Quartz resonator tester circuit. Radio designer RI0142

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 markings. Traveling through the vast expanses of the Internet and trying to assemble and run various quartz tester circuits, it was decided to come up with something of our own. After many experiments with different generators, both on different digital logics and on transistors, I chose the 74HC4060, although it was also not possible to eliminate self-oscillations, but as it turned out, this does not create interference during the operation of the device.

Quartz meter circuit

The device is based on two CD74HC4060 generators (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-frequency ones I had were hour quartz, and the highest frequency was non-harmonic quartz at 30 MHz. Due to their tendency to self-excite, it was decided to switch the generators simply by switching the supply voltage, which is indicated by the corresponding LEDs. After the generators, I installed a logic repeater. It might be better to install capacitors instead of resistors R6 and R7 (I haven’t checked it myself).

As it turned out, the device runs not only quartz, but also all sorts of filters with two or more legs, which were successfully connected to the appropriate connectors. One “biped” similar to a ceramic capacitor was launched at 4 MHz, which was later successfully used instead of a quartz resonator.

The photographs show that two types of connectors are used to test radio components. The first is made from parts of panels - for lead-out parts, and the second is a fragment of the board glued and soldered to the tracks through the corresponding holes - for SMD quartz resonators. To display information, a simplified frequency meter is used on a PIC16F628 or PIC16F628A microcontroller, which automatically switches the measurement limit, that is, the frequency on the indicator will be either in kHz or MHz. About the 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 serve for illumination, are not routed, but anyone who needs can add tracks and details for themselves. I didn’t turn on the backlight because I used a non-backlit indicator from some phone on the same controller, but at first there was a Winstar one. In addition to WH1601A, you can use WH1602B - two-line, but the second line will not be used. Instead of a transistor in the circuit, you can use any of the same conductivity, preferably with a larger h21. The board has two power inputs, one from a mini USB, the other through a bridge and 7805. There is also space for a stabilizer in another case.

Device setup

When tuning with the S1 button, turn on the low-frequency mode (the VD1 LED will light up) and by inserting a quartz resonator at 32768 Hz into the corresponding connector (preferably from the computer motherboard), use the tuning capacitor C11 to set the frequency on the indicator to 32768 Hz. Resistor R8 sets the maximum sensitivity. All files - boards, firmware, datasheets for the radio elements used and more, download in the archive. The author of the project is nefedot.

ARCHIVE:

A frequency meter is a useful device in a radio amateur's laboratory (especially in the absence of an oscilloscope).

In addition to the frequency meter, I personally often lacked a quartz resonator tester - too many defective products began to arrive from China. It has happened more than once that you assemble a device, program the microcontroller, record fuses so that it is clocked by an external quartz and that’s it - after recording the fuses, the programmer stops seeing the MK. The reason is “broken” quartz, less often - a “buggy” microcontroller (or carefully relabeled by the Chinese with the addition, for example, of the letter “A” at the end). And I came across up to 5% of the batch with such faulty quartzes. By the way, a fairly well-known Chinese set of frequency counters I absolutely did not like the quartz tester on a PIC microcontroller and an LED display from Aliexpress, because often instead of the frequency it showed either the weather in Zimbabwe or the frequencies of “uninteresting” harmonics (or maybe I was unlucky).

We offer for consideration another device that was made a few days ago. This is a quartz resonator tester for checking the efficiency (operability) of quartz used in many devices, at least in electronic watches. The whole system is extremely simple, but this is precisely the simplicity that was required.

  • The tester consists of several electronic components:
  • 2 NPN BC547C transistors
  • 2 capacitors 10nF
  • 2 capacitors 220pF
  • 2 resistors 1k
  • 1 resistor 3k3
  • 1 47k resistor

1 LED

Powered by 6 AA 1.5 V batteries (or Krona). The body is made from a candy box and covered with colored tape.

Schematic diagram of a quartz tester

The diagram looks like this:

Second version of the scheme:

To check, insert quartz into SN1, then switch the switch to the ON position. If the LED lights up brightly, the quartz resonator is working. And if after turning on the LED does not light up or lights up very weakly, then we are dealing with a damaged radio element.

A quartz resonator is an electronic device based on the piezoelectric effect, as well as mechanical resonance. It is used by radio stations, where it sets the carrier frequency in clocks and timers, fixing an interval of 1 second in them.

What is it and why is it needed

The device is a source that provides high-precision harmonic oscillations. Compared with analogues, it has greater operating efficiency and stable parameters.

The first examples of modern devices appeared on radio stations in 1920-1930. as elements that have stable operation and are capable of setting the carrier frequency. They:

  • replaced crystal resonators operating on Rochelle salt, which appeared in 1917 as a result of the invention of Alexander M. Nicholson and were characterized by instability;
  • replaced the previously used circuit with a coil and a capacitor, which did not have a high quality factor (up to 300) and depended on temperature changes.

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 period equal to 1 second.

The devices are used today in:

  • quartz watches, ensuring their accuracy regardless of ambient temperature;
  • measuring instruments, guaranteeing them high accuracy of indicators;
  • marine echo sounders, which are used in research and creation of bottom maps, recording reefs, shoals, and searching for objects in the water;
  • circuits corresponding to reference oscillators that synthesize frequencies;
  • circuits used in wave indication of SSB or telegraph signal;
  • radio stations with DSB signal with intermediate frequency;
  • bandpass filters of superheterodyne receivers, which are more stable and high quality than LC filters.

The devices are manufactured with different housings. They are divided into output ones, used in volumetric mounting, and SMD, used in surface mounting.

Their operation depends on the reliability of the switching circuit, which affects:

  • frequency deviation from the required value, parameter stability;
  • rate of aging of the device;
  • load capacity.

Properties of a quartz resonator

It is superior to previously existing analogues, which makes the device indispensable in many electronic circuits and explains the scope of use of the device. This is confirmed by the fact that in the first decade since its invention, more than 100 thousand devices were produced in the USA (not counting other countries).

Among the positive properties of quartz resonators that explain the popularity and demand for devices:

  • good quality factor, the values ​​of which – 104-106 – exceed the parameters of previously used analogues (they have a quality factor of 300);
  • small dimensions, which can be measured in fractions of a millimeter;
  • resistance to temperature and its fluctuations;
  • long service life;
  • ease of manufacture;
  • the ability to build high-quality cascade filters without using manual settings.

Quartz resonators also have disadvantages:

  • external elements allow you to adjust the frequency in a narrow range;
  • have a fragile design;
  • cannot tolerate excessive heat.


Operating principle of a quartz resonator

The device operates on the basis of the piezoelectric effect, which manifests itself on a low-temperature quartz plate. The element is cut out from a solid 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). They are then 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 alternating voltage, the quartz plate, which has piezoelectric properties, bends, contracts, and shifts (depending on the type of crystal processing). At the same time, a back-EMF appears in it, as happens in an inductor located in an oscillatory circuit.

When a voltage is applied with a frequency that matches the natural vibrations of the plate, resonance is observed in the device. Simultaneously:

  • the quartz element increases the amplitude of vibrations;
  • The resonator resistance is greatly reduced.

The energy required to maintain oscillations is low in the case of equal frequencies.

Designation of a quartz resonator on an electrical diagram

The device is designated similarly to a capacitor. Difference: a rectangle is placed between the vertical segments - a symbol of a plate made of a quartz crystal. A gap separates the sides of the rectangle and the capacitor plate. Nearby on the diagram there may be a letter designation of the device - QX.


How to check a quartz resonator

Problems with small appliances arise if they receive a strong blow. This happens when devices containing resonators fall. The latter fail and require replacement according to the same parameters.

Checking the resonator for functionality requires a tester. It is assembled according to a circuit based on the 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, protected by installing a protective capacitor. The power supply for the switching circuit is constant – 9V. Plus, a frequency meter is connected to the input of the transistor, and to its output through a capacitor, which records the frequency parameters of the resonator.

The diagram is used when setting up the oscillation circuit. When the resonator is working properly, 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 detects the presence of a frequency, but it is either much different from the nominal value, or when the case is heated with a soldering iron, it changes greatly.

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A set of components for assembling a frequency meter with the function of a quartz resonator tester.

Simple and inexpensive, developed on the basis of a PIC microcontroller with the ability to take into account the frequency shift of superheterodyne receivers in measurements with a five-digit LED indicator, convenient and intuitive.

Functions

  • The display resolution automatically switches to ensure maximum reading accuracy with a 5-digit display.
    The measurement duration (gate time) during which the input pulses are counted is also automatically changed.
  • If the frequency meter is used for measurements on shortwave receivers or transmitters, you may need to add or subtract the frequency offset value from the measured frequency. The offset frequency is in many cases equal to the intermediate frequency, since the frequency meter is usually connected to the receiver's variable frequency generator.
  • To measure the oscillating frequency of quartz, simply connect it to the connector labeled “Crystal under test”

Additional Information

Main features:

Frequency measurement range: 1 Hz - 50 MHz

Measurement of quartz for general use in generation frequency in the range: 1 MHz - 50 MHz

Automatic band switching

Programmable settings for the added and subtracted value of the frequency shift during adjustments and measurements in VHF receivers and transmitters.

Maximum input voltage 5 Volts

Energy saving mode when powered from an autonomous current source

It is possible to use 5V from the USB interface

Minimum number of components, simple assembly and configuration

Questions and answers

  • Hello, can I order this product in quantity of 1 piece?
    • Yes, of course you can!
  • Hello. What voltage range of the measured frequency is allowed at the input in frequency meter mode?
    • TTL logic level, up to 5 Volts
  • Hello. What is the maximum input voltage for this frequency meter?
    • 5 Volt
  • Hello, when will this construction set go on sale, in particular in the Chip and Dip store?
    • Good afternoon The product is now at the stage of acceptance into the finished goods warehouse, I think within a week it will be available for order through our online store. Regarding Chip and Dip, this question should be asked directly to them.
  • Good day! Tell me what's the matter. The frequency meter shows the same number all the time. 65.370
    • This is the first time we have heard about such a problem. When assembled correctly, the device starts working immediately and does not require configuration. See installation and ensure correct installation of all components. The value of constant resistors must be checked with a multimeter before installation.