March 2012 Archives

Well, no, its not a Transformer, but it does have an inductor!

Everynow and then you get an email out of the blue, which just makes you happy:

"Please construct submersible sound target to use for Pajama Shark training"

Well, it was exciting because the application is fun!  The device needed to be water-proof, and operate below a range of 375hz.  (this link explains why!)  

The sealed pvc staff itself contains an Atmel attiny13 and a utility 2 watt audio amp.  Previous incarnations of this device utilized a cd 4093, and then an arduino for the pulse trains.  However, this version is intended for pcb's.  Therefore, we used this opportunity to prototype a utility amplifier/function generator with all the benefits of programmable mcu control!  The output of the device is an induction driver, or "exciter."  Essentially, we're using the PVC pipe as our speaker.  Once ready to go, the capsule was filled with desiccant and bubble packing to keep everything dry and stable.

We'll see how well the sharks salivate!

Here you can see the driver attached to the end of the tube capsule:

The wire-wrapped side of the proto:

And a shot of the toggle switch (don't mind the excess silicone!)

There are now two of these devices in use, and both are based on the PCB version of the prototype!  The sharks were recently (late july 2012) released on to live display, and have successfully associated the audio tone with a midnight snack :)  Here's a a bit of coverage from local ktvu.

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Light to Frequency Generator Update

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i heart square waves!

Sometime ago I posted code and a schematic for the LTF Generator.  Well, here's the board for those interested!  Perhaps I'll upload a video, and attach a link for batchpcb should there be enough interest...As a recap, this unit takes data from two tls230r light to frequency converters, and uses an arduino to create simple syncopation, outputting on a standard headphone jack.

Although, if i get around to it, i may just pair it all down to the essentials: boot the arduino for an attiny, throw in a power amp, and reduce the size threefold.  I should do that right now. 

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national engineering day 2012

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It's never to early to start STEM!

In lieu of a proper 7 days, National Engineering week was condensed into one saturday at the California Academy of Sciences.  Children and adults were exposed to the fundamentals of structure, load balancing, buoyancy, aerodynamics, and electronics-- all via hands on stations peopled by interns.  Except for my table :)

A couple robots, some fancy hacks and transmitted video were used to get interests going.  Then a step-by-step explanation on the "how" of a transistor & the concept of a positive feedback loop (detailed in the cds transistor candle post).  Most groups would spend a solid amount of time at the table, either encouraged by the robots, or by genuine interest in the transistor explanation.

Of the many questions that were asked of me, at least two could have had better repsponses:

Q:  What's a good book to learn C?  

A:  The internet, but if you really need a book o'reilly is a good start.  What's most important is the discipline of learning a programming language, and, how you apply it.  You can code C strictly for computing i.e. a program which converts celsius to fahrenheit, or go a little further and program a microcontroller device which takes actual temperature readings.  Obviously the "device" option takes more effort, but its more hands on.  And learning how to manipulate data across applications, from input (temp reading), to computation (too hot?), to output (close blinds & send email) is important.  Also fun!

Q:  How did you learn how to solder?

A:  By failing at it constantly.  But the best advice I can give is that your soldering can only be as good as your soldering iron.  Learning with a cheapo pen iron is masochistic, as those units poorly regulate temperature, and tend to have lazy tips.  A solid $50 iron makes everything a lot easier (but always remember to frequently tin the tip and keep it cool when not in use!)  If your tip is hot but solder won't stick to it, get another tip!

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