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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Electronic bone. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur [an error occurred while processing this directive] Everyone is familiar with an ordinary dice - a cube, on the edges of which from one to six dot marks are applied. It is known that it was the analysis of the results of throwing such a die that formed the basis of the theory of probability. For a long time, dice have been an indispensable element of many games. But it turns out that this "tool" can also be made on the basis of electronics. Such a "bone" does not stand on edge, does not fall to the floor, and you do not have to throw it up. You just need to press the button, and after a few seconds the next result will drop out. There are various options for implementing such a design. A schematic diagram of one of them is shown in Fig. 1. In it, the dropped number is displayed on the digital indicator HG1, the segments of which are switched by electronic keys on transistors VT1-VT9 [1]. The device also contains a counter, made on the chip DD2, and a pulse generator on the elements DD1.1, DD1.2. The pulse repetition rate depends on the voltage on the capacitor C1 and changes as it is discharged from 10 Hz to fractions of a hertz.
As you know, the K176IEZ chip is a divider by 6 counter with a built-in decoder. At the output of the decoder, codes appear alternately corresponding to the displayed numbers from 0 to 5. But since the dice is characterized by numbers from 1 to 6, it is necessary that the indicator display a six instead of zero. To this end, the counter is equipped with an additional decoder, made on the elements DD1.3, DD1.4 and transistors VT2, VT9. Note that the presence of zero-level signals at the outputs c and e of the DD0 chip can be considered a sign of the number 2. The display of any other digit in the range from 1 to 5 is characterized by the presence of a logic 1 level on at least one of them. Therefore, at the moment when a low-level voltage appears at the outputs, the indicator should display the number 0 instead of 6. When using a seven-segment indicator, this means that it is necessary to extinguish segment b and light d. This is exactly what the additional decoder does. Setting zero levels at pins 11 and 13 of the DD2 chip leads to the same signal at the output of the DD1.4 element. As a result, transistors VT2 and VT9 open. The first of them closes VT3, which leads to the extinction of segment b of the HG1 indicator. The second shunts the transistor VT8, due to which segment g is turned on. Thus, the required number 6 is formed. The device works as follows. In the initial (shown in the diagram) state of the SB1 button contact, the HG1 indicator displays one of the numbers from 1 to 6. When the button is pressed, the capacitor C1 is quickly charged through the resistor R2, as a result of which the generator starts generating rectangular pulses with a repetition rate of approximately 10 Hz. From its output, the signals are sent to the counter DD2. and continuously flashing numbers appear on the HG1 indicator. After the SB1 button is released, the capacitor C1 begins to discharge, the generator frequency gradually decreases and the speed of the digits on the indicator decreases. After about 3 seconds, the counter DD2 stops and one of the numbers from 1 to 1 is displayed on the HG6 indicator. Its state remains unchanged until the next press of the SB1 button. The device is powered by the mains. Excess voltage extinguishes capacitor C6 (nominal voltage of at least 600 V). Resistor R15 limits the current through this capacitor, and R14 discharges it after the device is disconnected from the network. A constant voltage of about 24 V is formed by the zener diodes VD2, VD3. The power dissipated by them is small, so their use without a heat sink is acceptable. A voltage drop of about 10 V is created across the resistor R9, which is used to power the microcircuits DD1, DD2 and transistors VT1-VT9. The power consumed by the device does not exceed 2 watts. It should be noted that all its elements are under mains voltage. In this regard, they must be carefully isolated from the body, if it is made of metal. Instead of IV-6, you can use a seven-segment LED indicator, for example, AL305A or AL305Zh. using the recommendations given in [1]. However, it is best to make the indicator in the traditional dice shape, with dots instead of numbers. In other words, in this case, a universal face of the cube will be obtained, on which from one to six LED "dots" will light up. It is this indicator that is used in the second version of the device (Fig. 2). Here, the starting circuit (SB1, R1 and C1) and the pulse generator (elements DD1.1, DD1.2. VD1, C2, C3, R2-R5) are similar to those described above. The counter-divider by 6 is made on flip-flops DD2, DD4 and element DD1.3, just as it was done in [2]. Timing diagrams explaining its operation are shown in fig. 3.
Since the inputs of triggers DD2.2, DD4.1 and DD4.2 are connected to the direct outputs of the previous ones, the counter on them works in subtraction mode. He counts in binary. Its information outputs are pins 1 of the DD4 chip (high order) and 13.1 of the DD2 chip (middle and low order, respectively). The state of the counter changes along the edge of the signal generated by the element DD1.2. Turning on the generator with the SB1 button leads to the appearance of rectangular pulses at the input C of the trigger DD2.1 and the input S of DD4.2. At the same time, a signal with a logic level of 0 is set at the inverse output of the latter, enabling the operation of the DD2.2 trigger at input C, and the counter starts counting. When it counts up to 0. on the direct outputs of triggers DD2.1. DD2.2 and DD4.1 is set to zero. After that, the very first drop from O to 1 at the output of element D01.2 translates the named outputs, and with them the inverse output DD4.2. into a singular state. The output signal DD4.2 resets the trigger DD2.1 at the input R. As a result, the counter goes into the state corresponding to the number 5. The next pulse generated by the element DD1.3 (in Fig. 3 it is highlighted in hatching) translates the inverse output of the trigger DD4.2. XNUMX to the zero state, thus allowing further counting. When the counter reaches zero again, the cycle will repeat. A decoder assembled on a DD3 chip and a DD1.4 element. is constructed in such a way that the states 5. 4, 3. 2. 1 and 0 of the counter correspond to the numbers 5. 6.1, 2. 3 and 4 on the "face" of the dice. This follows from the table below, which shows the correspondence between the signal levels at the outputs of the counter, decoder and the state of the LEDs HL1-HL7. In this case, the burning LED in the table corresponds to the number 1. The extinguished LED - 0. Since the current consumed by the device does not exceed 60 mA. it can be powered both from the mains and from batteries "Krona", "Korund". When using mains power, it is permissible to use the same transformerless source as in the first variant. However, in this case, a voltage of 9 V is required. In connection with this, one of the D815D zener diodes (for example, VD3) must be replaced with D815V. and the other (VD2) - to any low-power silicon diode, for example, KD105B (its cathode is connected to the VD3 cathode). The location of the LEDs HL1-HL7 on the edge of this variant of the dice is shown in Fig. 4. In both devices, instead of microcircuits of the K176 series, it is permissible to use their counterparts from the K561, 564 series. In the second device, to replace the KT315G transistors. KT361G will suit any of these series, and AL307BM LEDs - any emitting in the visible spectral range. The diode assembly KTS405A can be replaced with KTS405B. KTs405V, KTs402A-KTs402V or four diodes KD105A-KD105V, including them according to the rectifier bridge circuit. Literature
Author: V.Bannikov, Moscow
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