# THE REFEREE SIGNALS

Do you think what is common between math and electronics? Readers familiar with digital technology, recall that the mathematical laws of Boolean algebra the basis for the action of logic circuits. But that’s not all. It turns out that in mathematics, and electronics often use this concept as a comparison. But if you have to compare them with other numeric values, in electronics there is a comparison of the electrical signals. To perform such operations even created special devices — Comparators.

Curiously, the Comparators close “relatives” the familiar triggers. What is their similarity? First, information on the outputs of these devices is encoded by only two logic levels high and low; second, the change from one logical state to another only in the presence of a definite combination of signals at the inputs.

How and what is the principle of operation Comparators? For now, let’s digress from our story and let us imagine a sports competition in athletics, for example running. Once the athlete came to the finish line, his result is compared with the record time for that distance. If the runner failed to exceed the world record, in such cases we say that “the record stood”. But if the time during which the athlete overcame the distance, was smaller than a record, that runner now becomes a record, and its result will be logged from now on, instead of all sports reference books as the highest achievement.

A similar situation can be seen for example in the work of a simple comparator. Such a device has two input and output. To one of the inputs is often served voltage or current, constant in time, the so-called reference signal. With him there is a comparison of the signal level of which is unknown.
Suppose we want to compare the voltage of the battery from a pocket lantern fixed voltages applied to the reference input of the comparator. If the battery is deeply discharged and its voltage is below the reference, then any changes in the output of the comparator will occur. But if the battery potential exceeds a reference voltage, the comparator will switch and its output will appear a signal different from the original.

Isn’t the analogy with the competition in the race quite justified. Judge for yourself. The input signal is less than the reference (time runner worse record) is the logic state of the comparator does not change (the highest achievement remains the same). Input signal exceeds the reference (the athlete better world achievements) is the logic state of the comparator is reversed (the record is getting higher). Thus, we can say that as if the comparator performs the role of arbiter for determining which of the signals turned out great.

We introduced you to the principle of only one type of Comparators. In fact, they are much more characterized by various signs. For example, in the technique often used Comparators that can compare two continuously varying signal. Such a device switches from one logic state to another when the levels of the input signals coincide. There are Comparators that produce the coincidence of input signals, short single pulse or a series of a certain number of pulses existing at the time of coincidence of the polarities of the input signals.

R and S. 1. Diagram of the comparator by operational amplifier:

Fig. 2. Schematic diagram of the slot machine.

Fig. 3. Schematic diagram of the power supply.

R and S. 4. The circuit Board of the gaming machine with the layout of the elements.

R and S. 5. The circuit Board of the power source with the layout of the elements.

Fig. 6. The appearance of the gaming machine:
1 — the first remote, 2 a variable resistor RZ, 3 — power cord 4 — fuse holder 5 – power switch 6 indicator lamp, 7 – casing, 8 — the second controller, 9 is a variable resistor R6, 10 — meter, 11 — switch SAI, a 12 — SV1 button, 13 led.

Comparators are used in many fields of electronics. However, the most important area of their “activity” devices, which are based on the conversion of analog signals into logic. Here is a simple example — a digital voltmeter. One of its main nodes of the comparator controls the operation of the pulse generator. Suppose we want to determine the output voltage of the low voltage of the AC power supply. How does in this case, the measuring device? One input of the comparator is the supply voltage, and the second linearly varying. While they are not equal, the oscillator produces pulses. At the moment when the magnitude of the voltages at the inputs of the comparator match, it will switch, and generation will cease. Pulses prosummirovat counters, voltmeter and it displayed the result of the measurement. The generator device is configured so that when switching of the comparator, the number of produced pulses will correspond to the numeric value of the measured voltage with an accuracy of, for example, to tenths or hundredths of a volt.

From the above it is easy to conclude that the Comparators successfully combines the properties of analog and digital devices as their main purpose — conversion of signals.

A simple comparator can be assembled on operational amplifier. The scheme of such a device is shown in figure 1. The inverting input of op-amp through a current limiting resistor 1?1 gives a reference voltage. Non-inverting input plays the role of

measuring. Signal it is fed through the limiting resistor R2. To turn OU to the comparator in the scheme introduced feedback circuit formed by the resistor R3.

The principle of operation of such a device is simple. In the initial state, the output voltage of the operational amplifier is zero. If you submit on the measuring input of the comparator a voltage value which is smaller than the reference, the state of Oh will not change. When the voltage on the measuring input exceeds the reference, the output voltage starts to increase. Through the feedback circuit it will go on a measuring input, which in turn will lead to the increase of the input current. In the result, the output voltage will increase even more. In short, the process becomes an avalanche and the voltage at the output of op amp jump will increase up to the maximum level. Thus, the comparator will switch from a “zero” state to “single”. Isn’t it all very simple?

Well, now that we got acquainted with the structure and principle of operation Comparators, you can move on to their practical application. For this we offer you to build a simple electronic game. It is based on guessing one opponent of the actions of another. Participate in the competition two.

So, imagine a small box on the front panel which has an indicator light, push button switch, toggle switch and the electrical device, for example, a voltmeter. This is the main block. Connected two remote remote, dimmer controls.
Allocate roles, the participants proceed to the game. It begins with the fact that it takes her remote and turns the controller to any angle (within free movement). The second player does not see these actions. His task — as accurately as possible to repeat the opponent’s move. For example, it released three attempts. Guessing takes his remote and turns the regulator on the necessary, in his opinion, the corner. He then presses a button and evaluates your progress. If the indicator lamp lights up, it means the regulator is turned enough. The absence of a light signal indicates that the controller is turned more than necessary. Further guesses decides that he; now to do is turn the knob forward (if the indicator is illuminated) or back (if the indicator is not lit). Making another attempt, he again presses the button and the indicator evaluates its second move. Then turn the knob a third time and now includes a toggle switch. The voltmeter will prove the final result of the game. If the needle remained at zero, so guessing exactly “calculated move of the opponent. If it has deviated from its original position, the idea of driving remained unsolved^ the greater the deflection of the voltmeter, the more advantage wins it. The count result produced by the scale of the measuring device. Of course, in our case it will not be volts, and some conventional units.

Periodically exchanging roles, players can compete with each other, and then compare who have an intuitive sense developed . better. If you wish to participate in the contest a lot, it can be done round Robin to make a table of results and determine the winner. In short, use options of this slot machine you can find many, the main thing — to show a little imagination and imagination.

Note that the device is feature — it shows the final result, the value of which, in strict mathematical language, taken in its absolute value, i.e. without taking into account the sign of the difference. To define it; you must additionally press the button. If it is not lit, it means that the second player has been a bust. When the indicator is on, then guesses “have fallen short” to the opponent.

So, to understand the rules of the game, you can get acquainted with the contents of the slot machine. Its concept is shown in figure 2. As expected, the “heart” of this device — a comparator. It is assembled according to the familiar scheme at the operational amplifier DA1. Resistors R4, R5 and R10 limit the input and output currents of the chip, protecting it from overload, a R8 forms a feedback circuit. As an indicator applied HL1 led button switch on SB1. The role of the measuring device performs voltmeter DC voltage PV1, set in the diagonal of the rectifier bridge VD1—VD4. His shoulders included, in turn, between the inputs of the comparator. The measuring circuit of the voltmeter is switched by the switch SA1. Resistors R1, R3, R7 and R2, R6, R9 to form two controllable voltage divider. While the variable resistors R3 and R6 perform the functions of the regulators that are installed in the remote control.

How does a slot machine? For example, it took the first panel and set the engine variable resistor R3 to the middle position. The voltage from the top according to the scheme of the divisor will go into the reference input of the comparator (inverting input of op-amp) and both the diodes VD3, VD4 are the rectifier bridge. Now comes into play guessing. He takes his remote and turns the engine, the variable resistor R6. As a result, the voltage lower on the scheme of the divider is fed to the measuring input of the comparator (non-inverting input of op-amp) and both the diodes VD1, VD2. If the voltage level at pin 10 DA1 will be lower than at terminal 9, the operational amplifier will be in the “zero” state. By pressing the SB1 button the player is satisfied in this light HL1. If the voltage on the measuring input of the comparator exceeds the voltage on the reference input, the OPAMP will switch to the opposite state, and its output appears logical unit, the led will not illuminate.

It should be noted that switching of the operational amplifier occurs when izmerenie voltage exceeds the reference by about 0.3 V. Therefore, the exact match of input voltages (and, therefore, the provisions of the regulators R3 and R6) N1.1 continues to burn. By participating in the game, forget about it.

After all attempts of the second player is exhausted, he turns on the switch БА1. If the voltages on both wires of the comparator coincide, the pointer of the voltmeter, as we have said, will remain at the zero point of the scale. If the voltage on one input will exceed the voltage on another input, the arrow will deviate from zero and show the difference of the input voltages. Since the instrument is included in the diagonal of the rectifier bridge, no matter which of the inputs of the OPAMP the voltage level was bolas. ‘ the polarity of the voltage on the voltmeter will always be one and the same. Naturally, the needle also deviates in one direction only. To determine whose the remote controller is rotated more at the end of the game, as we have already suggested, you can click БВ1 and as indicator НL1 to make a final conclusion.

Powered gaming machine from the network of the stabilized source of the so-called artificial mid-point (Fig. 3). If the design uses a microchip К140УД1Б, the output voltage of the power supply must be 12 V. When using IMS К140УД14 voltage should be reduced to 9. Mark the Zener diode for the latter case shown in parentheses.

The manufacturer of the slot machine start with the circuit Board shown in figure 4. It is better to make from a sheet of foil Micarta or fiberglass thickness of 1 — 2 mm size 35X30 mm. From one end, drill two mounting holes 0, 3 mm the power supply Elements located on the circuit Board size 75X30 mm, made of the same foil material (Fig. 5). The transistor needs heatsink.

About the details. Operational amplifier — К140УД1Б or К140УД1 A. Transistor — any of the series КТ601 — КТ603, КТ801, КТВ05, КТ815, КТ817, КТ819. For power source with voltage of 12 V suitable Zener Д811, Д813, Д814Г, Д814Д or КС211. If the power supply voltage must be reduced to 9 V, you can use Zener Д809, D810, Д818А—Д818Г, Д814Б or Д814В. Diodes —Уй4 — any of series D2, D7, D9, Д1В, D20, Д206, Д220, Д223, D226, Д237. Rectifier unit — KTS405 with any alphabetic index or four medium-power diode connected in bridge circuit. Led brand AL 102 or АЛ307. Voltmeter DC voltage measuring range of 5-6 V. If this is not found, then the measuring device can be applied milliammeter with series-connected limiting resistor the required resistance. The capacitor C1 — C50-6 C50 or-16, S2 and Sz — K50-24. Fixed and variable resistors — any brand. Network transformer — low-power with a secondary voltage 12-18 V. a light Bulb H1-2 — stamps MH-2 or MH-3. Toggle switches and push button switch — any type. The fuse should be rated at not more than 0.5 A. ХР1 — standard network plug.

The appearance of the gaming machine shown in figure 6. Case for it can be made of plastic, plywood or aluminum. Fit and ready, such as a plastic box from under the thread. On the front panel of the device fix the measuring device, toggle switches, push button switch, led and neon lamp. On one of the side walls, install the fuse holder. Apply appropriate labelling about authorities. Circuit Board and power transformer attach to the base case. Resistor R11 should be connected directly to one terminal “of neonki”. All necessary connections, run the thin wire in isolation.

On the rear of the enclosure drill three holes: one for the network cable, and the two cords that connect the device with a remote control. As enclosures for them, like dish soap. The variable resistors provide decorative handles. For greater convenience around each regulator is possible to put several labels — it is easier to navigate, hoping their actions.

The slot machine requires establishing. If you have not made errors in the installation and used serviceable parts, you can be sure it is working.

V. ANTSEV