Overview sensor wireless network. Senses of wireless network. In the last time the applications based on wireless data transfer have been growing. The benefits ...
Overview sensor wireless network Senses of wireless network In the last time the applications based on wireless data transfer have been growing. The benefits of the using wireless data transfer are: In an application that has a lot of devices for data acquisition the data transfer between them is also completely. In some real entities (complex building, greenhouse, manufacturer plants etc.) there are a lot of obstacles for example the wall corners, several trees, the pillars, pumps in greenhouse etc. or several machines (photocopy, fax machines etc.), doors, windows, tables, chairs, personal computers, power supplier modules, production lines etc.. All of these obstacles are the stumbling block for the laying data and power supplier cables. The wire communication needs a lot of cables, in mostly case (e.g. in a network with more 20 devices) the laying of the cables in the whole network is on the brink of the impossible task. The maintenance of a cable network in the future is very difficult and it’s normally prone to failure and confusion. In this situation we prefer to use the wireless communication in order to enable the data transfer in the whole network. In a wireless network usually is used the frequency band 315, 433, 868 and 915 MHz. This frequency band is free and it’s used mainly in the application for Industry, Scientific and Medical. The suppliers don’t need a license from the government. In a modern wireless network we can program the nodes so that the power consumption is optimized. Wireless network are currently used mostly in the field of remote control, security, technical measurement
Technologies of the sensor In present the sensors are the parts of the devices mostly; we meet the sensors in camera, air condition, refrigerator etc... The new technology in material science, physic, chemistry, micro devices enables the additional features in the sensors. The sensors have now smaller dimension, consume less and less energy. At once they have better precision, better sensitivities, the working range are large (for example temperature sensor s have a working range from minus 20 degree to some 100 degree) and they are more resistant against an industrial hazardous environment (dust, high moisture etc.) and the form of sensor is mostly adapted to real application. The integration grad in sensor is more complete, on the market we can find a lot of sensors which are combined with customer defined micro controller. This new tendency enables the flexibility of the sensors. Most actual sensors on the market have the standard interface SPI or I2C which enables the connection to micro controller easier. 1
Power supplier for the sensor wireless network The sunshine is a big physical characteristic in every greenhouse; the plants in a greenhouse need the sunshine for biological growing. At once the energy of the sunshine is won by the solar panel for a sensor wireless network. During a day the sunshine energy is won and on one side it is directly used for the sensor nodes, router nodes, repeater in the network and on another side it will be saved in the rechargeable batteries. In the night the network still work by using of the energy from the batteries. One another serious consideration is a combination of wind and solar energy for the powering the sensor wireless network in a greenhouse. In the chapter above we mention also the obstacles in a real entity, if we use the solar panel in a greenhouse for a powering the problem with the laying the cables is partially resolved, because we only lay the power cables from a power supplier unit (consist of solar panel, battery and MPPT circuitry) for the nodes in a region nearly unit. Power supplier unit
Battery
MPPT circuitry
Solar panel
Sensor nodes in a segment nearly this power supplier unit
A feature of power supplier unit is the using of Maximum Power Point Tracking (MPPT). This technique tries to get the maximum possible power from one or more solar panels, as the natural consequence the using coefficient of the solar panel higher.
Technology of sensor wireless network
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In the project sensor wireless network the sensors and wireless transmission are combined. The humidity sensors are the parts of the node; it measures the temperature and moisture of closely environment; it sends this data via the interface I2C directly to a micro controller. The micro controller on the node processes this raw data; the measured temperature and moisture and some additional information (for example: the ID of the node and acquisition time) are packed in a frame and in the end this frame will be sent via wireless interface to the next node or to central node. The central node is connected directly to laptop or personal computer (PC) via USB interface. It collects all data from all sensor nodes in the whole network and sends them to a user application which runs on the computer or laptop. The user application receives the data in real time. The data will be represented graphically on the screen. We can see chronologically sequence both temperature and moisture separately of each node and save these data into an excel file. Furthermore from a user application we can send a command from via central node in order to modify the currently setting of the nodes in the network. For example in the maintenance phase we have to set or justify the real time of nodes.
Overview of a sensor wireless network
Sensor node
Sensor node
Sensor node
PC/Laptop with application
Central node Sensor node USB port Sensor node Sensor node
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