Timeline for Looking for an extremely low power RTC module (and more!)
Current License: CC BY-SA 4.0
18 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 22 at 23:05 | answer | added | Paul Jon | timeline score: 0 | |
| Jul 7, 2021 at 6:00 | history | tweeted | twitter.com/StackElectronix/status/1412652620808871938 | ||
| Jul 1, 2021 at 20:44 | comment | added | le_top | RV-3028-C7 uses about 40nA typically. It has a unix time, but no exact date alarm. The XTAL is integrated. The ppm is optimum at about 25°C. Maybe one could have only the RTC running, let it generate an interrupt once a week to let it wakeup a uC that checks the date using the I2C and if not met, just go to sleep again by disabling the power switch. You can also get several ICs (at different times, different batches, etc) and pick the one that consumes the least. Worst case is 60nA, so about 26mAh needed for 50 years of operation of the RTC alone. | |
| Jun 30, 2021 at 8:44 | comment | added | Neil_UK | That timekeeping accuracy could be a killer. Is the clock allowed to have some sort of display (low power of course, like a clock motor that ticks once per day or month instead of once per second) to allow you to track the timekeeping error and anticipate the beep? | |
| Jun 30, 2021 at 7:18 | comment | added | D.A.S. | aging from std XT Crystals can be 1 ppm / yr. Think of a better design and all the experience you need to make something with an MTBF of 50 years | |
| Jun 29, 2021 at 23:19 | comment | added | ishmandoo | @TonyStewartEE75 20ppm on 50 years is almost 9 hours. Hmm, that's pushing it... | |
| Jun 29, 2021 at 23:18 | comment | added | ishmandoo | @RealMagnetics thanks, those are great suggestions. I don't suppose temperature compensation is passive? Hopefully that requirement doesn't break the bank battery-wise. | |
| Jun 29, 2021 at 23:16 | comment | added | ishmandoo | @Neil_UK The most important thing is that I be able to prepare for and hear the beep. An uncertainty of a few hours or so would be great, can just sit around and wait. Uncertainty of a day would mean staying up all night or something. As for environment, it'll be in a normal living room or something. | |
| Jun 29, 2021 at 23:13 | comment | added | ishmandoo | @TonyStewartEE75 I think a solar cell makes a lot of sense, thanks! | |
| Jun 29, 2021 at 16:19 | answer | added | hacktastical | timeline score: 2 | |
| Jun 29, 2021 at 12:04 | comment | added | user16324 | The smaller MSP430 CPUs can sleep with the RTC clock running (to wake up some programmable time in the future) on less than 1 uA. Then the programming (and maybe a 1 second 1mA LED flash every year) is entirely under your control. Remember to account for 20ppm or so crystal accuracy and drift ... what is 20ppm of 50 years (1.5 Gigaseconds)? | |
| Jun 29, 2021 at 6:16 | answer | added | Damien | timeline score: 2 | |
| Jun 29, 2021 at 5:06 | comment | added | Real Magnetics | You should use a Lithium thionyl chloride battery instead. These are used in long lasting remote applications such as power-meters for homes. I also recommend that you find a temperature compensated RTC module, because uncompensated crystal oscillators can drift significantly with temperature, unless you are ok with several 10's of hours of time drift. | |
| Jun 29, 2021 at 4:22 | comment | added | Neil_UK | 50 years +/- 1 second, or +/- 1 year? What accuracy timekeepig? A low drain CMOS oscillator could take less than 1 uA, CD4060 says typical quiescent is 40 nA, but that goes up radically with temperature, what's your environmental specification? | |
| Jun 29, 2021 at 3:17 | review | Close votes | |||
| Jul 7, 2021 at 3:05 | |||||
| Jun 29, 2021 at 2:47 | comment | added | D.A.S. | A 32 bit counter will hit 100 yrs on 1 cycle, with a slow clock but you might be anxious that it won’t work. You better add a solar cell. | |
| Jun 29, 2021 at 2:15 | review | First posts | |||
| Jun 29, 2021 at 11:10 | |||||
| Jun 29, 2021 at 2:14 | history | asked | ishmandoo | CC BY-SA 4.0 |