The existing garbage charging standards in China are relatively low, and the government has to invest a large part of the funds every year to supplement garbage disposal enterprises. After the garbage charging system is reformed, it can not only make up for government and enterprise investment, but also urge residents to strengthen their awareness of waste reduction and resource recycling, and promote waste reduction, recycling, and harmlessness.
Many developed countries have implemented garbage measurement and charging. The experience of Japan, South Korea and the United States is to calculate the cost based on garbage bags. Residents spend more when they throw more garbage and buy more bags; another form is directly charged according to the weight of garbage Barrels of garbage cost a certain amount of extra money, which can avoid the "one size fits all" practice of charging households or per capita.
This paper designs a garbage weighing and charging control system based on single chip microcomputer. Compared with other control systems, the single-chip system has the advantages of small size and low cost.
1 System requirements and selection of main controller
The working principle of the system is as follows: The garbage bin consists of 3 different bins, which collect kitchen waste (bin 1), paper and plastic recyclable garbage (bin 2) and other non-recyclable garbage (bin 3). A suitable size input door is installed at the top of each box, and a weighing platform is installed at the bottom. When the residents are ready to put in the garbage, they take out the recharge card. When the balance in the card is sufficient, they can open box 1, box 2 or box 3 to put in the garbage. Among them, box 1 and box 3 are reduced according to weighing, and box 2 is charged according to weighing. In order to prevent different types of garbage from being thrown wrong, the input door of each box can be made different. For example, the control door of the paper input box should be made into a flat mouth, only allowing paper or newspapers and magazines to be input. The hardware structure of the control system is shown in Figure 1.
Compared with other controllers, the single chip microcomputer has the advantages of small size, low price and high cost performance. Therefore, this control system uses the currently most used AT89 S51 single chip microcomputer as the main controller, which can easily communicate with the radio frequency circuit, display circuit, communication circuit, The interface connection of A / D conversion circuit forms a complete control system.
2 IC card and card reader circuit
Non-contact IC card is also called radio frequency card. Compared with contact IC card, it solves the problems of passive and contact-free. It has the advantages of high reliability and easy operation. The current popular Mifare1 card and controller are selected in this design. The antenna coil connected to the dedicated card reader chip continuously emits a set of electromagnetic waves of 13.56 MHz fixed frequency. When the Mifare1 card is close, the LC series resonant circuit in the card resonates, causing the capacitor to charge and charge. When the capacitor charge reaches 2 V At this time, the capacitor is used as a power supply to provide the working voltage for the circuit on the card, and the data in the card is transmitted or received in the controller and saved [1].
MFRC500 is a highly integrated card reader chip for contactless communication at 13.56 MHz. It integrates all types of passive contactless communication methods and protocols at 13.56 MHz. It supports Mifare1 card. The interface circuit with AT89S51 is shown in Figure 2. According to the system requirements, the functions that the corresponding part of the control program needs to achieve are as follows [2]:
(1) When there is no card swiping, the system is in a waiting state; when there is a card swiping, identify the information in the card, including user information, card balance, and internal storage area of ​​the system, and call the display program.
(2) Payment methods can be recharge and bookkeeping. This design uses a recharge method to deduct food waste and non-recyclable waste, and paper and plastic waste can be recharged to the card.
3 Design of weighing module and display module
(1) Selection of load cell
Electronic price scales, platform scales and other occasions are suitable for the selection of aluminum alloy cantilever beam sensors. Deformation caused by bending, strain gauges are pasted on the upper and lower sides of the area where the curved surface is concentrated to form a full-bridge measurement circuit. Figure 3 shows the CYT-204 series cantilever beam load cell. The range is 0 ~ 0.1 T, with high accuracy and low drift. The output is 0 ~ 5 V, which is easy to interface with the microcontroller. The size is 130 mm & TImes; 32 mm & TImes; 32 mm, Easy to install [3].
(2) Design of A / D conversion circuit and display circuit
TLC2543 is TI's 12-bit serial analog-to-digital converter, which uses a switched capacitor successive approximation technique to complete the A / D conversion process. The serial input structure can save the I / O resources of the single-chip microcomputer, and has the characteristics of simple interface, moderate price and high resolution. It is widely used in instruments and meters, so TLC2543 is used in this system for A / D conversion element.
The display devices commonly used in the control system are LED display and LCD display, in which LCD can display characters in addition to numbers, so this design uses the currently very common LCD1602 display module to display the weighing results.
The display control program realizes the display of user information, including name, house number and card balance. When the user presses the box selection button, the garbage weight charging device opens the corresponding input door. After the user completes the garbage, according to the type and weight of the garbage, the balance in the card can be increased or deducted and displayed.
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