NRF52832 Low power scan - using CR2032

[Avi]

I am trying to develop a low power scanner with nrf52832 which is is acting as both central and peripheral (beacon) 

I need to detect other tags like itself transmitting nearby (max 2m). Their advertisement interval  can be adjusted 

I need to identify the tag only if it is more than 2min in the range of the receiver 

I thought about the following ways:

1) Scan only 2 times per 2 minutes. For example Scan for 200 msec then sleep for 1 min and then scan again

The peripheral will advertise at 100msec rate.

2) Scan only 1 channel e.g. 37, the advertising will be on channel 37 as well

3) Use tilt switch for that will disable and scanning and the advertising if the tag doesn't move

Are there more ways to enable low power device (scanner + beacon)?

It is hard to estimate the power consumption...

What is the power consumption of the receiver doing partial scanning with window of 200msec every 2 min?

[Jørgen Holmefjord]

Hi,

You can also save some power by doing passive scanning, compared to active scanning, if the beacons do not use scan response packets to increase the size of the advertised data. Enabling the DCDC regulator will also reduce the current consumption when the RADIO or CPU is active, when running from a 3 V power source. The lower peak current draws will increase the lifetime of the battery.

I created a test program with your specifications and measured its current consumption with our Power Profiler Kit.

This is the average current over 2 minutes:

And this is a zoomed image of the time when the radio is active/scanning:

Attached the project for reference: ble_app_beacon_scanner_low_power_sdk16.zip

These measurements do not include any advertising part, but you can get an idea of the advertising current from the Online Power Profiler.

Best regards,
Jørgen

[Avi]

Thanks. The picture is not clear.

Is it 14uA avarage?

Does it mean that with 220mAH battery, I will get 654 days?

[Jørgen Holmefjord]

Yes, ~14.3 uA average. With ideal battery conditions, the battery could last that long, but it will depend on various conditions. 

Also, note that additional processing of data from the scanned beacon/advertising packets in the application will increase the current consumption.

[Avi]

Thank you