Design and simulation of LED color control conversion circuit based on Multisim 10

The current design of digital integrated circuits is relatively modular. EDA technology refers to the automatic design of electronic products using computers as a working platform, integrating the latest achievements of applied electronic technology, computer technology, information processing and intelligent technology. Using EDA tools, electronic designers can design electronic systems from concepts, algorithms, protocols, etc. A lot of work can be done by computers, and the entire process of electronic products from circuit design, performance analysis to IC layout or PCB layout design can be automatically processed on computers.

Multisim 10 is an electronic circuit design and simulation tool. In scientific research, circuit simulation tools are mainly used for circuit design and simulation. Compared with other EDA software, it has a more intuitive human-computer interaction interface, especially the instruments in its instrument library are exactly the same as the actual instruments in real experiments.

LED electronic display screen is composed of semiconductor light-emitting diode pixels arranged evenly. Different materials can be used to make LED pixels of different colors. LED display screens display pictures with bright colors and strong three-dimensional sense, which are as quiet as oil paintings and as dynamic as movies. They are widely used in stations, docks, airports, shopping malls, hotels, securities markets, industrial enterprise management and other public places.

For example, in billboards or entertainment venues, LED display screens are often designed to change in a continuous cycle according to a certain pattern to achieve good viewing experience.

The following introduces how to design an 8×8 LED dot matrix controller using Multisim 10 as the design platform, using the bidirectional universal shift register 74LS194, LED and character signal generator to achieve multiple groups of light-emitting diodes displaying in a certain pattern.

1. Design and simulation of color control conversion circuit

The color control conversion circuit is mainly composed of three parts: the setting of the character signal generator, the setting of the bidirectional universal shift register group and the setting of the 8×8 dot matrix LED tube.

1.1 Setting up the character signal generator

A word generator is an instrument that can generate 32-channel (bit) synchronous logic signals, also known as a digital logic signal source, which can be used to test digital logic circuits. A word generator can send digital or binary digital signals into a circuit to drive or test the circuit.

In this circuit, the 0~7 pins of the character signal generator correspond to A, B, C, D, SL, SR, S0, S1 of the first 74LS194; the 8~15 pins correspond to A, B, C, D, SL, SR, S0, S1 of the second 74LS194; the 16~23 pins correspond to A, B, C, D, SL, SR, S0, S1 of the third 74LS194; the 24~31 pins correspond to A, B, C, D, SL, SR, S0, S1 of the fourth 74LS194. Therefore, the transformation of the character signal is the transformation of the input terminals of these four 74LS194. As shown in Figure 1.

1.2 Main control circuit and simulation design results

The 8×8 dot matrix LED color light conversion control circuit is composed of a character signal generator, a bidirectional shift register and an LED dot matrix. Its design is shown in Figure 2.

1.2.1 74LS194 logical function and circuit design process

74LS194 has three functions: parallel input and output, left shift, and right shift. Among them, A~D are parallel input terminals, QA~QD are parallel output terminals, S1 and S0 are mode control terminals. When ~CLR is 1 and the clock rising edge arrives, if S1S0=11, then parallel input and output, QD~QA=D~A; if S1S0=10, left shift, QD~QA=QC~QASL; if S1S0=00, right shift, QD~QA=SRQC~QA.SR is the right shift serial input terminal, SL is the left shift serial input terminal, ~CLR is the direct unconditional clear terminal, CLR is the clock pulse input terminal, VCC is connected to the power supply, and GND is the ground.

In this circuit, the output terminals QA, QB, QC, QD of the first 74LS194 correspond to the 1st row, 2nd row, 3rd row, and 4th row of the LED matrix respectively; the output terminals QA, QB, QC, QD of the second 74LS194 correspond to the 5th row, 6th row, 7th row, and 8th row of the LED matrix respectively; the output terminals QA, QB, QC, QD of the third 74LS194 correspond to the 1st column, 2nd column, 3rd column, and 4th column of the LED matrix respectively; the output terminals QA, QB, QC, QD of the fourth 74LS194 correspond to the 5th column, 6th column, 7th column, and 8th column of the LED matrix respectively. Therefore, the QA, QB, QC, QD values ​​of the 74LS194 determine the state of the LED light-emitting diode.

1.2.2 Design and working principle of 8×8 LED dot matrix

An 8×8 dot matrix LED display requires a total of 64 light-emitting diodes, and each light-emitting diode is placed at the intersection of a row line and a column line.

When the corresponding row is set to a high level and the corresponding column is set to a low level, the light-emitting diode at the intersection of the row line and the column line is lit; if all the light-emitting diodes in a row are to be lit, the corresponding row is set to a high level and all the columns are set to a low level; if all the light-emitting diodes in a column are to be lit, all the rows are set to a high level and the corresponding columns are set to a low level.

1.2.3 Simulation Results

The change of colored lights is mainly achieved by processing the parameter value of the character signal generator and controlling the on or off of the LED light-emitting tube to realize scrolling display. The results and the parameter values ​​of the character signal generator are described as follows.

(1) Line-by-line scrolling function (scrolling order is from top to bottom, then from bottom to top):

① Use the merge-in and merge-out functions to realize the line-by-line scrolling function. The character signal parameter values ​​are shown in Table 1, which are cyclically represented from top to bottom and from left to right.

② Use the functions of merge in and out, right shift, and left shift. The character signal parameter values ​​are shown in Table 2, which are cyclically represented from top to bottom and from left to right.

(2) Use the merge in and out, left shift, and right shift functions to realize the column-by-column scrolling function (the scrolling order is from left to right, and then from right to left). The character signal parameter values ​​are shown in Table 3, which are cyclically represented from top to bottom and from left to right.

(3) Use the merge-in and merge-out functions to achieve point-by-point scrolling display (the scrolling order is 1st row, 1st column, 1st row, 2nd column...8th row, 8th column).

The character signal parameter values ​​are shown in Table 4, which are cyclically represented from top to bottom and from left to right.

2 Conclusion

Using Multisim 10 to design and simulate the various unit circuits and the overall circuit of the colored light change control circuit can easily and quickly build the circuit, and can quickly find and modify the circuit. After the circuit design simulation is completed, the actual circuit is built, thereby reducing costs and improving design efficiency.