, shearing or bending occurs (depending on how the quartz was cut). The oscillating crystal in such cases does work like an inductor. If the frequency of the voltage that is supplied is equal to or very close to its own values, then less energy is required with significant differences to maintain operation. Now we can move on to lighting. main problem, because of which, in fact, this article is being written about a quartz resonator. How to check its performance? 3 methods were selected, which will be discussed.

Method number 1

Here, the KT368 transistor plays the role of a generator. Its frequency is determined by a quartz resonator. When power is supplied, the generator starts to work. It creates impulses that are equal to the frequency of its main resonance. Their sequence passes through the capacitor, which is designated as C3 (100r). It filters the DC component, and then the pulse itself is transmitted to an analog frequency meter, which is built on two D9B diodes and such passive elements: capacitor C4 (1n), resistor R3 (100k) and a microammeter. All other elements serve for the stability of the circuit and so that nothing burns out. Depending on the set frequency, the voltage that is on the capacitor C4 can change. This is a fairly approximate method and its advantage is ease. And, accordingly, the higher the voltage, the higher the frequency of the resonator. But there are certain limitations: you should try it on this circuit only if it is in the approximate range of three to ten MHz. Checking quartz resonators that goes beyond these values ​​\u200b\u200busually does not fall under amateur radio electronics, but a drawing will be considered below, which has a range of 1-10 MHz.

Method number 2

To increase the accuracy, you can connect a frequency meter or an oscilloscope to the generator output. Then it will be possible to calculate the desired indicator using the Lissajous figures. But keep in mind that in such cases, the quartz is excited, both at the harmonics and at the fundamental frequency, which, in turn, can give a significant deviation. Look at the given diagrams (this and the previous one). As you can see, there are different ways look for a frequency, and then you have to experiment. The main thing is to follow safety precautions.

Checking two quartz resonators at once

This circuit will allow you to determine whether two quartz resistors that operate within one to ten MHz are operational. Also, thanks to it, you can recognize the shock signals that go between frequencies. Therefore, you can not only determine the performance, but also select quartz resistors that are most suitable for each other in terms of their performance. The circuit is implemented with two master oscillators. The first of them works with a ZQ1 quartz resonator and is implemented on a KT315B transistor. To check the performance, the output voltage must be greater than 1.2 V, and you should press the SB1 button. The specified indicator corresponds to the signal high level and logical unit. Depending on the quartz resonator, the required value for testing can be increased (you can increase the voltage for each test by 0.1A-0.2V to that recommended in the official instructions for using the mechanism). In this case, the output DD1.2 will have 1, and DD1.3 - 0. Also, reporting on the operation of the crystal oscillator, the HL1 LED will light up. The second mechanism works similarly and will be reported by HL2. If they are started at the same time, the HL4 LED will still be on.

When the frequencies of two generators are compared, their output signals from DD1.2 and DD1.5 are sent to DD2.1 DD2.2. At the outputs of the second inverters, the circuit receives a signal with pulse width modulation to then compare the scores. You can see this visually by blinking the HL4 LED. To improve accuracy, add a frequency counter or oscilloscope. If the real indicators differ by kilohertz, then to determine a higher-frequency quartz, press the SB2 button. Then the first resonator will decrease its values, and the tone of the beats of the light signals will be less. Then we can confidently say that ZQ1 is more high-frequency than ZQ2.

Features of checks

When checking always:

1. Read the instructions that the quartz resonator has;
2. Stick to safety precautions.

Possible causes of failure

There are quite a few ways to disable your quartz resonator. Some of the most popular are worth checking out in order to avoid any problems in the future:

1. Falls from a height. The most popular reason. Remember: always keep workplace V in perfect order and watch your actions.
2. Presence constant voltage. In general, quartz resonators are not afraid of it. But there were precedents. To test operation, connect a 1000 mF capacitor in series - this step will return it to service or avoid negative consequences.
3. Signal amplitude too high. Decide this problem can be done in different ways:

• Take the generation frequency a little to the side so that it differs from the main indicator of the mechanical resonance of quartz. This is a more difficult option.
• Lower the number of volts that feed the generator itself. This is an easier option.
• Check if the quartz resonator is really out of order. So, the reason for the drop in activity may be flux or foreign particles (in this case, it is necessary to clean it thoroughly). It may also be that the insulation has been used too actively, and it has lost its properties. For a control check on this item, you can solder a “three-point” on KT315 and check with an axle (at the same time, activity can be compared).

Conclusion

The article discussed how to check the performance of such elements. electrical circuits, as the frequency of a quartz resonator, as well as their property. Ways were discussed to establish necessary information, as well as possible reasons why they fail during operation. But to avoid negative consequences, always work with a clear head - and then the work of the quartz resonator will be less disturbing.

A frequency meter is a useful device in a radio amateur laboratory (especially if an oscilloscope is not available). In addition to the frequency meter, I personally often lacked a quartz resonator tester - too much marriage began to come from China. It happened more than once that you assemble a device, program a microcontroller, record fuses so that it is clocked from an external quartz and that's it - after recording the fuses, the programmer stops seeing the MK. The reason is a “broken” quartz, less often a “buggy” microcontroller (or carefully re-marked by the Chinese with the addition, for example, the letter “A” at the end). And I came across up to 5% of such faulty quartz from the batch. By the way, a fairly well-known Chinese set of frequency meter with a quartz tester on a PIC microcontroller and an LED display from Aliexpress, I categorically did not like it, because often instead of the frequency it showed either the weather in Zimbabwe, or the frequencies of "uninteresting" harmonics (well, or I was not lucky).

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.

Quartz meter circuit

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.

About device details

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 at 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 set the backlight because I used an indicator without backlight from some phone on the same controller, but at first it 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.

Instrument setup

When setting up with the S1 button, turn on the LF mode (the VD1 LED will light up) and plug a 32768 Hz quartz resonator into the appropriate connector (preferably with motherboard computer) with a tuning capacitor C11, set the frequency to 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

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 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.