I’ve learned a bunch about making circuit boards at work recently, so I decided to re-do the ol’ strobe guitar tuner project from 3 or 4 years ago.  The original still works… sort of.  I have to power it from...

More like version 0.1, every part of it was bad in some way.  We did robotic self-tuning monochords—single-string musical instruments—last spring in the mechatronics class.  The students did pretty well. Most of their robots were designed along similar lines: they...

I originally wrote code for the MS5541C pressure sensor using bit banging, and described the result of my investigation in the previous log entry.  At the end I mentioned that the sensor’s weird digital interface is kind of like SPI,...

The MS5541C is kind of an oddball sensor, BUUUUUUUT it’s small, it can be used underwater (with appropriate waterproofing), it’s cheapish (~$30), and Digikey sells it. It’s a pain to get running though, because of its hardware interface (50 mil...

It’s pretty hard to get a watertight object out of our Makerbot Thing-O-Matic.  The walls of printed objects are pretty solid, but unexpectedly porous; even a thick block printed with 100% infill will allow water to penetrate it due to...

I tried a solenoid I scavenged from underwater valves on my 3D printed valve system and it didn’t work (duh).  It was just too weak.  The original valve spreads the force from the high-pressure side across a larger area, so...

I’m having trouble with the upper valve that will allow air to be released from the hull (thus decreasing buoyancy and giving some downward thrust).  I mean, I’m having trouble with everything, but that’s why I’m doing this, right?  Anyway,...

It turned out doing software UART was a terrible idea.  The processor is way too slow to support a reasonable baud rate.  I did figure out how to use a comparator though: the key phrase I was missing was “rail-to-rail.” ...

The range on the infrared channel, which I discussed in the last entry, is probably enough; but I’d like to increase it a bit.  With more range I can space modules farther apart if needed, and hopefully be able to...

Here’s how I’d like to communicate between modules in the AUV: This is how it works: For the transmitter I’m using a TSAL6100 infrared emitter.  The LED is rated to operate at 100 mA, which the 15 Ω resistor generates...

The hull is done for now.  As I mentioned before, I have some improvements in mind (mainly to get rid of the outer bolts), but it took about 34 hours to print all eight pieces and I’m not eager to...

I printed four copies of the semidemihemisphere and refined it a bit as I went.  Here’s the whole thing, including the hull that I covered in my last log entry.  The only difference in the hull is I removed the...