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Project Graeae

Posted by jeremy on October 8, 2011

I saw Steve Hoefer's project Tacit in passing here, and without reading a thing about it, looking at any code or even the pinout diagram. decided that we could do it better. That's just how we roll. Ol' Steve was recently interviewed by CNN.  Good job, buddy!  I don't know if it's turning out "better" or not, but we're pretty happy with the results thus far.  Besides dropping one of the sensors (I tried two, but it just got confusing), we added a Mesmic 2125, changed the dual servos to a single vibe motor from Radio Shack, switched to a Sippino w/ a 328, and added a three color LED, a buzzer, and a momentary tactile switch.  While the last three things aren't yet functional, when they are, it will undoubtedly be cool.

As a side note, the vibration motor is hot-glued inside of a section of a bic pen case to keep it free-moving and clean.

The project name started out as ST-Hap (ess-tee hap), but too many people were mispronouncing it (sthap sounds like a new mastabratory euphamism). After not so much consideration, Graeae was born. Some people with a penchant for mythology or a morbid facination with Latin will recognize the name as that of the three "Grey Women" or "Stygian Witches".  The old hags had but one eye and one tooth to share between the three of them.  This portion of the project is the eye.  The tooth will come later.

So I started off with the worst proto board I've ever had the displeasure of soldering on.  The Radio Shack 276-158B.  Avoid them.  Since our sensor set was more limited, I didn't need the whole board.  I cut off one edge (A-I) and left the full length.  After playing Tetris with the parts for a while, I figured out that not every thing that I had picked out for the project was going to fit on it in a pretty manner.  Who knew.  


So I decided to put the 2125 underneath the Sippino.  The problem with the 2125's is that the pins on top are exposed.  If I were to set the tight little Sippino on top, something was sure to go wrong.  Clippy clippy, some black tape and some ShapeLock polymorph saved the day!  This stuff is super cool.  Everyone should have a big bag of it laying around.  Problem solved.




The other side sat nicely on the edge of the buzzer, so it was a double win for support.

Soldered everything together, using a pin header as a power distribution and grounding block....


....and voila!  That is one ugly solder job, no?

When I get some time, I'd like to add a voltage sensor that makes the buzzer beep when the battery is getting low, a light sensor (who doesn't think a blind person asking "Who turned out the lights?" wouldn't be funny?), and make the tri-color light blink when it gets dark.  Canes have conspicuity tape all over them for a reason.

The functionality is this:

There are three modes that are dictated by the accelerometer.  Flat, sideways, and at-rest.  Sideways, aka short-range mode, works just like a cane.  Hand in a relaxed position for typical sweeps. As the sensor finds a close object, the duty cycle, or stregth, of the vibration motor is inversley proportional to it's distance.  An object that is close will make it vibe harder than an object further away.  Flat mode, aka long-range mode, changes the maximum distance that makes the vibe motor actually come on.  It's more for getting the general size of a room and your position in relation to the walls and large objects.  Rest mode is just that.  When you are walking normally with your hand at your side, the motor doesn't respond at all until you lift your hand significantly and point it at something.  I just got irritated with it buzzing when I was just standing there, so that's where the accelerometer idea actually came from.

And of course CODE!!!!!!


We'll keep this updated as the rest of the features are added, so check back.


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