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Wireless

The iSENSE Wireless Subsystem allows users to retrieve data from sensors that are not directly plugged into the host computer.

The Wireless Subsystem has two components: a “Base Unit,” which is plugged in via USB to the host computer, and a “Remote Unit.” The Remote Unit can communicate wirelessly with the Base, or it too can plug directly into the host computer via USB.

The Remote Unit includes several useful built-in sensors (such as temperature, light, humidity, and sound). It also has ports for several external sensors. It includes a battery-based power supply, allowing it to operate in the field for extended periods of time without human intervention.

The Remote Unit also includes a real-time clock, allowing it to time-stamp sensor readings that are taken using its store-and-forward mode (see below).

The Wireless Subsystem three operating modes:

1. Query mode. A program running on the website will be able to query the sensor through the base station for the values that it needs for the experiment and automatically save that information to the database.
2. Wireless tether mode. In this mode, the Base Unit is plugged into the host computer. The Base Unit communicates wirelessly with a Remote Unit. The wireless system acts as a simple bridge, allowing the Desktop Client to read data from the sensors on the Remote Unit. The wireless range should be about 50 to 100 feet.
3. Store-and-forward mode. In this mode, the Remote Unit is configured to collect data on its own. The Remote Unit is brought to a location distant from the Base Unit (e.g., outside, or worn on the body). The Remote Unit collects and stores data for some period of time. It timestamps this data using its built-in realtime clock. Data are later retrieved from the Remote Unit (see below).

Retrieving Data from the Remote Unit

There are two ways to retrieve data collected by the Remote Unit:

1. Direct plug-in. If a Remote Unit is directly plugged into a computer running the Desktop Client, the user is prompted to log into the Data Store and upload the data from the previously-configured experiment that the Remote has been running.
2. Wireless through Base Unit. The data from the Remote can also be retrieved wirelessly. The Desktop Client uses the Base Unit to establish communication with the Remote when it is brought into range.

Configuring the Remote Unit for An Experiment

When setting up the Remote Unit for an experiment, various configuration data about the experiment should be stored on the Remote Unit.

Of course, the essential information required to actually perform the data collection must be provided to the Remote: e.g., which sensors are to be sampled, how frequently, over what period of time, etc.

Additionally, for later uploading of the experimental data to the Data Store, other configuration information, validated by the Data Store, should be saved:

• username of the person or group conducting the experiment
• name of the experiment

This way, when the experimental data are later uploaded, the Desktop Client can automatically properly install the data into the Data Store.

Summary

The diagram below summarizes these different operating modes.

Supported sensors -

• SunSPOT (Small Programmable Object Technology)
  • Vernier analog sensors
  • GPS
  • Cricket analog sensors
• Cricket (Handy Board)
• Scratch board
• Vernier GO Temp USB
• Machine Science Data Collector