ADC + BEACON + BATTERY LIFE

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Mon, 11 Jun 2018 07:15:55 GMT

4 µA is the average current consumption. If you run it for 1 hour, you will have consumed 4 µAh.

RE: ADC + BEACON + BATTERY LIFE

Nakul Nair — Mon, 11 Jun 2018 06:33:17 GMT

The 4µA for SAADC low power example is it 4µA per sample or 4µAH. If it is 4µAH then I can add that to the 14µA which will give a total of ~18µAH. Is this correct?

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Fri, 08 Jun 2018 14:27:36 GMT

That depends on the advertising settings, etc. of the beacon. You can check this with the nRF52 Online Power Profiler. The SAADC Low Power example have an average consumption of ~4µA. Lets say you have a beacon advertising 20 bytes at a interval of 1000ms, with 0 dBm output power and 3V battery, this should give an average consumption of 14 µA. With an ideal consumption rate, this should give you ~12222 hours of battery usage, or ~1.4 years. You will most likely end up below this, maybe approximately 1 year? This will depend on your batteries and the end consumtion of your application. I would recommend getting a Power Profiler Kit for easy current measurement of your application.

RE: ADC + BEACON + BATTERY LIFE

Nakul Nair — Fri, 08 Jun 2018 11:51:58 GMT

Hi Jorgen,

What would be the battery life of a CR2032 coin cell battery with a 220 mAh capacity if we are using the above example of ADC+beacon.

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Mon, 08 May 2017 13:47:19 GMT

Good luck! Please accept the answer bu clicking the checkmark next to it if this was helpful.

RE: ADC + BEACON + BATTERY LIFE

SHUBHAM — Mon, 08 May 2017 13:46:15 GMT

OK thanks a lot. I'll go through that

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Mon, 08 May 2017 13:45:01 GMT

Yes, the Low power example on GitHub, which I linked in my answer above show how to use RTC to trigger the SAADC sampling on nRF52.

RE: ADC + BEACON + BATTERY LIFE

SHUBHAM — Mon, 08 May 2017 13:42:44 GMT

yes that's why i am thinking of using RTC with ADC. for nrf52 is there any example code to show saadc with RTC.

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Mon, 08 May 2017 13:38:18 GMT

That does not sound like a good idea with regards to current consumption, but if you could provide code snippet of your current solution I could help you improve it.

RE: ADC + BEACON + BATTERY LIFE

SHUBHAM — Mon, 08 May 2017 12:57:26 GMT

yes you are write bot i'm calling fun. nrf_drv_saadc_sample(); in a LOOP.

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Mon, 08 May 2017 12:55:30 GMT

What do you mean by "poling method"? In general, the recommended way to do this is to use RTC/app_timer to trigger the sample task and update the advertising data at a given interval. This is shown in the example I linked above.

RE: ADC + BEACON + BATTERY LIFE

SHUBHAM — Mon, 08 May 2017 11:52:44 GMT

Thanks a lot for your prompt response
one more thing is that i am using poling method to update advertising packet along with power_manage() function. Is this method is OK or should i use something else.

RE: ADC + BEACON + BATTERY LIFE

AmbystomaLabs — Mon, 08 May 2017 11:46:55 GMT

See also this recent post on using the ADC: devzone.nordicsemi.com/.../

RE: ADC + BEACON + BATTERY LIFE

Jørgen Holmefjord — Mon, 08 May 2017 11:42:22 GMT

Hi,

When the SAADC peripheral in nRF52832 is enabled, the current consumption will increase due to EasyDMA being active. To decrease the current consumption, you need to disable the SAADC peripheral between sampling. If you only measure battery voltage, you should not need a high sample rate.

A low power SAADC example for SDK 11 is available in this GitHub repository. In SDK 12 and 13, there is a low power mode in the driver. It can be activated by setting SAADC_CONFIG_LP_MODE in sdk_config.h.

The current consumption of the SAADC peripheral:

I_(ADC,CONV) (ADC current during ACQuisition and CONVersion): 700 µA
EasyDMA current: ~1.5 mA

Best regards,

Jørgen