A highly reliable remote control circuit composed of a single wireless transceiver integrated chip NRF401

NRF401 is the latest digital transmission frequency band 433MHz single-chip wireless transceiver integrated chip launched by Norwegian Nordic Company. The chip integrates high-frequency transmission, high-frequency reception, PLL synthesis, FSK modulation, FSK demodulation, multi-channel switching and other functions. It has the characteristics of excellent performance, low power consumption and easy use. NRF401 has very few peripheral components and no debugging components, which brings great convenience to development and production. 1． Parameters of NRF401 Working channel: 433.92MHz/434.33MHz; Modulation method: FSK; Frequency offset: 15kHz; RF output power 0.4kΩ3V: 1 0dBm; receiving sensitivity 0.4kΩ, BR=20 kbit/s BER<10 : -105dBm; maximum transmission bit rate: 20k bit/s; applicable voltage range: 2.7V ~ 5.25V; receiving state power consumption: 250μA; transmitting state power consumption: 8mA; waiting state power consumption: 8μA. 2. Pin Functions of NRF401 See Figure 1 for the pin arrangement of NRF401. Among them, the pin is the input terminal of the reference oscillator; the pin is the 3V~5V positive power input terminal; the pin is the ground; the pin is the filter access terminal; the pin is the inductor input terminal of the voltage controlled oscillator; the pin is The transmitting data input terminal; the pin is the receiving data output terminal; the pin is the RF power setting input terminal; the CS pin is the channel selection input terminal, CS=0 is 433.92MHz (Channel#1), CS=1 is 433.33MH z（Channel #2); Pins and pins are antenna interfaces; pins are power on/off selection input terminals, PWR_UP=1 means power on (Operating mode), PWR_UP=0 means power off (Stan dby mode); the pin is the input terminal for selecting the working mode. , TXEN=1 is the sending mode, TXEN=0 is the receiving mode; the pin is the reference oscillator output. 3. Typical application circuit of NR F401 Figure 1 is a typical application circuit of NRF401. In the figure, the antenna ports ANT1 and ANT2 are output to a 600Ω printed antenna. C9 and C10 are the resonant capacitances of the antenna loop, and R4 is used to appropriately reduce the Q value of the antenna loop. The maximum transmit power of this circuit is 10dBm, the receiving sensitivity is as high as -105dBm, and the maximum distance in open areas can reach 1,000 meters. If you want to increase the use distance, you can add a 600Ω/50Ω balanced unbalanced conversion circuit to the ANT1 and ANT2 output ports, and connect the input and output amplification and conversion circuits. 4. The circuit of a highly reliable wireless remote control circuit composed of NRF401 is shown in Figure 2. This circuit is both a transmitting circuit and a receiving circuit. The single-chip computer IC2 PIC16C57 controls the transceiver status of NRF401 and completes encoding and decoding. When a key is pressed, IC2 receives the input low-level signal and sends a high-level signal from the pin to IC1, causing the NRF401 to enter the transmitting state. At the same time, it randomly selects different crystal oscillators, and with the cooperation of the CS end, the transmitting frequency is within 432.84MHz, 433.25MHz, 433.92MHz, 434.33MHz, 435.01MHz Jump between six frequency points of 35.42MHz. At each frequency point, two frames of the same data information are transmitted to the DIN end, and then jump to the next frequency point. The transmission timing is shown in Figure 3. It is in receiving state when no key is pressed. At this time, the IC2 pin sends a low level to make the NRF401 enter the receiving state. At the same time, each crystal oscillator is strobed in sequence, and with the cooperation of the CS end, the receiving frequency is at 432.84MHz, 433.25MHz, and 433.92 MHz, 434.33MHz , 435.01MHz, 435.42MHz sequentially changes from low to high. The working time of each receiving frequency point is 7 times the working time of the transmitting frequency point to ensure that a complete transmission information can be received within the working time of each receiving frequency point. The receiving working sequence is shown in Figure 4. The received information is decoded by IC2 and sent out from the corresponding key port. Since the working time of the receiving state at each frequency point is 7 times that of the transmitting state, when several transmitters with different transmitting frequency hopping patterns work at the same time, the information of each transmitter can be received in time-sharing and corresponding output can be made. When two or more remote controls are used at the same time in this remote control system, the control information of each remote control can be executed, which overcomes the problem that two remote controls cannot be used at the same time in a remote control system with a single working frequency. The multi-frequency working mode also greatly enhances the anti-interference ability of the system. In remote control systems that require very high reliability, the remote control can learn whether the operation has been executed through the information sent back by the receiver. 24LC01 in the circuit is used to store the sequence and encoding data of the transmit frequency jump.