(I) System Introduction
The wireless temperature acquisition system consists of a central data concentrator and an indoor temperature collector. The central data concentrator is connected with the computer through RS232 or RS485, and is used to set the working mode of the temperature collector and report the collected temperature value to the computer for display. The temperature collector is placed in the residential user's home.
The work mode of the central data concentrator is: in addition to sending data once according to preset time intervals, it can also send an alarm signal to the computer when the temperature exceeds the user's preset temperature upper and lower limit indicators, and according to preset different The temperature data is reported in intervals until the temperature returns within the set upper and lower limits. A center can access up to 500 temperature collectors.
In addition to temperature acquisition, the system can also control remote devices according to system management needs, remote temperature acquisition/monitors, and multiple TTL level, analog and digital interfaces.
(II) Central Data Concentrator
main indicators:
• Frequency: 2.4 GHz–2.488 GHz free band, 83 channels, 3822 channels
• Receiver sensitivity: -105 dBm; Output power: up to 20dBm
• Control Microcontroller Configuration: Atmega88/Atmega128
• Memory: 4k/16k bits
• Visual communication distance: 1000-1500 meters
• Transmission speed: 250 kbits/sec, 38.4 kps, 19.2kps, ....1.2kps, etc. can be set
• Direct-sequence spread spectrum: DSSS communication, strong anti-interference, high confidentiality;
• Highly integrated, with few isolated components, high reliability, and low cost
• Provides two RS232 or RS485 interfaces, providing I2C interface and multiple TTL level interfaces;
• 12-MHz input clock operation
• Maximum received signal –20 –6 dBm
• With measuring battery voltage function
• Operating temperature –40° to 85°C
• Emission current: about 250 mA
• Receive current: about 30 mA
• Operating voltage 220 V AC (DC 5 - 9 V supply interface available but ripple factor < 10mV required)
• Antenna type: External antenna
• Data rate: 250kps (DSSS mode) 1Mps (GFSK mode)
• Crystal startup time: < 1mS
• Frequency Stabilization Time: < 100uS
• Transceiver conversion time: 30uS (transmit => receive & receive => transmit)
• Module size: 65 X 30 mm x 6 mm (Designed according to user's requirement)
Typical applications: long-distance data transmission module, data acquisition and relay, etc.
• The transmit power, channel channel, and module number can be set by the user by wired or wireless.
• With automatic data transfer/relay function. (c) Relay Concentrator
The relay concentrator has the same transmission function as the central data concentrator (but cannot communicate with the host computer), and it plays a role in connecting the indoor temperature collector and the central data concentrator, and can increase the indoor temperature collector to the central data center. Transmitter distance and transmission reliability. Can achieve three levels of interconnection or multi-level interconnection.
(four) indoor temperature collector
The indoor temperature collector is powered by a No. 5 lithium battery. No battery replacement and no external wiring are required during the heating season.
A central data concentrator can access up to 500 temperature collectors.
1, the main features
Built-in DS18B20; real-time temperature acquisition, host computer over limit alarm;
Operating frequency: 2400MHz ~ 2483MHz, each channel bandwidth 1MHz, a total of 3822 channels available for user selection;
Using direct sequence spread spectrum technology with strong anti-interference ability, it can work in harsh working environment and work reliably and stably.
Bidirectional communication distance (temperature acquisition and monitoring): greater than 1000 meters (line of sight)
Data interface mode: RS232/RS485;
Communication parameters: baud rate 9600bps, 8 data bits, 1 stop bit, no parity;
Data acquisition frequency: 2 seconds to 3600 seconds (can be set);
2, power supply
The central data concentrators and relay concentrators are powered by AC power or solar cells; the indoor temperature collectors are powered by lithium batteries.
The frequency of the acquisition of the root is different, the battery time is different, and the battery-power usage time is at least one year to two years.
3, size
60 x 50 x 20 mm.
(5) System advantages and disadvantages:
1. Advantages: The indoor temperature collector is placed in the home of the resident and no external power supply is required. The power supply of the resident's home is not used. The cost is relatively low and the performance is stable.
2. Disadvantages: Relatively concentrated transmission distance (diameter 2000-3000 meters), central concentrators and relay concentrators need to be erected or placed high. Try to avoid blocking.
By installing a GPRS module at the signal center, the transmission distance can be unlimited
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