Wireless rail car model battery powered motion debugging

01 radio track

1. Problem/goal

When you assemble the mechanical parts of the car model into a car model for the first time, the next step is to test whether the car model can run. Since it has just been assembled, it is not possible to ensure that every link is normal. In order to facilitate debugging, check the possible mechanical and electronic faults inside the car model. Therefore, it is recommended to use the battery cable to let the car model run first. In this way, faults in the power receiving coil, high-frequency rectification module, and farad energy storage capacitor module can be eliminated during the installation process of the car model, and inaccurate parameters in the software can also be ignored. Let the car model run on battery power. ·In this way, it can be proved that the main control board, motor drive board and electromagnetic signal amplification board are normal. The following is an introduction to the test steps and precautions in the case of battery power supply. This part was assisted by Yu Jiajun from class 24.

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2. Preparation

The preparatory work includes two parts. The first one is based on the assembly video and the model car model. ·Everyone will form a complete car model from the given parts of the car model. The second part is to make sure that the debugger is pre-installed on the control board. If the main board of the car model does not have a debugging program installed, then you can download the " battery test code " in the comprehensive test code in the given information to the ESP32 chip on the main control circuit board of the car model according to the method of how to download the program to the car model through the computer. middle.

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Firstly, remove the plug of the original farad capacitor connected to the main board. This part is located in the center of the bottom of the main control circuit board on the top of the car model. The power outlets of the two yellow shells are actually connected in parallel. The one on the left is used to input the power from the farad capacitor, and the one on the right is to send the power to the last motor drive circuit board. Connect the given 7.4V lithium battery to the vacant voltage socket of the main control board, turn on the power of the main control board, and all the circuit boards of the car model will be powered on. Since the battery is relatively heavy, it is recommended to secure it in the middle of the car model, so that the center of gravity of the car model remains in the middle position when the car model is running, and in this position, the battery security is more secure.

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Please note that there is a dial switch on the top right of the dual motor drive circuit board at the end of the car model, which can be used to control whether the motors of the car model move or not, so that the software can be modified without powering off the main board During the process, the motor can be turned off to run, so the car model remains still. When the switch is on the right, the motor stops moving. When the switch is on the left, the car model starts to move. In this way, it is possible to control whether the car model is running without powering off the system. This is very beneficial for temporary program adjustments. The power of the motor drive circuit board comes from the power interface of the main board, and this power interface is connected in parallel with another power interface next to it. It can accept the electric energy from the farad energy storage capacitor, or the electric energy from the lithium battery.

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3. No track debugging

The non-track debugging is to run the car model directly on the ordinary ground. Since the electromagnetic navigation is not used, the car model may deviate when it is running. Since the friction coefficient of the ordinary floor is different from that of the actual track, but the actual difference is not large, it is recommended to increase the value of the duty part of the parameter controlling the motor speed duty cycle in the code, so as to achieve higher speed and higher motor power. At this time, due to the unevenness of the floor, the motion trajectory will not be a straight line, which is normal.

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When the host motor controls the duty ratio parameter duty to 120, the car model is running. It can be seen that the car model is underpowered and can hardly run on a flat ground. After increasing the motor control duty to 150 and 240, the car model will move faster. It runs faster on flat ground or on a track. The buzzing sound you hear comes from the two coreless motors of the car model. This is because the PWM frequency of the drive motor is 5000Hz, which just falls within the range of human hearing.

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4. Track debugging

The car model is not tested on the track, only the mechanical performance of the car model, the quality of the main control circuit board and the motor drive board can be tested. If you run it on the track, you can further check the electromagnetic detection board in front of the car model, and the electromagnetic signal amplification detection board is good or bad. If the car model can run along the track, it can prove that the electromagnetic signal induction and detection circuit is working properly. At this time, there is another important parameter that needs to be adjusted by everyone, that is, the midpoint value of the car model servo. When the car model runs along a straight line, it is hoped that the car model is just near the center line of the track. If it deviates, you need to adjust the value of the center position of the servo in the control program. In addition, it is also necessary to check whether the infinite power receiving coil on the chassis of the car model is scratched against the track. If there is friction, it may cause excessive resistance to the running of the car model and affect the running speed of the car model.

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Please test the operation of the motor drive with PWM duty cycle values of 120, 150, and 240 respectively. In the case of battery power supply, the larger the value of the duty cycle, the faster the car model runs. But please note that in the future, in the case of wireless charging power supply, it is not necessarily the faster the duty cycle will run. During the debugging process, if the car model does not move and the motor is blocked, it is necessary to lift the car model in time, otherwise the motor may be burned. Please observe the impact of the battery on the center of gravity of the car model, which will also affect the position of the car model on the track when it is running.

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5. Precautions for debugging

Through the car model debugging under the battery power supply, not only to prepare for the competition task 1, but more importantly, to adjust the mechanical installation of the car model, the height of the chassis, the motor transmission and the steering gear linkage. Lay the foundation for the subsequent wireless charging operation. Please note that the lithium battery power connector has polarity, the red line corresponds to the positive pole, and the pin has a right-angle edge. The black wire corresponds to the negative pole, and the pin is round. It is necessary to observe whether the car model is running in the center of the track on the track, and adjust the constant of the center position of the steering gear in the control program. Yes, the car model can always keep running in the center of the track. This can greatly improve the future car models to accept unlimited electric power.

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As mentioned above, the middle position parameter of the servo in the program is the value of the Servo Center Mid variable here. You can adjust the left and right offset of the car model when it is running upright by changing this value.

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6. Practice/Experiment

This article discusses the debugging method of the radio rail car model under the condition of battery power supply. Through this debugging, it can be verified whether the mechanical assembly of the car model is intact, and whether the main control circuit board and the motor drive board are working normally. In terms of software, adjust the center position parameters of the steering gear, which will lay the foundation for debugging under the wireless electromagnetic power supply. If there is a problem in this process, please check the mechanical and electronic problems of the car model in time. During this process, you can also use the Thonny software on the computer to complete some software tests on the car model. Some software programming tests and exercises can be done only with USB power.

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02 Lecture information

1. Lecture video