LED scales are widely used in a wide variety of radio equipment, where they are used as indicators of the level of a sound (or other) signal. They can differ in the number of channels, LEDs in the scale and display characteristics - linear, logarithmic or, for example, with an "extended" range.
There are specialized microcircuits for these purposes, with the help of which it is not difficult to make such an indicator. But even with the use of discrete elements of widespread use, it is not difficult to assemble an "LED scale".
According to the scheme given in the article, you can make a similar indicator with wide possibilities, for its use in a wide variety of equipment.
This circuit was based on a version of the LED indicator of the power level of the audio amplifier. (UMZCH), published a few years ago on one of the sites (I don't remember which one anymore), but under the authorship A.I.Shikhatova. Schemes like this can be found in other sources.
The indicator scale displays signal levels from zero to maximum power and has a logarithmic dependence of the characteristic.
The number of diodes between cells can be different. For example - one (VD7) or two diodes (VD1, VD2). You can turn on more diodes, achieving the ignition interval you need between adjacent LEDs, but this must be done within reasonable limits.
If one diode is connected between all the cells in this circuit, then the maximum value of the indicator will correspond to a power of about 20W (with a load of 4 Ohm). And with two diodes connected in series, this value will be about 30W. Thus, by varying the number of diodes between the cells, or the number of the cells themselves, you can build an indicator for any range you need. Low power silicon diodes such as D220, D223, KD503 or similar imported ones are suitable as these diodes.
The LEDs are controlled using transistor switches. Transistors (the same, therefore all are designated as VT1), you can use any low-power, n-p-n structures. Their power depends on the type of LEDs they control and, depending on this, should be about 150 mW or more.
To obtain a clearer ignition threshold, it is better to choose transistors with a current gain of at least 100.
LEDs can be anything. The values of the resistances of the resistors R1... R6 depend on the value of the operating currents of the LEDs. For example, if the current of the HL1 LED is 10 mA, the resistance of the resistor R1 should be about 1 kΩ. With a current of 20 mA - 560 Ohm, with a current of 30 mA - 360 Ohm.
More precisely, the resistance of these resistors can be selected experimentally, in the process of final adjustment of the indicator, according to the optimal brightness of the glow.
The VD diode at the input of the circuit can be applied to almost any type and average power. It serves to rectify the AC voltage of the input audio signal. If this indicator is needed to display the magnitude of the constant current / voltage, then this diode is not necessary to be installed in the circuit. Resistor R limits the input swing to the desired level, and capacitors C1 and C2 make the scale "travel" smoother.