Signal level indicator connection circuit. Radio constructor - LED indicator of low-frequency signal level. Pinout of gas-discharge indicators of the IN series

Hi all. I used to assemble such circuits using light bulbs, and when LEDs became more readily available, . When the Internet appeared, such an abundance of schemes poured in, but arose big problem- you solder a circuit, and it either doesn’t work at all or works but not as it should, and then you start conducting experiments with it, achieving the desired result. But during the time you tinker with the circuit, you learn a lot of interesting things, you understand which detail affects what, and in general you develop to the fullest. Here are several really tested and 100% working schemes that you can safely do.

Collection of AF LED indicator circuits

Here are a few more level indicator circuits adjusted to good blinking from music

Here’s another strobe controlled by a sound signal that I once made, maybe it will be useful for someone else:

I made these two strobe lights, one like a policeman, the other just like a disco.

This indicator was still soldering.

And this indicator was amplified under a powerful load.

And regarding this indicator, the LEDs must all be the same color; this is a prerequisite, since the scale itself is passive.

Now here’s an interesting circuit, somehow I got a two-color LED, so I decided to make it blink beautifully to the music - this is the circuit that came out.

But even this specialized circuit indicator like 3915 and it requires its own control circuit, the most suitable one is the same as in the diagram, the parts are also selected according to best work. Since it has a very sensitive input, a divider is added at the signal input. A resistor R7 was added to prevent the first LED from lighting up. But the circuit converts perfectly into a simple active frequency filter. Let’s take this figure as an example, it all depends on the capacity of the input capacitor C1 and the additional capacitor C5, which is placed between the collector and the common wire.

In this way, you can make three frequency channels and already apply this whole thing to the DMU. To begin with, you can solder just such a pre-drive amplifier with regulators for each channel, and load an LM with control circuits configured to its frequency range.

Also, if anyone needs the indicator to work purely on drums, or in other words, an instrument that sets the beat of a melody, this version of the control circuit is very suitable for these purposes.

And lastly, in the wiring of the microcircuit there is such a resistor R6, through it the common plus is supplied to the LEDs, it can be disconnected from the main plus and connected to such a breaker circuit, then the LEDs in the column will not only glow, but also flicker in addition, the effect is cool, I did this too.

Discuss the article SOUND LEVEL INDICATORS ON LED

Indicator on LM3915

The LM3915 integrated circuit is specially designed to build an LED level indicator and allows you to visually evaluate the level and change sound signal in the form of a light “column”, “ruler” or a luminous point moving on a conventional scale. The successful design of the LM3915 chip has ensured its worthy place in LED indicator circuits. The wizard invites you to assemble a sound indicator using LM3915 and 10 LEDs. Below is detailed instructions for assembling a sound indicator circuit with your own hands with photos and video illustrations. Even a novice electronics engineer can assemble a sound indicator.

How to assemble an LED level indicator on LM3915 with your own hands

The design of the LM3915 microcircuit consists of ten similar types enclosed in a package operational amplifiers comparators. The direct inputs of the amplifiers are connected through a line of resistive dividers selected so that the LEDs in the amplifier load are turned on according to a logarithmic dependence. The return inputs of the amplifiers receive an input signal, which is generated by a buffer amplifier (pin 5). The design of the microcircuit also includes an integrated stabilizer (pins 3, 7, 8), as well as a key for setting the operating mode of the indicator (pin 9). The microcircuit has a wide supply voltage range from 3 to 25 Volts. Magnitude reference voltage set in the range from 1.2 to 12 Volts by external resistors. The indicator scale corresponds to a signal level of 30 dB in 3 dB steps. The output current is adjustable from 1 to 30 mA.

Assembly of the indicator is simplified by purchasing a set of parts in the online store using the link https: //ali.pub/2c62ph . The kit includes a board, a microcircuit, LEDs and all the necessary wiring (resistors, capacitors and connectors).

Set of parts “Sound level indicator for LM3915”

Details of the “Sound Level Indicator for LM3915” kit

The sound indicator circuit on the LM3915 is shown in the photo.

Operating principle. A supply voltage of 12 Volts is supplied to the third pin of the LM3915. It is also supplied to the LEDs through the limiting resistor R2. Resistors R1 and R8 equalize the brightness of the red LEDs on the scale. Also, a voltage of 12 Volts is supplied to the jumper for controlling the operating mode of the indicator (pin 9). When the jumper is closed, the circuit ensures that only one LED lights up, corresponding to the signal level. When the jumper is open, the circuit operates in the “column” effect mode, the input signal level is proportional to the height of the illuminated column or the length of the line. The divider assembled on R3, R4 and R7 limits the input signal level. Fine tuning of the divider is carried out by multi-turn tuning resistance R4. Divider R9 R6 sets the offset for the upper level of the logarithmic rule of the microcircuit resistance (pin 6). The lower level of the resistance slide rule (pin 4) is connected to the common wire. Resistor R5 (pin 7) increases the reference voltage and affects the brightness of the LEDs. R5 sets the current through the LEDs and is calculated by the formula: R5=12.5/Iled, where Iled is the current of one LED, A. The sound level indicator works as follows. At the moment when the input signal overcomes the lower level threshold plus the resistance at the direct input of the first comparator, the first LED (pin 1) will light up. A further increase in the sound signal will lead to the comparators being activated one by one, which will be indicated by the corresponding LED. According to the instructions, in order to avoid damage to the microcircuit, you should not exceed the 20 mA limit for the current supplied to the LEDs.

Assembling the sound signal indicator

We check the availability and ratings of parts.
Resistances: R1, R5 R8 – 1 kOhm; R2 – 100 Ohm; R3 – 10 kOhm; R4 – 50 kOhm, any trimmer; R6 – 2.2 kOhm (560 Ohm); R7 – 10 Ohm; R9 – 20 kOhm. Capacitors C1, C2 – 0.1 µF. We decipher resistor values ​​by color code. See photo.

To assemble the circuit you will need a low-power soldering iron, soldering flux, solder and side cutters. The assembly sequence may be different.

1. We install the resistors on the board according to the nominal value and solder them, and also, according to the key drawn on the board, we install and solder the bed for the microcircuit.
2. Similarly, we solder a variable resistor, capacitors, and connection sockets.

   Option 2 for installing LEDs on the level indicator board on LM3915

3. We check the correct assembly and soldering, and correct errors if necessary.
4. We insert the microcircuit into the crib using the key drawn on the board.
5. We supply 12 Volts from the power supply.
6. We send a signal from the telephone output of any gadget. If all the parts are installed correctly and are in good working order, the circuit will work. Watch the video. The audio signal level at the input is set by trimming resistor R4. Watch the video.
   

Placing the LM3915 chip on the crib comes in handy. The microcircuit has relatives LM3914 and LM3916 with linear and stretched scales. The microcircuits are absolutely identical in pinouts. Therefore, on the basis of this circuit, you can easily assemble a voltage, power indicator, or an indicator for monitoring any parameter.

A set of parts for assembling an LED audio signal level indicator on the LM3915 can be purchased from the following link http://ali.pub/2z6xyo . If you want to seriously practice soldering simple designs The master recommends purchasing a set of 9 sets, which will greatly save your shipping costs. Here is the link to purchase http://ali.pub/2bkb42 . The master collected all the sets and they started working.

Success and growth of skills in soldering.

UMZCHs look beautiful and stylish, just where to find them... There is a way out - we will make a meter in which the role of the arrow will be played by light-emitting diodes controlled by a microcircuit. LM3916- this is a special chip for LED indicators level.

Diagram of an LED indicator

The LEDs are connected via connectors J3 - J12 (only one row of LEDs is shown in the diagram). The indicator circuit will require a bipolar power supply for proper operation. The positive supply potential of the LED strips should be below +25 V and, in combination with the negative voltage, should not exceed 36 V. The minimum voltage level depends on the operating voltage of the LEDs. For example, if the LED is 1.9V, and we have 7 LEDs per pin, then the minimum positive voltage will be 7 x 1.9V + 1.5V (voltage drop across the LM3916) = 14.8 volts. Green LEDs tend to have a slightly higher voltage of 2.2-2.4V, so +18V will be sufficient in most cases.

The LED current is determined by resistor R1_REF, and with a resistance of 2.2 kOhm there will be 5 mA.
Formula for calculation: Iled = 10 x (1.2 V / R1_REF)

You can use TL072, TL082, LM358 as a dual operational amplifier at the input. The output mode can be set by 3-pin jumper JP1. The maximum input voltage for LM3916 is 1.2V, and R8-R7 can be used to adjust the input level.

Video of the indicator

LED color of your choice. Used here green LEDs for negative levels, yellow- 0dB and red for positive audio signal level. For this you need rectangular LEDs. Archive with drawings printed circuit boards Can .

Below are circuit diagrams and articles on the topic “signal strength indicator” on the radio electronics and radio hobby website.

What is a “signal strength indicator” and where is it used, circuit diagrams homemade devices which relate to the term "signal strength indicator".

LM3915 – integrated circuit(IC) manufactured by Texas Instruments, responds to changes in the input signal and outputs a signal to one or several of its outputs. Thanks to its design feature ICs have become widespread in LED indicator circuits. Since the LED indicator based on LM3915 operates on a logarithmic scale, it has found practical application in displaying and monitoring the signal level in audio amplifiers.

The LM3915 should not be confused with its relatives LM3914 and LM3916, which have a similar layout and pin assignment. The 3914 series IC has a linear characteristic and is ideal for measuring linear quantities (current, voltage), while the 3916 series IC is more universal and is capable of driving different types of loads.

Brief description of LM3915

The LM3915 block diagram consists of ten identical operational amplifiers operating on the comparator principle. The direct inputs of the op-amp are connected through a chain of resistive dividers with different resistance values. Thanks to this, the LEDs in the load light up according to a logarithmic dependence. The inverse inputs receive an input signal, which is processed by a buffer op-amp (pin 5).

The internal structure of the IC includes a low-power integrated stabilizer connected to pins 3, 7, 8 and a device for setting the glow mode (pin 9). The supply voltage range is 3–25V. The reference voltage can be set in the range from 1.2 to 12V using external resistors. The entire scale corresponds to a signal level of 30 dB in 3 dB steps. The output current can be set from 1 to 30 mA.

Sound indicator circuit and principle of its operation

As can be seen from the figure, the fundamental electrical diagram The sound level indicator consists of two capacitors, nine resistors and a microcircuit, the load for which is ten LEDs. For easy connection of power and audio signals, it can be supplemented with two solder connectors. Anyone, even a beginner radio amateur, can assemble such a simple device.

A typical connection provides power from a 12V source, which is supplied to the third pin of the LM3915. It also goes to the LEDs through the current-limiting resistor R2 and two filter capacitors C1 and C2. Resistors R1 and R8 serve to reduce the brightness of the last two red LEDs and are optional. 12V also comes to the jumper, which controls the operating mode of the IC through pin 9. In the open state, the circuit operates in the “point” mode, i.e. one LED corresponding to the input signal lights up. Closing the jumper switches the circuit to the “column” mode, when the input signal level is proportional to the height of the illuminated column.

A resistive divider assembled at R3, R4 and R7 limits the input signal level. More precise adjustment is carried out by multi-turn trimming resistor R4. Resistor R9 sets the bias for the upper level (pin 6), the exact value of which is determined by resistance R6. The lower level (pin 4) is connected to the common wire. Resistor R5 (pin 7.8) increases the reference voltage and affects the brightness of the LEDs. It is R5 that sets the current through the LEDs and is calculated using the formula:

R5=12.5/I LED, where I LED is the current of one LED, A.

The sound level indicator works as follows. At the moment when the input signal overcomes the lower level threshold plus the resistance at the direct input of the first comparator, the first LED (pin 1) will light up. A further increase in the sound signal will lead to the comparators being activated one by one, which will be indicated by the corresponding LED. To avoid overheating of the IC case, the LED current should not exceed 20 mA. Still, this is an indicator, not a New Year's garland.

Printed circuit board and assembly parts

The printed circuit board of the sound level indicator in lay format can be downloaded. It has dimensions 65x28 mm. Assembly requires precision parts. Resistors type MLT-0.125W:

• R1, R5 R8 – 1 kOhm;
• R2 – 100 Ohm;
• R3 – 10 kOhm;
• R4 – 50 kOhm, any trimmer;
• R6 – 560 Ohm;
• R7 – 10 Ohm;
• R9 – 20 kOhm.

Capacitors C1, C2 – 0.1 µF. It is recommended to solder the LM3915 IC not directly, but through a special socket for the chip. The load can use ultra-bright LEDs of any color, even purple. But these are personal aesthetic preferences. To display a stereo signal, you will need two identical boards with independent inputs. More details about the LM3915 can be found in technical description Here.

The performance of this indicator has been proven in practice by many amateur radio clubs and is still available in the form of MasterKits.

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