Adding some simple monitoring tools, and Internet ready devices, your existing network connection brings your real world to your wired world.

Internet based Monitoring using low cost solutions.

Gary Drake | www.BroadbandSentry.com

Internet based Monitoring using low cost solutions.
  by Gary Drake - www.BroadbandSentry.com

Adding some simple monitoring tools, and Internet ready devices, your existing network connection brings your real world to your wired world.


1)         Introduction

With the universal availability of Broadband connections, access to the web, Cell Phones and home networking hardware, all the pieces for simple and low cost home monitoring are a reality. These communications tools can be applied to the home alerting of water in the basement, heating or cooling system failures, Web Cam images, open doors, or windows, and complete alarm systems interfaces. Adding some simple monitoring tools, and Internet ready devices, your existing network connection brings your real world to your wired world.

2)         Introducing the use of print servers and other web-enabled tools 

The simplest hardware and software solution is to use a device know as a Ethernet print server. Ethernet print servers are used to share a printer across the Ethernet network. This function allowed multiple computers to use a printer located anywhere on a network, much like having it connected to computer and shared for others to use. The print server is a stand-alone device, it is connected to the printer, becoming the printer's connection to the network. No other computers are required to be operating for it to function. Printer Servers have their own Web pages for setup and status reporting on the attached printer. Setup pages may provide options such as password protection and Ethernet settings (IP Address.)

The Printer Server has the ability to report the status of the attached printer. Normally three conditions are reported, Online, Off line, and Error/Out of Paper. The exact wording, choice of words or capitalization of status message does vary depending on the supplier of the print server.

We effectively get two inputs, not very many but enough to have a single printer server tell us the condition of our home.

Three connections to the printer server are:

Pin 12 Pin 32  
Low Low Offline
Low high Online
High Low Out Of Paper
high high Offline

The two status inputs have built in pull up resistors, creating default conditions. By closing a switch or relay connecting either input to Ground (pins 19 to 30), the printer server reports a status change.

A simple connector and terminal block or barrier block can be used to make the connections. The connector used on the back of a printer is known as a 36 pin Parallel interface, IEEE1284 cable, or also known as a Centronics Interface.

When this connector is combined with a 2 or 4 position terminal barrier block or Euro barrier block you have a convenient to use interface. Next, connect a switch that closes based on your requirements. Temperature and water are two examples we will explore in detail.

3)         Temperature:

For a temperature sensor, a trip to your local Hardware/Building supply store for the simplest wall thermostat will do. The single function milli-volt thermostat that opens, and closes a switch based on the temperature set point is all we need. Use two thermostats if a high and low temperature range is desired. A simple electrical box makes a serviceable mounting fixture for the thermostat and connectors.

 

The connector for the print server can be mounted directly on the back of the electrical box.

Placing, a two-position barrier strip on the back of the electrical box gives access to the second status input.

 

You now have a free standing temperature sensor to connect to your print server. We have now completed the simple home sentry to monitor for temperature, too cold, or too hot. Regardless of which part of the world one lives, extremes of cold or hot can be damaging to plants, pets, and your home. Your print server now has one of its two inputs used temperature limits (remember you can use two thermostats if you want a range of temperatures).

4)         Water Sensor

A water switch using a float and a magnetic switch is a very effective solution. The switch is available from electronics component suppliers on the web. Using other parts available from your local Hardware/Building supply store the sensor can be assembled.

The two wires are connected to one of the printer server's status bits. One wire to a Ground in the print server, the other to one of the status pins. When the float is raised, the switch is closed, causing change in print server status.

Combining the two examples, we have now constructed the bare minimum of a quick and simple temperature and water leak sensor using low cost components.

Extensions are many; including using more then one printer server to monitor additional sensors. Both wired and wireless printer servers are available from numerous suppliers. Other sensors such as magnetic door sensors can be added, answering the question "did we close the garage door".

We started this article using a simple, low cost off the shelf print server. A number of vendors sell programmable modules that allow for more inputs, outputs, and customizing your web page. These modules will allow for more customization; however, this also requires much more understanding of software and computer systems.

5)         Internet Connections

DSL or Cable users have an always-on connection, this is great for application that can use monitoring as we described but require more attention to security. To place more than one computer or printer server on a connection requires a router, and preferably a firewall router. Firewall routers manage access to your local network. The router portion implements the multi-connection portion, this holds true with or without the firewall option.

There are many choices of firewall/router, the deciding factor will most likely be based on how your IP address is assigned. If you have a fixed IP address, it never changes, then almost any firewall router will work. However if you have Dynamic IP, then your IP address changes as your ISP decides. Having your IP address change makes your network hard to find, remember all the names used for reaching web sites, etc. are converted using DNS (Dynamic Name Servers). A solution exists; there are a number of services that support Dynamic IP updating DNS Servers. This updating requires software or hardware on your network to communicate the change in IP address to the service. Programs are available to run with a number of operating systems, but of course require a computer to function. An alternative is to use a firewall/router that supports this function. Some of these Dynamic DNS servers are free or very low cost.

Now that we have a network name, called a Domain Name, associated to an IP address your home network can be found. The next step is to assign a TCP/IP port address on the Internet side of the router. This port address is translated by the router into the IP address of your devices on your local network. 

For example:

www.network.com:80 map's to 192.168.0.2:80

Some network configurations may require port mapping as well as IP address mapping, for these Proxy serves maybe required. Several are available for various operating systems, some are free, and some are built in to the operating system. The Proxy server requires a computer to be running but does expand the options. Proxy servers do not normally need to be exceptionally fast, but do require two Ethernet cards.

You now have a functional system to retrieve information from your home or office, using your desktop computer or mobile phone. Of course this requires you to access your network and view the status from your print server. The ability to check on your home or office is nice but having to remember the network and print server details is very useful.  Wouldn't it be nice if these devices could reach you on your mobile phone, PDA, or email with meaningful messages.

6)         So let's automate!

The existence of always on Internet connection, low cost Ethernet devices, and numerous connectivity options lead us to creating www.BroadBandSentry.com .

BroadbandSentry.com is a web-based collection of services that support the query of web-connected devices. BroadBandSentry.com will query network devices, accept email message commands, and  UDP messages, then alert you. It's alerts are based on the criteria you have selected. Alerts can be sent by Email or Mobile Phone to your family, or neighbors, completely at your control.

At BroadbandSentry.com using the print server example we discussed in the beginning of this article, the following configuration will check for the On-Line status and send an email alert when the string is found, or not found as the case maybe.

- Enabled    24147 / http://myhome.dns.com/factory.spi?io4=0 / ... Delete this SentryPoint    String Found
  NetGear PS101@ http://
myhome.dns.com /factory.spi?io4=0 : 4141   User: ...  Password: ...
    Frequency: 5 Minutes    Add the update Frequency Add an Frequency
    Times of operations:   00:00:00 - 00:00:00      Enter the times of operation Enter the times of operation
     HTTP request from IP address, .. Delete this event     Add a State to this Function Add an State to this Function
         String Found Delete this state     Add a Action to this State Add an Action to this State
            Find this sting: On-Line
             Send SMS Delete this action     Customize this Action Customize this Action
                 5082468257, test1 Delete this item     Edit this Message Edit this SMS

 

- Enabled    24147 / http:// myhome.dns.com /factory.spi?io4=0 / ... Delete this SentryPoint    String Found
  NetGear PS101@ http:// myhome.dns.com /factory.spi?io4=0 : 4141   User: ...  Password: ...
    Frequency: 5 Minutes    Add the update Frequency Add an Frequency
    Times of operations:   00:00:00 - 00:00:00      Enter the times of operation Enter the times of operation
     HTTP request from IP address, .. Delete this event     Add a State to this Function Add an State to this Function
         String Found Delete this state     Add a Action to this State Add an Action to this State
            Find this sting: Out Of Paper
             Send SMS Delete this action     Customize this Action Customize this Action
                 5082468257, test1 Delete this item     Edit this Message Edit this SMS

In these examples we used HTTP protocol to read the status of a Print Server, this same protocol can be used to read any web page. Numerous WEB enabled modules can be used to monitor your own systems

The combination of www.BroadbandSentry.com with widely available Ethernet Internet web enabled device and building blocks open up a new world of uses for applying the Internet to the real world!

Broadbandsentry is a trademark of C.S.D. inc. www.broadbandsentry.com


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