Thursday, September 20, 2012

I try to get out, but they just pull me back in...

The FSAE team wanted to resurrect the 2012 failcar to show off during Cooper Union's annual Fall Festival as a way to lure in unsuspecting freshmen to join the team. One of the major problems in realizing that dream is that the power distribution on the car utterly sucked and probably doesn't work anymore. So, like any respectable engineer, I decided that I could make a new system from scratch that would be better in every way possible. Since I'm not actively participating this year (wait, I guess this is the first time I mentioned that?), I also decided that this project would be a good segue for the next person in charge of the engine and electrical subsystems.

Here is the product of about three days of work:
The schematic. Ain't it pretty? I taught my protégé the fine art of mitering everything so that it looks professional. Ignore the crossed wires though...
Here's the board. The huge traces are because it's rated for automotive things -- 15A pumps, 15A fans, etc. The big rectangular blocks at the sides are kickass solderable lug terminals. The connector at the bottom is a 35-pin right angle ampseal connector.

Since everything had to get done in less than two weeks (and really in the last three days...), we milled the board in-house on 1/2 oz one-sided copper clad using a 1/32" endmill, which is why the trace clearances are so big on the board. I can't decide if this is a stupid and abusive way to use our expensive CNC mill or only just stupid. There are a couple of designed-in flywires on the board since there was literally no way to put more fat traces on the top layer.

Actual board pictures are forthcoming once I get off my butt and take them. The amount of solder I laid on the traces is amusingly stupendous.

Here are the pictures:
The copper side of the board. Look at those huge blobs of solder! The flywires  are some conduction paths that wouldn't fit on the board. The rectangular bits poking out on the right are the lug slots.

Topside. Looks pretty neat...

Tall, dark, and handsome. Enjoys long walks on the beach and switching motor loads.

Tuesday, September 4, 2012

Equalizer... the stereo one octave edition?

I'm still in GA for a few hours until my flight for NYC leaves, so I spent a few hours reworking my ghetto equalizer. Since more features are always better (amirite guise?), I've changed the design from a mono five band eq to a a stereo eight band eq -- pretty much the threshold at which the thing actually becomes useful instead of a toy.

I changed the design to use the Dangerous Prototypes Sick of Beige PCB profile template because it's more thought out than the mess of arbitrarily placed standoff holes that I had before. The board is also supposedly more "aesthetically pleasing" because the aspect ratio is the Golden Ratio. I personally think that that's a load of garbage, but hey, if anything can make this even more beautiful than I plan on making it, why not? Anyway, the board currently looks like this:

I don't have nearly half the components placed and everything is just in a big blob right now, but... ROUNDED EDGES~!

I'm still sticking to the super awesome OPA1644 opamps, graciously and unknowingly sponsored by TI through their sample program. I'm using the TSSOP packaging this time instead of SOIC. TSSOP is a surface mounted device packaging standard, and SOIC is another. The acronyms are typical irrelevant nonsense, so have this picture instead:

A scaled up picture of SOIC vs TSSOP.
Yeah, this board is basically going to be awesome.

Saturday, September 1, 2012


A few weeks ago, my friend Xo invited me to build a robot at the GT Invention Studio for the robot battle competition at Dragon*Con. Since I have more money than sense, I immediately accepted his offer and bought a roundtrip ticket to Georgia.

My stay in Georgia was only going to be a week, so I knew that I had to come up with a simple and robust design since I wouldn't have any time to do any fancy machining or even time to properly debug and battle test my bot. I whipped together a wedge in solidworks:

...not far from the robot's actual geometry
But more seriously, I did design this wedge:

The design consists of two motors attached to gearboxes that are wrapped in a steel cage, and a top steel sheet that has two bends in it. The wedges in the initial design are symmetric. The design is about 3.1 pounds, which is slightly over the 3 lb weight limit of the 'beetle' category I am going to compete in. The design is strong, stiff, and most importantly, very easy to manufacture on a waterjet, a cool little machine that the guys at GT have.

So, anyway, here's the product of about four days of almost nonstop design and fabrication work:

I christen thee "Critical Space Item." May you rip other robots to shreds and achieve great victory... The dings are some battle testing from facing the bot off against a 12 lb robot...

The top shell is the only change from the original design: instead of a symmetric wedge, the wedge on the front is at about a thirty degree angle relative to horizontal and it also has compound bends on the sides to deflect attacks on the wheels. The back looks like this:

GT seems to have an unhealthy fascination with yellowjackets...
The holes all over the shell are to remove unnecessary weight and make it go fast. The slots in the front of the bot are filled with button head screws to make the robot front-heavy and less jittery when moving. It's only somewhat effective; the bot is a skittery crackhead when it comes to turning and runs at 15+ MPH. The bumpers on the wheels are a lame attempt to deflect rear attacks; they tend to bend in practice.

The competition is tomorrow. I hope my bot doesn't get totally destroyed because I'd like to use it as a Roomba back in the office...