3.3V step up regulator voltage monitoring

[fhenryco]

Hi

I'm using the 3.3V step regulator with my 3.3V mini pro

https://www.aliexpress.com/item/1-PC-NEW-DC-0-8-3-3V-to-DC-3-3V-StepUP-Boost-Power-Mini/32724005061.html?aff_platform=aaf&cpt=1494762865525&sk=rvbiMby&aff_trace_key=f164064565154598a619c92cc4a33fd3-1494762865525-04564-rvbiMby

and' i'm very satisfied with this solution because the mini pro without led and regulator removed has as promissed a very low consumption.

But then if i really want to monitor the battery voltage its a little bit less easy than simply monitor the arduino Vcc (output of the regulator) because requires an additional voltage divider and analog read. This would allow to monitor the progressive linear decrease of the battery voltage with time. But i'm wondering if after all , it would be enough only monitoring the Vcc, since as the battery will get out of juice, this should result in the step up regulator not being able to maintain the 3.3V. What i'm wondering is how sudden will be the drop in the regulator output voltage as the battery will progressively get out of juice because if it's too fast, then monitoring this output (rather than the inout of the regulator) is of course useless...

[flopp]

What voltage is your battery?

This is one way to measure voltage
https://forum.arduino.cc/index.php?topic=356752.0

[fhenryco]

This post is deleted!

[fhenryco]

@flopp yes your link is to the method i'm currently using to monitor Vcc which is about 3.3V. But my battery is actually 2 AA in series which output voltage is 3.3 V only when new...and should decrease progressively. My question is: is it necessary to monitor the Voltage of this battery or is it safe to only monitor the Vcc which is the output of the step up 3.3V regulator ?

[flopp]

@fhenryco
If you measure after the step-up you will never know when it will "die".
You need to measure before step-up to see battery level

[fhenryco]

@flopp Ok but are you sure ? i mean if the step up fails to output 3.3V when battery level gets too low, monitoring a decrease of the regulator output (to arduino Vcc) might indicate death coming soon ... and after all this is all i need to know except if "coming soon" means " too soon" to react and prevent failure by changing battery

[flopp]

@fhenryco
If battery is below 0,8 step-up will not work and your Arduino will not work.
If battery is 2.3 you will get 3.3 output from step-up

[scalz]

stepup will simply fail, you'll get brownout, transmit problems etc..so you won't know anything in the end..
it's better to monitor your batt voltage. you don't need a voltage divider for this, as your batt voltage will always be <= vcc. So Analogread your batt voltage, and your range will be 0 to 3.3v.

[flopp]

@scalz is correct, use analog input to read batteries.
My link at top was to measure what voltage the Arduino I see getting. Sorry for leading you in wrong direction

[fhenryco]

ok thank you

[fhenryco]

actually, as i now remember i was using the voltage divider to reduce the battery voltage below the reference internal voltage ~ 1.1V ... this is some people advice for better accuracy. I'm now wondering if i can avoid this (the voltage divider) and still have a correct precision

[mfalkvidd]

@fhenryco what precision do you need?

[fhenryco]

well i don't need great precision, just need to be alerted
when the battery voltage is getting dangerously low

[mfalkvidd]

@fhenryco then the method recommended by scalz and flopp will be great.