Detailed explanation: Design of wireless ward caller based on single chip microcomputer
Clinical help-seeking calls are an important means of transmitting clinical information. The ward caller is an emergency call tool for patients to request a doctor or nurse on duty to diagnose or care. The patient's request can be quickly transmitted to the doctor or nurse on duty, and in the monitoring center of the duty room. Keeping accurate and complete records on the computer is one of the necessary equipment to improve the level of care in hospitals and hospitals. The pros and cons of the call system are directly related to the safety of the patients, and have always been widely valued by major hospitals.
It requires timely, accurate and reliable, simple and feasible, and conducive to promotion. Most of the traditional ward call systems in China use wired transmission, which has the defects of complicated installation and wiring, difficulty in inspection and maintenance, poor anti-interference ability, difficulty in expanding the ward, high cost and unsightly. To overcome the above deficiencies, this study introduces a wireless ward caller that uses a dedicated RF module and uses a microcontroller to control it.
This not only solves the problems of complex wiring, but also improves the level of medical services and adapts to the needs of modern society.
1 hardware circuit design
The design consists of a pager and a host, using a radio frequency transceiver chip to operate the system near the band 433 MHz. The system uses a single chip encoding/decoding, each pager has a unique identification code, and the identification code can be modified at any time. When the user presses the transmit button, the identification code is transmitted and waits for the response of the receiver. After receiving the service request, the host identifies the application from which the pager is issued based on the identification code, and gives an audible prompt and a display call. The identification number of the device. If several pagers call at the same time in a short time, the hosts are stored in sequential order and then rotated in sequence.
The block diagram of the connection between the calling extension and the receiving host is shown in Figure 1 and Figure 2. The extension is controlled by the DIP switch to control the setting of the address bit. When the call to button is pressed, its address is read into the MCU, and then sent to the transmitting chip for transmission. The extension is used to make a call, and the code is completed by using a single-chip microcomputer. The core circuit of the extension is the connection circuit between the single-chip microcomputer and the radio frequency chip. The host is responsible for receiving signals from the extension and decoding, displaying and alarming.
The host also has a keyboard for checking and deleting records, so the keyboard should be connected with a keyboard, display and alarm circuit.
Figure 1 Call extension block diagram
Figure 2 Receiver block diagram
1.1 Extension circuit design
The extension is composed of an 8-bit DIP switch, a single-chip microcomputer, a wireless transceiver chip and corresponding peripheral circuits. The extension uses a portable design and is powered by a battery. In addition to the power consumption and volume, the minimum voltage of the chip needs to be considered when selecting components. Therefore, the single-chip microcomputer selects Arr89c2051, which can work stably under the voltage of 3V. Moreover, it has the core of AT89C51, the instruction system is the same, and the I/O interface required on the extension is also very small, so the AT89C2051 can fully meet the requirements.
1.1.1 Design of extension number setting circuit
The extension uses an 8-bit DIP switch to manually locate the extension's address, as shown in Figure 3.
If you need to move the extension to another bed, you only need to change the state of the dial switch to change the extension number.
Figure 3 extension number setting circuit
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