h a l f b a k e r yThe leaning tower of Piezo
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How much energy can be stored in a AA-size battery?
I'm guesstimating that the spring might take a force
of about 10N (1kg) to wind, and that the total travel
made by the key might be 1m, giving you 10J of
energy. |
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If the device draws 10mA @1.5V, that's 15mW of
power, meaning that it would run for 60 hours (or,
allowing for losses, maybe 10-20 hours) which is not
insignificant! |
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I can see survivalists going nuts over these. |
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"Aha!" says yer friendly, neighbourhood aerial bread braiser, "I can mfd this !"... but I can't 'cuz they're different... [+] <link> |
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Neet idea of you loose the keyhole and just have a
twisty portion that you turn like when you're taking
the twist top off of a bottle. |
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//Neet idea of you loose the keyhole and just have a twisty portion... |
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(suspects the good doctor has imbibed of the contents of said bottle..) |
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[Max-B] The linked article says the Trevor Bayliss wind-up battery gives 3V at 55-60mW for 40 minutes which is within an order of magnitude of orders of magnitude of what you were saying. |
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"AA" --why not also "AAA" and "C" and "D" cell-sizes? |
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The Energizer bunny is gonna be pissed. (+) |
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Yeah, yeah, you could make it last for hours, and it could be wound by twisting it... but I'm pretty sure it would be best if it needs a key, and only lasts a minute. |
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[Vernon] Haha, you're mad! |
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I love the thought of the teeny key. Now I'll need a wee bitty
key chain to keep it on. Wow. |
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I want a battery powered winding device to go with it. |
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Lots of prior art on this (links). |
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Why do all of these things use hand cranks, twisting
or shaking? What's needed is a pull cord similar to
the one used to start a lawn-mower. Design the
battery to come apart into two pieces to form
handles. Using a string allows a nice long power
stroke with much less hardware. Use fishing line for
the string, making it easy to replace when broken. |
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// All told you are looking at well less than
1/2,000th the capacity of a rechargeable. // |
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Which is fine for many applications. Many
measuring devices last for multiple years on a
single battery depending on how often they are
used. These might operate for a single use session
on a single winding. A wind-up battery won't die
of old age and start leaking. Of course many such
devices use coin cell batteries. Also, it would be
annoying to open the battery compartment every
time to wind them. Maybe that's the reason for
the smell key hole. Drill a matching hole through
the case and inset the key without opening the
battery compartment. |
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