At present, the application of intelligent toddler pants.training pants.pull-ups has not yet been popularized in the market, but most manufacturers have certain expectations when proposing product concepts. Intelligence depends not only on software, but also on the design of hardware. In particular, the product is to be worn on the human body. How to successfully collect information and be harmless to the human body requires the designer to study hard. This article will provide some reference opinions for the improvement of smart products with some typical circuit designs.
Microprocessor is the core device of the whole hardware design, it not only controls various peripherals, but also has strong computing ability to process various signals. The microprocessor used is commonly used in smart sensors, portable instruments and precision instrument monitoring. The second is the redox reaction between glucose and glucose oxidase, and the resulting current is usually at the UA level or even the NA level. For such small currents, a 24-bit high-resolution ADC needs to collect the weak electrical signals generated by the system sensors. Third, the processor has a variety of common interfaces such as UART serial port, PC, SPI, etc., which can easily control external chips and realize corresponding functions and data exchange.
At the same time, the chip power consumption is extremely low. Under normal circumstances, the maximum working current value is only 2.3ma, the sleep state can be as low as 20ua, and it can be powered by 3V or 5V power supply. In this design, the 5V power supply is selected to simulate different power pins in the chip to distinguish the digital power supply. The chip can download programs through the serial port, which is convenient for early functional debugging. The ADuC834 enters the serial download mode through the combination of the PSEN pin and the RST pin, and the correct programming of the program can be realized. The other lo ports and pins of the microprocessor will be connected to modules such as data acquisition, wireless communication, screen display, push buttons, potentiostatic circuits, temperature sensors, etc.
After the component selection is complete, the design and layout of the schematic and PCB board are related to the inspection quality of the system. Good design can give full play to the performance of components and make inspection results more accurate and reliable; on the contrary, it will not only affect product quality, but also bring unexpected problems. Therefore, attention should be paid to the selection of chip decoupling capacitors, the wiring between components, and layout.
In the design, it is necessary to add bypass or decoupling capacitors on the chip pins, mainly to reduce the noise on the power supply, generally at the signal input end, to reduce the interference of the noise generated by the equipment to the power supply circuit, mainly used for power supply and signal output. Therefore, ceramic 0.1uF capacitors or 10F capacitors are used for the power port of each chip. After the selection and circuit schematic design are completed, the models of various components must be imported into the PCB file for layout and wiring. The layout of the components should be as large as possible before the small, the difficult and the easy, and the analog devices and the digital devices should be separated.
When wiring the PCB, try to widen the power line and the ground line; the wiring between the signal lines should be as parallel as possible; at the same time, pay attention to the crosstalk between the wires, generally follow the 3W principle, and the angle of wiring should be at an obtuse angle of more than 90 degrees; pads Through the tear is stronger, the welding surface is enlarged; the circuit grounding line adopts the mixed analog and digital separation of single-point and multi-point grounding, and finally connects through the resistance. Based on these rules, the design of the PCB board is carried out for the detection device of the system.
Because the hardware circuit design is relatively complex, the above design method may still have some inevitable defects. However, judging from the dynamics of some toddler pants, training pants, and pull-ups brand leaders in the market, products of the same type have been gradually manufactured and started to be implemented.