The baby sleep monitoring system designed by MSP430 single-chip microcomputer includes a multi-point urine humidity detecting module, a sound detecting module, an sound and light alarm module and a wireless transmission module. The low-power MSP430 is used as the main control. The DHT11 chip is used to detect the temperature and humidity. The temperature and humidity information processed by the MCU is sent to the receiving end by the nRF24L01. When the temperature and humidity exceed the threshold or the baby is crying, the sound and light alarm is given. After actual testing, the system runs reliably, low power consumption, low cost, high practicability, and has a promotion value.
In today's increasingly social and working rhythm, women tend to balance work and family, especially for the first time, both to take care of the baby and to do housework. New mothers are often in a hurry. The baby sleeps most of the day, how to monitor it, how to calm down when the baby wakes up, how to solve the problem of urinary diarrhea has been plagued by busy new mothers. Most households choose to use convenient diapers, but in addition to high expenses, the diaper is easy to breed bacteria. If it is not replaced in time, it will cause rashes and pose a hidden danger to the baby's health. Cotton diapers are healthy and comfortable, but need to be replaced in time. Most of the existing urine and urine testing devices on the market are single-point measurement, and there is a possibility of underreporting.
The designed remote baby urine monitoring system can effectively solve this problem for new mothers. In the abnormal alarm section, two main conditions are detected: 1) the baby is wet; 2) the baby is crying due to discomfort or need to take care of it. The system uses multi-point urine and wet detection and sound detection alarms, which can detect the baby's wet or crying situation, and prevent the false negatives and false positives caused by the environmental sounds such as the baby's normal turning movement or speaking steps. The system embeds the multi-point urine humidity monitoring module and the audio detection module under the water-repellent layer of the urine barrier, and has low power consumption, convenient separation and cleaning, and has practical value.
1 system overall design
Figure 1 shows the block diagram of the system structure. The system consists of a multi-point urine monitoring module, a sound detection module, a wireless transmission module, and an audible and visual alarm module, all of which are based on the low-power single-chip MSP4 30. The multi-point urine humidity monitoring module monitors the humidity in real time. When the system detects that the humidity exceeds the threshold or detects that the baby is crying, the wireless transmission module sends a signal to make the receiving terminal sound and light alarm, so that the mother can work in other rooms or do housework with confidence. Don't worry about affecting your baby's sleep, and don't worry if your baby can't wake up in time.
Figure 1 System block diagram
2 system hardware design
Taking into account the low power consumption of the system, the microprocessor uses a 16-bit microcontroller from Texas Instruments, which features an ultra-low-power, mixed-signal processor with a reduced instruction set (RISC) capable of 1.8 to 3.6 V. Working under voltage. It has an operating mode and five low-power modes. In low-power mode, the CPU can be awakened by interrupts with a response time of less than 6μs, making it ideal for long-term battery operation. At the same time, it is small in size, perfect in interface, and has strong computing power, which is very suitable as the main control chip of sleep monitoring system.
2.1 multi-point temperature urine humidity detection module
The temperature measurement can make the system automatically shut down. When the multi-point temperature is equal to the ambient temperature, no baby is sleeping on it. At this time, the system automatically cuts off the power, greatly reducing the battery consumption and prolonging the use time. The next time you use it, you can restart it with a low power design.
Measurements with a single point humidity sensor are easily missed because:
1) Male and female babies have different urinary wet areas, and individual sensors are prone to errors.
2) The baby will move when sleeping. The humidity sensitive surface of the multi-point urine wetness detecting module is placed in the permeation layer of the urine pad, and the remaining circuit parts are placed under the water blocking layer of the urine insulating pad. When the signal received by the humidity signal detected by one of the sensors exceeds the threshold value, the main control single chip microcomputer The RF chip is triggered, and the signal is sent to make the receiver perform an audible and visual alarm. Multi-point measurement and control is more efficient and reliable than single sensing components of other similar products.
The multi-point temperature wetness detection module uses a DHT11 digital temperature and humidity sensor with a calibrated digital signal output. The sensor includes a resistive wet sensor and an NTC temperature measuring element, and is connected to a high performance 8-bit microcontroller. Ultra-fast response, strong anti-interference ability, and high cost performance. DHT11 adopts 3.3~5.5 V DC power supply, humidity measurement range 20-90% RH, humidity measurement accuracy ±5% RH, humidity resolution 1% RH, fully interchangeable, long-term stability "±1% RH/year. The single-wire serial interface outputs digital signals, making system integration quick and easy. Ultra-small size and low power consumption make it suitable for multi-point urine and moisture detection.
The multi-point urine temperature sensor connection method is shown in Figure 2. The power supply is connected to the ground and the MCU power supply. The 4-channel data interface is connected to the 5.1 k pull-up resistor and the P1 port of the MCU.
Figure 2 Multi-point wet temperature sensor connection
2.2 Sound Detection Module
The sound detection alarm should be triggered only by the baby crying, and ignore the adult voice (30 ~ 3 000 Hz) and other environmental sounds such as footsteps to avoid false triggering, so the system only detects the sound above 1 500 Hz, when the frequency band When the amplitude of the sound in the range exceeds the threshold, the wireless transmission module sends a signal to make the receiving terminal sound and light alarm, and the sound threshold is adjusted by the user according to the actual environment.
Figure 3 sound detection module circuit
The sound detection module circuit shown in Figure 3 converts the analog signal collected by the microphone into a digital signal by the AD7794, and is filtered by the single chip microcomputer. The result of the treatment is judged to be the baby crying to trigger the radio frequency chip. The AD7794 is suitable for high precision measurement applications and features low power consumption, low noise, and complete input termination.
2.3 Wireless transmission and reception module
Radio frequency transmission and reception need to ensure the reliability of transmission, requiring low bit error rate, strong anti-interference ability, and transmission distance of more than 15 meters. In addition, combined with low power requirements, the nRF24 L01 wireless chip is selected as the radio frequency integrated circuit. The nRF24L01 is a single-chip wireless transceiver chip produced by NORDIC. It operates mainly in the ISM band of 2.4 to 2.5 GHz, and the conversion time between bands is less than 200 μs. The output power channel selection and protocol settings can be set via the SPI interface. When operating in transmit mode with a transmit power of 0dBm, the current consumption is 11.3 mA, the receive mode consumes 12.3 mA, and the current consumption is lower in power-down mode and standby mode. The wireless transmission module is composed of a signal transmitting unit and a signal receiving unit, and data interaction between the two is performed by wireless transmission, and the wireless transmission of data is completed together. The indoor transmission distance can reach 30 m, and the wireless transmission speed can reach 1 Mbit/s. In use, only one piece of nRF24 L01 and a few peripheral components can complete the RF transceiver function, which greatly reduces the size of the system.
When the nRF24L01 is connected with the MSP430 MCU, the serial communication module USART1 of the MSP430 MCU is used as the SPI to provide synchronous communication, mainly for command and data communication between the two. The pins P1.4, P3.0, P1.3, P3.3, P3.2, and P3.1 of the MSP430 are configured as general-purpose I/O pins, which are respectively CE, CSN, SCK, MOSI, MISO of nRF24L01. The IRQ connection controls the operation of the nRF24L01. The connection circuit is shown in Figure 4.
Figure 4 wireless communication circuit
The system is a portable system that is battery powered and requires a low power design. The RF chip transmits the signal only when the MCU detects that the measured signal exceeds the threshold. Otherwise, the nRF 24L01 is in the power-down state to reduce the power consumption.
2.4 sound and light alarm module
The purpose of this design is to send the baby's wet and dry information and crying information to the device (such as a wristband) that the guardian carries with them by wireless transmission. This component receives the signal and makes the alarm on the device work. The system uses sound and light two-level alarm at the receiving end, first light reminds, if the guard does not turn off the reminder after 30s, the buzzer will sound a reminder, the volume of the buzzer can be adjusted.
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