Buck step down convertor uses a lot of power?

If it drops 0.2V/day, it'll drop 6V in 30 days, and it won't last a year. How about you connect up your multimeter and find out exactly how much current your clock takes? If it's too low to see easily, set the meter to 200mV and measure across a resistor.

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 Thanks, 
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Reply to
Winfield Hill
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9.6 milliamps

Andy

Reply to
AK

Is that how much current your clock draws or how much the contraption you are powering your clock from is drawing? The typical current consumption for an LCD atomic clock is somewhere around 100uA or less.

They should last about two years on a fresh pair of AA batteries!

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Regards, 
Martin Brown
Reply to
Martin Brown

If you used a R&Z supply consuming 12mA, that would eat

12mA x 24 = 288mAh/day so would run about 4 days per Ah of battery capacity. Of course discharging the battery below 50% will hasten its demise. A suitable switched mode regulator should get several times that long, but it still doesn't sound like it would survive the year. Lead acids just aren't a good choice for clocks.

NT

Reply to
tabbypurr

Comsumption of the clock. And it's a custom contraption.

:-)

The clock loses accuracy if voltage gets below 2.9.

As you can see here, the clock has a large LED display.

"

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"

It has to draw a whole lot more than 100 ua.

Reply to
AK

Thanks. I will probably go back to the AA source.

Andy

Reply to
AK

It looks like a fairly standard large display LCD unit to me. You should be able to find one that will last a couple of years on a pair of AA cells. Some will even support external temperature sensors as well.

??? Its an atomic clock - it should reset itself daily if it drifts even slightly. A quartz xtal clock will typically be good to a few tens of seconds a month drift disciplined by an off the air MSF signal it will stay within fractions of a second. Mine all keep good time even on low battery but the display eventually becomes too low contrast to read!

That is an LCD display. It really shouldn't draw that much current unless you have the backlight stuck on permanently.

It really shouldn't.

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Regards, 
Martin Brown
Reply to
Martin Brown

For dry cell power it should work down to 1V per cell will it run from 5V? can you give it 3 cells in series?

For an non-matrix LCD display with a slow update rate 0.1 mA sounds fine

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Reply to
Jasen Betts

Ok but that was a miscalculation, due to the down converter. When you can find another converter (see other replies) that uses less current ("quiescent current" is what you look for) it could be an option to use that battery. Else I would go for a new battery with the correct voltage and more capacity, like a pair of D alkaline cells or a larger Lithium cell.

Reply to
Rob

Funny, every one I've had used a single AA battery. Can't say what the current is but I only expect them to run a year. Never actually checked.

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Reply to
gnuarm.deletethisbit

It is obviously possible to run them on a single cell just like LCD watches do but many of them do use a pair of AA batteries. The important point here is that no MSF clock of modern design should be drawing 10mA.

LCDs can be a bit dim on a single cell voltage unless you draw a bit more current to run them from a voltage doubler.

The first one I ever built in the 1970's using an NE567 tone decoder did draw ~10mA but using discrete components and it had no display at all.

These days almost all of them are a standard receiver module, decode display module and an LCD display. The only clever bit is how they discipline the local crystal oscillator and so how often they have to turn on the receiver. Cheap and cheerful ones run it continuously. eg.

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Takes about 50uA and the display module is about the same.

The really smart ones tune the seconds divider for the 32kHz clock in fractional pulses so that the local clock second is phase locked to MSF and it predicts how long to allow it to free run before forcing synchronisation again. Most measure temperature, pressure and predict the phase of the moon these days for good measure.

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Regards, 
Martin Brown
Reply to
Martin Brown

I decided to look at the LCD in the clock.

When I took the board apart from the case, there was no longer anything displaying. After reattaching it, the display came back on with the current time. Apparently, the board needs physical contact with the display?

Andy Andy

Reply to
AK

There was no receiver module like what your link shows.

I now wonder if I got a "fake" atomic clock.

:-)

Andy

Reply to
AK

t
.
d

In the United States, the signals received by radio controlled clocks origi nate from NIST Radio Station WWVB, which is located near Fort Collins, Colo rado. WWVB broadcasts on a frequency of 60 kHz. Your radio controlled clock actually has a miniature radio receiver inside, which is permanently tuned to receive the 60 kHz signal.

Reply to
AK

Mass produced they may just go with the bare chip but they will certainly have the crystals (or ceramic) filters if it is genuine.

Was there a coil on a ferrite rod in it? If there was then following the leads from that should find a blob like preamp IC and 60kHz and 77KhZ xtals. If not then it seems your atomic clock isn't.

There will also probably be a 32768Hz watch xtal as well.

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Regards, 
Martin Brown
Reply to
Martin Brown

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