Sealed/semi-hermetic packaging

Op Sun, 26 Jun 2011 19:11:01 +0200 schreef Hans-Bernhard Br=F6ker =

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Don't tell me that all the electric toothbrushes you've ever seen had =

power connectors.

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What about burn marks on my table?

er =

Your mobile phone has a power connector, no?

Unless there is a secret way to mechanically "unlock" the device.

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Or a constraint on maximum drop height.

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Actually, the electric toothbrush I used as a kid had two

*contacts*. The bottom of the toothbrush was one (like the "-" terminal of a "battery") and, located about two inches above this (that 2 inches being how far the toothbrush "sat" in the charger base) was another, *wider* "ring" that contacted a surface on the top of the charger.

(I think the actual battery in the toothbrush was located in this

2 inch section as well -- so this may have just been convenient)

This is similar to my thinking re: having the two halves of the device case represent the two "contacts" (for power). Sure, if you examine the device, it becomes obvious that this is, indeed, the case. But, this "connector" doesn't have the typical characteristics of a "connector" -- its "sealed", doesn't create a place for stuff to "accumulate", doesn't have "pins" that are likely to bend/break off (or become clogged), etc.

And, there are really generous constraints on *alignment*! (unlike traditional connectors that must be mated "deliberately*")

I think "secrets" are a thing of the past given the ease with which people can share that information, nowadays. E.g., could you imagine how successful the original telephone "calling card" scheme would be nowadays???

ROTFLMFAO!

[...]

Just to be clear, the electric toothbrush I use (I'm a recent convert) has no -- count'em, zero -- external electrical contacts.

The "base unit" with the wall-plug that the... what? "drive unit"? sits on to recharge has a plastic post, and there are coils inside the base unit post and inside the bottom of the "drive unit". These two coils form a transformer, coupling the AC from the base unit into the coil inside the "drive unit", where it is presumably rectified, limited, and fed into the cell/battery inside the "drive unit".

So no contacts of any kind. Nada.

If you're already aware of all this, please feel free to ignore the above paragraph. Your comments introduced the possibility that you did not have experience with this type of charging system, hence my comments.

But... that brings up another possibility: _capacitive_ coupling. Instead of bringing actual metal onto the device surface, why not just have "contact areas" covered with insulation (e.g. embedded plastic squares with metal plates behind them) and capacitively couple into "the box"? Data would go in and out using the same techniques one would use for inductive coupling.

I should warn you that my comments are all purely theoretical. I have never built a system using this approach, and, in particular, I've never tried providing several watts (say 5V/400mA) using either method, so I can't comment on efficiency.

End of distraction. Time to go do some Real Work.

Frank

--
    "A man should never be ashamed to own that he has been in the
     wrong, which is but saying, in other words, that he is wiser
     today than yesterday."  -- Jonathan Swift

Yes. The toothbrush *I* was refering to was made in the 1960's :>

I think there are also "charging mats" now sold to help you charge your "portable devices" without plugging them in (though I am not sure I see the value of *attaching* the pickup coil to the device just to avoid attaching the charger!)

:>

I think you'd be hard pressed to get power across those plates efficiently.

I thought *work* was the distraction??

Sorry, I just couldn't leave this unanswered.

Antonio Prohias was a Cuban cartoonist who drew the "Spy vs. Spy" comic strip for MAD magazine. Words can't do the strip justice, so I'll just point you at a few samples:

Spy vs. Spy Headquarters: IMAGES

and, for general information:

Enjoy!

Frank

--
   "We are what we repeatedly do.  Excellence, then, is not
    an art, but a habit."    -- Aristotle

Ah, 'nuff said!

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I didn't know which post to reply to so, I picked this one.

The 'coasters' that they give you at restaurants while waiting for a table are somewhat water-resistant, are wireless receivers, and are recharged without opening. They have contacts on the outside as mentioned already. Sorta consumer level device I guess.

Also, a transparent window might be used to solar/light recharge such a device.

Some type of moving pendulum could operate a generator - likely through some clockwork mechanisms. That however seems unduly heavy and complex.

Grrrr... you could've trimmed some of the previous postings! :>

I had to think about this for a while: "coasters", "restaurants"... all I could think of was a *real* coaster onto which you would set a beverage.

[I don't frequent restaurants; when I do, it's usually with an RSVP; and the restaurants around here aren't likely to use this sort of technology (can you spell "boondocks"?)]

My previous experience with those devices -- as "fobs" -- comes to the rescue, though. Perhaps they are now repackaged in a flatter shape?

Yes, the sort of thing I was thinking about. Though their charge-to-use ratio is much different than I would be looking at. I.e., I imagine those sit in your hands for a short while (tens of minutes) and then get thrown back on a charger? Even if the establishment underbought the necessary quantity, I imagine even a rechargeable coin cell could handle their needs for a rather long time -- at least until the end of dinner service (at which point, they would sit on the charger for HOURS)

Yes, but my (limited) understanding of photovoltaics suggests that a large window/panel would be needed and/or a long charging period. I have a small "cell phone charger" (maybe 12 sq in) that takes a considerable time to charge a phone -- even in bright light.

Sort of like a self-winding watch?

It's a short range pager. The common "coaster" design is illustrated at:

These have unique IDs, and the front desk pages you when your table is ready, and the device blinks and vibrates. Some designs, including the "coaster" design, are stackable (in the link you can see the upper set of contacts), and a whole pile of them can be stacked on a single charger station (see illustration on third page of link).

In that application small size is not too appealing, they'd probably tend to wander off even more than they do. OTOH, rugged (and water/wine/beer-proof) is clearly a requirement.

I've seen applications where power is fed in via optic fibre. The light is converted used in circuitry which then communicates data back out via the fibre.

I cannot remember the application - it was a experimental physics apparatus of some kind.

A similar system has been used to measure the current in high voltage lines. The current transformer is sitting on the phase voltage (hundreds of kV), the measurement electronics is powered by a laser on the ground potential through a fiber and solar cell. An other fiber is used to return the actual measurement back to ground potential.

Understood.

Ah, these are considerably larger than the device I used. It was more like a "fob" (like a remote control for a garage door opener or keyless ignition on a car) but with a large (rigid plastic) "flag" attached.

The flag served as a convenient place for the establishment to advertise their name (just in case you forget what you are waiting to *eat*! :< ) *and*, to make it hard for you to carelessly put the device in your pocket and later forget it is there!

The device I used just beeped. I.e., it needed next to *no* power to operate. By contrast, all those LEDs and that vibrator/motor probably *need* the power that those larger cells can deliver (ref: the above URL)

OK.

Understood. So, they've opted for "contact" power transfer.

And, they appear not to have a need to make them tamperproof (I suspect they are relatively low cost).

I'd also wager they are water *resistant* but not water *proof*? (i.e., drop one into a pitcher of beer...)

They do come in a variety of shapes and sizes. Space for an ad and a guaranteed return postage notice seem pretty standard. And having the name of the resturaunt is not that silly - many of these have several hundred feet range, and you can wander around the neighbooring shops while you wait. And then there's often more than one restaurant in the area.

Bright lights and strong vibration - often necessary if you're having a drink in a noisy bar before dinner, or you've put the thing in your pocket.

Never tried. I suspect dunking one in a pitcher would have an adverse impact on getting seated for dinner... ;-)

The ones I've seen seem to be reasonably well sealed, although probably not against any serious immersion. LRS (one of the big vendors) makes a separate line that they call waterproof.

Ah, good point.

I think these things were deliberately made "impossible to pocket". Sort of like going to a gas/service station, asking to use the rest room and being handed the key -- chained to a sizable length of 2x4! (i.e., you will not *lose* this *or* walk off with it!)

Though I can't imagine them being stolen -- the waitress wouldn't seat you without surrendering it! :-/

Not to mention rendering the beer undrinkable! (I guess that depends on your current state of inebriation...)

So, they must have anticipated this need if they deliberately made a product to address it...

I dunno why my post yesterday didn't show-up. If you guys see it, sry for the repost.

I just wanted tomention that there is a 'consumer' device that meets some of the original criteria. The 'coasters' often given to guests waiting to be seated at restaurants. They have contacts for recharging, are somewhat water-resistant, seem robust and receive wireless communication.

Also, a transparent window might allow for solar/light recharging as well as infrred/optical data transfer. There may also be water resistant TOS-link bulkhead connectors, or similar, available.

One 'consumer'-ish device which meets some of the original requirements is the 'coaster' handed out to restaurant guests waiting for seating. They seem robust, water resistant, recive wireless communication and are charged in a stack thru metal studs.

And a device might be able to solar/light charge thru a transparent window. Optical communication might also take place thru the window. There may also be TOS-link or other optical bulkhead connectors that would maintain a watertight seal.

wow - what is up with the slow postings? 3 days? sorry for all the repetition guys.

What's up is that you're posting via what's easily the single daftest USENET server in the world: googlegroups. Looks like they've started this year's round of the "Google groups' next top screw-up". Last season, the winning entry was "Threads? Nobody needs 'em", the one before that it was "Quotes are for wussies". Looks like "You thought yesterday's news was stale? Try three days!" is the winner this time round. Not to mention "We're Google! We're BIG! So of course most of the SPAM in USENET should be originating from _us_!", which has been their show's running gag for years now.

But there's also something wrong here that's not at all Google's fault: for that message I just replied to, you full-quoted your entire previous article, for no reason whatsoever, That's two lines of original text, hidden behind a 60 lines of irrelevant quote. So please, next time, could you think about snipping your quoted material to the pertinent bits? TIA.

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