Generator on K561LA7 with frequency control. Rectangular pulse generator on K561LA7 Chip k561la7 in electronic designs

A device for creating the effect of lights running from the center to the edges of the sun. Number of LEDs - 18 pcs. Upit.= 3...12V.

To adjust the flicker frequency, change the values ​​of resistors R1, R2, R3 or capacitors C1, C2, C3. For example, doubling R1, R2, R3 (20k) will halve the frequency. When replacing capacitors C1, C2, C3, increase the capacitance (22uF). It is possible to replace K561LA7 with K561LE5 or with a complete foreign analogue of CD4011. The values ​​of the resistors R7, R8, R9 depend on the supply voltage and on the LEDs used. With a resistance of 51 ohms and a supply voltage of 9V, the current through the LEDs will be slightly less than 20mA. If you need an economical device and you use bright LEDs at low current, then the resistance of the resistors can be significantly increased (up to 200 ohms and even more).

Even better, with a 9V supply, use a serial connection of LEDs:

Below are the drawings of printed circuit boards of two options: the sun and the windmill:


Also often viewed with this scheme:
Measurement technique

Generator on K561LA7 with frequency control

Digital microcircuits can implement not only mathematical logic. One example of alternative functionality is clock generators.

In its simplest form, the generator is nothing more than an oscillatory circuit assembled on the basis of a capacitor and resistance (the so-called RC circuit). However, such circuits are characterized by low quality of the output signal and non-linearity of the generated pulses.

To give them the correct "square" shape will be able to microcircuits that implement a simple logic "AND-NOT", such as K561LA7 or analogues. But more about everything.

Description K561LA7

The microcircuit implements the logic of four independent elements "AND-NOT" (circuit with pinout below).

Rice. 1. K561LA7

Rated voltage for power supply - 10 V, maximum - no more than 15 V.

It can operate at almost any temperature (from -45 to +85°C), consumes very little current (up to 0.3 μA) and has a short delay time (80 ns).

Direct analogues include the CD4011A chip. However, in the described task, the following can also be applied:

  • K176LE5 (direct replacement is acceptable without changing the circuit);
  • Chips from the K561 series;
  • K176PU2 / or PU1;
  • As well as other microcircuits that implement the logic of four or more independent inverters.

Just in case, here is a truth table.

Rice. 2. Truth table

Simple frequency generator

The circuit shown below will form a meander (rectangular pulses).

Rice. 3. The scheme that will form the meander

In fact, you can do without the last block D1.4.

Oscillations are set by the C1R1 circuit, and the logic elements convert the sinusoidal signal into a rectangular one, cutting off the rise and fall edges according to the inversion logic (there is an input signal that exceeds the threshold value - it is output to 0, absent - a logical unit is output).

The disadvantage of such a generator is the inability to control the frequency (it is fixed and is determined by the value of the capacitor with a resistor) and influence the pause time, pulse duration (or their ratio - that is, the duty cycle).

Regulated generator

The circuit shown below allows you to separately adjust the pause time and pulse duration.

Rice. 4. A circuit that allows you to separately adjust the pause time and pulse duration

The tuning resistors R2 and R3 are responsible for this logic. The frequency range is slightly regulated, and therefore, for its cardinal change, it is possible to provide for the inclusion of several capacitors of different capacities (to replace C1), which are included in the circuit alternately.

Another version with the ability to control the duty cycle (based on the circuit of the same multivibrator).

Rice. 5. A variant of the circuit with the ability to control the duty cycle

It can be called almost universal for various kinds of experiments with GTIs (clock pulse generators).

It looks like this.

Rice. 6. Diagram with different waveform

The value of resistors and capacitors is not particularly important and can be changed to suit your needs.

As you can see above, there are three outputs at once with a rectangular signal (meander), triangular and sine.

Each of them can be changed by the appropriate trimmers.


Publication date: 06.03.2018

Readers' opinions
  • Vitaly / 17.05.2019 - 16:50
    Tell me how to increase the amplitude of the signal if in the first circuit put c1 on 100p for example? And how to calculate the correct resistor?
  • Anton / 31.08.2018 - 22:04
    Good enough.

The k561la7 chip was popular and even loved at one time. Quite deservedly, since at that time it was a kind of "universal soldier", which made it possible to build not only logic, but also various generators, and even amplify analog signals. It's funny that even today a lot of queries like description of the chip K561LA7, analogue k561la7, generator on k561la7, square-wave generator on K561LA7 and so on.

Unfortunately, not everything is so simple with this generally useful microcircuit ...

I was surprised to find that, for example, Texas Instruments still release something full of analogue what is - chip CD4011A. For the curious, here is a link to the documentation page or datasheet on TI's CD4011A.

note that pinout k561la7 is different from the usual layout 4x 2I-NOT TTL (k155la3 and company).

The microcircuit is really convenient:

  • Negligible input leakage current is a hallmark of all CMOS logic
  • Current consumption in static mode - usually fractions of microamps
  • Ability to work from 3 to 15 volts of supply voltage
  • Symmetrical, albeit small (less than a milliamp) load capacity of the outputs
  • The microcircuit was available even in difficult Soviet times. Today, in general - 3 rubles a little thing, or even cheaper.

In order to quickly mock up one arm of the DCC booster bridge, I habitually used k561la7 to build a classic CMOS relaxation oscillator.

Resistor R2 and capacitor C1 set the generation frequency approximately equal to 0.7/R2C1. Resistor R1 limits the discharge current of capacitor C1 through the protective diodes at the input of the first inverter Q1.

The principle of operation of the generator is briefly as follows: the capacitor covers two inverters with positive feedback, thus obtaining a latch, a trigger. Do a thought experiment: replace the capacitor and R1 with a conductor, while the influence of R2 can be neglected (but only for a short time).

Through R2, a current is supplied to the upper plate of the capacitor according to the scheme, recharging the capacitor "in the other direction", that is, preventing our latch from remaining in the same state indefinitely. This current determines the time for recharging the capacitor, and, consequently, the frequency of generation. Since the RF latch is covered by positive feedback exactly as in the thought experiment just carried out - switching should ideally occur at the highest possible speed for the keys: the slightest increase in voltage at the output of Q2 is directly fed to input Q1, which leads to a decrease in the voltage at the output Q1 and an even greater increase in the voltage at the output of Q2.

Waveforms at the input and output of Q1:

Here's how unattractive everything looks at outputs Q1 and Q2:

  • R1 = 91 kΩ
  • R2 = 33 kΩ
  • C1 = 10 nF
  • C2 = 2.2 nF
  • F = 1.3 kHz

For serious design, I personally would not use this square wave generator. Even a simple one has better stability and produces a very clean rectangle.

Please, if this material has helped you in any way, or even just evoked pleasant nostalgic memories - share it with others. To do this, simply "click" on the icon of the network in which you are registered, so that your friends will receive a link to this article. Thank you!

Simple radio circuits for beginners

In this article, we will consider several simple electronic devices based on K561LA7 and K176LA7 logic circuits. In principle, these microcircuits are almost the same and have the same purpose. Despite a slight difference in some parameters, they are practically interchangeable.

Briefly about the K561LA7 chip

Chips K561LA7 and K176LA7 are four elements 2I-NOT. Structurally, they are made in a black plastic case with 14 pins. The first output of the microcircuit is indicated as a label (the so-called key) on the case. It can be either a dot or a notch. The appearance of the microcircuits and the pinout are shown in the figures.

The power supply of the microcircuits is 9 volts, the supply voltage is applied to the outputs: output 7 is "common", output 14 is "+".
When mounting microcircuits, it is necessary to be careful with the pinout - accidental installation of the microcircuit "inside out" disables it. It is desirable to solder chips with a soldering iron with a power of no more than 25 watts.

Recall that these microcircuits were called "logical" because they have only two states - either "logical zero" or "logical one". Moreover, at the level "one" means a voltage close to the supply voltage. Consequently, with a decrease in the supply voltage of the microcircuit itself, the level of the "Logical unit" will be less.
Let's do a little experiment (Figure 3)

First, let's turn the 2I-NOT chip element into NOT simply by connecting the inputs for this. We will connect an LED to the output of the microcircuit, and we will apply voltage to the input through a variable resistor, while controlling the voltage. In order for the LED to light up, it is necessary to obtain a voltage equal to logical "1" at the output of the microcircuit (this is pin 3). You can control the voltage using any multimeter by including it in the DC voltage measurement mode (in the diagram it is PA1).
But let's play a little with power - first we connect one 4.5 Volt battery. Since the microcircuit is an inverter, therefore, in order to get "1" at the output of the microcircuit, it is necessary, on the contrary, to apply a logical "0" to the input of the microcircuit. Therefore, we will start our experiment with a logical "1" - that is, the resistor slider should be in the upper position. Rotating the variable resistor slider, wait for the moment when the LED lights up. The voltage at the variable resistor engine, and therefore at the input of the microcircuit, will be about 2.5 volts.
If we connect a second battery, then we will already get 9 Volts, and in this case our LED will light up at an input voltage of about 4 Volts.

Here, by the way, it is necessary to give a little clarification.: it is quite possible that in your experiment there may be other results different from the above. There is nothing surprising in this: in the first two, there are no completely identical microcircuits and their parameters will differ in any case, secondly, a logic microcircuit can recognize any decrease in the input signal as a logical "0", and in our case we lowered the input voltage to twice, and thirdly, in this experiment, we are trying to make the digital microcircuit work in the analog mode (that is, the control signal passes smoothly for us), and the microcircuit, in turn, works as it should - when a certain threshold is reached, it flips the logical state instantly. But after all, this very threshold may differ for different microcircuits.
However, the purpose of our experiment was simple - we needed to prove that the logic levels directly depend on the supply voltage.
Another caveat: this is only possible with CMOS microcircuits that are not very critical to the supply voltage. With microcircuits of the TTL series, things are different - their power supply plays a huge role and during operation a deviation of no more than 5% is allowed

Well, a brief acquaintance is over, let's move on to practice ...

Simple time relay

The device diagram is shown in Figure 4. The microcircuit element is turned on here in the same way as in the experiment above: the inputs are closed. While the button button S1 is open, the capacitor C1 is in a charged state and no current flows through it. However, the input of the microcircuit is also connected to the "common" wire (through the resistor R1) and therefore a logical "0" will be present at the input of the microcircuit. Since the microcircuit element is an inverter, it means that the output of the microcircuit will be a logical "1" and the LED will be on.
We close the button. A logical "1" will appear at the input of the microcircuit and, therefore, the output will be "0", the LED will turn off. But when the button is closed, the capacitor C1 will instantly discharge. And this means that after we release the button in the capacitor, the charging process will begin and while it continues, an electric current will flow through it, maintaining the level of logical "1" at the input of the microcircuit. That is, it turns out that the LED will not light up until the capacitor C1 is charged. The charge time of the capacitor can be changed by selecting the capacitance of the capacitor or by changing the resistance of the resistor R1.

Scheme two

At first glance, almost the same as the previous one, but the button with the time-setting capacitor is turned on a little differently. And it will also work a little differently - in standby mode, the LED does not light up, when the button is closed, the LED will light up immediately, and go out with a delay.

Simple flasher

If you turn on the microcircuit as shown in the figure, then we will get a generator of light pulses. In fact, this is the simplest multivibrator, the principle of which has been described in detail on this page.
The pulse frequency is regulated by resistor R1 (you can even set a variable) and capacitor C1.

Controlled flasher

Let's slightly change the flasher circuit (which was higher in Figure 6) by introducing into it a circuit from the time relay already familiar to us - button S1 and capacitor C2.

What we get: when the button S1 is closed, the input of the element D1.1 will be a logical "0". This is a 2I-NOT element and therefore it doesn’t matter what happens at the second input - the output will be "1" in any case.
This same "1" will go to the input of the second element (which is D1.2) and, therefore, the logical "0" will firmly sit at the output of this element. And if so, the LED will light up and will burn constantly.
As soon as we release the S1 button, the charge of the capacitor C2 begins. During the charge time, current will flow through it while holding the logic "0" level at pin 2 of the microcircuit. As soon as the capacitor is charged, the current through it will stop, the multivibrator will start working in its normal mode - the LED will blink.
In the following diagram, the same chain is also introduced, but it is switched on in a different way: when you press the button, the LED will start flashing and after some time it will turn on permanently.

Simple squeaker

There is nothing particularly unusual in this circuit: we all know that if a speaker or earphone is connected to the output of the multivibrator, it will begin to make intermittent sounds. At low frequencies it will just be a "tick" and at higher frequencies it will be a squeak.
For the experiment, the scheme shown below is of greater interest:

Here again, the time relay familiar to us - we close the button S1, open it and after a while the device starts to beep.

Based on the K561LA7 microcircuit, it is possible to assemble a generator that can be applied in practice to generate pulses for any systems or pulses, after amplification through transistors or thyristors, can control lighting devices (LEDs, lamps). As a result, on this chip it is possible to assemble a garland or running lights. Further in the article, you will find a schematic diagram of connecting the K561LA7 microcircuit, a printed circuit board with the location of radio elements on it, and a description of the assembly.

The principle of operation of the garland on the KA561 LA7 chip

The microcircuit begins to generate pulses in the first of 4 elements 2I-NOT. The duration of the LED glow pulse depends on the value of the capacitor C1 for the first element and, respectively, C2 and C3 for the second and third. Transistors are actually controlled "keys", when a control voltage is applied from the microcircuit elements to the base, when opened, they pass electric current from the power source and feed the LED chains.
Power is supplied from a 9 V power supply with a rated current of at least 100 mA. With proper installation, the electrical circuit does not need to be configured and is immediately operational.

The designation of radio elements in a garland and their denominations according to the above diagram

R1, R2, R3 3 mΩ - 3 pcs.;
R4, R5, R6 75-82 Ohm - 3 pcs.;
C1, C2, C3 0.1 microfarad - 3 pcs.;
НL1-HL9 LED AL307 - 9 pcs.;
D1 chip K561LA7 - 1 pc.;

The board shows the paths for etching, the dimensions of the textolite and the location of the radio elements during soldering. For etching the board, it is possible to use a board with one-sided copper coating. In this case, all 9 LEDs are installed on the board, if the LEDs are assembled into a chain - a garland, and not mounted on the board, then its dimensions can be reduced.

Technical characteristics of the K561LA7 chip:

Supply voltage 3-15 V;
- 4 logical elements 2I-NOT.

Loading...
Top