Re: [time-nuts] Ultra low power RTC

Hi > On Mar 7, 2018, at 6:33 PM, Mike Cook wrote: > > >> Le 7 mars 2018 à 11:10, Attila Kinali a écrit : >> >> On Tue, 6 Mar 2018 21:57:32 -0500 >> Bob kb8tq wrote: >> >>> Assuming you are going to run it off a battery. What’s the self

Re: [time-nuts] Ultra low power RTC

On Thu, 8 Mar 2018 00:33:58 +0100 Mike Cook wrote: > This is interesting. When you talk of self discharge, is there any way > of harnessing that. Is that what the chip manufactures are doing? No. It's a chemical reaction inside the cell. The energy is turned into heat

Re: [time-nuts] Ultra low power RTC

> Le 7 mars 2018 à 11:10, Attila Kinali a écrit : > > On Tue, 6 Mar 2018 21:57:32 -0500 > Bob kb8tq wrote: > >> Assuming you are going to run it off a battery. What’s the self discharge >> rate on a reasonable battery? > > With supply currents below 100nA

[time-nuts] Ultra low power RTC

A friend of mine is a product engineer for one of the largest (the largest?) makers of RTC chips. He groans about the (rather pointless) quest for the lowest power RTC chips. Making robust, stable, accurate oscillators that run at nanowatts is a losing proposition. At those levels external

Re: [time-nuts] Ultra low power RTC

On Wed, 7 Mar 2018 12:06:43 -0500 Bob kb8tq wrote: > Ok, so energy harvesting from Lazy Bob in his arm chair makes a button cell > look like a giant power source ….. Giant is an understatement. For comparison, a single brain cell uses approximately 0.5nW of power. A human body

Re: [time-nuts] Ultra low power RTC

Hi Ok, so energy harvesting from Lazy Bob in his arm chair makes a button cell look like a giant power source ….. You likely aren’t going to win any ADEV competitions with that oscillator. They did go to a *lot* of effort to squeeze out that last nano watt. Bob > On Mar 7, 2018, at 11:47 AM,

Re: [time-nuts] Ultra low power RTC

> Since we don’t often *need* the smallest cell made *and* we’re probably > talking lifetime of the cell….. does 22 na vs 33 na matter? It gets even more amazing ... "A 1.5 nW, 32.768 kHz XTAL Oscillator Operational From a 0.3 V Supply"

Re: [time-nuts] Ultra low power RTC

Hi I’ve designed watch guts (long ago). It was at a time that you used an analog (motor) movement if you wanted really low power. The CMOS / LCD’s of that era were power hogs by comparison. What you can put in a small / thin watch isn’t what you would use on a RTC board. My suspicion is that

Re: [time-nuts] Ultra low power RTC

On Wed, 7 Mar 2018 08:27:00 -0500 Bob kb8tq wrote: > Since we don’t often *need* the smallest cell made *and* we’re probably > talking lifetime of the cell….. does 22 na vs 33 na matter? Not really. It starts to matter when you are space limited and don't have space for a

Re: [time-nuts] Ultra low power RTC

Hi Since we don’t often *need* the smallest cell made *and* we’re probably talking lifetime of the cell….. does 22 na vs 33 na matter? …. hmmm …. CR2032 ( which is the smallest I would use) is rated at 0.22 AH. A nano amp for a year is about 8 uA hours a year. So 30 na for 20 years is

Re: [time-nuts] Ultra low power RTC

On Tue, 6 Mar 2018 21:57:32 -0500 Bob kb8tq wrote: > Assuming you are going to run it off a battery. What’s the self discharge > rate on a reasonable battery? With supply currents below 100nA you can assume that you are likely to be limited by the self-discharge using coin sized

[time-nuts] Ultra low power RTC

Probably 20+ years for a lithium coin cell... basically the shelf life of the cell. I have a card of 24 year old CR-2032's that are still above 3V, and no sign of leakage. BTW, never handle a coin cell (particularly in watch applications) with your fingers... your grubby fingerprints are

Re: [time-nuts] Ultra low power RTC

Hi Assuming you are going to run it off a battery. What’s the self discharge rate on a reasonable battery? Bob > On Mar 6, 2018, at 8:34 PM, Attila Kinali wrote: > > On Tue, 6 Mar 2018 22:59:34 + > Mark Sims wrote: > >> Sparkfun is selling an

Re: [time-nuts] Ultra low power RTC

On Tue, 6 Mar 2018 22:59:34 + Mark Sims wrote: > Sparkfun is selling an interesting RTC clock chip board. > It draws 22 nA. It has a rather novel clock generator... > a tuning fork crystal disciplines an RC oscillator every few minutes. > They claim 3 minutes per year

Re: [time-nuts] Ultra low power RTC

I would have thought better. I built a nixie clock from Tubeclocks.com . Granted it is in a pretty constant temperature, but I doubt that clock varies less than 3 seconds per year. Peter, the designer, sent me some code that takes a 1PPS but I never got it running

[time-nuts] Ultra low power RTC

Sparkfun is selling an interesting RTC clock chip board. It draws 22 nA. It has a rather novel clock generator... a tuning fork crystal disciplines an RC oscillator every few minutes. They claim 3 minutes per year drift. https://www.sparkfun.com/products/14642