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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Four way traffic light. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur The composition of the first version of the traffic light (Fig. 8) includes a master generator on logic elements DD1.1, DD1.2, a binary counter DD2, logic elements DD1.3, DD1.4, DD3.1 -DD3.4 and transistor switches VT1- VT5, controlling their groups of LEDs of the same color. The LEDs in the groups are marked in two directions: 1 and 2. Since each group has two series-connected LEDs, this means that, for example, one of the green LEDs of the HL1, HL2 pair is directed in one direction, and the other in the opposite direction. Then the green LEDs HL11 and HL12 should be located in a perpendicular direction, also one in each direction.
Consider the operation of the device, using not only the circuit, but also the signal diagram (Fig. 9) at its various points. The master oscillator generates signals with a frequency of about 1,5 Hz. They go to the counting input (pin 10) of the DD2 chip, so pulse sequences of different frequencies will begin to appear at its outputs.
Suppose that at first the red light of direction 1 is on (LEDs HL7, HL8, diagram 4, period t0-t1; in the future, the diagram number and the corresponding period will be indicated in brackets), since pin 4 DD2 is low and transistor VT3 is open. At the same time, the green light of direction 2 (9, t0-t1) will light up, since there will be a high level at pin 10 of the DD3.3 element (8, t0-t1), and at pin 11 of the DD1.4 element there will also be a high level (diagram 5, period t0 - t1). After eight pulses at the output of the buffer element DD1.3 (1, t1) and with the beginning of the ninth pulse, a high logic level (5, t2) will appear at pin 3 of the counter DD1. Element DD1.4 will start switching pulses coming from pin 10 of element DD1.3 (1, t1 - t2). Since the output of the element DD3.2 is high (7, t1-12), the diode VD1 is closed. A high level (10, t3.3-8) will remain at pin 1 of the DD12 element, so pulses (3.4, t9-t1) will appear at the output of the DD2 element, which will turn the green LEDs HL11, HL12 into a flashing mode. Red LEDs HL7, HL8 will continue to glow (4, t1-t2). At the end of four pulses, a high level will appear at pin 7 DD2 (2, t2). At pin 5 of the counter, there is also a high level (3, t2-t3), so the DD3.2 element will go into a low level state at the output (7, t2-t3). The yellow LEDs HL3-HL6 of four directions will flash. The opened diode VD1 low level (5, t2-t3) will transfer the element DD3.4 to a high level state at the output (9, t2-t3). The green LEDs HL11, HL12 will go out, and the red LEDs HL7, HL8 will continue to light for another four pulses (4, t2-t3). Then a high level at pin 4 of the counter (4, t3) will turn off the red LEDs HL7, HL8. At the same time, all yellow LEDs will also go out, since low levels at pins 7 (2, t3) and 5 (3, t3) of the counter will transfer the DD3.2 element to a high level state at the output (7, t3). A high level at pin 4 DD2 (4, t3) will light up the red LEDs HL9, HL10 of the other direction. The green LEDs HL1, HL2 will also turn on, because high levels will appear at pins 1 (5, t3) and 2 (4, t3) of the DD3.1 element. This will continue for another eight pulses at the output of the element DD1.3(1, t3-t4). Then a high level at pin 13 of the element DD1.4 (3, t4-t5) will allow the passage of pulses from the output of the element DD1.3 to BxoflDD3.1 (5, t4-t5). LEDs HL1 and HL2 will start flashing After four pulses, a low level at the output of the DD3.2 element (7, t5-t6) will turn off these LEDs and turn on the yellow HL3-HL6. Red LEDs HL9, HL10 continue to burn all this time (8, t3-t6). With the arrival of the next, 33rd pulse (from the beginning of the traffic light), the device will go to its original state (1 - 6, t6) - red LEDs HL7, HL8 and green LEDs HL11, HL12 will flash, and the rest will go out. The processes described above will then be repeated. In addition to those indicated in the diagram, in place of DD1, DD3 it is permissible to use K564LA7, K176LA7 microcircuits. Transistors - any of the KT361, KT3107 series, VD1 diode - any of the KD503, KD521, KD522 series, LEDs - any domestic or imported ones with the highest light output and the corresponding glow color. Depending on the dimensions of the traffic light, you can use both miniature LEDs with a diameter of about 3 mm, and larger ones with a diameter of 10 ... 12 mm. LEDs are placed in the body of a four-way traffic light or in single traffic lights, installing three LEDs in each (one of each color) and connecting them in accordance with Fig. 10.
At busy intersections, in addition to traffic lights for cars, two-color traffic lights for pedestrians are installed, working in concert with car traffic. Therefore, the second version of the traffic light, more complex (Fig. 11), is supplemented by pedestrian traffic lights.
The logic of the traffic light is as follows. At first, it works like the previous one - the green light is on in one direction while the red light is on in the other. Then the green light goes into pulse mode, after which the yellow light turns on and the colors change to the other direction. At the same time, red light is on at all times in pedestrian traffic lights. After passing the glow cycle in the other direction, the yellow light turns on, after which all the main (car) traffic lights turn red, and the pedestrian ones turn green. At the end of a certain time, the green "pedestrian" light goes out, the main traffic lights turn yellow, and then the cycle begins again. In this design, in addition, the ratio of the duration of the glow of the primary color to the duration of the yellow glow (as in real traffic lights) is increased, and this ratio can be changed within a small range. Consider the device and operation of a traffic light according to its schematic diagram together with the signal diagram (Fig. 12) at various points in the structure. The traffic light consists of a master oscillator on the elements DD1.1, DD1.2, a binary counter DD2, microcircuits DD3-DD5, transistor switches VT1-VT8 and LEDs HL1-HL20.
The master oscillator generates oscillations with a frequency determined by the position of the trimmer resistor R2 and the values of the elements C1, C2, R3, R4. The closer the engine is to the top output of the resistor according to the circuit, the lower the generator frequency, and vice versa. The generator pulses are fed to the input of the counter DD2 (pin 10) and to pin 1 of the buffer inverter DD5.1. At the beginning of the cycle, the red LEDs HL7 and HL8 of the same direction will be lit, since pin 4 of the counter has a low logic level (4,t0-t2). The green LEDs HL11, HL12 of the perpendicular direction of movement (14, t0-t2) will also light up, because the inputs of the DD3.3 element have high levels (6 and t0-t2). At the same time, the red LEDs HL17-HL20 of the "pedestrian" traffic light (17, t0-t2) will light up. The device will be in this state for 16 clock pulses of the generator (1-17, t0-t2). The seventeenth pulse will put the counter into a high level state at pin 5 (3, t2-t3), pin 12 of the DD1.4 element will receive pulses from the output of the DD1.3 element through the resistor R7 (6, t2-t3). Green LEDs HL11, HL12 will go into blinking mode. After eight flashes, these LEDs will go out, since the DD3.2 element will go into a low level state at the output (11, t3-t4). The opened diode VD4 will transfer the element DD3.3 to a high level state at the output (14, t3-t4). The yellow LEDs HL5, HL6 of one direction (11, t3-t4) and the same LEDs HL1, HL2 of the other direction will turn on - after all, all inputs of the DD4.1 element will have high levels (2,3,13, t3-t4), and the transistor VT1 will open with diode VD2 (15, t3-t4). At the same time, a low level through the VD1 diode will go to the trimmer resistor engine and shunt its lower part according to the circuit (9, t3-t4). The oscillator frequency will increase (1, t3-t4), which will reduce the duration of the yellow signal. After the next eight clock pulses, the red HL7, HL8 and yellow HL1, HL2, HL5, HL6 LEDs will turn off, but the red HL9, HL10 (13, t4-t6) and green HL3, HL4 (10, t4-t6) will light up. A high level at the cathode of the VD1 diode will switch the generator to normal mode - the generator frequency will drop to the original (1 and 15, t4-t6). The red LEDs HL17-HL20 will still glow (17, t4-t6). The device will now run one cycle for the other direction. After 16 clock pulses, the green LEDs HL3, HL4 will go into blinking mode - a high level at pin 5 of the counter (3, t8-t7) will allow the passage of clock pulses to the element DD1.4. After eight flashes (10, t8-t7), the HL3, HL4 LEDs will go out, since the DD3.2 element at its output will transfer the DD4 element through the diode VD6 (11 and 7, t8-t1.4) to a high level state at the output ( 10, t7-18). The yellow LEDs HL5, HL6 (11, t7-t8) will flash. In the other direction, the yellow LEDs HL1, HL2 will not light during this period (15, t7-t8), but the red LEDs HL9, HL10 continue to glow (13, t7-t8). A low level from pin 14 of the DD3.2 element (11, t7-t8) through the VD5 diode will again increase the generator pulse frequency for the duration of the yellow LEDs (9 and t7-t8). At the end of eight clock pulses, the flashing red LEDs HL9, HL10 (7, t8-t12) of the other direction will be added to the red LEDs HL8, HL11 that continue to burn in one direction. The "car" traffic lights will be lit red signals prohibiting movement in all directions. At the same time, the red LEDs HL17-HL20 of the "pedestrian" traffic lights (17, t8-t10) will go out, and the green LEDs HL13-HL16 (16, t8-t10) will light up. They will glow for 16 clock pulses (t8-t10). Then a high level at the output of the element DD3.4 (16, t10-t11) will turn off the green LEDs HL13-HL16 and turn on the red HL17-HL20. High levels at pins 5 and 6 of the counter (3 and 5, respectively, t10-t11) will transfer the element DD3.1 to a low level state at the output (15, t10-t11). The yellow LEDs HL1, HL2 will light up, the generator frequency will increase (1 and 9, t10-t11). In the other direction, the red LEDs HL7, HL8 (12, t10-t11) will still be on. After the next eight clock pulses, the yellow LEDs HL7, HL8 will go out, because at this moment (tn) high levels at pins 7, 5, 6 of the counter (2,3,5, t11) using the DD4.2 element and the DD5.3 inverter will form a short reset pulse (8, t11), which will go to pin 11 of the counter. Now the counter will be set to its initial state, the cycle of the traffic light will repeat. In this design, you can use the same details as in the previous one. LEDs HL1-HL12 of the main traffic lights should be mounted in the same way as in the first option. But LEDs of "pedestrian" traffic lights will be added to the main ones, which should be interconnected in accordance with Fig. 13.
Establishing the device is reduced to setting the desired ratio of the duration of the glow of the main signals to the duration of the yellow light using a tuning resistor R2. When the yellow light is turned on, the generator frequency is maximum, and when the main signals are turned on, it is determined by a tuning resistor. The closer its engine is to the top output according to the circuit, the lower the frequency of the generator. Therefore, by changing the fundamental frequency of the generator within certain limits, it will be possible to select the ratio of durations indicated above. Literature
Author: I.Potachin, Fokino, Bryansk region
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