Digital frequency meter. Frequency meter on K176 series chips

The first digital IC design made by radio amateurs in the 80s and 90s was usually an electronic clock or frequency meter.
Such a frequency meter can still be used today when calibrating instruments, or used as a reading device in generators and amateur transmitters, when setting up various radio-electronic devices. The device may be of interest to those who have K155 series microcircuits lying around idle, or who are starting to get acquainted with automation and computer devices.

The described device allows you to measure the frequency of electrical oscillations, the period and duration of pulses, and can also work as a pulse counter. Operating frequency from a few Hertz to several tens of MHz with an input voltage of up to 50 mV. The maximum operating frequency of counters on K155IE2 integrated circuits is about 15 MHz. However, it should be borne in mind that the actual speed of flip-flops and counters exceeds the specified value by 1.5... 2 times, so individual instances of TTL microcircuits allow operation at higher frequencies.

The minimum LSB price is 0.1 Hz when measuring frequency and 0.1 μs when measuring period and duration.
The operating principle of the frequency meter is based on measuring the number of pulses arriving at the counter input within a strictly defined time.

The circuit diagram is shown in Fig. 1

The signal under study is fed through connector X1 and capacitor C1 to the input of the rectangular pulse shaper.

The wideband amplifier-limiter is assembled using transistors V1, V2 and V3. Field-effect transistor V1 provides the device with high input resistance. Diodes V1 and V2 protect transistor V1 from damage if it accidentally comes into contact with the input of a high voltage device. Chain C2-R2 carries out frequency correction of the amplifier input.

Transistor V4, connected as an emitter follower, matches the output of the amplifier-limiter with the input of logic element D6,1 of microcircuit D6, which ensures the further formation of rectangular pulses, which, through an electronic switch, are sent to the control device on chip D9, and pulses of reference frequency that open key for a certain time. A burst of pulses appears at the output of this key. The number of pulses in a packet is counted by a binary decimal counter; its state after closing the key is displayed by a digital display unit.

In the pulse counting mode, the control device blocks the reference frequency source, the binary decimal counter continuously counts the pulses arriving at its input, and the digital display unit displays the counting results. The counter readings are reset by pressing the “Reset” button.

The master clock generator is assembled on a D1 (LA3) chip and a Z1 quartz resonator at a frequency of 1024 kHz. The frequency divider is assembled on K155IE8 microcircuits; K155IE5 and four K155IE1. In the measurement mode, the accuracy of the “MHz”, “kHz” and “Hz” settings is set by push-button switches SA4 and SA5.

The power supply of the frequency meter (Fig. 3) consists of transformer T1, from winding II of which, after the rectifier VDS1, a voltage stabilizer on the DA1 microcircuit and a filter on capacitors C4 - C11, a voltage of +5V is supplied to power the microcircuits.

A voltage of 170V from winding III of transformer Tr1 through diode VD5 is used to power gas-discharge digital indicators H1..H6.

In the pulse shaper, the field-effect transistor KP303D (V3) can be replaced with KP303 or KP307 with any letter index, transistor KT347 (V5) with KT326, and KT368 (V6, V7) with KT306.

Choke L1 type D-0.1 or homemade - 45 turns of PEV-2 0.17 wire, wound on a frame with a diameter of 8 mm. All switches are P2K type.

Setting up the device comes down to checking the correct installation and measuring the supply voltages. A correctly assembled frequency meter confidently performs its functions; the only “capricious” unit is the input driver, the configuration of which must be given maximum effort. Having replaced R3 and R4 with variable resistors 2.2 kOhm and 100 Ohm, you need to set the voltage on resistor R5 to approximately 0.1...0.2V. Having supplied a sinusoidal voltage with an amplitude of about 0.5V from the signal generator to the input of the shaper, and replacing resistor R6 with a variable resistor with a nominal value of 2.2 kOhm, it is necessary to adjust it so that rectangular pulses appear at the output of element D6.1. Gradually lowering the input level and increasing the frequency, it is necessary to select elements R6 and SZ to achieve stable operation of the shaper over the entire operating range. You may have to select the resistance of resistor R9. During the installation process, all variable resistors should have leads no longer than 1...2 cm.

When the installation is completed, they should be unsoldered one at a time and replaced with constant resistors of a suitable value, each time checking the operation of the driver.

In the design, instead of IN-17 indicators, gas-discharge indicators IN-8-2, IN-12, etc. can be used.

In the pulse shaper, KT368 transistors can be replaced with KT316 or GT311; instead of KT347, you can use KT363, GT313 or GT328. Diodes V1, V2 and V4 can be replaced with KD521, KD522.

* This circuit was assembled by me back in 1988 in the same housing with a sound generator and was used as a digital scale.

As an independent device, it was designed recently, so it is possible that an error could have crept somewhere in the circuit diagram and design of the printed circuit board.

Bibliography:

To help a radio amateur No. 084, 1983

Digital Devices on Integrated Circuits - Radio and Communications Publishing House, 1984.

Radio magazine: 1977, No. 5, No. 9, No. 10; 1978, no. 5; 1980, no. 1; 1981, no. 10; 1982, no. 1, no. 11; No. 12.

Amateur radio digital devices. - M.: Radio and Communications, 1982.

Scheme of a very simple digital frequency meter based on foreign components

Good afternoon, dear radio amateurs!
Welcome to the website ““

In this article on the site Radio amateur we'll look at another simple one amateur radio diagram – frequency meter. The frequency meter is assembled on a foreign element base, which is sometimes more affordable than domestic ones. The scheme is simple and easy to repeat for a beginner radio amateur.

Frequency meter circuit:

Frequency meter made on HFC4026BEY measuring counters, CD40 series microcircuits and seven-segment LED indicators with a common cathode HDSP-H211H. With a power supply voltage of 12 volts, the frequency meter can measure frequencies from 1 Hz to 10 MHz.

The HFC4026BEY chip is a representative of high-speed CMOS logic and contains a decimal counter and decoder for a seven-segment common-cathode LED indicator. Input pulses are supplied to input “C”, which has a Schmitt trigger, which makes it possible to significantly simplify the circuit of the input pulse shaper. In addition, the input of the counter “C” can be closed by applying a logical one to pin 2 of the microcircuit. Thus, there is no need for an external key device that transmits pulses to the counter input during the measurement period. You can turn off the indication by applying a logical zero to pin 3. All this simplifies the frequency meter control circuit.

The input amplifier is made using transistor VT1 according to the switch circuit. It converts the input signal into pulses of arbitrary shape. The squareness of the pulses is given by a Schmitt trigger located at the “C” input of the microcircuit. Diodes VD1-VD4 limit the amplitude of the input signal. The reference signal generator is made on the CD4060B chip. In the case of using a quartz resonator with a frequency of 32768 Hz, a frequency of 4 Hz is removed from pin 2 of the microcircuit, which is supplied to the control circuit consisting of a decimal counter D2 and two RS flip-flops on the D3 chip. If you use a 16384 Hz resonator (from Chinese alarm clocks), the 4 Hz frequency will need to be removed not from pin 2 of the microcircuit, but from pin 1.

The CD4060B chip can be replaced with another analogue of the xx4060 type (for example, NJM4060). The CD4017B microcircuit can also be replaced with another analogue of the xx4017 type, or with the domestic K561 IE8, K176 IE8 microcircuit. The CD4001B microcircuit is a direct analogue of our K561IE5, K176IE5 microcircuits. The HFC4026BEY chip can be replaced with its complete analog CD4026, but the maximum measured frequency will be 2 MHz. The input circuit of the frequency meter is primitive; it can be replaced with some more advanced unit.

The parameters of the proposed frequency meter are given in table. 1.

This frequency meter, in my opinion, has a number of advantages compared to the previous ones:

Modern cheap and easily accessible element base;
- maximum measured frequency - 200 MHz;
- combination of a frequency meter and a digital scale in one device;
- the possibility of increasing the maximum measured frequency to 1.2 GHz with minor modifications to the input part of the device;
- possibility of switching during operation of up to 4 inverters.
Frequency measurement is carried out in the classical way: counting the number of pulses over a fixed time interval.

The input signal through capacitor C4 is supplied to the base of transistor VT1, which amplifies the input signal to the level required for normal operation of the DD2 chip. The DD2 193IEZ microcircuit is a high-frequency frequency divider, the division coefficient of which is 10. Due to the fact that in the K1816BE31 microcontroller used the maximum frequency of the counting input T1 is f = Fkv/24, where Fkv is the frequency of the quartz used, and in the frequency meter Fkv = 8.8672 MHz, the signal from the high-frequency divider is fed to an additional frequency divider, which is a decimal counter DD3. The frequency measurement process begins with zeroing the divider DD3, the reset signal of which comes from pin 12 of the microcontroller DD4. The signal allowing the passage of the measured signal to the decimal divider comes from pin 13 of DD4 through the inverter DD1.1 to pin 12 of DD1.3.

At the end of the fixed measurement time interval, a high level appears at pin 13 of DD4, which through the inverter DD1.1 prohibits the passage of the measured signal to the divider DD3, and the process of converting the accumulated time pulses into frequency begins, as well as preparing data for display.

This device has the ability to operate in both high-frequency and low-frequency ranges. When operating in the low-frequency range, switch S1 must be set to the upper position and the signal must be applied to input 2 (pin 9) of the frequency meter board. To measure frequencies from 1 Hz to 20 MHz, you must use the driver proposed in.

The microcontroller operating program is located in the DD8 ROM, the DD5 chip is used to multiplex the microcontroller addresses. The ROM firmware for operating the device as a frequency meter is shown in Table 2.

To obtain maximum efficiency from using the microcontroller, the device uses dynamic indication.

When using this device as a digital scale, it is necessary to apply a high level to pin 22 of DD8 using switch S2.3. The IF value is selected by connecting pins 10 and 11 of the DD4 chip to ground. Input 3 (pin 5) of the frequency meter board is designed to turn on the selected intermediate frequency (for example, when switching from receiving to transmitting). When the device is operating in digital scale mode, the low-order digits of the indicator show hundreds of hertz. Operation of the device in digital scale mode corresponds to a different ROM firmware.

The printed circuit board (Fig. 2, Fig. 3, Fig. 4) is made of double-sided fiberglass with dimensions of 100x130 mm. The indicator is attached directly to the printed circuit board with two clamps made from ordinary mounting wire. A socket is provided for installing the DD8 chip. When laying out the board, it was necessary to place transistor VT1 as close as possible to DD2. Around VT1 and DD2, as much foil as possible is left on both sides in order to shield high-frequency circuits. The design uses IV-18 as the HL1 indicator, as it is the most popular in amateur radio designs. If it is necessary to miniaturize the design, the IV-18 indicator can be replaced with the IV-21, which has significantly smaller overall dimensions. In this case, it is necessary to reduce the filament voltage and the negative voltage at the cathode according to the specifications. It is advisable to use the DD1 microcircuit of the 1533 series as a higher frequency one.

To power the frequency meter, you can use the power supply described in detail in. You only need to increase the voltage from -20 V to -30 V and the filament voltage to 4.8 V when using the IV-18 indicator. In the specified power supply circuit, it is advisable to replace the KD503 diode with a KS133 zener diode, which eliminates false illumination of the indicator segments.

Setting up the frequency meter should begin by checking for breaks in all connecting conductors of the printed circuit board without exception, then check for the absence of short circuits in the connecting conductors adjacent to the printed circuit board. Immediately after applying power to the frequency meter, check the current consumption at +5 V. It should not exceed 250 mA. Then measure the voltage at the collector VT1, it should be within 2.0 V...3.0 V. The specified voltage is set by selecting resistor R3. With error-free installation, serviceable parts and no errors in the program, the final adjustment of the device consists of accurately setting the frequencies of the microcontroller master oscillator using capacitor C7 in accordance with the readings of a standard frequency meter.

Thanks to the software-controlled measurement process, it is possible to use non-decimal high-frequency dividers by slightly modifying the microcontroller program. The author tested microcircuits 193PP1 (division coefficient - 704), 193IE6 (division coefficient - 256) in this device. Tests have shown that the maximum frequency of the measured signal reaches 1 GHz. The 193PTs1 microcircuit turned out to be the most preferable, because it has an input amplifier. The K181BE51 microcontroller can be replaced with K1816BE31, K1830BE31, K1830BE51 or their foreign analogues - 8031, 80C31. If the 193IEZ microcircuit is missing, you can replace it with the K500IE137 microcircuit, turning it on according to the standard circuit.

Literature
1. Biryukov S. Digital frequency meter//Radio. - 1981.-N10.-C.44.
2. Khlyupin N. Digital frequency meter // Radio amateur. - 1994. - N 11.
3. Stashin V.V. Design of digital devices. - 1990.

List of radioelements

This article is intended for those who do not want to “bother” with MK.

Every radio amateur in the process of his creative activity is faced with the need to equip his “laboratory” with the necessary measuring instruments.
One of the devices is a frequency meter. Those who have the opportunity buy ready-made ones, while others assemble their own structure according to their capabilities.
Nowadays there are many different designs made on MK, but they are also found on digital microcircuits (as they say, “Google to the rescue!”).
After an “audit” in my bins, it was discovered that there were digital microcircuits of the series 155, 555, 1533, 176, 561, 514ID1(2) (simple logic - LA, LE, LN, TM, medium complexity - IE, IR, ID , still 80-90 years of production, throw them away - the “toad” crushed!) on which you can assemble a simple device from those components that were at hand at the moment.
I just wanted to be creative, so I started developing a frequency meter.

Picture 1.
Appearance of the frequency meter.

Frequency meter block diagram:

Figure 2.
Block diagram of the frequency meter.

Input device-former.

I took the circuit from the Radio magazine of the 80s (I don’t remember exactly, but it looks like Biryukov’s frequency meter). I repeated it before and was pleased with the work. The shaper uses K155LA8 (works confidently at frequencies up to 15-20 MHz). When using 1533 series microcircuits (counters, input driver) in the frequency meter, the operating frequency of the frequency meter is 30-40 MHz.

Figure 3.
Input shaper and 3G measuring intervals.

Master oscillator, measuring interval generator.

The master oscillator is assembled on a clock MS of the K176 series, shown in Figure 3 along with the input driver.
Switching on the MS K176IE12 is standard, there are no differences. Frequencies of 32.768 kHz, 128 Hz, 1.024 kHz, 1 Hz are generated. Only 1 Hz is used in emergencies. To generate a control signal for the control unit, this frequency is divided by 2 (0.5 Hz) MS K561TM2 (CD4013A) (one D-trigger is used).

Figure 4.
Interval signals.

Signal generator for resetting counters KR1533IE2 and writing to storage registers K555IR16

Assembled on the K555(155)AG3 MS (two standby multivibrators in one housing), you can also use two K155AG1 MSs (see Fig. No. 3).
Based on the decline in the control signal of MS AG3, the first motor generates a Rom pulse - writing to the storage registers. Based on the decline of the Rom pulse, the second pulse is generated to reset the triggers of the KR1533IE2 Reset counters.

Figure 5.
Reset signal.

For frequency measurement, a block was assembled with 2 K555IR16 and 4 K555(155)LE1 (I found the circuit on the Internet, I just slightly adjusted the existing elementary base for myself).
You can simplify the frequency meter and not assemble a circuit for suppressing insignificant zeros (Figure No. 9 shows a circuit of a frequency meter without a circuit for suppressing insignificant zeros), in this case all the indicators will simply light up, see for yourself which is best for you.
I put it together because it’s just more pleasant for me to look at the frequency meter display.

Figure 6. Scheme for suppressing insignificant zeros.

The inclusion of KR1533IE2 counters, K555IR16 registers, and KR514ID2 decoders is standard, according to the documentation.

Figure 7.
Connection diagram for counters and decoders.

The entire emergency situation is assembled on 5 boards:
1, 2 - counters, registers and decoders (each board has 4 decades);
3 - block for suppressing insignificant zeros;
4 - master oscillator, measuring interval shaper, Rom and Reset signal shaper;
5 - power supply.

Board sizes: 1 and 2 - 70x105, 3 and 4 - 43x100; 5 - 50x110.

Figure 8.
Connecting a zero-suppression circuit in a frequency meter.

Power unit. Assembled on two MS 7805. The inclusions are standard, as recommended by the manufacturer. To make a decision on the power supply, measurements of the emergency current consumption were carried out, and the possibility of using a UPS and power supply with PWM stabilization was also checked. We tested: a UPS assembled on TNY266PN (5V, 2A), a PWM power supply based on LM2576T-ADJ (5V, 1.5A). General comments - the emergency system does not work correctly, because... Pulses pass through the power circuit at the frequency of the drivers (for TNY266PN about 130 kHz, for LM2576T-ADJ - 50 kHz). The use of filters did not reveal any significant changes. So, I settled on an ordinary power supply - trans, diode bridge, electrolytes and two MS 7805. The current consumption of the entire emergency (all “8” on the indicators) is about 0.8A, when the indicators are off - 0.4A.

Figure 9.
Frequency meter circuit without a circuit for suppressing insignificant zeros.

In the power supply I used two MS 7805 to power the emergency system. One stabilizer MS powers the input driver board, the decoder control unit (cancellation of insignificant zeros) and one counter-decoder board. The second MS 7805 powers another board of counter-decoders and indicators. You can assemble a power supply on one 7805, but it will heat up decently, and there will be a problem with heat dissipation. In emergency situations, you can use MS series 155, 555, 1533. It all depends on the capabilities….

Figure 10, 11, 12, 13.
Frequency meter design.

Possible replacement: K176IE12 (MM5368) with K176IE18, K176IE5 (CD4033E); KR1533IE2 on K155IE2 (SN7490AN, SN7490AJ), K555IE2 (SN74LS90); K555IR16 (74LS295N) can be replaced with K155IR1 (SN7495N, SN7495J) (they differ in one pin), or used to store information K555(155)TM5(7) (SN74LS77, SN74LS75); KR514ID2 (MSD101) decoder for indicators with OA, you can also use KR514ID1 (MSD047) decoder for indicators with OK; K155LA8 (SN7403PC) 4 elements 2I-NOT with an open collector - on K555LA8; K555AG3 (SN74LS123) on K155AG3 (SN74123N, SN74123J), or two K155AG1 (SN74121); K561TM2 (CD4013A) to K176TM2 (CD4013E). K555LE1 (SN74LS02).

P.S. You can use various indicators with OA, only the current consumption per segment should not exceed the output load capacity of the decoder. Limiting resistors depend on the type of indicator used (in my case, 270 ohms).

Below in the archive there are all the necessary files and materials for assembling the frequency meter.

Good luck to everyone and all the best!

The signal under study is fed to the input of the pulse voltage former. At its output, rectangular electrical oscillations are formed, corresponding to the frequency of the input signal, which are then sent to the electronic key. Pulses of a standard frequency also arrive here through the control device, opening the key for a certain time. A burst of pulses appears at the output of the electronic key. The number of pulses in a packet is counted by a binary-decimal counter. Its state after closing the key is displayed by a digital indication unit operating during the duration of the reference pulse, i.e. one second.
In the pulse counting mode, the control device blocks the reference frequency source, the binary decimal counter continuously counts the pulses arriving at its input, and the digital display unit displays the counting results.

The schematic diagram of the frequency meter is shown in Fig. 2. The voltage pulse former is assembled on the K155LD1 (DD1) microcircuit and is a complicated Schmitt trigger. Resistor R1 limits the input current, and diode VD1 protects the microcircuit from changes in input voltage of negative polarity. Resistor R3 limits the lower limit of the input signal voltage. From the output of the driver (pin 9 of the microcircuit), rectangular pulses are supplied to one of the inputs of the logical element DD11.1, which performs the function of an electronic key.

The block of reference frequencies includes a generator based on elements DD2.1 - DD2.3, the pulse frequency of which is stabilized by a quartz resonator ZQ1 and a seven-step frequency divider on microcircuits DD3 - DD9. The frequency of the quartz resonator is 8 MHz. The DD3 chip divides the frequency by 8, and the chips of each subsequent stage divide the frequency by 10. The pulse frequency at the output of DD9 is 1 Hz. The range of measured frequencies is set by switch SA1. To more accurately measure the signal frequency with switch SA1, it is necessary to select the appropriate measurement range, moving from a higher frequency region to a low frequency one. The control device consists of a trigger DD10.1 and DD10.2, inverters DD11.3, DD11.4 and a transistor VT1, forming a standby multivibrator. The input C of the trigger DD10.1 receives pulses from the reference frequency block and it switches to a single state and with a logical 1 signal it opens the electronic key DD11.1 From this moment, the pulses of the measured frequency pass through the key and inverter D11.2 and enter the input of the counter DD12. At the edge of the next pulse, DD10.1 takes the initial state and switches the trigger DD10.2 to the single state.

In turn, the DD10.2 trigger with a logical zero level at the inverse output blocks the input of the control device from the influence of pulses of a reference frequency, and with a logical one level at the direct output it starts the standby multivibrator. The electronic key is closed with a logical level of 0 at the direct output DD10.1. The indication of the number of pulses in a packet arriving at the counter input begins. With the appearance of logical level 1 at the direct output of trigger DD10.2, capacitor C3 begins to charge through resistor R9. As it charges, the voltage at the base of transistor VT1 increases. When it reaches 0.6 V, the transistor will open and the voltage at its collector will decrease to almost zero. The logical 1 signal that appears at the output of element DD11.3 affects the R0 input of microcircuits DD12, DD14, DD16, as a result of which the counter is reset to 0. The measurement indication stops. At the same time, a logical 0 signal appears at pin 11 of the DD11.4 inverter, switches the DD10.2 trigger and the standby multivibrator to their original state. Capacitor C3 is discharged through diode VD2 and microcircuit DD10.2. With the appearance of the next reference frequency pulse at the DD10.1 input, the next cycle of operation of the device in measurement mode begins. To switch the frequency meter to continuous pulse counting mode, set switch SA2 to the “counting” position. In this case, the trigger DD11.1 switches and 1 appears at its direct output. The DD11.1 key is open and through it pulses are continuously sent to the input of the pulse counter. The counter readings are reset by pressing the “reset” button. The frequency meter power supply (Fig. 3) consists of transformer T1, rectifier VD3, voltage stabilizer VD5, VT2 and a filter on capacitors C9 - C11, providing a voltage of 5 V to power the microcircuits.

The voltage from winding III of the transformer is supplied through the diode VD5 to the power circuit of gas-discharge digital indicators. Construction and details. The frequency meter parts are mounted on printed circuit boards. Gas-discharge indicators IN1 were used as indicators. The transformer of the T1 power supply is made on a magnetic core ШЛ 20х32. Winding 1 contains 111650 turns of PEV-1 0.1 wire, winding 2 contains 55 turns of PEV-1 0.47, winding 3 – 1500 turns of PEV-1 0.1 wire. Transistor T2 is installed on the radiator. Instead of a pulse shaper on the K155LD1 microcircuit, you can assemble a shaper according to the circuit in Fig. 4

In addition, the design increased the number of digital indicators to five and, accordingly, the number of K155IE2 counter chips and K155ID1 decoder chips. The expansion of the digital display provides a more convenient display of information. Setting up the device comes down to checking the correct installation and measuring the supply voltages. A correctly assembled frequency meter confidently performs its functions. Naturally, vacuum indicators can be replaced with more modern, LED type ALS, and microcircuits with similar new series.

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