Atomic CLock with pure 120v ac?

For flexibility of placement, quartz wall clocks have run on batteries for many years. Having a visible power cable is ugly.

Radio controlled clocks have inherited this design requirement unfortunately.

USB Power adaptors are pretty small, some not that larger than a plug. Have a look at iPod or mobile phone accessories. If necessary adjust the voltage downwards with a suitable series regulator. Single transistor, resistor, capacitor and a zener should do it.

--
Adrian C

This Atomic Clock works off either AC or DC:

tandard/5071A/

at

Ah. You want a WWV receiver clock.

Another quite valid reason for "atomic" clocks being run from batteries is that the clocks query the time sources for the exact time during the night, when signal propagation is best. If the clock loses power during the day, it needs to reset itself when power is restored, but probably won't be able to receive a signal strong enough to be able to make a correction of the time until late at night. Being on battery power solves this problem by never having a loss of power except when the batteries finally die.

--
Dave M
A woman has the last word in any argument. Anything a man says after
that is the beginning of a new argument.

Demand for this product is low. Most people prefer freedom of placement over annual battery replacement. Clocks that project time on the ceiling usually have AC adapters to support the power demand. Mine were distributed by LaCrosse and Oregon Scientific. No idea of current catalog. and no adaptor? That's a problem on several fronts. Anything that plugs in the wall has an additional mountain of testing/certification, paperwork and development costs involved. If you purchase an approved/listed wall wart, all of those problems go away. Most vendors take that route.

(Online specs?) Much obliged.

that

BioStrategist

Bimbos]

If you don't want a backlight , how much HF electronic smog/ mains coupling is available these days in the average domestic situation. Enough to power LCD and short burst ULF receiver operation ?

Your question appears to be about Radio Clocks rather than Atomic Clocks, why not call it what it is?

(Private citizens tend not to own atomic clocks, they normally reside in laboratories, and atomic clocks are powered by mains electricity, not batteries, although there is likely to be an uninterruptable power supply associated with them.)

--
FatallyFlawed

Well, that is true sometimes, but I have had good results replacing the battery in the middle of the day. The clock normally resets just fine.

I am very seldom up in the middle of the night to replace the battery.

Bill

I think you mean WWVB 60KHz clocks. Atomic clocks are cesium and rubidium standards.

The problem is that consumer "atomic" clocks only update roughly once per day. The receiver turns on, usually in the middle of the night when 60KHz propagation is best, update, and turn off to conserve battery power. There are continuously operating WWVH receivers available, but not at consumer prices. The batteries also act as a UPS, allowing the clock to continue operating without waiting for night time for WWVB to update the clock.

Heath GC-1000 WWV receiver. I have one that I'm slowly rebuilding. Nifty and rather unique device.

They sell for about $230 on eBay. An unbuilt kit sold for $700.

I'm not sure what problem you're trying to solve, but if you don't like replacing a single AA battery every year, you might consider replacing it with a rechargeable battery and solar charger. These already exist:

For the retro effect, I suggest a wind up or hand crank type generator for charging the battery.

If that's too much effort, I suggest the atomic water clock:

Just add fresh water every 6 months.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Ummm... there are plenty of mere mortals that own cesium and rhubidium standards that drive test equipment and sometimes clocks. The 1 pps output from a GPS or cesium standard is quite useful for driving clocks.

Such atomic frequency standards are also available rather economically on eBay. For example: $86 for rubidium. (Note that rubidium is not really a primary standard but is good enough for most applications). Personally, I prefer a GPSDO (GPS diciplined oscillator) which is more accurate and draws somewhat less power: $158

As for requiring mains electricity, note that the power requirements for the miniature rubidium and cesium fountains makes it possible to operate from batteries. The unit above runs on 12V and burns 11 watts after stabilization. Last time I checked, the GPS satellites, which have internal Kernco cesium clocks, do not require a 20,000km extension cord.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Much obliged. I like the idea of solar, but I doubt it charges well enough. Tried solar clocks in 1985 and 1990 do dismay.

- = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist

---{Nothing herein constitutes advice. Everything fully disclaimed.}--- [Homeland Security means private firearms not lazy obstructive guards] [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

Solar works for me. I have a solar calculator, solar am/fm/sw emergency radio, solar powered calculator, solar camera battery charger, and various solar chargers. Note that not all of these work in the same way. For example, the solar calculator is an either/or proposition. It either runs on solar or silver-oxide battery. The battery is NOT charged by the solar cells.

The limiting factor is the battery type and the self discharge rate, not the solar chargers output. If you use NiMH batteries, which tend to self-discharge at a rather high rate, the solar charger is unlikely to keep up. NiCd are better, but not much. Lead acid are marginal. Supercaps suck. However, Li-Ion and LiPo batteries work quite well for such things.

If you want to play, you'll need a LiPo charger that will work with a solar cell. This is what I use:

Note that the LiPo battery is a nominal 3.7VDC. Fortunately, most "atomic" clocks run on two AAA batteries, which is close enough.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Can Americium be used to build an atomic clock? I understand a little about how cesium and rubidium atoms are used to build atomic clocks but since Americium is used in many smoke detectors wouldn't that be a great science fair project or a Maker Faire project? The world's first truly atomic wall clock? Of course, I suppose it could be argued that radium on clock hands qualify the clock as atomic if radioactivity is the only metric. Eric

Probably not. Anything that will vaporize at reasonable temperatures to form a "fountain" or produces an RF excited gas cell can be used. Americium-241 is solid and melts at about 2600C:

Compare with Cesium-133 boiling at 671C and Rubidium-87 at 688C:

Actually, it doesn't need to vaporize the entire contents to work.

100C is usually sufficient to create some usable gas. I just wanted to illustrate the relative difference in temperatures required.

Ummm... I suggest you read The Radioactive Boy Scout before proceeding.

It's closer than you might suspect. See:

It draws only 0.1 watts. I think it's based on Thallium-205, but I'm not sure. You don't want to know the price.

That reminds me. To vaporize radioactive materials into a gas is not exactly a safe thing to do. The slightest leak, and you've zapped the user. Triple seal the physics package will help, but there's always going to be someone with a can opener and a product liability attorney for a brother in law.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:

the 2300 mAH AA Everready NiMH(not pre-charged) that I bought at WalMart seem to not have a high discharge rate. I use them for my LED bicycle lighting system. the NiMH cells came with a "smart charger". I charge them maybe once a month.

they hold a charge a lot longer than the DeWalt 9.6V NiCd packs for my drill-driver.(and don't have the dendrite problem...) :-)

I also have some pre-charged,low self-discharge NiMH cells but they are only 2100 mAH.

I'm not saying that is the case for ALL NiMH cells..... but they -may- be improving on that self-discharge rate.

It also irks me that the NiMH cells in the stores don't list the mAH rating on the packages.

--
Jim Yanik
jyanik
at
localnet
dot com

To prevent AC line noise from drowning out the time signal?

All the clocks in my house are atomic clocks except for the one on the microwave and stove, and I never have to reset them except for battery changes. Read your owners manual. Battery change is done once a year on new years day. They do DST changes automatically. The only thing to reset is timezone.

With typical NiMH, I loose about 20% of charge in the first 24 hrs, and then about 1% per day. I've confirmed this with my own tinkering. After about 3 months, I typically have a half dead battery. It varies hugely with temperature:

With the LSD (low self discharge) NiMH batteries, I find that it loses about 10% on the first day, and then very slowly drifts toward about

75% capacity within about 3 months, and then sits there forever. However, such batteries also have less capacity than typical NiMH cells, so you end up with about the same capacity after a few months.

The problem with using such batteries is that the clock needs to be able to operate over a long period of time. It could be designed to operate with a battery permanently at 50% capacity, but that would be a waste of money for the battery. Using LiIon would be cheaper and not waste any capacity.

However, LiIon and LiPo have another problem. They self deteriorate at full capacity and at high temperatures.

See Table 3. Therefore, Lithium batteries aren't going to work for the clock. I guess one needs to use the same approach as the smart meter vendors are doing. High capacity, non-rechargeable, seems to be the best.

My Skil something drill and NiCd packs are in my car, which tends to get rather warm. During the summer, I'll have a nearly dead battery pack from self-discharge in about a month. During the winter, the pack will probably last all winter.

Notice how all the specs are at 25C. Reality requires a higher test temperature.

Not a problem. All the specs are lies, but that's ok, because nobody really understands them. The capacity tests are usually an unrealistically low discharge rates resulting in inflated figures. I'll give Sanyo credit for using C/5 discharge rate, which is more realistic:

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Try the Sanyo Eneloop cells; they claim about 85% after a year of storage, and my experience using them in my camera confirms that.

Isaac

You didn't use your camera for a year?

Hint: Accelerated lifetime tests are usually done at elevated temperatures and for short periods. They are then extrapolated back to room temperatures and longer periods. The curves are well behaved and apply to all chemistries after the initial self-discharge.

The 3rd generation Eneloop claims 70% after 5 years. How to recognize which Eneloop generation: 1st gen - No crown icon 2nd gen - Crown icon near plus sign 3rd gen - Crown and metallic colored letters.

I have a set of Eneloop and they are better than ordinary NiMH for self discharge. However, when I counted how many pictures the camera (Canon S5-IS) would take before the charge indicator began to complain, I found that in the short term (about 2 weeks), the ordinary NiMH batteries took more pictures. In the long run, the Eneloop batteries did better. My undocumented wild guess(tm) is that the break even point is at about 2 months. That's because the initial (i.e. immediately after a full charge) for the ordinary NiMH battery is about 2200ma-hr, while the Eneloop are about 1900ma-hr.

This weekend (ham radio field day), I took about 30 photos with a set of no-name 2300ma-hr NiMh batteries when the charge indicator appeared. The batteries were charged about 4 months ago. I switched to a set of 1st generation Eneloop batteries, that I had charged about

7 months ago, and had previously shot about 100 photos. The charge indicator showed 50%. However, after another 50 photos, the charge indicator still showed 50% implying that there was plenty of capacity left. Yep, Eneloop are good batteries for cameras.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

+1

Jonesy