DIY audio power LED indicator. Do-it-yourself audio signal level LED indicator on the LM3915. Sound level LED indicator on lm3915

In this video tutorial, the author of the "Soldering TV" blog will conduct a master class on assembling an audio signal level indicator on the LM3915 microcircuit, which consists of 10 comparators connected to a resistive signal divider tap located in the microcircuit. The peculiarity of this divider is that it builds a logarithmic display scale, in contrast to the same LM3914, in which the divider is linear, and, accordingly, a linear display scale.

The diagram of this device is taken from the Chinese, with redrawing. The third pin is 12V power supply; and the second is the earth. Also, the ninth pin of the microcircuit is connected to the power supply through the button - this is the mode selection. When shorted to plus, a linear scale will be adopted. In other words, let's say the level has reached minus 6 dB - the last yellow light is on, and everything behind it. If the button is opened, then pin 9 will not be connected to anything, only one LED will be on. The LEDs are powered through a 100 Ohm resistor R6, and they have a common positive bus. The fifth pin of the microcircuit is the signal input, it passes through a 10 kOhm constant resistor and through the extreme and middle terminals of a 50 kOhm variable resistor for settings of different levels. That is, this indicator can change both the input signal and the output. And for the latter, it needs to be adjusted, since the output signal is much stronger than the input signal.

It is connected to 12 V through a 20 kOhm resistor - pin 6 of the microcircuit. This is the top end of the divider. It is connected through a 560 Ohm resistor R5 to pin 8 of the microcircuit, which is responsible for setting the built-in reference power supply. 4 output is shorted from 2 and further to ground. Output 4 is the lower end of the divider. It turns out that the upper end of the divider, 6, is connected directly to the non-inverting output, to the 10th comparator, which is responsible for the last red LED. And pin 4 is no longer connected directly, but through a 1 kOhm resistor to the non-inverting output, comparator No. 1, which goes to the lowest one. And then resistors go along the chain to each subsequent comparator. That is, this is exactly what the signal level is achieved. This was an explanation about the conclusions of the microcircuit and the meaning of the indication.

Indicator operation.

Now let's look at how the circuit works. To do this, let's turn on modeling. We connect the oscilloscope to pin A. The arrows show the movement of the current. As you can see, the button going to pin 9 of the microcircuit is open, and only one LED lights up. If this button is closed, then an indication column will appear. It can be seen that the generator has a sinusoid with a division of 1 V, and a level of 12. If the level is reduced, 4 green, 3 green lamps light up. The level will be higher. And set it to 1 Hz.

What happens if you send a unipolar signal? At first, the readings reach zero and after that they immediately go up. In other words, when increasing, the indicators light up, in the opposite case - we do not see them. However, if you move everything above zero, they will fall to zero only when the sinusoid touches the bottom of zero.

The work of the physical part.

Let's see the printed circuit board. Toner has already been applied. After this procedure, do not touch the board immediately, let it cool down. and this work is done like this: first you need to soak the board a little in water and start rubbing very carefully.

A permanent marker was used to mark the track. produced by ferric chloride. The solution, once prepared, can be used several times. However, this is possible if you take 100 g per 1.2 l of water.

You need to pickle in a separate bowl, and in no case take the dishes that are used for food. So, we immerse the prepared board in the solution. Very neat work, you need to take care of your hands. Etching takes about 15-20 minutes if the solution is not so new.

When the board acquires a pinkish tint, it means that etching has begun. After it, you need to make holes for the parts. After the board is drilled, you need to clean it up a little, for example, with an eraser or sandpaper.

Now let's get down to the soldering process itself. But first you need to tin the board. Multi-turn trimmer resistor. The diagram indicates 50 kOhm, I have it 47 kOhm. And LEDs. Let's start soldering with resistors. First, by 20 kOhm and everything is sequential according to the diagram. Next, we will solder the socket for the microcircuits. There is one caveat here. It is necessary to move the 20 kΩ resistor sideways so that it does not interfere.

After the preliminary work done, we turn to the LEDs. These LEDs go through resistors, therefore, they are red. Plus is always on the right. Now it remains to connect the wires and insert the microcircuit using the key.

Final check of circuit operation. Let's start with the minimum volume, then move on to the maximum. We use the phone as a sound source. As you can see, it works!

DIY LED sound indicator. Simple circuit on two transistors, which controls the blinking of the LED indicators at different sounds.

The blinking will match the rhythm or rate of change of the sound. Soldering is quite simple and any curious person armed with a soldering iron can handle the assembly of the circuit. The author shares his experience in the photo and demonstrates the work of the assembled circuit in the video. All parts, including the printed circuit board, are purchased in the online store at a ridiculous price.

How to assemble a sound indicator with your own hands

A simple circuit with beautiful functionality that allows you to feel the combination of sound and light or become part of an automation, warning or safety system, although other uses of the circuit are also possible. The operating voltage of the sound indicator is 3-4.5 Volts.

The principle of operation of the sound indicator circuit

The sound indicator circuit includes a microphone sound amplifier and a stage for controlling the glow of the LEDs.

1. The circuit is powered through the JP pin header. The capacitor smooths out voltage fluctuations. Power is supplied to the built-in microphone amplification circuit through resistor R1.
2. The amplified microphone signal is sent through a 10uF capacitor to the base of Q1. The signal from the collector of Q1 drives Q2.
3. Transistor Q2 controls LEDs D1-D5.
4. If more high voltage power supply of the circuit, it is necessary to install an additional resistance in the power circuit with a nominal value of R4 10 ... 100 Ohm.

Assembling the circuit

First you need to unpack the package with parts and check the presence and marking of the parts. You can find out the resistance of the resistors, either by measuring the resistance with a tester, or decipher it on the marking of the resistor. Ratings and number of parts are shown in the table.

NO.	Component name	PCB markers	parameter	QTY
1	Resistor	R1	4.7K	1
2	Resistor	R2	1M	1
3	Resistor	R3	10K	1
4		C1	47uF	1
5	Electrolytic capacitor	C2	1uF	1
6	S9012 bipolar transistor	Q1, Q2	TO-92	2
7	Microphone	microphone		1
8	Light-emitting diode	D1-D7	3mm	5-7
9	Pin block		2.54mm 2P	1
10	printed circuit board		29 * 30mm	1

1. The assembly can be started in any order. The author began the assembly by installing the LEDs. The LED has polar electrodes. Installation hint is shown in the photo. It is convenient to install three LEDs first. Solder the leads to the board and cut off the protruding leads with side cutters.
2. Next, the remaining two LEDs are soldered. The transistors are installed using the key drawn on the board. Electrolytic capacitors are also polarized. The negative electrode is marked on the body, if something is not clear, see.
3. We check the correctness of the installation of parts and soldering. We supply power, for example, from three AA batteries. Watch the video of the operation of the sound indicator circuit.

Despite its simplicity, a variety of devices can be assembled on the basis of the circuit, for example:

• the "QUIET" signaling device (we install the scheme for illumination of the "quieter" transponder);
• to design an indicator of the need to clean the computer from dust due to the increased noise of the processor or video card fan;
• a light signaling device for knocking on the door or manipulating the lock, just lean the microphone against the lock or door leaf;
• make an automatic headlight switch in a radio-controlled toy, with the noise of the motor, the headlights will turn on.

A set of parts for assembling an LED sound indicator can be purchased at the following link http://s.click.aliexpress.com/e/eqNvB6y ... If you want to seriously practice soldering simple structures, the Master recommends purchasing a set of 9 sets, which will greatly save your shipping costs. Here is the link to buy http://ali.pub/2bkb42 ... The master has collected all the sets and they worked.

I wish you success and growth in your soldering skills.

You can, of course, use a microcircuit instead of transistors as the main component, but in my opinion a device made on a chip has a smaller range of creative thought, that is, you cannot make such fine tuning, which can be installed in a transistor version. The transistor topology makes it possible to flexibly configure various parameters with the required indication range, soft signal response to LEDs and the same smooth attenuation. The indicator chain can be assembled with almost any number of LEDs, if only there is a desire and a need for it. p>

Although in fairness it should be noted that transistor circuits with big amount installed LEDs require a lot of time to debug and adjust them. But on the other hand, it is pleasant to work with such a structure later, it is very difficult to disable it. But even in the event of an emergency situation with any of the cells, everything can be repaired without any problems. Clip-on indicator of output power does not require large financial costs for its manufacture, the most popular silicon transistors of the KT315 type are used. Any radio amateur is well acquainted with such semiconductors, many began their journey in electronics precisely with the use of such transistors.

The amplifier output power indicator circuit shown here has a logarithmic scale, given that the output power will be more than 110 watts. If, for simplicity, we made a scale of a linear type, then, for example, at 4-6 W, the LEDs would not be able to open, or we would have to make a ruler of about 120 cells. Therefore, a display device designed for powerful amplifiers must be assembled so that there is a logarithmic relationship with respect to the amplifier output power and the number of LEDs installed.

Peak indicator schematic diagram

Peak output power indicator and its presented circuit is absolutely simple, and is made with identical cells displaying visual indications, each of which indicates a different level of output voltage of the amplifier. Here is a diagram for 5 indication points:

Circuit of the peak indicator of the output power of the amplifier on transistors KT315

According to the principle of the scheme shown above, you can easily make an indication for ten points.

Once in a friend's car I saw LEDs blinking to the beat of the music. I was eager to do the same for myself. To begin with, I will decorate the speakers in the computer, and then I will solder the car as well. The friend did not know how and what was there and blinking. I had to look for something on the Internet myself. One person was very helpful in finding and creating a simple wiring diagram. There are only 3 parts in the circuit, which can be purchased almost everywhere: an LED, a tuned resistor, a diode. The very principled electrical circuit as follows:

The level indicator turns out to be very easy to assemble. It can be assembled even by a person with trembling and inexperienced hands :) Put the resistor from about 1 to 22 kilo-ohms - this will be enough. The diode was set to KD226. This rectifier diode is any capable of withstanding the entire load, of course with some margin. Diodes VD3-VD6 are silicon, with a forward voltage drop of 0.7 ... 1 V and an allowable current of at least 300 mA.

A slightly complicated diagram is capable of showing five different signal levels, but they can be reduced, for example, to two, or increased.

However, with an increase, it should be remembered that by increasing their number, the power consumption of the entire indicator also increases, and the more it takes for the indication, the less it will reach the speaker, therefore, if you overdo it with the number of levels, dips in the sound may appear.

In general, it turned out to be a very simple and interesting design of the LED sound indicator. Instead of dim darkness, lighting effects appeared in the room.

Hello everyone. I used to collect such circuits on light bulbs, and when LEDs appeared more freely available,. When the Internet appeared, in general, such an abundance of circuits poured in, but a big problem appeared - you solder the circuit, and it either does not work at all, or it does not work at all, and then you begin to experiment with it, to achieve the desired result. But during the time that you tinker with the scheme, you learn a lot of interesting things, you understand what detail affects what, you develop in general to the fullest. Here are some really tested and 100% working schemes that you can safely do.

Collection of diagrams of LED indicators of AF

Here are a few more level indicator circuits tailored for good blinking from music.

Here's another stroboscope controlled by a sound signal somehow I did, maybe someone else will do it:

Here are two stroboscopic I did, one like a policeman, the other just a disco.

This indicator was still soldered.

And this indicator strengthened under a powerful load.

And about this indicator, here the LEDs must be all of 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, and I decided to make it blink beautifully to the music - this is the circuit that came out.

But even such a specialized indicator circuit as 3915 requires its own control circuit, the most suitable one is the same as in the circuit, the details are also selected according to best work... Since it has a very sensitive input, a divider is added at the signal input. Added resistor R7 to keep the first LED off. But the circuit converts perfectly into a simple active frequency filter. Take, for example, this figure, it all depends on the capacity of the input capacitor C1 and the additional C5, which is placed between the collector and the common wire.

Thus, you can make three frequency channels and already apply the whole thing for the CMU, for a start, you can solder such a pre-swing amplifier with regulators for each channel, and load the LM-ku with control circuits tuned to the outputs of the regulators (variable resistors) your frequency range.

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

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

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