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.
This was a fun little LCD project I spent an afternoon putting together. It’s based on a whole family of single button obstacle avoidance games. In short you move your helicopter up and down to avoid obstacles, scoring points for the distance travelled before inevitably crashing.
Update: I have confirmed that the output is still well within the spontaneous emission range and I am doubtful I can build an exciter with enough power. The paper uses a 532 nm Nd:YAG laser with a 7ns pulse duration and samples were performed at energies of 1.6mJ and 3.7mJ. This means that their source had an approximate power output between 229kW and 529kW.
The principal behind the design is you suspend a bunch of reflective balls in a laser dye and shake them really fast so the balls behave as though they are suspended. The laser dye is then excited by an external source and by changing the vibration frequency you can filter out different wavelengths of laser light emitted by the dye.
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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