https://devzone.nordicsemi.com/f/nordic-q-a/58954/a-question-about-the-power-consumption-of-an-observer-that-reacts-when-it-receives-an-advertising-msgHello. I&#39;m trying to make a product by running nrf51822 as an observer role. This product will only use passive scanning and will not transmit any data. How much energy do you expect it will take for this observer to react without missing the adven-USTelligent Community 13Wed, 11 Mar 2020 14:59:26 GMThttps://devzone.nordicsemi.com/thread/239376?ContentTypeID=1Wed, 11 Mar 2020 14:59:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:45dd15f6-8e6e-4ae2-8762-a6f488628103Edvin<p>Hello,</p> <p>Please be aware that scanning is a power costly procedure. When you are in a connection, the radio will only be used in short bursts, but when you are scanning you need to keep the radio in RX for a long time (in your case 100%). This is why the phone is typically the central/scanning device in a BLE connection establishment, because it has a bigger battery (which is also often charged).</p> <p></p> <p>If you look in the <a href="https://infocenter.nordicsemi.com/topic/struct_nrf51/struct/nrf51822_ps.html?cp=5_4_0" rel="noopener noreferrer" target="_blank">product specification v3.3</a>, page 50 and 51, you can see the current consumption of the radio (depending on whether you have the DC/DC regulator or not).</p> <p>It will use 13 or 9 mA only on the radio. In addition you will have to add the CPU for your application, and the current consumption drawn by your peripherals.</p> <p></p> <p>If this is too much, perhaps you should consider entering a connection if you need to transfer critical data, and then reduce the scan duty cycle (only scan 50%, or less, depending on your battery requirements).</p> <p></p> <p>Best regards,</p> <p>Edvin</p><div style="clear:both;"></div>