Connecting ESP32 to internet in LowPower setup.

[vladoportos]

Hello all,
This might be a stupid question but I'm getting bit overwhelmed with possibilities and would like to focus on one that is the best.

I need connect multiple ESP32 to local LAN ( or Internet ) but I need it at low power 3.3V batteries, this mean sleep for about 24hours than wake up, check server if something changed specifically for that device ( so it have to broadcast identification first and than read the response ), if something changed than do action and back to sleep...

I do not need long distances like LPWAN ( which sounds great, low power and long distance... but licensed and need expensive hub to talk to normal web servers... )
Bluetooth - nice low power consumption, range is not that great though and I'm not sure if it can be made in a sense Server + many clients checking from time to time ( possibly multiple clients checking at once )
WiFi - classic solution that I understand , its just AP and clients.. simple enough.. battery inefficient though.. ( would be nice to have wifi mesh capability, but since like 99% of the devices will be in deep sleep, it would not work. I don't know though...gathering information about it now )

What else is there ? Some low power radio communication like LPWAN. or just stick with wifi and get a bigger batteries ?

[boarchuz]

Does it matter how power hungry WiFi is if it's only going to be awake for 5 seconds once every 24 hours?

[JoeSensoric]

I have several battery-driven ESP32 boards running which wake-up, read sensors, start Wifi, send data with a single HTTP-request and go to deep sleep. That all takes 4 to 5 seconds. I made some calculations about battery consumption and the active Wifi part is the relevant part when you really power down all peripherals during deep sleep. For example I power the sensor chips with an output GPIO port which is possible if the sensor needs only a few mA. So in deep sleep there is no current to these modules.
Bluetooth communication would need much less power but is limited (as you wrote)

[vladoportos]

Thats what I'm looking into, I heard claims that somebody had the chip running over year on small button 3V batteries ( two), Basically I need the chip to wake up at night ( once every day ), connect to server via wifi, read reply and perform some action.. than immediately go to sleep, but I doubt that can be done one 3V batteries like CR2035 or something like that.. also I'm curious how would I go about disconnecting everything from power like sensor ( if they need more mA and can't be powered from output pin ) .. maybe some kind of relay ?

[JoeSensoric]

The WiFi hardware needs more than 150 mA for a few seconds, this peek needs to be handled by the battery. I thing a CR2032 / CR2035 coin cell cannot handle this.
See: https://electronics.stackexchange.com/q ... ifications

With the ESP32, sending Bluetooth BLE advertising seems to be the fastest and most battery-saving way, but this is just a connection-less "ping" used in the beacon devices.

For some use cases a smaller controller with a low-power transceiver in the 866 / 915 MHz band is a better solution. I have an old controller measuring temperature every 10 minutes and sending it to a special receiver board. It's running on one CR2032 for several years now!

[vladoportos]

Yes, I ended up with Lora module seems to be the only solution for now.