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Topic: Temperature Sensing on a Farm (Read 3907 times) previous topic - next topic


Jun 06, 2011, 02:21 pm Last Edit: Jun 06, 2011, 02:34 pm by dcb Reason: 1
I have to say I would be very tempted to use an inexpensive laser module here (dissect a $3 cat toy) on the greenhouse end, and simply connect the uart tx pin to it through a driver and point it at a photo transistor driving the uart rx pin to receive the data.  Then embed a checksum and a "timestamp" and a station ID in the data and have the stations send the the same data several times at different intervals to help ensure you can get a clean reading from them on a regular basis.

So you would have a laser and an arduino plus whatever sensors at each greenhouse pointing their lasers at a centralized arduino that captures the data.

It may even take less power this way vs rf, as the signal is so focused.  3 D-cells might run this thing for a year or more?  And if the receiver is expecting regular communications from each greenhouse, it can notify you if it hasn't heard from one within the expected timeframe.


PaulS made a really good point.  One must make sure to balance the devices since XBees work in pairs at a minimum.  You can construct an unreliable network by not keep close tabs on a nodes range and match it with a device that can receive and transmit to it.  The laser led idea is a good one, but the code to support it is a great deal more complex than just adding a repeater XBee somewhere to pass on data.  Using a laser to communicate is fun, but you get to figure out retries, error detection and correction yourself.  The wire library can help with this if you decide to go that way.

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