Design of Four-way Color Light Controller Based on Multisim

When designing control system circuits, using Multisim simulation software to design, simulate and analyze control system circuits can greatly reduce costs, save time and improve design quality. This article will use Multisim as the working platform and four-way colored lights as an example to introduce the design and simulation process of the control system.

1 System Design

Use Multisim to design a four-way color light controller. It requires the system to automatically complete a three-beat cycle demonstration from the initial state according to the specified program after startup. The first beat: the four-way color lights gradually light up from left to right, the light is on for 1 second, and the total time is 4 seconds; the second beat: the four-way color lights gradually turn off from right to left. It takes a total of 4 seconds; the third beat: the four-way color lights light up at the same time for 0.5 seconds, and then dim at the same time, and repeat 4 times, which also takes 4 seconds.

According to system requirements, the system hardware block diagram is designed as shown in Figure 1.

The signal generator uses a pulse per second generator to provide a clock signal with a frequency of 1Hz; the quaternary frequency divider divides the 1Hz clock signal into four and generates a clock signal of 0.25Hz (i.e. 4S); the ternary beat controller generates a control signal of 3 beat cycles; the beat program executor completes the system action at each beat, that is, the left shift, right shift, clearing and sending functions of the data. This can be completed by the bidirectional shift register 74LS194; the lighting circuit completes the system cycle demonstration, and LED simulation is used here.

1.1 Signal Generator

The signal generator is a 555 connected into a multivibrator to generate a 1Hz pulse signal. In order to simplify the circuit design, a 1Hz pulse signal source is selected to replace the signal generator.

1.2 Quaternary Divider

The frequency divider can be constructed by various types of quaternary counters. Here, the D flip-flop in 74LS74N is used to connect the quaternary asynchronous down counter as shown in Figure 2.

Figure 3 shows the waveform of a quaternary asynchronous subtraction counter.

1.3 Ternary beat controller

This system has three different working beats, which are represented by three codes (10, 01, 11) of the state (Q1, Q0). The D flip-flop in 74LS74N and the NAND gate in 74LS00D are selected to form the ternary counter shown in Figure 4.

1.4 Beat Program Controller

The two-phase shift register is 74LS194, which is the core device for generating moving light signals. Figure 5 is the logic diagram and function table of 74LS194. The register consists of 4 RS flip-flops and their input control circuits. It has four working modes: parallel registration, left shift registration, right shift registration and hold. ***** is the clear terminal, and low level is effective; CLK is the rising edge trigger, SL and SR are the left shift and right shift serial input terminals respectively; SO and S1 are two control input terminals, and their state combination can complete the four control functions of hold, right shift, left shift and parallel input. When S1=0 and S0=0, the circuit maintains the original state: when S1=0 and SO=1, the data is sent to the register from the right shift input terminal SR; when s1=1 and S0=0, the data is sent to the register from the left shift input terminal SL; when S1=1 and S0=1, the data is preset from the DCBA parallel input terminal.

This design uses the 74LS194 register to control the light to cycle through four beats:

·QD, QC, QB, QA are 1 in sequence, and the corresponding lights light up in sequence;

QD, QC, QB, QA are 0 in turn, and the corresponding lights are turned off in turn;

·QD, QC, QB, and QA are all 1 at the same time, and the four lights are on at the same time;

QD, QC, QB, and QA are all 0, and the four lights are off at the same time.

In order to complete the task of the beat program executor, the timing of S1, SO, and CLK must be coordinated with the timing of the input signal.

2 System Simulation

The simulation schematic diagram is created as shown in Figure 6.

2.1 Simulation debugging

Multisim simulation software is very convenient for debugging circuits. You can change components, modify parameters, measure data, and observe waveforms at any time. This system did not work properly during debugging. After observing with an oscilloscope, it was found that the signal had burrs. After adding resistors and capacitors, the system worked normally; CLK was inverted by the inverter and loaded, which can play a delay role; the beat program executor is used to complete the system action under each beat, that is, the left shift, right shift, clear and send functions of the data. QD, QC, QB, and QA directly drive X1, X2, X3, and X4 to complete the system cycle demonstration.

3 Conclusion

The design can be carried out with the help of Multisim simulation software, which can not only verify the correctness of theoretical calculations, reduce the trouble of patching circuit device parameters, but also simplify the process of repeated experiments; it can also reduce experimental costs and greatly shorten the development cycle. Practice has proved that this design has achieved the purpose of controlling four-way colored lights.