Course Design of Automotive Tail Light Controller

1. Car taillight controller content

Basic design requirements: The design system simulates the signals on both sides of the car's taillights, with 3 signals on each side.

Indicator lights (simulated by LEDs) with the following modes:

( 1 ) When the car is moving forward, all the indicator lights are off.

( 2 ) When the car turns right, the three indicator lights on the right side light up in right cycle sequence.

( 3 ) When the car turns left, the three indicator lights on the left light up in left-turn sequence.

( 4 ) When the car brakes temporarily, the indicator light flashes at the same time.

The overall circuit requires double-panel wiring, and status transitions can be displayed with digital tubes (optional)

2.1 Car taillight controller

2.1.1 Design block diagram

Figure 1   Car taillight control circuit design block diagram

2.1.2 Overview of the whole machine

In the car taillight control circuit, the car taillight has four different states: normal operation, right turn, left turn and temporary braking. When driving normally, the left and right taillights of the car are all off; when the car turns right, the right taillights of the car light up sequentially from the inside to the outside; when the car turns left, the left taillights of the car light up sequentially from the inside out. Lights up cycle; when the car brakes temporarily, all tail lights flash simultaneously with CP .

3.1 Car taillight control circuit unit (No. 5) (unit circuit diagram, design process and principle description)

3.1.1Ternary counter

The ternary counter consists of flip-flop 74ls161 . 74ls161 is a hexadecimal synchronous counter with a 4 -digit initial value that can be preset , as shown in Figure 3.1.1 :

Figure 3.1.1

Using the synchronous number setting method, the preset number is 1101. When CLK generates a rising edge, it starts counting. When the count reaches 1111 , it returns to the preset number and counts again. Thus, the 74ls161 hexadecimal counter realizes the ternary counter function, as shown in Figure 3.1.2 :

Figure 3.1.2

3.1.2 Decoding circuit

As shown in Figure 3.1.3 , the decoding circuit is composed of 3-8 decoders 74ls138 and 6 NAND gates 74ls00 . The three input terminals A , B , and C of 74ls138 are connected to S1 , Q1 , and Q0 respectively , among which Q1 and Q0 are the output terminals of the ternary counter. When S1=0 , enable signal A=E1=1 , and the counting status is 00 , 01 , and 10 , Y1 , Y2 , and Y3 output low levels in order ( Y5 , Y6 , Y7 , and output high levels are invalid). The NAND gate outputs high levels in sequence; when S1 =1 and enable A=E1=1, Y5 , Y6 , and Y7 output low levels in order ( Y1 , Y2 , Y3 output high levels are inactive), after the NAND After the gate, the output is high level in sequence; when E1=0 and A=1 , all the outputs of 74ls138 are all high level, and after passing through the NAND gate, they are all low level; when G=0 , A=CP , the NAND gate The output flashes with the frequency of CP pulses.

Figure 3.1.3

3.3.3 Switch control circuit, switches S1 and S0

List the logical function table of switches, signal CP and enable signals E1 and A

Table 3.1.1

（1）、汽车尾灯控制器三进制计数器设计时。使用4位二进制74ls161通过预置数法改成。方案一是预置数0000，Q1、Q0输出00、01、10。方案二是预置数1101，输出01、10、11。最后选择使用方案二，使用方案一需要Q1、Q0通过非门、与非门给预置数控制端（LOAD）置数控制。使用方案二只需要使用一个与非门便能完成置数控制。方案二可以减少非门的使用，从而降低PCB布线难度。

（2）、汽车尾灯控制器设计译码电路74ls138时。若三进制计数器使用方案一，LED驱动电路接入的是74ls138输出端Y0、Y1、Y2、Y4、Y5、Y6。但最终三进制计数器的选择方案二，那么我们LED驱动电路接入的便是Y1、Y2、Y3、Y5、Y6、Y7。同时由于需要LED从里向外依次闪烁，所以LED1驱动接的是Y3，LED3驱动接的Y1。

( 3 ) When designing the switch control circuit of the automobile taillight controller. The original plan one is to use a 74ls10 , a 74ls00 , a 74ls04 , a 74ls32 and a 74ls86 . Finally, I chose to use option 2, which uses two 74ls10 and one 74ls86 . Using option two can reduce the use of chips and simplify the circuit diagram.

5. Simulation diagram of the whole machine logic circuit