Output indicators are currently very popular, especially for their use in modernizing rare equipment. Many radio amateurs remember very well the Soviet power amplifier Radiotehnika U-101 from the Riga plant of the same name. In the early 80s, the plant began producing a new model, the international standard (dimensional) music complex “Radiotehnika K-101 stereo”. Overall, this combine was a very good complex. But the amplifier, or rather the output power indicator built into it, was either imperfect or there were design errors.

Nevertheless, when the device was new, it did not cause any complaints, but over time it began to cause some inconvenience with its not clear and dim glow of the scale, or in general some element in the control circuit failed. Recently I also became the owner of such an amplifier. Of course, I had no desire to restore the standard indicator, and initially I already intended to install pointers in the device. Moreover, I had several of these in stock, and in my opinion it’s not difficult to find them on radio markets. But be that as it may, I began restoration and partial modernization in order to establish dial indicators of the output signal Radiotehnika U-101 on K157DA1. p>

First, I took three-millimeter plastic and cut out 3 rectangular pieces from it, and then glued the indicators together using dichloroethane. Plastic strips should be adjusted so that they are the same width as the indicators and do not protrude beyond the perimeter. Here the photo shows a design with a natural window size in the front panel of the power amplifier.

I made windows in the glass from the standard indicator and put them on new dial indicators. It is advisable to process the glass with a small fine file or needle so that it fits tightly into place. Then I glued it all together again with dichloroethane. Of course, this whole operation must be done very carefully, since this is a front panel and should look accordingly.

Here comes a crucial stage.
There is a small gap on top of the indicators, relative to the window in the glass. So let it remain like that, it will be convenient to place SMD LEDs there for illumination.

Now you need to solder the wires to the LEDs and place them in the gap between the indicator and the glass with a small amount of super glue.

I also cut out a strip of plastic and attached it to the side walls. After it is still attached to the glue, the structure will acquire even greater rigidity and will serve as the basis for installing a control board on it.

This photo shows the standard installation location for the indicator. There you can also see a red connector with wires; it is designed to supply power to the control board. It will certainly be needed in the future.

At this stage it is necessary assembled module try on how he becomes. The fact is that this design is not fastened with any screws, but is simply pressed against the chassis by the front panel power amplifier. Therefore, it is necessary to ensure the tightest possible fit. Under the wires coming from the LEDs, use a round needle file to make a small cut in the chassis.

Schematic diagram and printed circuit board of the control module

When making my amplifier, I firmly decided to make 8-10 cells LED indicator output power per channel (4 channels). There are plenty of schemes of such indicators, you just need to choose according to your parameters. On this moment The choice of chips on which you can assemble an ULF output power indicator is very large, for example: KA2283, LB1412, LM3915, etc. What could be simpler than buying such a chip and assembling an indicator circuit) At one time I took a slightly different route...

Preface

To make output power indicators for my ULF, I chose a transistor circuit. You may ask: why not on microcircuits? - I will try to explain the pros and cons.

One of the advantages is that by assembling on transistors, you can debug the indicator circuit with maximum flexibility to the parameters you need, set the desired display range and smoothness of response as you like, the number of indication cells - at least a hundred, as long as you have enough patience to adjust them.

You can also use any supply voltage (within reason), it is very difficult to burn such a circuit, and if one cell malfunctions, you can quickly fix everything. Of the minuses, I would like to note that you will have to spend a lot of time adjusting this circuit to your tastes. Whether to do it on a microcircuit or transistors is up to you, based on your capabilities and needs.

We assemble output power indicators using the most common and cheap KT315 transistors. I think every radio amateur has come across these miniature colored radio components at least once in his life; many have them lying around in packs of several hundred and idle.

Rice. 1. Transistors KT315, KT361

The scale of my ULF will be logarithmic, based on the fact that the maximum output power will be about 100 Watts. If you make a linear one, then at 5 Watts nothing will even glow, or you will have to make a scale of 100 cells. For powerful ULFs, it is necessary that there be a logarithmic relationship between the output power of the amplifier and the number of luminous cells.

Schematic diagram

The circuit is outrageously simple and consists of identical cells, each of which is configured to indicate the desired voltage level at the ULF output. Here is a diagram for 5 indication cells:

Rice. 2. Circuit diagram of the ULF output power indicator using KT315 transistors and LEDs

Above is a circuit for 5 display cells; by cloning the cells you can get a circuit for 10 cells, which is exactly what I assembled for my ULF:

Rice. 3. Diagram of the ULF output power indicator for 10 cells (click to enlarge)

The ratings of the parts in this circuit are designed for a supply voltage of about 12 Volts, not counting the Rx resistors - which need to be selected.

I’ll tell you how the circuit works, everything is very simple: the signal from the output of the low-frequency amplifier goes to resistor Rin, after which we cut off half a wave with diode D6 and then constant pressure applied to the input of each cell. The indication cell is a threshold key device that lights up the LED when a certain level at the input is reached.

Capacitor C1 is needed so that, even with a very large signal amplitude, the smooth switching off of the cells is maintained, and capacitor C2 delays the lighting of the last LED for a certain fraction of a second to show that the maximum signal level - peak - has been reached. The first LED indicates the beginning of the scale and is therefore constantly lit.

Parts and installation

Now about the radio components: select capacitors C1 and C2 to your liking, I took each 22 μF at 63 V (I don’t recommend taking it for a lower voltage for ULF with an output of 100 Watt), the resistors are all MLT-0.25 or 0.125. All transistors are KT315, preferably with the letter B. LEDs are any that you can get.

Rice. 4. Printed circuit board for ULF output power indicator for 10 cells (click to enlarge)

Rice. 5. Arrangement of components on printed circuit board ULF output power indicator

I didn’t mark all the components on the printed circuit board because the cells are identical and you can figure out what to solder and where without much effort.

As a result of my labors, four miniature scarves were obtained:

Rice. 6. Ready-made 4 indication channels for ULF with a power of 100 Watts per channel.

Settings

First, let's adjust the brightness of the LEDs. We determine what resistor resistance we need to achieve the desired brightness of the LEDs. We connect a 1-6 kOhm variable resistor in series to the LED and supply this power chain with the voltage from which the entire circuit will be powered, for me - 12V.

We twist the variable and achieve a confident and beautiful glow. We turn off everything and measure the resistance of the variable with a tester, here are the values ​​for R19, R2, R4, R6, R8... This method is experimental, you can also look in the reference book for the maximum forward current of the LED and calculate the resistance using Ohm's law.

The longest and most important stage of setup is setting the indication thresholds for each cell! We will configure each cell by selecting the Rx resistance for it. Since I will have 4 such circuits of 10 cells each, we will first debug this circuit for one channel, and it will be very easy to configure others based on it, using the latter as a standard.

Instead of Rx in the first cell, we put a variable resistor of 68-33k in place and connect the structure to an amplifier (preferably to some stationary, factory one with its own scale), apply voltage to the circuit and turn on the music so that it can be heard, but at a low volume. Using a variable resistor, we achieve a beautiful wink of the LED, then turn off the power to the circuit and measure the resistance of the variable, solder it in instead constant resistor Rx to the first cell.

Now we go to the last cell and do the same thing only by driving the amplifier to the maximum limit.

Attention!!! If you have very “friendly” neighbors, then you can not use speaker systems, but get by with a connected one instead speaker system a 4-8 Ohm resistor, although the pleasure from setting it up will not be the same))

Using a variable resistor, we achieve a confident glow of the LED in the last cell. All other cells, except the first and last (we have already configured them), you configure as you like, by eye, while marking the power value for each cell on the amplifier indicator. Setting up and calibrating the scale is up to you)

Having debugged the circuit for one channel (10 cells) and soldered the second one, you will also have to select resistors, since each transistor has its own gain. But you don’t need any amplifier anymore and the neighbors will get a small timeout - we simply solder the inputs of two circuits and supply voltage there, for example from a power supply, and select the Rx resistances to achieve symmetry in the glow of the indicator cells.

Conclusion

That's all I wanted to tell you about making ULF output power indicators using LEDs and cheap KT315 transistors. Write your opinions and notes in the comments...

UPD: Yuri Glushnev sent his printed circuit board in SprintLayout format - Download.

I remember a carefree childhood - while visiting a classmate, we listened to music. Amplifier “Radiotekhnika-001-stereo”, the indicators sway gently to the beat of the music... Then it was the ultimate dream. And it seemed blasphemous when the father of a classmate (the man was fond of amateur radio) replaced the standard dial indicators with a luminescent one of an ugly green color. And the amplifier lost some of its charm, and I didn’t want to listen to it anymore...

I want a switch!

And many years have passed. And so I slowly (sometimes it seems too slowly) assemble a tube amplifier. And everyone has long understood that the level indicator on an amplifier is a bonus. Especially now, when the channels in the source almost never differ in level, and the concept of “stereo balance regulator” has sunk into oblivion. And yet, I want a dial “display meter” for the front panel, and that’s it! Ascetic design, with yellow lighting.
Since the display indicator is not an important part of the amplifier (it does not affect the speed and stability), its construction and adjustment was carried out already on the sounding unit. The indicator head itself was selected and purchased a long time ago:

We managed to find a double one, with a yellowish panel. The backlight from the manufacturer was made with a 12 Volt coaxial incandescent lamp. Which was successfully replaced with 4 yellow LEDs. But that happened later.
In the meantime, I had to think about how to connect microammeters to the amplifier output? And it must be connected through a special logarithmic amplifier, since the dynamic range of sound is much greater than the operating range of a microammeter. Theoretically, everyone who has encountered homemade dial indicators knows this.

A legend of deep antiquity... K157DA1

A special microcircuit for this was released in the USSR - K157DA1. The microcircuit has no analogues abroad. The connection diagram is simple, although according to the datasheet, bipolar power is required (inconvenient). But the microcircuit works successfully even from unipolar power supply. Moreover, the use of transistors instead of diodes in the circuit allows you to expand the range of displayed values ​​up to 40 dB:

Various variations of this scheme are a dime a dozen on the Internet. Well, what can I say... It didn’t work out for me.

The first copy successfully burned due to improperly supplied power. Within a month I got two more things, but it was too late, I switched to another circuit (on LM324), kindly provided to me AlexD. Just for fun, I later turned on the board with DA1. I didn’t like it, there was no smooth movement. The modification of the circuit was carried out in close cooperation with Alexey, for which once again “danke shon”!

Numero due - LM324

Then there was the mentioned option on LM324. But it never worked for me as I wanted. Dangling arrows, it must be selected by the depth of the OS. And in fact, the nutrition needs to be bipolar, maybe it’s all due to an incorrectly organized midpoint. No, laziness was born before me. And together with laziness we gave birth to this:

Century XXI, Attyny13

Simple and tasteful: we straighten and smooth the signal, then feed it to the ADC of the microcontroller. We process it in software and, using the built-in PWM, output it to the load (resistor). Processing includes almost only natural logarithms (Attyny13 was created for such simple tasks, and so that the firmware could be baked in a hurry).

And this is where the fun begins for me. The natural logarithm function is available in the library of mathematical functions for Atmel controllers and is located in the file math.h. But it just doesn’t fit into this controller - there’s not enough memory. It’s not possible to solve the problem head-on, so we begin to wrinkle our forehead. The use of a more powerful controller was not considered - not interesting. There seems to be enough memory, and it’s convenient, and inexpensive, and the dimensions are not large. The first thing that came to mind was to replace this function with a similar one, but simpler. And give it shape by playing with the coefficients. Let us recall the graph of the inverse function. Not “screw it!”, but remember! If you move the lower right square upward relative to the X axis, and slightly move the coefficients back and forth, then it is quite possible to adjust it to the desired shape. Here it is, a formula that replaces the logarithm: Y=-8196/(X+28)+284. Can you imagine the horror of a controller doomed to calculate these values ​​thousands of times per second at the whim of the owner, who wanted to remember his “golden childhood”?

But unpleasant emotions were also guaranteed for the owner of the controller. Short integer values ​​were not enough to process the results, and the input and output had to be just that. For me, translating data presentation formats in controllers from one to another has always been difficult. The wrinkles on my forehead multiplied.

The second option was born- calculate everything in advance, and the controller will simply select data from the array that corresponds to the input values ​​and throw them out. Preparing values, setting an array - compilation error. The array dimension is too large for this controller. But making several arrays and tinkering with them depending on the input value of the ADC is not kosher. Thoughts about Newton's binomial swarmed, but were rejected due to non-constructiveness.

Here a phrase from a lecturer in higher mathematics from a university came to mind: “Using a cubic spline approximation, you can describe any function.” Well, we don’t need a cubic one, but a linear spline will do just fine! Thus, I practiced a little in OO Calc, and wrote a system of equations that fairly accurately replicate the graph of a logarithmic function using line segments:
if (n>=141) x=2*n+2020; else if (n>=66) x=5*n+1600; else if (n>=38) x=9*n+1330; else if (n>=21) x=15*n+1110; else if (n>=5) x=40*n+600; else if (n>0) x=160*n+50; if (n==0) x=0;
Everything is intentionally multiplied by 10 so that the discarded “tails” are smaller. I then divide it in the program before displaying it on indicators.
And here are the graphs:

I am sure that such a solution will immediately come to mind for many of you and seem obvious. However, I am sure that this will be new to someone and will be useful in the future. By at least, as a tool in your arsenal, it will not be superfluous to have.

Video

Summary and notes on the diagram

The display indicator worked perfectly the first time it was turned on. Several firmwares were uploaded. The simplest one turned out to be the most successful.
According to the scheme: During the setup process, capacitors C1 and C2 were replaced with 10.0 µF - they ensure smoothness. Trimmer resistors at the input reduce the maximum signal to 5 Volts. Theoretically, it would be necessary to install a zener diode with a resistor, but laziness... Well, you already know which of us was born first:laughing: I loaded the amplifier with the maximum signal from my point of view (so that the equivalents at the output became heated), and brought the resistors to 5 Volt. I've had enough. Then I applied 1 kHz from the generator to the input and synchronized the channels, slightly reducing the readings of one of the microammeters. R4 and R5 depend on the total deflection current of the microammeters; they are indicated in the diagram for 50 μA, I have these.

The circuit can be tuned. Tinka has 2 legs left free. No one is stopping you from sticking LEDs there to indicate overload, it was once fashionable. Not my thing - I don’t like it when something on the amplifier blinks, that’s why I didn’t do it. The implementation is elementary: at a certain level we light the LED and keep it lit for N milliseconds. Level and N are adjusted to taste, like salt and pepper. Just remember that one of the free legs is Reset. This means that you should do your experiments on one channel, because if you install the appropriate fuse when flashing the firmware, Reset will become just a port, and you won’t be able to change the controller after that.

Files

And files: project in CVAVR, firmware, diagram in Plan.
I’m not giving a sign, it’s unnecessary: ​​the likelihood that someone will have such a microammeter and need to attach a controller to it tends to zero. And looking at the diagram, you can imagine what a simple board it is
▼ 🕗 09/24/12 ⚖️ 55.23 Kb ⇣ 431 Hello, reader! My name is Igor, I'm 45, I'm a Siberian and an avid amateur electronics engineer. I came up with, created and have been maintaining this wonderful site since 2006.
For more than 10 years, our magazine has existed only at my expense.

Good! The freebie is over. If you want files and useful articles, help me!

I suggest for repetition schematic diagram sound dial indicator. The circuit is made on the Soviet K157DA1 microcircuit. The device is made for a two-channel power amplifier.

The circuit is powered unipolarly - 9 volts, and is made using a simple voltage stabilizer made on the 78L09 microcircuit - it is shown in the diagram.

The device is connected to the output of a power amplifier, although its sensitivity is quite sufficient for picking up sound from the linear input.

The device is configured using variable resistors with a nominal value of 30K and capacitors C7 and C8. Variable resistors adjust the position of the needle at maximum power, and capacitors adjust the return time of the needle.

This dial indicator is assembled on a printed circuit board, which is mounted on the housing of the indicator heads.

The indicator heads were taken from an old Soviet tape recorder. Also, almost any beautiful switches with a total deflection current of 50-200 μA are suitable here. If you wish, as is fashionable now, you can make blue or green LED backlight scales. Author of the article: M. Pelekh

It is no secret that the sound of a system largely depends on the signal level in its sections. By monitoring the signal in the transition sections of the circuit, we can judge the operation of various functional blocks: gain, introduced distortion, etc. There are also cases when the resulting signal simply cannot be heard. In cases where it is not possible to control the signal by ear, various types of level indicators are used.
For observation, both pointer instruments and special devices that ensure the operation of “column” indicators can be used. So, let's look at their work in more detail.

1 Scale indicators
1.1 The simplest scale indicator.

This type of indicator is the simplest of all existing ones. The scale indicator consists of a pointer device and a divider. A simplified diagram of the indicator is shown in Fig.1.

Microammeters with a total deviation current of 100 - 500 μA are most often used as meters. Such devices are designed for D.C., so for them to work sound signal needs to be rectified with a diode. A resistor is designed to convert voltage into current. Strictly speaking, the device measures the current passing through the resistor. It is calculated simply, according to Ohm’s law (there was such a thing. Georgy Semenych Ohm) for a section of the circuit. It should be taken into account that the voltage after the diode will be 2 times less. The brand of diode is not important, so any one operating at a frequency greater than 20 kHz will do. So, the calculation: R = 0.5U/I
where: R – resistor resistance (Ohm)
U - Maximum measured voltage (V)
I – total deflection current of the indicator (A)

It is much more convenient to evaluate the signal level by giving it some inertia. Those. the indicator shows the average level value. This can be easily achieved by connecting an electrolytic capacitor in parallel with the device, but it should be taken into account that in this case the voltage on the device will increase (root of 2) times. Such an indicator can be used to measure the output power of an amplifier. What to do if the level of the measured signal is not enough to “stir up” the device? In this case, guys like transistor and operational amplifier(hereinafter referred to as OU).

If you can measure the current through a resistor, then you can also measure the collector current of the transistor. To do this, we need the transistor itself and a collector load (the same resistor). The diagram of a scale indicator on a transistor is shown in Fig.2

Fig.2

Everything is simple here too. The transistor amplifies the current signal, but otherwise everything works the same. The collector current of the transistor must exceed the total deflection current of the device by at least 2 times (this is calmer for both the transistor and you), i.e. if the total deviation current is 100 μA, then the collector current must be at least 200 μA. As a matter of fact, this is relevant for milliammeters, because 50 mA “whistles” through the weakest transistor. Now we look at the reference book and find in it the current transfer coefficient h 21e. We calculate the input current: I b = I k /h 21E where:
I b – input current

R1 is calculated according to Ohm's law for a section of the circuit: R=U e /I k where:
R – resistance R1
U e – supply voltage
I k – total deviation current = collector current

R2 is designed to suppress voltage at the base. When selecting it, you need to achieve maximum sensitivity with minimal needle deviation in the absence of a signal. R3 regulates sensitivity and its resistance is practically not critical.

There are cases when the signal needs to be amplified not only by current, but also by voltage. In this case, the indicator circuit is supplemented with a cascade with OE. Such an indicator is used, for example, in the Comet 212 tape recorder. Its diagram is shown on Fig.3

Fig.3

Such indicators have high sensitivity and input resistance, therefore, they make minimal changes to the measured signal. One way to use an op-amp - a voltage-current converter - is shown in Fig.4.

Fig.4

Such an indicator has a lower input resistance, but is very simple to calculate and manufacture. Let's calculate the resistance R1: R=U s /I max where:
R – input resistor resistance
U s – Maximum level signal
I max – total deviation current

Diodes are selected according to the same criteria as in other circuits.
If the signal level is low and/or high input impedance is required, a repeater can be used. Its diagram is shown on Fig.5.

Fig.5

For reliable operation of diodes, output voltage It is recommended to raise it to 2-3 V. So, in the calculations we start from the output voltage of the op-amp. First of all, let's find out the gain we need: K = U out / U in. Now let's calculate resistors R1 and R2: K=1+(R2/R1)
There seem to be no restrictions in the choice of denominations, but it is not recommended to set R1 to less than 1 kOhm. Now let's calculate R3: R=U o /I where:
R – resistance R3
U o – op-amp output voltage
I – total deviation current

2 Peak (LED) indicators

2.1 Analog indicator

Perhaps the most popular type of indicators at present. Let's start with the simplest ones. On Fig.6 The diagram of a signal/peak indicator based on a comparator is shown. Let's consider the principle of operation. The response threshold is set by the reference voltage, which is set at the inverting input of the op-amp by the divider R1R2. When the signal at the direct input exceeds the reference voltage, +U p appears at the op-amp output, VT1 opens and VD2 lights up. When the signal is below the reference voltage, –U p operates at the op-amp output. In this case, VT2 is open and VD2 lights up. Now let's calculate this miracle. Let's start with the comparator. First, let's select the response voltage (reference voltage) and resistor R2 within the range of 3 - 68 kOhm. Let's calculate the current in the reference voltage source I att =U op /R b where:
I att – current through R2 (the current of the inverting input can be neglected)
U op – reference voltage
R b – resistance R2

Fig.6

Now let's calculate R1. R1=(U e -U op)/ I att where:
U e – power supply voltage
U op – reference voltage (operation voltage)
I att – current through R2

Limiting resistor R6 is selected according to the formula R1=U e/I LED where:
R – resistance R6
U e – supply voltage
I LED – direct LED current (recommended to be selected within 5 – 15 mA)
Compensating resistors R4, R5 are selected from the reference book and correspond to the minimum load resistance for the selected op-amp.

Let's start with a limit level indicator with one LED ( Fig.7). This indicator is based on a Schmitt trigger. As is known, the Schmitt trigger has some hysteresis those. The actuation threshold is different from the release threshold. The difference between these thresholds (the width of the hysteresis loop) is determined by the ratio of R2 to R1 since The Schmitt trigger is an amplifier with a positive feedback. Limiting resistor R4 is calculated according to the same principle as in the previous circuit. The limiting resistor in the base circuit is calculated based on the load capacity of the LE. For CMOS (CMOS logic is recommended), the output current is approximately 1.5 mA. First, let's calculate the input current of the transistor stage: I b =I LED /h 21E where:

Fig.7

I b – input current of the transistor stage
I LED – direct LED current (it is recommended to set 5 – 15 mA)
h 21E – current transfer coefficient

If the input current does not exceed the load capacity of the LE, you can do without R3, otherwise it can be calculated using the formula: R=(E/I b)-Z where:
R–R3
E – supply voltage
I b – input current
Z – cascade input impedance

To measure the signal in a “column”, you can assemble a multi-level indicator ( Fig.8). This indicator is simple, but its sensitivity is low and is only suitable for measuring signals from 3 volts and above. The LE response thresholds are set by trimming resistors. The indicator uses TTL elements; if CMOS is used, an amplification stage should be installed at the output of each LE.

Fig.8

The simplest option for making them. Some diagrams are shown on Fig.9

Fig.9

You can also use other display amplifiers. You can ask the store or Yandex for connection diagrams for them.

3. Peak (luminescent) indicators

At one time they were used in domestic technology, now they are widely used in music centers. Such indicators are very complex to manufacture (they include specialized microcircuits and microcontrollers) and to connect (they require several power supplies). I do not recommend using them in amateur equipment.

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
	1.1 The simplest scale indicator
VD1	Diode		1			To notepad
R1	Resistor		1			To notepad
PA1	Microammeter		1			To notepad
	Fig.2
VT1	Transistor		1			To notepad
VD1	Diode		1			To notepad
R1	Resistor		1			To notepad
R2	Resistor		1			To notepad
R3	Variable resistor	10 kOhm	1			To notepad
PA1	Microammeter		1			To notepad
	Fig.3
VT1, VT2	Bipolar transistor	KT315A	2			To notepad
VD1	Diode	D9E	1			To notepad
C1		10 µF	1			To notepad
C2	Electrolytic capacitor	1 µF	1			To notepad
R1	Resistor	750 Ohm	1			To notepad
R2	Resistor	6.8 kOhm	1			To notepad
R3, R5	Resistor	100 kOhm	2			To notepad
R4	Trimmer resistor	47 kOhm	1			To notepad
R6	Resistor	22 kOhm	1			To notepad
PA1	Microammeter		1			To notepad
	Fig.4
	OU		1			To notepad
	Diode bridge		1			To notepad
R1	Resistor		1			To notepad
PA1	Microammeter		1			To notepad
	Fig.5
	OU		1			To notepad
	Diode bridge		1			To notepad
R1	Resistor		1			To notepad
R2	Resistor		1			To notepad
R3	Resistor		1			To notepad
PA1	Microammeter		1			To notepad
	2.1 Analog indicator
	Fig.6
	OU		1			To notepad
VT1	Transistor	N-P-N	1			To notepad
VT2	Transistor	P-N-P	1			To notepad
VD1	Diode		1			To notepad
R1, R2	Resistor		2			To notepad
R3	Trimmer resistor		1			To notepad
R4, R5	Resistor		2			To notepad
R6	Resistor		1			To notepad
HL1, VD2	Light-emitting diode		2			To notepad
	Fig.7
DD1	Logic IC		1			To notepad
VT1	Transistor	N-P-N	1			To notepad
R1	Resistor		1			To notepad
R2	Resistor		1			To notepad
R3	Resistor		1			To notepad
R4	Resistor		1			To notepad
HL1	Light-emitting diode		1			To notepad
	Fig.8
DD1	Logic IC		1			To notepad
R1-R4	Resistor		4			To notepad
R5-R8	Trimmer resistor		4			To notepad
HL1-HL4	Light-emitting diode		4			To notepad
	Fig.9
	Chip	A277D	1			To notepad
	Electrolytic capacitor	100 µF	1			To notepad
	Variable resistor	10 kOhm	1			To notepad
	Resistor	1 kOhm	1			To notepad
	Resistor	56 kOhm	1			To notepad
	Resistor	13 kOhm	1			To notepad
	Resistor	12 kOhm	1			To notepad
	Light-emitting diode		12