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Measuring the battery voltage with nRF52832

nigheo gravatar image

asked 2016-06-14 17:26:28 +0200

Hi!

To measure the voltage level of a coin cell CR2450 can be done in different ways. You can use the comparator, the low power comparator or the ADC. I wonder which one is the most adequate to use and affects least the current consumption? The CR2450 is the only power supplay in the system and the voltage is 3,0V when it has full capacity and 2,0V when it's discharged.

BR, Nixon

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stefanbirnir gravatar image

answered 2016-06-17 12:13:22 +0200

Hi Nixon

All options can be low current, also the SAADC when used for battery measuring. I suspect the LPCOMP/COMP and Power Failure warnings generate more of low battery warning events, while the SAADC provides actual battery monitoring. If you use the SAADC to sample once a second or less, I suspect it will add less than 1uA to the current consumption. This is not given though, you have to set the SAADC up correctly in order to achieve low current. The default saadc example in the nRF5 SDK 11.0.0 conumes around 2mA. I attach a low power SAADC example for you to explore, which uses RTC to trigger sampling. I have tested it with SDK 11.0.0 and nRF52832 revision 1. The SAADC is only enabled before sampling and disabled when sampling completes to avoid high current consumption of the EasyDMA.

saadc_low_power_with_rtc.zip

This example is sampling on an intput pin. To sample the battery voltage which the nRF52832 IC is powered with, configure the SAADC channel you use to be single ended, the input on PSELP as VDD and gain as 1/6, which will measure the battery voltage directly and give the SAADC range from 0V to 3.6V.

Let me know if my message is unclear or if there are any questions

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Hi,

Found Intresting, Still i have one quick query, What are the setting available in Resistor ladder? As we will require to do so. we are measuring 3V(CR2032) battery with ADC internal ref=0.6V.

Bimal ( 2017-05-17 10:33:59 +0200 )editconvert to answer

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Asked: 2016-06-14 17:26:28 +0200

Seen: 978 times

Last updated: Jun 17 '16