I'm working with a project to collect temperature data from about 50 cabins that are located close together. It therefore seems easiest to use 50 Lora nodes with temperature sensors and one gateway.
So I'm searching for a way to use multiple Lora nodes to create a sensor network. From what I've gathered it might be more cost and time effective to buy a readymade gateway such the Dragino. But I can't seem to find any good guides on how to create a small Lora node? I live in Europe and therefore want to use 433Hz frequency. I'm thinking something like a RFM96 and an Arduino nano should do the trick? Or is there easier solutions?
Since there is little documentation about this I hope others can find this useful as well.
Thanks in advance!
Best Answer
Maybe if......
The 50 cabins each send temperature data once every 10 minutes using battery power this could be handled by a system that does not rely on a receive protocol to tell the "transmitter" when to transmit. This could massively sustain battery life because you are not wasting several mA of current continuously keeping the radio listening.
In the 9 minutes, 59.9 seconds between transmissions your battery consumption could be as low as a few microamps. During transmission (0.1 seconds) you might need 20 mA so the average current is: -
Background (say 10 uA) plus 20 mA/6600 = 10 uA + 3 uA = 13 uA.
Channel usage per cabin transmitter is 0.1 seconds every 660 seconds so, with 50 transmitters this means the channel average utilization is 5/660 = 0.75%. Each transmitter could randomly time its transmission based on a unique address so that on average it was ten minutes (with plus or minus 5 minutes as the random factor).
Collision probability would be low but you'd get a cabin's temperature the next time in all probability. It's all down to how you want to play it.
This type of system would use 50 transmitters and one receiver. The receiver does all the data collection for the 50 cabins.
Quite cheap (I would use FM) transmitters could be used but each would need a little MCU to format the transmission with preamble, address, payload data and checksum. The little MCU would also do the random timing thing.
The receiver (AC powered) would convert a received transmission back to the payload data (having proven that the checksum tallied) and the address of the cabin would also be detected in the transmission.
Similar question.
Maybe a LoRa module could be put into shut-down mode to conserve battery life thus you get a similar solution that wouldn't require an MCU to format the data to make it suitable for a transmission?