Author Topic: Please help selecting RFM69HCW vs RFM95_LoRA for outdoor agriculture field use  (Read 243 times)

lowpowerfarm

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Hi,

I am designing/building some of automation for an agriculture field and need advice on choosing appropriate transceiver (RFM69HCW or RFM95_LoRA) to pair with the Moteino.

Here is the field setup:
~20 hectare area (approx 1500ft x 1500ft). Automation consists of ~30 soil moisture/ph sensors, ~20 irrigation valves -- all will battery powered. A central hub (wall powered, placed in one corner of the field) will poll/control these. This will be a private network and there is no need to integrate with any public gateways/networks. Farthest distance between central hub to the sensor/valve would be ~2000ft, with plants/shrubs (of ~7ft) in between them. I do not see need for high bit/transmission data rates. Sensors will periodic transmit data, irrigation valves will need bi-directional comms, with few bytes of control commands.

I plan to use Moteino for both sensor and valve control. As I said, need advice on choosing the appropriate transceiver (RFM69HCW or RFM95_LoRA).

RFM69HCW seems to be well supported via the RFM69 library compared to LoRa. Unsure how RF will perform with these many nodes and does one of these transceivers offer clear advantage over the other? Finally anything else that I should take into account w.r.t RF/Range/Antennas while I am designing this system?

Thanks in advance!

Felix

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Hi,
I would recommend trying HCW first. Do a little pilot test between the most common/dense/farthest points of communication. Use the standard settings found in the RFM69 library.
See what your RSSI is with standard provided wire/monopole antennas. Perhaps you could use a Dipole on your gateway since that is the most important node and could use a little gain.
From past experience and feedback, even with this simple no frills setup the HCW-915 will be more than appropriate.
Keep the monopole perpendicular to the PCB. For the dipole position won't matter since it has its own ground element, but keep it away from metal parts, orient it towards your node field.

Each use case and environment is different. I believe the upfront effort and cost to evaluate the HCW might pay off later if you find it can do the job. Otherwise the LoRa will surely handle it but comes at increased cost.

Let me know your findings and any other questions you might have.
FWIW - I offer customized/integrated solutions as well if you end up going that route and wanting to make a single PCB with everything on it, I can prototype and produce the boards here in the USA.

lowpowerfarm

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Thanks for your prompt reply.

Will prototype with RFM69HCW and see how things pan out. Thanks for the tips on RF Antenna. w.r.t mounting, is it OK if just the central hub mounted at an elevation (say on a 10ft pole) and rest of the nodes (sensor+valve-control) are at ground level, with shrubs/trees in between them, or do these nodes also need to be mounted high up?

Yes, will report back once I have something useful/working (need to decide if I can use `TomWS` (excellent) hardware design for battery valve control (will start a separate thread for that), or build something different).

Cheers!


Felix

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Elevation is always ideal, if you can achieve it, at least 1 end will also help.

lowpowerfarm

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Hi,

Speaking of range and transmit power, is it correct to assume that LDO-less variant of Moteino (aka Moteino 8Mhz variant) may NOT be a good fit for valve control given the limited (13dBm?) transmit power, and the fact that valve controller may be far away from the control/central hub (~2000ft).

Or am I misunderstanding this, and I can use HCW (20dBm) radio with 8Mhz variant too?

Thanks!

Felix

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The 8mhz will use a few uA less (~3uA quiescent current drained by the LDO) since the LDO is not present. Otherwise you can use whatever transceiver you want, HCW or CW. I would recommend with HCW for any project, you can dial down the power to 13dBm if you really want to, or anywhere in between using the RFM69_ATC functions.

The LDO-less Moteino-8mhz runs at half the speed of regular 3.3V Moteinos based on atmega328p, the advantage being a bit lower power and ability to go down below 3V operation, allowing you to run from a variety of batteries.