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MagPi issue 18: Plant-Monitoring network

Mon Nov 04, 2013 9:04 pm

The article in MagPi #18 on a Plant Monitoring Wireless Network suggests using the 2.4GHz band ATmega128RF module from Dresden Elektronik for the wireless nodes.

I see these are available at DigiKey for about $25 each. If you're willing to spend that much money, I think it is also worth considering something like a Moteino which is slightly cheaper*, capable of longer range, and available in three frequency bands (433, 868, 915 MHz). This is an Arduino (ATmega328p) with HopeRF RFM12B / RFM69W / RFM69HW radio module.

I'm not affiliated with the LowPowerLab company selling Moteinos but I recently bought several of them, and found them to work well. The RFM69HW module has been tested to have over 1 mile of range (clear line of sight, diopole antenna, at 1200 bps) and its bitrates go up to 300 kbps (tradeoff is lower range). The 2.4 GHz ATmega128RF module can go even faster, but plant growing conditions don't change by the millisecond so a remote plant monitor probably doesn't need broadband speeds. The Moteino does need a wire antenna about 9 cm long (or more depending on frequency), while the 2.4GHz module has a super-compact onboard ceramic antenna. But the 2.4GHz frequency is more quickly absorbed by water, for example if there are a lot of plant leaves between your node and your central station.

*(at least if you are in the US, not counting overseas shipping, tariffs etc.)

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