Low Power LoRa data collection

Another strange project on the horizon and thought I would ask if any one has any great ideas.

I need to relay temperature data from about 20 CubeCells with temperature sensors in an environment that is not easy to get to. The unit’s all need to be battery powered including the relay node.

    /     |    |    \

[sensor1] ~ [sensor20]

relay1 can see relay2 and the gateway but not the sensors
relay2 can see the sensors and relay1 but not the gateway.

I was thinking that if I synch all the timers then wake everyting up at the same time and get them to transmit the readings then once all the readings are received i can put the system back to sleep but not sure how accurate the timer’s are while in sleep mode.

I guess the alternative would be to add an RTC in to the mix.

Or possibly wake the sensor up with the LoRa set to listen only, if it receives a beacon telling it to transmit its data then transmit it otherwise go back to sleep. Then use the relay’s to control the beacon when they wake up. I’m mindful that it is quite possible the units could miss a transmission window an that may thrown off the data being logged.

any thoughts on this would be welcomed.

perhaps this is a starting point:

Perfect, Thank you :slight_smile: