[tgsovlerkhgsel]

> Lower powered I would expect

With the right software, ESP32 can be incredibly low power. Like "months on 3xAA batteries" for watching a pin with the ultra low power subsystem and then occasionally waking up and making a HTTPS call over WiFi.

[_flux]

That's not lower power, is it? E.g. RuuviTags can run 3 years or longer while sending sensor data 2.5 times per second, with a single CR2477 (3V 1000mAh). A single AA alkaline battery has 1.5V and 2100-2700 mAh (https://batteryskills.com/aa-battery-comparison-chart/ , somehow this data was difficult to find so I'll add this link :)).

Bluetooth is lower energy than WiFi, but in your scenario the energy used for the radio is quite low anyway.

[tgsovlerkhgsel]

There definitely are lower-powered options; I mostly meant that as an example that as an hobbyist, an ESP32 - possibly even on a standard dev board! - could easily be good enough for your use case.

I never did a formal study to see how much of that power use was standby vs. power-on usage, how much of the standby usage was the ESP32 vs. the board/voltage regulators/pulldowns, how much of the power on usage was radio vs. e.g. all the crypto (we're doing asymmetric crypto for the TLS handshakes on batteries here, that isn't going to be cheap!) etc.

I just slapped it together and found it good enough to not care further.

[benterix]

nRF52832 are famous for their low energy usage, it's hard to compete with them. However, ESP32 is much more universal.

[_flux]

Actually I've read claims that ESP32 C6s are pretty decent battery-consumption-wise. So much so that I bought a few, hoping to make at least a doorbell out of it. Alas I don't have a device to measure microampers, so I guess I'll just see how long they're fare..

[BenjiWiebe]

You can use ohms law - let it draw power through a 10k resistor, and put your multimeter across the resistor. Every .01 volt is 1 uA. This also means that if you're powering it with 3.3v and it browns out at 3.0v, you'll only be able to draw 30uA before browning out.

You can use a different resistor according to the power draw and how sensitive your volt meter is.

You'll probably need to power it up with the resistor shorted, and only remove the short once it's in sleep mode, to measure the current.

[ale42]

This is just kind-of low-power. Some microcontrollers (e.g. PICs) can have sleep consumptions measured in nanoamperes. Months to years on a coin cell... just, they would need an external wifi module, which is highly inconvenient.

[benterix]

Do you have an example of such a setup handy?

[tgsovlerkhgsel]

No, it was an undocumented one-off using a random cheap devboard from Aliexpress (i.e. not some specifically optimized circuit!), built (IIRC) using the Arduino IDE - aside from spending the time to find and configure the low power mode properly, this was done in the dumbest, most naive way possible, and still worked.