05-11-2012, 03:54 PM
Networked Embedded Greenhouse Monitoring and Control
Networked Embedded.pdf (Size: 219.11 KB / Downloads: 38)
Abstract
Networked embedded systems have become quite
important nowdays, especially for monitoring and control of
distance and dislocated objects. Small greenhouses are typical
examples. First, they are usually located far away from the
owners house, and second, the plant grow is an example of the
process which need constant 24 hours monitoring.
In this paper networked embedded greenhouse monitoring and
control based on simple embeded web servers and 1-wire
protocol for conecting sensors and actuators is described.
Hardware and software architecture of embedded web servers is
analysed and the experimental results of monitoring and control
of laboratory greenhouse is presented.
INTRODUCTION
Today, advances in sensors, actuators and
microprocessor technology, both on hardware and
software level, have enabled distributed implementation of
sensor and control actions over sensor/actuators networks.
If we connect such local sensor/actuators, private networks
to global network (Internet) additional features could be
exhibit. The monitored and controled system could become
accessible from almoust anywhere. The process parameters
data display, remote control, system testing and system
reconfiguration could be done using standard browsers on
workstation computers. That alows us to use large screens,
menus, buttons, on-line helps, instead of simple alpha –
numeric displays usually connected to such embedded
devices.
EMBEDDED WEB SERVERS SYSTEMDESIGN
Embedded systems require web server software that
enhance their networking functionality without taking up
vital system resources. Web enabling of devices is possible
by adding web server software to existing embedded
system. Requirements for embedded Web servers are:
- Small memory footprint: Server must use very little
memory and it must not fragment memory. Many
embedded devices use simple memory allocators that
cannot manage memory effectively. This problem is
usually solved by using statically allocated or preallocated
memory blocks.
Protocols
Although TCP/IP (Transmission Control
Protocol/Internet Protocol) is the main communication
protocol that enables connection of different devices in
networks, it is not implemented in full. Only the necessary
parts are used and parts that are not needed for this sort of
communication are excluded. Furthermore, TCP/IP
protocol is basis for upper level network protocols which
will be used in embedded systems. If the system uses RS-
232C or modem link then point-to-point (PPP) or serial-line
Internet protocol (SLIP) is needed. File transfer protocol
(FTP) is used for uploading new files and programs to the
system. Opposite to the receiver-driven information flow
through Web browser, information flow could be devicedriven.
Using Simple Mail Transfer Protocol (SMTP)
application can periodically send information via e-mail.
System Design
In a new system design, system hardware will be chosen
according to the overall requirements of the system.
Application software needs to be developed in order to
achieve the required system functionality. System designer
must compromise between hardware and software solutions
for each problem. Hardware solutions are easier to design,
faster and more accurate in operation. Software solution
results in smaller production cost and system modifications
are simpler. Particularly, connection to Internet must be
considered. When embedded processor is located in the
vicinity of local network installation, 10Mbps Ethernet
interface is chosen. Otherwise, serial port is used to transfer
data over telephone or radio channel.
CONCLUSION
In this paper we have presented network embedded
greenhouse monitoring and control based on embedded
Web server unit which gather and route data from local
sensor/actuator network to global network - Internet.
The developed experimental system, based on TINI
embedded Web server, collect data from distributed sensors
and activate connected actuators using simple 1-wire local
network. On the other side Web server is connected to
Internet through Ethernet or dial-up network. The
developed system shows all advantages of Network
Embeddes System Tecnology (NEST), like the possibility
of changing physical topology and low dimensions and cost
in comparison with PC based system, preserving the full
funcionality at the same time.