Help with backup circuit for digital clock

[KeepItSimpleStupid]

spec needs a pat on the back once in a while. He's new here.

BTW: I'm following the thread but I would like a 60 Hz backup unit which would switch from power line to external oscillator. You get better long time accuracy using the power grid. Trouble is not even on the list of projects that needs doing. I did have a MM5369 (color burst to 60 Hz) and a 9V battery, but it never worked some 35 years ago. I know more now.

Here's the clock: https://www.electro-tech-online.com/threads/screwwwwss.147698/#post-1258711 Not much room to work either, The full "Blueprint" SHOULD be under a rug somewhere.

 

[the_engineeer]

That's another good idea, this little retro clock idea of mine really ballooned into something truly awesome!

Please keep in mind though that I live in Sweden - we have 50Hz power lines... To make this an "universal" clock module there should be a jumper or a dip switch where you can choose 50 or 60 Hz mains.

And this circuit should perhaps be an optional module for the presumptive builder, one of my original project ideas was to NOT have a built in power supply but simply be able to power it from any 5V/1A source - but don't get me wrong, it is a perfect addon!

...and while we're at it, why don't a make a GPS time input module for the really accurate min's and sec's?

 

[the_engineeer]

Hy again eng
To fit separate Xtal oscillator:

(1) Remove all components from CD4060 pins 10 and 11
(2) Connect CD4060 pin 11 (reset) to 0V
(3) Connect clock module pin 1 (output) to CD4060 pin 10.
(4) Connect clock module pin 11 (reset) to 0V
(5) Connect clock module pin 3 (GND) to 0V
(6) Connect clock module pin 4 (VDD) to back-up battery positive

spec

Wow, that simple?!
And that mod even reduces the number of components, perfect!

 

[spec]

Wow, that simple?!
And that mod even reduces the number of components, perfect!

Glad you are pleased: I was surprised that a clock module was so cheap and consumed so little power.

(just leave a message asking the moderators to delete any erroneous posts- they are pretty efficient on ETO and it wont be long before they are gone)

spec

 

[KeepItSimpleStupid]

(just leave a message asking the moderators to delete any erroneous posts- they are pretty efficient on ETO and it wont be long before they are gone)

e.g. Use the "Report" button and ask the mods to delete the post presumably after you have edited edited to something like <self deleted> or <double post> etc.

 

[the_engineeer]

I've made the PCB layouts now, still have to go through them a couple times more and perhaps make a prototype of the "UPS" module but I managed to reach one of my project goals - to fit everything between the display legs

 

[spec]

I've made the PCB layouts now, still have to go through them a couple times more and perhaps make a prototype of the "UPS" module but I managed to reach one of my project goals - to fit everything between the display legs

View attachment 98787

Pretty neat eng, especially as you are just starting with the ECAD package.

spec

 

[the_engineeer]

Thanks!
BTW, I found a much smaller LiIon battery with almost the same mAh - 100 vs 120 for the LIR2450:

https://www.varta-microbattery.com/applications/mb_data/documents/data_sheets/DS63165.pdf

 

[spec]

Thanks!
BTW, I found a much smaller LiIon battery with almost the same mAh - 100 vs 120 for the LIR2450:

https://www.varta-microbattery.com/applications/mb_data/documents/data_sheets/DS63165.pdf

Brilliant

spec

 

[the_engineeer]

Hy engineer, this is what I have come up with for the revised clock backup battery circuit.
Once again, the parts are hellish expensive.

spec

ISSUE 3 of 2016_04_05

View attachment 98662
​

DATA SHEETS & SOURCES
(1) Comparator & Voltage Reference, Texas Instruments TLV3012
https://www.ti.com/lit/ds/symlink/tlv3011.pdf
https://uk.rs-online.com/web/p/comp...3743D544C5633303131267374613D544C563330313126
(2) LiIon battery 120mA/hr, Multicomponents LIR2450
https://www.farnell.com/datasheets/1475807.pdf
https://uk.farnell.com/multicomp/lir2450/coin-cell-lithium-120mah-3-6v/dp/2009025?MER=BN-2009025
(3) Complimentary MOSFETS, NXP PMCPB5530X
**broken link removed**
https://uk.farnell.com/nxp/pmcpb553...id|99301984448|kword|pmcpb5530x|match|p|plid|

NOTES
(1) The above circuit is optimized for a long battery life. Charging current averages around 20mA which represents 20ma/120mAh = 17% of C. But the charging current tails off as the final float voltage of 4V is approached. The discharge current is around 340uA, to keep the oscillator and counters working, and this current is terminated when the battery voltage drops to 3V. All these factors are good for maximizing battery life. Here is an article about extending LiIon battery life: **broken link removed**
(2) The two spare NMOSFETs are only there because they come in the same case as the PMOSFETS.
(3) The NXP PMOSFETs type PMV48 (SOT23) can be used in place of the PMOSFETs in the NXP PMCPB5530X (SOT1118) if the case style is preferred for hand soldering.

ERRATA

Long time no see...
I've been busy doing actual salary-paying work, but now I have a little free time again to continue with this project.
Regarding R3 and R6, it seems that 0603 resistors with 1.42 / 2.23 MOhms are very hard to find. Do you think that 1.43 and 2.21 will suffice?
I'd rather not go up in package size for these, if it's not absolutely necessary.

 

[audioguru]

The Varta Li-Ion coin cell withstands their overcharge test with 12V at 300mA for 12 hours and it doesn't explode nor catch on fire!

 

[spec]

Long time no see...
I've been busy doing actual salary-paying work, but now I have a little free time again to continue with this project.
Regarding R3 and R6, it seems that 0603 resistors with 1.42 / 2.23 MOhms are very hard to find. Do you think that 1.43 and 2.21 will suffice?
I'd rather not go up in package size for these, if it's not absolutely necessary.

Hi engineer,

Nice to see you back.

Being paid for work is always handy.

The resistor values that you want to use will be fine.

spec