Lichuang smart car

1Project background

      The original intention of this project was when I was sorting things out and saw the four-wheel drive car I played with when I was a child. Although it was covered with dust and left in a cardboard box, I always had some feelings when I accidentally took it out. Let's all reminisce about our childhood memories together. Although it looks old, Xiu Xiu can still run fast!

       I can't help but think of the scene when I came home from school every afternoon and turned on the TV. I lifted up a small stool and squatted in front of the TV to watch the cartoon "Four Wheel Brothers" being broadcast. It should have been Star TV or Golden Eagle Cartoon at that time, and the Four Wheel Brothers were accompanying me. During our childhood, it is undoubtedly the childhood dream of every boy and girl to own a cool four-wheel drive car!

      Looking at the calendar, it seems that EDA has not launched a project live broadcast for a long time. I am really sorry for waiting for so long. There are a lot of things going on in the second half of 2020, and I have done some cases, but they are not enough to share with everyone, so the live broadcast cases have been postponed until now. 2021 is a new year. This year we will arrange some high-quality open source projects for everyone to learn from and carry out a large number of activities for everyone to learn professional skills at zero cost . I also hope that everyone will support us and give us more encouragement and suggestions!

      Due to the above background, the design of Lichuanghao started. The first is the choice of solution. We adopted the design solution of Jixiaoxin’s four-wheel drive smart car and integrated all the modules onto the motherboard to make it more portable. In addition, Jixiaoxin’s teaching video cannot be more detailed. He was also my mentor when I started playing with cars. It is highly recommended that everyone who wants to learn smart car design watch Ji Xiaoxin’s teaching video: click to view the video

      With ideas and plans in mind, we started taking action. Drawing, editing, and model design. The first proofing, the plan modification, the second proofing, the third proofing. The model is printed for the first time, the model is printed for the second time, the model is printed for the third time, and the model is printed for the fourth time. I believe everyone has a deep understanding of the running-in and difficulties during this period, and it is necessary to perfectly adapt the circuit board to the casing. During this period, I also made a special trip to Huaqiangbei to find suitable and cheap motors and batteries. The final product is completed, the final draft of the model is printed in resin, color nylon printing is completed, and functional testing is completed. The Lichuanghao design project was successfully completed! This car commemorates our childhood. Currently, it only provides basic tracking and obstacle avoidance functions. We hope that everyone can improve it on this basis and realize more fun functions. Go for it, Lichuanghao! !

2Function introduction

(1) The power supply part of the car is powered by a 7.4V lithium battery, and is designed to prevent reverse connection;

(2) Onboard power check circuit to realize low voltage alarm function;

(3) Use the RZ7899 motor driver chip to drive the N20 DC motor, and the software simulates PWM to control the motor speed ;

(4) Infrared and obstacle avoidance are implemented using two different infrared tube solutions, and a comparator circuit is designed combined with an operational amplifier;

(5) Add two car lights to the front to flash the lights in an emergency to simulate car functions;

(6) Reserve the 2.4G wireless communication module interface to facilitate later expansion of wireless control functions;

(7) The car comes with a matching 3D shell file to facilitate the design of a customized shell.

3 Detailed circuit description

3.1 Power input circuit

      The power supply part of the car is powered by a 7.4V lithium battery, and a diode anti-reverse connection design is added. The AMS1117-3.3V step-down voltage is used to power the microcontroller, and LED1 is the power indicator light. If you want to pursue a higher-performance car, you can replace it with a switching power supply circuit to enhance heat dissipation.

3.2 Power drive circuit

      The motor circuit uses the RZ7899 motor-specific drive chip, which is suitable for application circuits such as automatic valve motor drive and electromagnetic door lock drive. It controls the motor forward, backward and braking through the logic input ports BI and FI, and can control the motor speed with the PWM output of the microcontroller. This application circuit has excellent anti-interference capabilities, small standby current, low output internal resistance and other excellent functions. When welding, be sure to connect a 104 ceramic capacitor in parallel to the motor. Of course, if you have a better idea, you can change the drive circuit to make the car more powerful!

3.3 Tracking and obstacle avoidance circuit

      The tracking and obstacle avoidance circuits are designed using an LM393 voltage comparator and an infrared pair tube. When the infrared receiving tube receives the reflected signal, the forward input voltage of the op amp is close to 0, and the output of the comparator is low. level, the LED will light up at this time. Detect the pin status of the IO port through the pins of the microcontroller, allowing the car to realize the function of walking along the black line and avoiding obstacles. Another solution for obstacle avoidance is to use ultrasound. You can also try it yourself.

3.4 Car light circuit

      The car light circuit uses a two-color LED light to achieve a three-color display effect of red, green and yellow, and is controlled by a PNP transistor. When the car encounters a special situation while walking, the light lights up and flashes to indicate the front. In the case of a mini smart car, high-brightness LEDs are used as car lights, which you can also refer to.

      For the remaining circuits, please click on the schematic diagram and PCB diagram below for reference.

4 Summary

      Seeing this, have you learned the key points of smart car design? If you have any questions or ideas, please leave a comment under the project. If you think the project is good, remember to like and save it~

      The solicitation for Lichuang EDA smart cars has ended. Click the link to view the outstanding award-winning works. Come and take a look at your smart cars: https://oshwhub.com/recommend/zhi_neng_xiao_che