Proportional remote control system based on single chip microcomputer STCl2C2052AD

introduction

Remote control technology, also known as remote control technology, refers to the remote control of the controlled target. It is widely used in industrial control , household appliances, radio sports, children's toys and other fields. Remote control technology can be divided into single-channel remote control and multi-channel remote control, and can also be divided into switch type remote control and proportional remote control.

This article mainly introduces the control circuit using the single-chip microcomputer part, including the transmitter circuit and the receiver circuit. The transmitter uses the potentiometer voltage division as the proportional control signal, which is converted into a digital signal by the 4-way A/D circuit. The digital signals of each channel together with the two-way switch quantity are multi-channel encoded by the single-chip microcomputer. The encoded signal is sent out by the serial port and finally transmitted by the transmitter module. The receiver is mainly responsible for amplifying the received signal and demodulating the encoded signal from it. Finally, the servo converts the electrical signal received by the receiver into the corresponding mechanical action, thereby realizing the control of direction and speed.

In terms of appearance, there should be a proportional dial with a knob at the transmitting end of the remote control, which divides the 5 V voltage into 360° evenly. Each small unit of measurement represents a certain voltage value. When the knob is turned a certain angle, a certain voltage value is input to the transmitting microcontroller. At the same time, the transmitting microcontroller queries the current speed at a certain time interval and reads it into the microcontroller. It calculates the distance the model should move forward or the current speed according to the calculation formula and sets the initial value of the corresponding count/timer according to this value. Then the external drive circuit (servo) of the system converts the electrical signal received by the receiving microcontroller into a corresponding mechanical action, that is, moving forward a certain distance or accelerating or decelerating. When the timer overflows and generates an interrupt, the corresponding external drive circuit also sends a control signal almost at the same time to control the model to stop any action.

There are many advantages of using proportional remote control . For example: flexible control; the remote control distance can be adjusted and the maximum adjustment distance is farther than that of ordinary remote control; the speed of the model can be changed according to the user's wishes; the circuit is simple and has strong anti-interference ability; the servo mechanism (including gear box and servo motor) is simple, etc.

1 Basic principles of proportional remote control equipment

The functional block diagram of a general proportional remote control system is shown in Figure 1.

In Figure 1(a), the keyboard is used to generate the transmitter control signal; the encoder encodes the control signal; the display shows the controlled object and its controlled state category; the transmitter converts the control instruction into a radio signal with control information and amplifies the signal to meet the transmission power requirement.

In Figure 1(b), the decoder translates the coded signal into a control signal; the controller controls the controlled object; the receiver receives the radio signal sent by the transmitter, amplifies the received signal and demodulates the coded signal from it, and is generally used in conjunction with the transmitter. Since the receiver is installed on the model, it should generally be as small as possible and have high sensitivity to receive radio signals transmitted from a long distance.

The basic working principle of the remote control device is: the operator uses the remote control transmitter in his hand (turning the knob or joystick on the transmitter) to convert the instructions for controlling the model to move forward, backward, accelerate or decelerate into electrical signals and transmit them into the air; the remote control receiver mounted on the model receives these electrical signals and converts them into corresponding mechanical movements by the servo steering gear, thereby realizing remote control of the model.

2 Specific design of single chip microcomputer proportional remote control system

The wireless proportional remote control system is mainly composed of two parts: the transmitter and the receiver. The transmitter completes the transmission of the remote control command, and the receiver completes the implementation of the command. They can be designed separately during design.

2.1 Transmitter Circuit

Figure 2 shows the main circuit of the proportional remote control system transmitter designed using the STCl2C2052 AD single-chip microcomputer. The use of a single-chip microcomputer makes the entire circuit very simple. Port P1 is the input end of the proportional remote control signal; the proportional control signal is obtained through the voltage division of the potentiometer, and is converted into a digital signal by the 4-way A/D circuit. The digital signals of each channel together with the two-way switch quantity are multi-channel encoded by the single-chip microcomputer, and the encoded signal is sent out by the serial port and finally transmitted by the transmitter module. If you need to design a proportional remote control system with more channels, you can use the remaining unused P1 ports and connect an external potentiometer to expand the corresponding functions. When there is no control signal, the P1 port is high level. The control signal of the P1 port (low level is valid) is sent to the internal microcontroller for relevant processing by software control.

STCl2C2052AD is a 20-pin packaged single clock/machine cycle microcontroller compatible with the 8051 RISC CPU core. It is the core device of this design, and its speed is 12 times faster than the ordinary 8051; it has low power consumption; it has 256 bytes of RAM integrated on the chip; 15 general programmable I/0 ports, which can be set to 4 modes - quasi-bidirectional port/weak pull-up, push-pull/strong pull-up, input only/high impedance, open drain (where it is quasi-bidirectional port/weak pull-up mode after reset); it has EEPROM function on the chip; there are 2 16-bit timers/counters; it also integrates an RC oscillator internally, and the external crystal oscillator can be omitted when the accuracy requirement is not high; it has a wide operating voltage range and an independent on-chip watchdog timer; P1.7~P1. O has 8 high-precision, high-speed voltage input type 8-bit A/D converters , with a speed of up to 100 kHz, which can be used for temperature detection, battery voltage detection, spectrum detection, etc. After power-on reset, P1 port is a weak pull-up type I/0 port. Users can set any of the 8 channels to A/D conversion through software settings (ports that do not need to be used as A/D can continue to be used as I/O ports, and ports that need to be used as A/D must first be set to high-impedance input mode or open-drain mode). The microcontroller in this design can also be replaced by other 51 series microcontrollers of the same type with 20-pin packages. There are many design methods.

2.2 Receiving Circuit

The main function of the receiving circuit is to receive the modulated coded instruction signal emitted by the transmitter, and then amplify it and send it to the demodulation circuit. The demodulation circuit demodulates the modulated instruction coded signal and restores it to the coded signal. The instruction decoder decodes the coded instruction signal, and finally the driving circuit drives the execution circuit to realize the operation control of various instructions. Figure 3 is the main circuit of the receiver. The signal from the transmitter is input from P3.0 and sent to the P1 port. The corresponding port of P1 is controlled by software to output the control signal. The 4-bit A/D port of P1 port can be connected to different control terminals. Since it is a proportional remote control, the control signal of the output port should be sent to the servo circuit dedicated to the next level of proportional remote control.