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Topic: Atmega328p LoRa Node (RFM98w) - Power consumption too high! (Read 271 times) previous topic - next topic

mcgreg

Hi All,

I've created my own LoRa sender/recevier for Home Automation: Atmega328p with an BME280 Sensor and RFM98W LoRa chip to send the data.
Good news, it's working as expected, I can read the Sensor values and send it via the LoRa Module.

Since I wanted to run it on (2xAA or 2xAAA) battery, I'm using the "naked" atmega chip itself with the great Rocketscream library. So I read the data, in case the values changed i send it over LoRa and go to sleep for 4 minutes. With my multimeter I could measure around 9 microamps during sleep (see MultimeterAtmega.png).
I'm using 4 dBm while sending and limiting (via Software) the power consumption for the LoRa module to 45 mA. Even if  a multimeter is not the best thing to measure current peaks, I see something like 20-30 mA during LoRa activity.

Taking this into account, my calculation shows that 2xAAA battery show be enough for ~ 1 year:
1 second 30 mA, 239 seconds 9 uA --> 0,13 mAh. On 1000 mAh cells, it should last 320 days.

Anyhow, measuring against the VCC during runtime via software (https://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/), the voltage drops quickly and the batteries are empty after 30 days (see BatteryVoltage.png).

Any ideas how the expected lifetime of the battery is 10x smaller than expected?

Thank you in advance,

McGreg

mcgreg

For better understanding, here my wiring diagram.


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