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[Solved / Archived] RTC has not recovered to correct time after power failure (Witty Pi 4 Mini)

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(@ejwmac)
Posts: 17
Eminent Member Customer
Topic starter
 

Hello,

We have recently had a power failure at my location, that caused the device and the RPi Z2W to reboot after power was restored.

However, the Witty device RTC was set at what appeared to be the local US Time of your location, i left the system for a while to seee if it would recover but it did not??

After syncing with the network time manually, the RTC appears to have recovered.

But surely this is not the normal response after a power failure, is it? and nothing in the log file either?

I am writing an application for the RPi Zero that relies on the correct time,( without any manual intervention) so how can I ensure this after a power failure similar to the recent events, please?

Thank

 

JohnW

 

 
Posted : 02/11/2023 12:38 pm
(@ejwmac)
Posts: 17
Eminent Member Customer
Topic starter
 

Apologies, ref to "... local US Time of your location..." should have read US time or UUGear location.

 
Posted : 02/11/2023 2:05 pm
(@admin)
Posts: 362
Member Admin
 

You didn't mention which version of Witty Pi is used.

If it is Witty Pi 3/4 Mini, it has super capacitor to keep time when power is cut. Usually can keep time for a few hours, but it also depends on other fectors.

If it is Witty Pi 3/4, it needs the CR2032 battery to keep time when power is cut. If that battery was not installed, the time will immediately lose.

 

 
Posted : 02/11/2023 5:33 pm
(@ejwmac)
Posts: 17
Eminent Member Customer
Topic starter
 

Posted by: @admin

You didn't mention which version of Witty Pi is used.

If it is Witty Pi 3/4 Mini, it has super capacitor to keep time when power is cut. Usually can keep time for a few hours, but it also depends on other fectors.

If it is Witty Pi 3/4, it needs the CR2032 battery to keep time when power is cut. If that battery was not installed, the time will immediately lose.

 

 

It is the Witty Pi 4 Mini..... and I cannot say exactly how long the power was off but it could have been over 8 hours..

 

Thank You

 

 

 
Posted : 02/11/2023 5:54 pm
(@admin)
Posts: 362
Member Admin
 

Then it should be the case, that the super capacitor got drained for too long and its voltage droped under a value that can keep the time for the RTC.

If hours of power failure should be considered, you may connect a 3V battery to the 3V3 and GND pins in unpopulated pin header P3. You will also need to put a diode in serial to avoid unexpected charging to the battery.

 
Posted : 03/11/2023 11:59 am
(@ejwmac)
Posts: 17
Eminent Member Customer
Topic starter
 

Thanks for this., as my electronics knowledge is poor, would it be possible to point me in the direction of the circuit so i can see how this would be wired up please?

 

Thank You

JohnW

 
Posted : 03/11/2023 6:47 pm
(@admin)
Posts: 362
Member Admin
 

@ejwmac the drawing below shows what I mean.

1699275219-wp4m_bk_batt.jpg
 
Posted : 06/11/2023 1:53 pm
(@ejwmac)
Posts: 17
Eminent Member Customer
Topic starter
 

Hello,

 

Ok, Great thank You

 
Posted : 06/11/2023 2:49 pm
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