Improved indicator of the coming year. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Improved indicator of the coming year. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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In the article by I. Nechaev "Indicator of the coming year" in "Radio", 2001, No. 11, p. 54, 55, a device has been described in which LED indicators are used to display the coming year. In the description, two variants of the indicator were proposed - with a constant glow of digits and with a periodic change of digits in the least significant digit.

I propose another version of such an indicator (Fig. 8), somewhat complicated, but providing a bitwise ignition of the digits of the indication of the coming year, and then their smooth extinguishing.

(click to enlarge)

On three logic elements of the DD1 microcircuit, a master generator of rectangular pulses is made, the repetition rate of which depends on the resistance of the resistor R1 and the capacitance of the capacitor C1. From pin 10 of the element DD1,3, the pulses are fed to the counting input (pin 14) of the counter DD2 operating in the decoder mode. The outputs of the counter are connected to the S-inputs of the RS flip-flops of the DD3 microcircuit, and through the diodes VD2 - VD5 - to the emitter follower on the transistor VT5.

The trigger outputs of the DD3 chip are connected to emitter followers on transistors VT1 - VT4, loaded on the anodes of the LED indicators HG1 and HG2.

The device works like this. Pulses with a frequency of 1 ... 1,5 Hz from the master oscillator are fed to the counter DD2, at the outputs 0 - 9 of which sequentially high logic levels appear. Such levels, appearing at pins 3, 2, 4, 7, translate the RS-flip-flops of the DD3 chip into a high logic level at the outputs. In turn, these signals enable the operation of emitter followers on transistors VT1 - VT4. And since the cathodes of all indicator elements are connected through resistors R8 - R29 to an emitter follower on a VT5 transistor, which is open at a low level through a VD5 diode and resistor R2 during this period, the numbers on the indicators will sequentially light up, starting from the highest digit (top element HG1).

The next two pulses from the master oscillator will not change the state of the device - the LED indicators will continue to display the numbers of the coming year.

The next three pulses from the generator will lead to a high level at the top output of the resistor R2 in the circuit, since the diodes VD2 - VD4 perform the function of a logic element 3 OR. The diode VD5 will be closed, the discharge of the capacitor C4 through the resistor R3 will begin. The voltage at the base of the transistor VT5 relative to the common wire will gradually increase. The transistor will start to close, and the indicators will go out smoothly for 2...3 s.

The next pulse from the master oscillator will lead to a high level at pin 11 of the counter, as a result of which all RS flip-flops of the DD3 microcircuit will go to zero at the outputs, and a low level on resistor R2 will quickly charge capacitor C4 through diode VD5. The device will prepare for the next stage of work.

The whole cycle consists of 10 pulses of the generator: 4 pulses - sequential ignition of indicators (discharges); 2 pulses - all indicators are on; 3 pulses - smooth fading of indicators; 1 impulse - reset.

The device can be powered from any DC source with voltage of 9...15 V and permissible load current up to 200 mA. Diode VD1 serves as protection against incorrect connection of the power supply.

It is permissible to use microcircuits of the K564, KR1561 series in the device, and in place of DD1, microcircuits with the indices LA7, LE5, LE10, LN2 in the corresponding inclusion are suitable. Transistors VT1 - VT4 - any of the KT3102, KT315 series. In place of VT5, if the one indicated in the diagram is missing, you can install a composite transistor made according to the circuit shown in Fig. 9.

Improved indicator of the coming year

Diodes VD2-VD5 - any of the series KD521, KD522. In addition to indicators KIPTs22A, it is permissible to install KIPTs13B or KLTs201A, KLTs201B, KLTs202A, KLTs302A having a different pinout.

Details of the device are placed in the body of a toy of suitable dimensions, and the toy is hung on the branches of a Christmas tree. On the case, it is desirable to strengthen the connector for connecting the power supply.

Establishing the design consists in setting the desired switching frequency of the generator by selecting the resistor R1, as well as the rate of extinguishing the indicators by selecting the resistor R3.

By simplifying the design a little, it will be possible to change the logic of its work. To do this, you need to remove the transistor VT5, the diodes VD2 - VD5, the resistors R2 and R3, the capacitor C4, and the terminals of the resistors R8 - R29, right according to the diagram, should be connected to a common wire. The outputs 5, 6, 9 released from the counter should now be connected to its output 11. As a result of the changes, the device operation cycle will be as follows: 4 generator pulses - sequential ignition of the indicator bits, starting from the older one, 2 generator pulses - all indicators are on, 4 pulses - successive blanking of indicator digits, also starting from the highest one.

By the way, for some instances of LED indicators, ballast resistors R8 - R29 can be excluded, and resistors with a resistance of 270 ... 300 Ohms can be included instead in the emitter circuits of transistors VT1 - VT4. But if the brightness of the glow of individual elements of the indicators differs significantly, ballast resistors will have to be installed.

Author: I.Potachin, Fokino, Bryansk region

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