2017 Pro Mini Logger Build - Power Saving mod for RTC board

This is an optional self-contained change to the "standard" Cave Pearl ProMini Data Logger from 2017. The modification to the RTC module described here reduces the current draw of that component by approximately 0.1mA. This video accompanies the online tutorial at :
thecavepearlproject.org/2017/...
with further background information availiable at: www.mdpi.com/1424-8220/18/2/530

[@jarchdm]

Thank you for your real world advice, 95% of TH-cam tutorials are just bench / theoretical stuff. I made a timer that turns on and off a water feature following the real rising and setting of the sun, using the ds 3231 but it kept going off at unexpected times i narrowed it down to the ds resetting itself to 1/1/2000 8 am for some reason, I remembered seeing this video and looked it up again. Did the capacitor mod and so far so good. I guess turning on the relay gives such a jolt to the electrical system that the ds resets itself just like you said. So this was excellent. many thanks.

[@john543]

Have you looked at using the Macetech Chronodot V2? No need for ugly surgery. The V3 now has eeprom as well.

[@xsirfr1958]

Great mod! If you used a lower voltage drop diode like a schottky type, seems like the RTC can run even longer as the battery drains and VBAT drops. Vmin recommended is 2.3V for the DS3231.

[@edwardmallon4646]

I was wondering about the reverse leakage current through the shottky's going into the coincell. While small, it would potentially be there for years at a time on our long deployments (?)

[@roberttso6853]

@@edwardmallon4646 Good call! Schottky's are a lot leakier than the normal P/N diodes. The BAT54 schottky is spec'd at 2uA max for 35v reverse. With a max reverse of ~3V, the "charging" current into the battery would probably be less than 1uA.

[@mariuspetcu7482]

Hello Edward ,
Thank You for making this video, Thank You for Spending your time to Share with us from your knowledge and Thank You for smart choice using simple words to explain - for us , those no native English speakers ...
Now, I am struggling for more than 2 month now, in my attempt to make an Arduino Nano simple clock, some temperature from DS3231 and a TM1637 LED display ...
I have a "major" problem with DS3231 RTC module - I can upload the Code, I can see the time in Serial Monitor, even on TM1637 module, but when I Disconnect the Power of the Arduino from computer and plug the 5vDC PS the time has "left behind" at the moment I was upload the Sketch ...
Thos Mod You did to the RTC module will Solve this Issue or is a Program/Code's "fault" ?
Thank You and Bless You and your family ...

[@isabelfer6053]

Thank you very much. That seems the "right" way to use DS3231.

[@kychemclass5850]

Great to know. Thanks for sharing!

[@michaelthomsen8771]

Thanks for a very useful video! My guess as to what consumes the 100uA would be the Vref inside the "power control" circuit (datasheet page 10). When you're powering directly from Vbat this power control and thus Vref is likely mostly off. Now, my problem is that apparently the DS3231 on my board is a scrapped version that consumes about 350 uA *more* than specified. I guess cheap ebay stuff is cheap for a reason...

[@user-qo5mz6se4p]

I have a variant of the chip that uses high current too. I lifted the 32khz pin off the pad. I discovered that when that pin is directly wired to VCC then the power consumption drops to 1uA.

[@edwardmallon4646]

Folks watching this video might find our latest post interesting, as we now power the entire logger from just the coin cell on the RTC module. The two-part combination of a cheap ProMini clone with this RTC sleeps below 5uA, so should easily run for more than a year on the Cr2032:
thecavepearlproject.org/2022/03/09/powering-a-promini-logger-for-one-year-on-a-coin-cell/

[@oguzhanergin224]

Thank you, I checked two method, wich is the best way?

[@murraymadness4674]

Does the EEPROM consume any power? Don't really need it.

[@homo_sapiens_sapiens]

Thanks very much

[@roberttso6853]

Hey Ed. I just started reading some of your documentation - you have a ton of stuff! I've just scratched the surface. I need to make a low power data logger, (entirely powered by CR2032) and I will try to re-use what you have already created. One quick question: Regarding this power saving mod. Adding the 1N4148 diode won't do anything, since VBAT is already connected to the cathode of the existing diode. The new diode will be shorted. Am I missing something?

[@xsirfr1958]

My bad - I forgot you cut the VBAT trace, so the diode is surely needed!