Liangshan School learns smart cars

Function details 1. The four-wheel drive smart car can complete functional requirements according to customized program logic, such as Bluetooth control, forward, backward, left turn, right turn, braking, vehicle speed and other functions.

2. Configurable Bluetooth mode uses Bluetooth module to control the movement of the car.

3. The tracking function (reflective photoelectric switch) can be used to avoid obstacles, allowing the car to drive according to the set trajectory.

4. With power detection, ADC circuit is used to monitor (battery) voltage in real time.

5. The screen display status can display voltage, vehicle speed, temperature, humidity, etc.

6. Environmental monitoring uses the temperature and humidity module to detect the temperature and humidity of the environment.

7. Day and night monitoring uses photosensitive resistors to monitor the surrounding lighting environment in real time. During the day (strong light), the car lights are turned off to automatically adjust the lights.


Circuit Notes 1. The power supply uses 14500 lithium battery
5V to step down to 3.3V. The 3.3V system circuit uses long-lasting CJA1117B-3.3

2. The buzzer MCU controls the buzzer and uses NPN MMBT5551 transistor (the same as used in the video tutorial Transistors are different. PNP is used in the video, but many experts in the learning group said that the buzzer will be turned on and keep sounding after powering on. My personal understanding is that the characteristics of the transistor are EB conduction (voltage difference), and the MCU. The control port is 3.3V, and the buzzer positive is 5V. According to the characteristics of the PNP transistor, the transistor is turned on when it is powered on. Of course, the buzzer also has a voltage drop. I don’t know the specific voltage drop. In order to be safe, I directly put this The circuit is directly changed to NPN, so that even if the voltage difference is larger, there is no need to worry.)

3. LED vehicle left and right headlights, power indicator light, and driver version debugging light.

4. Two self-resetting switches on the button, used for function board debugging.

5. The motor drive circuit uses the r7889 chip to directly drive the motor forward and reverse.
Motor: N20/6V/200 rpm.

6. Bluetooth: Write a Bluetooth applet to install and connect with the mobile phone, and use the mobile phone to control the car.
Bluetooth signal: HC-40

7. Five-way tracking, tracking chip: ITR9909, placed under the front of the car, used to track and detect road conditions (black line) to drive according to the set track. (The five lines have the same route, and the screenshot value reflects one line)

8. Place the ultrasonic wave directly in front of the car, facing the front of the car, to detect roadblocks and detection distances.
Ultrasonic model: HC-SR04

9. Connect the three ADC battery detection resistors in series to make a voltage dividing circuit and connect the ADC function pins of the chip. Determine battery power based on voltage changes.

10. Lighting uses the ADC function of the MCU to detect changes in the resistance of the photoresistor, determine the light intensity, and complete the automatic car lights.

11. OLED screen display OLED, 0.96 inches. Used to display battery power, distance to obstacles ahead, light intensity, vehicle speed, trial changes of the car, etc.

12. Temperature and humidity environment detection DHT11, environmental monitoring, temperature and humidity monitoring.


PCB instructions 1. The size of the trolley is less than 10cm*10cm, and Lichuang can make free samples.
2. Pay attention to the ultrasonic, which is plugged in reversely. If the positive difference causes a short circuit, the entire car will not work. It will be fine if it is plugged in for a period of time. Remember not to take too long. If necessary, you can adjust it yourself, just rotate the 4-pin header 180 degrees.

Project summary 1. I don’t have any software foundation, so I learned software because of work needs. The hardware is currently working.
2. I have no basic knowledge of controlling a car with a mobile phone. I don’t even dare to think that I can actually complete this project, but I can’t stand the detailed video tutorials on software and hardware. I watch the video bit by bit and watch it over and over again until something goes wrong. , it’s my own problem, I always find something different when I read it again. I would like to thank the teachers for their dedication. I dare not say that I am getting started with my own qualitative improvement, but my personal improvement can be seen with the naked eye.