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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING LED strip running lights. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Lighting The device is used to create a lighting effect such as two light beams "scattering" in different directions. It can be used for decoration and lighting design of shop windows, dance floors, motorists use rulers with running lights as auxiliary brake lights. By combining several rulers, you can build a variety of luminous shapes, such as polygonal stars. The electrical circuit of the device is shown in Fig.1. The device can be conditionally divided into three functional blocks: a clock generator, a block for generating the lighting effect algorithm and an executing control device (14 LEDs).
The generator is built on two logic elements of the 4011 microcircuit, consisting of 4 logic elements 2I-NOT (the circuit can be replaced by the domestic analogue 564LA7, K561LA7. The frequency of the generator is determined by the capacitance of the capacitor O and the resistance of the resistor R1 and the potentiometer R16, designed to change the frequency of the generator. Experimentally established that the optimal frequency is obtained with a potentiometer resistance of about 100 kOhm. The function of serial ignition of LEDs in the line is performed using two four-digit shift registers of type 4015. Register 4015 has a serial input and parallel output; shift registers 564IR2, K561IR2, KR1554IR46 can be used as a replacement. As you know, a shift register is a digital element whose output bit registers are sequentially set to a high logic level with the arrival of a clock pulse. The output of the most significant bit of the register QD DD2.1 is used to reset the device, the remaining seven outputs are used to control the LEDs. After zeroing the register at the information input of the first shift register DD2.2 there is always a high level equal to the supply voltage. After the arrival of the next clock pulse from the clock generator, the state at the input D is rewritten to the output QA of the shift register DD2.2. At the same time, the clock pulse is received but the counting input CLK of the second shift register DD2.1, but at its information input there is a low level supplied from the last output of the shift register DD2.2, and the low level remains unchanged at the output. The arrival of the next clock leads to the movement of information from the output QA to the output QB register DD2.2. At the same time, a high level will be recorded again at the output QA, which is constantly present at the information input D of the first shift register. This situation is repeated twice more, and after the fourth clock pulse, all outputs of register DD2.2 will have a high logic level. At the same time, at the information input of the second shift register DD2.1, there is now a high level supplied from the QD output of the first register DD2.2. Then the fifth clock will lead to the rewriting of information from the input D to the output QA DD2.1. The next two clock pulses will lead to the appearance of a high level at the following outputs until the arrival of the eighth clock pulse, when a high level appears at the output of the QD register DD2.1. This high level goes to the RST inputs of both registers and resets them. Then the process is repeated from the beginning. Thus, sequential filling of the outputs of the registers is performed, which is used to control the line of LEDs. However, powering the LEDs directly from these outputs would limit the maximum current flowing through the LEDs, reducing their brightness. To use the maximum brightness of the LEDs, the device uses an output converter on an integrated circuit ULN2003 (analogues: Kl 109KT22, Kl 109KT23). ULN2003 ICs contain 7 Darlington transistors in their structure, they are usually used as buffer stages for matching 5- and 12-volt peripherals and for controlling seven-segment sign indicators in multiplexer systems. In the described device, each chip driver controls a pair of LEDs (Fig. 2).
Capacitors C2 and C3 perform the role of smoothing the supply and suppressing possible AC surges. Figure 3 shows the placement of elements on printed circuit boards, which are made on one-sided mounting, the jumpers between the printed conductors on the boards are marked with the letter Z.
Boards of the same size are mounted one above the other on spacer sleeves 2 ... 3 cm long and connected using round-head screws and nuts. You can connect the boards without using bushings, while for one connection you will need a screw 3 ... 4 cm long and three nuts. Screws are inserted into the upper printed circuit board, on which the LEDs are soldered, and clamped with nuts to the heads themselves. Then, the second nut is screwed onto the screws to a depth sufficient to place the lower printed circuit board on the axis of the screws, and the latter is clamped with the remaining nuts (Fig. 4).
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