Stalker, Ethernet Shield, Off-Grid Web Server

I have been searching the web for weeks trying to figure out if and how I can build a remote data logging system that has its own wifi area network using a stalker, ethernet shield and a wifi router.

Where I need help:

  1. General thoughts on this project, Can I do this with just a stalker board, ethernet shield and a wifi router?

  2. How to build a graph in html from a data file on the SD card? All the examples I have seen usually access java scripts or google api’s on a server somewhere else. This is not an option since the stalker will be in a remote location for months at a time.

Brief Project Description:
The project will monitor some sensors in a remote location (no cell phone coverage, no world wide internet access). The sensors will include temperature, humidity and light for now. The stalker will log the sensor data to the SD card.

Data Access:
An ethernet shield will be used to allow the stalker to be a webserver. The ethernet shield will be connected via RJ45 to a wifi router. The wifi router will be used to create a local wifi network.

A person in the area would then be able to get an IP address from the wifi router (ssid would be broadcast) and then access the stalker via its static IP over the wifi network.

The stalker web server would serve up serveral HTML pages.
Page 1: Live sensor data (page refreshes automatically every xx seconds)
Page 2: Sensor calibration page (use html form and GET method to parse URL and change sensor offsets)
Page 3: List of data files on SD card. Clicking on file name would download file to the persons device
Page 4: Historical Graphing of data files (this page would show a graph of the sensor data, from sd card, over time)

The devices used to access the stalker over wifi could be an Android phone/tablet, iphone/ipad, or even a laptop with wifi. Thus the use of the stalker as a webserver using HTML.

Progress to Date:
Connected sensors to Stalker.
Logging data to SD Card
Ethernet Shield connected to PC using RJ45
Built HTML Page 1 - showing sensor data with page refreshing every 10 seconds
Built HTML Page 2 - Parsing URL with GET method from Form to change sensor calibration/offsets
Have example code for tranferring data files from SD card over wifi but have not built the html page yet.

Any thoughts and input would be greatly appreciated!


I was able to use the HTML POST form method to pass data to the webserver versus using the GET method.

The wifi is working using a Netgear N150 wireless router. Need to find something that is lower power. This one is 12volts DC.

I have the Stalker Ethernet Shield connected to the N150 using RJ45. I can then use the browser on my Android phone (connected to the N150 Wifi) to access the Stalker webserver.

Next step is implement the file downloads then figure out how to do the graphing…