The remote control is a very common remote control device in our lives, with a wide range of applications. Although the application of this technology using infrared remote control has been extremely mature, there are still obvious shortcomings in use. Applying the advantages of Bluetooth device technology to the design of the remote control system can effectively improve the defects of the original remote control.
1. Bluetooth remote control system design scheme
The main components of the Bluetooth remote control system include Bluetooth module, MCU stand-alone chip, operating keyboard and speaker. The composition of these components makes the remote control a basic remote control device. In terms of function, when the key of the operating keyboard is pressed, the value of the pressed key will be encoded by the system, and the ASICC code will be formed and sent in the form of this code under the action of the Bluetooth module. After the connection between the Bluetooth module and the system is established, the corresponding receiver can send a sound signal to the remote control, and then the speakers of the components in the remote control will emit sound, which can be used to confirm the position of the remote control. Since the connection needs to be established first in the process of Bluetooth communication, it is necessary to consider the connection interruption in the middle. When the Bluetooth communication fails, the operating system will automatically restart the Bluetooth module, and re-establish the connection, and then resume communication.
2. Development process of remote control system based on Bluetooth technology
2.1 Hardware design of Bluetooth remote control
The hardware constituted by the Bluetooth remote control mainly has the following 8 aspects: ① Microcontroller of the remote control (MCU stand-alone chip): The microcontroller is the main control component in the remote control component, which can be connected to the keyboard to control the keyboard The running state is detected, and the key value of the keyboard can be coded. Connect it with the Bluetooth module in the form of a UART serial port to realize the communication state with the Bluetooth module, so that the Bluetooth connection can be realized, and the corresponding functions of data output and reading can be carried out. Connect it to the power amplifier module in the construction of the remote control, and the power amplifier module can be switched on and off. ②The Bluetooth module of the remote control: Generally, the BK8002 Bluetooth module is selected. The connection between it and the MCU single chip is realized through UART, which has the function of receiving instructions, and can send and receive data information through Bluetooth. At the same time, you need to connect the audio cable to the power amplifier to ensure that the speaker can output. ③The power amplifier module of the remote control: Connect the audio cable to the module, the module can amplify the audio signal, and output the amplified signal through the speaker. Of course, pay attention to the output volume can not be too loud, otherwise it will cause the phenomenon of successful overheating. ④The speaker of the remote control: its main function is to play audio. ⑤The keyboard of the remote control: can realize the reception of user input information. ⑥ The key of the remote control: when this button is pressed, the remote control system starts to supply power and can provide signals to the MCU microcontroller. ⑦The buzzer of the remote control: mainly used to remind the signal. ⑧ The power supply of the remote control: Generally, it is powered by a lithium battery and used at the same time as the voltage conversion chip to provide 3.3 volts for the MCU microcontroller and 5 volts for the Bluetooth module. Through the MCU single-chip microcomputer and the switch key to jointly control and realize the conduction.
2.2 Software design of Bluetooth remote control
The main program flow of the remote control based on Bluetooth technology mainly includes the following 8 aspects: ① The switch function of the remote control, when this button is pressed, the MCU microcontroller gets power, and at the same time it receives the signal from the switch button in the keyboard, when the system After detecting that this button has been pressed for 2 seconds, the power-on signal is sent out. At this time, the remote control receives power, which means it has been turned on. ②The Bluetooth handshake function of the remote control. When the Bluetooth module in the remote control receives power, its indication signal is ON. When the system detects this signal, the receiver pairing operation command is executed, otherwise it will automatically perform the Bluetooth operation. Reboot. After the pairing is successful, the Bluetooth module power supply regrets spitting out the signal indication of II. Once the password is sent after detection, the system will enter the data transmission mode, otherwise it will continue to wait for the Bluetooth connection. ③The key scan function of the remote control, this function can scan the keyboard, when the code of the key value is detected, it enters the code sending mode. ④ The key value sending function of the remote control. When the key is in the non-volume control state, the key code value is transmitted to the Bluetooth module through UART in the format of AT+ code value, and the baud rate of transmission is 9600. When the transmission is successful, the indication of the Bluetooth module is OK. ⑤The volume control function of the remote control sends volume control instructions to the Bluetooth module by controlling the volume control keys. If the instruction is sent successfully, the indication signal displayed by the Bluetooth module is successful. If it is not sent successfully after repeated many times, the Bluetooth module will restart automatically. In order to avoid overheating of the power amplifier, the volume should be limited by the maximum setting. ⑥Receiving audio signal function of the remote control, the functions of sending data and receiving audio in the Bluetooth module are independent of each other, so after the MCU MCU amplifies the power module, the receiver can directly send the audio signal . ⑦The warning and sleep function of the remote control. If there is a long-term disconnection during the Bluetooth handshake, the MCU's buzzer will receive the control and emit a sound to prompt. After the connection is established, if the keyboard is in a state of inactivity for a long time, the MCU will enter a sleep mode, and the Bluetooth module will automatically turn off, and will not recover until the button is pressed again. ⑧ The disconnected and automatic restart function of the remote control. When the established Bluetooth connection is disconnected, the MCU will control the Bluetooth module to restart.
Third, the development idea of remote control based on single-chip technology
The times are developing, and our requirements for life are getting higher and higher. Various remote controls have quietly entered our homes and work. However, the traditional remote control has simple production methods and single functions, and its application is limited. The design of the remote control in this article combines the advantages of the previous remote control and optimizes the previous shortcomings, and adds new elements, making our remote control more advanced. We use a single-chip microcomputer to carry out the remote control design. Using the characteristics of the single-chip microcomputer, a remote controller can control all electrical appliances, achieving the effect of one device with multiple functions. This research has made our lives more and more intelligent, saved the number of remote controls in our lives, and helped us set a new milestone in our technological development.
The full name of a single-chip microcomputer is a single-chip microcomputer, which is to integrate random access memory, read-only memory, central microprocessor, interface circuit and other components on a chip to form a microcomputer. The universal remote control is actually a requirement to increase the capacity of our memory. When coding, put all the codes of electrical appliances in it. When using the remote control, we look for different codes according to the input of different electrical appliances to control the functions of the electrical appliances.
Since the wireless waves generated by the previous wireless communication technology will cause certain interference to other wireless communication devices, it cannot be used in large quantities, and it is difficult to achieve multiple uses of one device. Therefore, the remote control relies on infrared communication based on the single-chip microcomputer. Infrared communication not only does not produce signal mutual interference, but also has a fast release speed. It uses infrared rays to propagate in the air, and the remote control transmits and the electrical appliance is responsible for receiving. When launching, we select the functional sending signal to enter the circuit through the infrared light-emitting diode after being coded for emission. When the electrical appliance receives this infrared signal, it is restored to the original signal through the circuit to control the electrical appliance.
4. Design method of remote control based on single chip microcomputer
4.1 The overall structure of the microcontroller remote control
First, we templated the structure of the microcontroller remote control, and then connected the templates together. The remote control mainly includes a receiving and sending module, a single-chip microcomputer, a key module, a power supply module, and a circuit control module. These modules constitute our remote control. We are designing these modules separately, and finally design the overall appearance to form our remote control.
4.2 MCU selection design
When we choose a single-chip microcomputer, there are many single-chip microcomputers to choose. Through repeated selection, we choose the single-chip microcomputer AT89S52. This single-chip microcomputer is a low-power, high-performance, 8KB in-system programmable Flash memory, and its internal data memory has 258Bytes (can be based on needs Expansion of external RAM), which can be used as the internal buffer for the normal operation of the CPU and a temporary memory for the pulse width and encoding of infrared commands during the learning process. The hardware circuit is based on the AT89S52 minimum system, and all other circuits are expanded on this basis. This high-performance microcontroller is widely used in the control industry. The single-chip microcomputer is connected with the circuit ports of each module.
4.3 Design of remote control sending module
When infrared is emitted, we use infrared light-emitting diode PH303 to emit infrared signals. When we press the function key, the single-chip computer finds the corresponding code and starts to pass through the circuit. When the current flows through the diode, the infrared light-emitting diode emits infrared rays. Since infrared has the characteristics of small distance and strong signal, we need to increase the signal strength of infrared to prevent the phenomenon that is difficult to control at long distance. We can use a pulse signal with a small output duty to enhance the intensity of the infrared signal. The method of a small output duty is generally to design the pulse circuit and control the single-chip microcomputer with software.
When designing the microcontroller remote control, we use the software method. When the remote control outputs a high level, the timing time is determined by the number of instructions and the instruction cycle, but the instruction cycle is fixed, then we should control the instructions number. Therefore, we can see that the duty cycle can be controlled by timing, so that we can output a pulse signal with the smallest duty cycle as possible. In other words, we can control the intensity of the infrared signal emitted by the software control instruction number.
4.4 Design of receiving module
For infrared receiving, we choose SM0038 this kind of receiving head. The working principle of this kind of receiving head is that when receiving 38KHZ infrared signal, it will convert this light signal into electrical signal, which will be amplified by the circuit, and then output stage The circuit performs reverse amplification and output. Its advantages are high performance and low price, and it is widely used in other fields.
4.5 Design of remote control button module
When designing the keyboard, we generally use a matrix keyboard to form a row and column structure to arrange the keys on the power supply, and then connect each key to the line. The order of the buttons is also related to our use. When arranging the buttons, we should put the buttons with close functions together, and separate those that are not related to the installation. This design makes it easy for us to grasp the use of our remote control as soon as possible when using the remote control. We should also set a button for selecting electrical appliances to select the electrical appliances we control.
The basic principle is that when the button is pressed, it is low level, and when no button is pressed, it is high level. Different keys have different functions, different signals when receiving, and then different signals have different codes. And under the different keys are switches, which use the opening and breaking of mechanical contacts. In the process of closing and opening, a voltage is generated through the mechanical contacts, but the mechanical contacts are elastic and will vibrate during opening and closing, which will cause the instability of the circuit. We must eliminate this button vibration, we choose to add a bistable circuit method.
4.6 Design of remote control power module
We usually choose 5V dry battery as the power source of the remote control. First of all, the purchase channels of batteries are more convenient, and they are sold in various supermarkets. Secondly, the dry battery is convenient to use. Compared with the rechargeable remote control, it saves raw materials. Such a battery does not need to consider its service life and does not need to introduce the principle of rechargeable batteries.
to sum up
In summary, through the introduction of the Bluetooth modular design, this article restores the implementation process of the Bluetooth remote control. It is found that compared with the infrared remote control, its communication accuracy is almost the same. In terms of system stability, due to the Bluetooth remote control When the connection is interrupted, it can be corrected to maintain the normal communication. The receiving distance is long and the receiving device can be misaligned to complete the remote control task, so the Bluetooth remote control is more stable.
In addition, single-chip remote controls are becoming more and more important in our lives. We need such convenient and quick tools to make our lives more convenient. Now the popularity of intelligence in our homes and industries is not high enough. The years when each electrical appliance can only be controlled with the corresponding remote control will soon pass, and the new era of multi-use is quietly coming. This article takes the design of the single-chip remote control as the main content, introduces the basic principles and design process of some single-chip remote controls, and solves the problem of incompatibility between the remote controls of different electrical appliances. With the further development of technology, our smart remote control will become more and more convenient and will introduce more functions. Smart remote control not only makes our electrical control more convenient, but also provides us with convenience for future remote monitoring research.