This is part of a project I have been playing with on and off for the last 9 months. It is similar in concept to a reverse geocaching box but with cooler locking mechanism. I have always appreciated the giant vault door bolt mechanisms and figured designing a laser cut version controlled by a servo would be an interesting learning exercise.
To accomplish the desired effect I had to solve a fairly simple geometry problem for the linkage mechanism. I figured this might be of use to someone else or my future self so I will walk through the derivation of the basic equations for finding functional linkage lengths.
I am in the middle of working on a project that relies heavily on the ability to select random items from an Amazon Web Services SimpleDB domain. A little bit of google-fu turned up an answer to a post over at Stack Overflow which described Amazons recommended approach. A really rough psuedo-code implementation looks like this:
The algorithm stores a randomizer field with a random value on all of the items; when you need a row, generate another random value and select the first item whose randomizer attribute is less than this new random value. Unfortunately this approach is broken.
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