Based on low-voltage power line technology unit call system design (1)

Traditional room call system generally have lines, not only the wiring installation cumbersome, maintenance inconvenient, low utilization rates, and real-time performance difference.

Although wireless calling system without wiring problems, but its reliability is poor, and radio waves interfere with other medical equipment, most hospitals do not adopt wireless calling System.

With the power line technology development, and application of low-voltage power line as a transmission medium, using spread spectrum, digital encoding, MCU control technology to achieve Ward call has been made possible.

This article uses power line technology designed a ward in the calling System.

1 room call system of basic requirements

Clinical assistance call is an important means of clinical information, Ward call system is the patient requested duty doctor or nurse for diagnosis or care of emergency call tool to the patient's request quickly routed to the doctor or nurse on duty and duty of monitoring Center computer on accurate and complete records, improving hospital and ward nursing standards of one of the necessary equipment.

Call the pros and cons of the system is directly related to patient safety, has always been the major focus of General Hospital. It calls for timely, accurate, reliable, simple and feasible, conducive to the promotion. Use power line carrier communication technology, single-chip multi-machine communication and computer monitoring and management technology design have call Queuing, ringing, display, save records for priority setting, and other functions of beds call system that meets the hospital ward management and care requirements.

2 ward call system design

2.1 system composition and working principle

Ward call system calls from several sources (typically per bed as one), modulation carrier module, coupled circuit and monitoring system form, as shown in Figure 1.

When you call a call signal source, in the monitoring system has the appropriate sound, light call signal and can show the call number. If a parallel bus extension, hundreds of calls between the source and the host of the wiring is too complex, so the system uses single-chip serial communication function, allowing the host to all the signal from the machine through the power line modem module, after ~ 220V civil power line transmission, for host and from the machine's bi-directional data transfer between.

Figure 1 system block diagram

The system uses a master and a slave, monitoring and control system (host) on the doctor on duty room (available through interface circuits and computer related, constitute monitoring centre), when the beds have call request for sound and light alarm, and displays the location of the beds.

Call source (from) on the wards, patients have the call, press the request button, the first call, and call the led is lit. Between the host and from the machine through the power line. Master and slave communication, host then click send to from the machine, the address information from the computer receives a host of address information, and your address are the same, then the host sends its own alarm information, no alarm information, the host sends an empty number (00).

2.2 SC1128 spread spectrum communications chip and transceiver circuit description

SC1128 chip is intended for power line carrier communication market and the development of dedicated spread-spectrum modulation/demodulation circuit.

As a result of the direct sequence spread spectrum, digital signal processing, direct digital synthesis and other new technologies, so the circuit application in power line communications with strong anti-jamming and attenuation properties. SC1128 chip integrates spread spectrum/despreading, modulation/demodulation, D/A conversion and A built-in electronic/D conversion, and output drivers, input signal amplification, watchdog, operating voltage detection and microcontroller (MCU) serial communication functions. The chip in a small multi-purpose application systems can serve to reduce system costs and improve the functionality of the system.

SC1128 chip transceiver circuit diagrams composed as shown in Figure 2, the signal from the power line via Coupler, band-pass filter and the front-stage amplifier into SC1128 chip.

After it is processed through a power amplifier and coupler to the power line, complete the signal on the power line to send and receive. Box one coupling coil, it can be launched in the third box signal coupled to a power line; can be received on the power line signal coupling to box 2. Box 2-fore receiving circuit, it will receive the signal filtering, zoom in, the level being fed SC1128 op amp (13 feet) for processing. Box 3 for power amplifier, it will issue a 24 foot SC1128 shunting signal for power amplification, the coupling coil fed into the power line. Box 4 as interior part SC1128 analog signal processing circuits, contains three levels of operational amplifier, which level amplifier gain adjustable.

Figure 2 SC1128 chip transceiver circuit diagrams composed of