The great mystery - not TB!

While waiting for an update, treg release, and general release, I thought I might as well bring up something that has been a mystery to me for many years.

I have a digital scale. Nothing fancy. The digital readout is like many watches - gray background and the numbers show up in black.

In the picture above, the background doesn’t look gray, but that must be the lighting.

While I’m not sure exactly how long I’ve had this scale, I brought it to Hawaii with me, which would be just over 18 years ago. And I had it for years before that, but I’m not sure how much I can pin it down. I know I bought it at my prior job before moving, but that covers a 9 year period. I’d say most likely it would be 3-7 years before moving here. So it must be at least 21 years old.

Here’s the thing. I would assume it must have a battery in it someplace. On the bottom, it does say, “No battery to replace”, but I always assumed that mean it just wasn’t user accessible.

Anyway, the mystery is, how on earth does this thing keep working for 21-25 years? I use it almost every day so it isn’t like it is sitting around unused!

A couple pictures of the bottom, in case that helps figure this out:

And a closeup of the text:

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I would presume it operates by using the compressive force of someone standing on the scale to generate a small amount of energy which is then stored for short term power usage in a capacitor.

A more modern version of this can be seen here:

Battery Free Automatic Power Generated Digital Bathroom Body Weight Scale by Red Rock

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I guess that could be the case. Just didn’t expect anything to last so long!

Also, I don’t know how long a capacitor can hold a charge, but to operate the scale, you first have to tap it and wait until it sets to zero (as seen on the picture). You don’t have to do much of a tap to activate that step, so I wouldn’t think that tap would create enough energy to charge it up to light up those zeros. So it would have to come from a prior moment, which would normally be a different day, to store up enough energy and retain it. I’ve gone on trips of 2.5 weeks and, when I first used the scale when I got back, it worked just fine. So any capacitor would have to be holding energy for quite awhile. But then, I don’t know a lot about capacitors, other than they can hold some energy. How efficiently and for how long, I don’t know.

The one in your link seems to be charged at the moment you press what looks like a button down a good distance. So the charge wouldn’t have to last very long. The tap on mine barely moves anything at all!

You can test that theory by putting the minimum weight on the scale that will register (ie a book) if it still powers on after, say 100 tries, it’s likely got a primary cell instead of a generation source.

A lithium battery typically has a 10 year shelf life. I suppose under special circumstances (and using a giant battery) 20 or 25 years might be possible.

Other battery sources are also possible but we are getting into the exotic range here: atomic batteries. Probably too expensive for a consumer scale. Then again ionizing smoke detectors have Americium isotopes as the beta source.

May be a long time before I take the time to run that test! :slight_smile:

But if it is generated, would be cool if the TB could do such a thing (in version 2!).

I certainly type hard and loud enough to generate all the power needed to keep my TB up and running.

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I wonder if it’s technically possible to generate enough piezoelectric current from typing on the TextBlade to extend the battery life.

It seems that the increased resistance to key movement might increase the RSI problems.

But would it require more resistance? If I understand prior comments from WT, they can adjust the pressure needed. So if this system did add resistance, perhaps they could reduce the normal resistance to end up the same.

Let’s not give them any more ideas until v1 gets released!

I thought I read somewhere they can considered this, but either the impact was negligible, or too complicated and costly (the original usage as a mobile keyboard was an estimated month usage), or, like you said, lower on the priority list awaiting a future version.