Communication
The plane itself is intended to be fully autonomous, capable to returning to the launch site with no communication to or from a ground-station. However, in the interest of both following the progress of an experiment in flight as well as retrieving a misdirected glider, we are equipping the glider with the ability to send updates on it's location, speed and heading to us on the ground.
Plan1: Sending SMS messages via GSM
Our first approach is to send SMS messages using a GSM phone or a GSM modem. SMS messages are only 160 bytes, but this should be enough space to include the essentials. Possible choices for a GSM radio to send in the glider are:
- Sony Ericsson GM28 GSM
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Operating Temperature: -30°C to +75°C Power: 5 - 32VDC Weight: 110 g
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The GM28 is an industrial GSM modem originally designed to be used in vending machines that need to call home for more supplies. The model might work well for our purposed as it doesn't use much power and has a connection for an external antenna. The modem is controlled via a serial connection using AT commands.
Questions: Will the modem work with pre-paid SIMs, Can we get a SIM that allows regular data to be stored in it, and what is the capacity? Can SMS messages easily be sent by the GM28? (Something maybe useful)
Prepaid SIM cards
Given the chance of losing the glider, it seems to make sense to use a pre-paid SIM card that would not require dealing with AT&T or TMobile to try and explain why we'd lost our third phone this year and needed another SIM issued. Here is a company that sells prepaid SIMs for the US (10 cents per SMS) Here's another that has SMS messages for 5 cents each. Coverage for Washington shown below...should be ok.
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