Wednesday, November 21, 2012

Bose Speakers!

About a month ago one of my professors invited me to be part of a speaker building seminar with Bose.  The purpose of this seminar was to expose us to the kind of stuff that Bose does, learn some basic acoustic theory and build some speakers!

The seminar was amazing, the guys from Bose explained some really cool features they put into their products. They showed us this "magic sound wand" which they could use to point at some location and make sounds seem like if it was coming from there. It was kinda spooky but awesome. We also learned a bunch about the use of crossover to give you better sound quality. One of the coolest things they showed was how they designed a new type of speaker cone which exhibits no parasitic harmonics under the audible range and thus was able to produce a pure note much better than a normal speaker cone. (I wish I had a video of this but they had a strobe going in the demo, so it was hard to film).

pink cone has parasitic modes, waffle cone (blue) gives you
 a much more pure note and no parasitics
bose dude holding the magic sound wand

The speaker building part was pretty fun too! We build two speaker cabinets out of PVC and MDF. At the end of the seminar we all put our speakers together and were able to play a 30 track piece in lobby 13!

speakers under construction


Sareena rudely interrupting my photo

Saturday, November 17, 2012

Tic Mag Toe v1.0

Hey guys!

As some of you know over the summer I became super interested in Magnetic Levitation. I started reading/learning about it and got super excited. I bought a maglev kit from Guy Marsden and it was super cool to see it levitate a pen.

Currently I am working on my own design using a switching mode converter and some analog feedback. Fun fact: it turns out that my Master's Thesis is going to be on modeling and control of Magnetic Bearings!

The previous examples I have mentioned are examples of active magnetic levitation, where a controller regulates the position of an object via feedback. Another kind of MagLev that exists is passive maglev which requires no active feedback. Turns out you can build a stable maglev system with no active control using Diamagnetic materials.

Diamagnetism is the property some materials have to repel magnetic fields. It is normally not a very strong effect but it is enough to make sheets of Pyrolytic Graphite levitate over strong neodymium magnets. My graduate advisor and I have been trying to think of uses of diamagnetism however given the forces involved are so low that we have not found any "real world" uses! I started to try and think of non-industrial non-real world uses and I thought it would be awesome to build a chess or checkers board with pieces made of pyrolytic graphite that levitate over the board. However given that the rare earth magnets are so expensive I decided to go with making a TicTacToe board first. I call this new creation Tic Mag Toe (im very proud of this name jajajaj...). I built a prototype this weekend:
tic mag toe v1.0
Getting the magnet in the checkerboard configuration was a little tricky cause they are crazy strong. We also had the world's first tic-mag-toe match:

I won it and became the undefeated world champion of Tic-Mag-Toe! However 10 minutes later Harry beat me twice... thus losing my glorious title to Canada.

My next step is to encase the magnet board into a nice laser cut frame and figure out a way to make nicer playing pieces. Then when I get enough money I'll go for the checkers board and maybe the chess board! For those of you wondering I got the supplies from the best source for strong magnets I could find online!

Tuesday, November 13, 2012

ThermoDynamic Bread!

Hey guys!

A lot of you have probably noticed that if you put 1 object in the microwave for X amount of time, then the temperature of the object goes up by some amount, however if you put two of the same objects for the same amount of time then each object will be individually less hot than in the first case. To me this was always an obvious fact that I learned from my early teenage years heating up tortillas in the microwave (I use tortillas as the example because it's funny cause I'm Latino).

At MIT I have learned that this is not an obvious fact for some people, one time during my junior year I had an argument with a freshman on the subject. He was convinced that if we put two sandwiches in the microwave for the same time as one, all three sandwiches will end up with the same temperature. I quickly tried to correct him but he gave me some stupid explanation on how the air will not heat up as much of you put two things instead of one thus making the efficiency higher blah blah blah... I tried to appeal to his inner scientist/engineer and talked about the first law of thermodynamics applied to microwaves but that did not work so then i just made fun of him which made him get kinda mad (sounds like I was being mean, but HEY! he asked for it! never mess with the FIRST LAW)

A couple of weeks ago I had the same argument with a friend who argued that formation of standing waves blah blah blah and that the temperature rise under the two conditions would be the same. (this case he was arguing that putting two Maruchan soups will heat each up the same as just putting one in. I tried to give my Thermo First Law speech AGAIN but it did not work so I was forced to do some late night experimenting: please enjoy!

 BAM! SCIENCE! I was right yet again, the single piece of bread exhibited a temp. rise that was 1.6 times greater than the two pieces of bread. However the question now is, why isn't that a factor 2? (half the mass means double temp. change for a same heat energy influx). That got me thinking on how the efficiency of the microwave varied with the properties of the food you cooked. (granted, the experimental set-up could be a total failure, thus I will be trying to repeat it in the next couple of days with cups of water instead of bread).

I started exploring the internets for answers I found some people that pretty much agreed with me (click here to see). Then some more people here. After this basic research it was obvious that the food properties (composition and geometry) and a lot to do with the linearity of the heating times, which adds an unknown for cooks in knowing how long to heat up things for. Interestingly fact: microwaves were initially unpopular because they were so "unpredictable" as far as heating times are concerned. (link to wikipedia microwave page

I will be conducting some more experiments of my own to check out how valid the linearity of heating times holds for things like water, bread and other random things.

Keep posted for the results! If you have any other "scientific experiments" or kitchen science questions that need to be answered please let me know and I'll do my best to address them in this blog!

Monday, November 12, 2012


Hey avid readers!

Sorry for the long delay, as a quick life update: in the last couple months I have started grad school at MIT (its going amazing!) and i joined the Electric Vehicle Team after my ex-roomie Victober infected me with the Electric Vehicle Fever. At the start of the school year, Victor and I worked on TinyCycle, after we finished it Victor and I took RailScooter and TinyCycle to the NYC Maker Faire, it was a day full of annoying delays (oversleeping, subway breaking down, forgetting to charge EVs etc etc) however it was a lot of fun and all the MIT folks raced their EVs around the power series track (Vicky and I also raced our EVs in the streets of Manhattan (not recommended) but that is another story...).

This whole experience left me really wanting a tiny electric motorcycle, just like TinyCycle. I looked around on craigslist and emailed/called/texted a couple of folks but never got an answer. Luckily for me  it turned out that one student group in 2.009 (MIT's Product Design Class) had taken apart a mini razor motorcycle as part of a class project and now it was sitting there alone in pieces. So i decided to do what every good samaritan would do... TAKE IT and give it a new home!. Thus my ChiquiCycle adventure started!

ChiquiCycle in Pieces
ChiquiCycle put together (no drive train or electronics)
It took me about a workday to put together all the parts I got from the 2.009 kids, it turns out they had lost the handlebars, the steering axle and most of the hardware. I eventually grabbed some scooter handlebars from MITERS, turned new steering axle pieces myself and grabbed some metric hardware from the shop. The motorcycle was now ready for its electronics! I started by procuring all the important parts: Motor, Controller and batteries. I had my ex-roomie victor help me with the battery pack (please see his excellent tutorial on how to assemble a Li battery pack!). The motor I used was this one and I decided to use a sketchy brushless motor controller from China that victor had laying around (in the near future Victober and I are planning to write a paper on sizing your motor and controller for your pocket bicycle).

We aimed to make the drive train assembly as simple as possible. I used an aluminum L-bracket to mount the motor. We took the driving sprocket out of the old motor the motorcycle came with. These sprockets normally come with a D shaped hole so it can transmit torque. I was lucky that the size of the sprocket bore was an M8 (same as my motor) this saved me the time it would take to machine an adapter. I pressed a spacer on the shaft then sanded the shaft to give it a D profile, put the sprocket on the shaft and finally machined a collar to constrain the sprocket axially.

my drive-train assembly
close up of driving sprocket mounting
The controller mounting was pretty easy (i just reused the mounting holes for the original brushless controller.

ChiquiCycle Frame with batteries, motor and controller! ALMOST DONE!

At this point ChiquiCycle was ready to roll!

We did some test runs (videos pending...) and it was obvious that we needed the controller to output more current to make our ride more exciting! With the help of Charles we hacked the motor controller to output more current and added hall effect sensors for motor startup. The scooter handlebars were making it impossible to ride chiquicycle semi-comfortably so I changed them to bicycle handle bars. I added a couple more pieces of the original plastic body and a Tesla decal and this was the "final" product:

ENTER CHIQUICYLE! (videos will be posted soon)

fun fact: I posted the above picture to the Tesla facebook page hoping that it would give me the opportunity to work at Tesla in the near future! I got over 130 "likes" from random people! My hope is that Elon Musk sees it and offers me a job in Tesla!

I'd like to thank the people that helped me out with this project, namely Victor, Charles, Lauren, Rango and Harry!

my awesome pit crew! (lauren and rango)
This project along with Victober's TinyCycle has pushed several friends to buy a tiny motorcycle! We are in the process of creating the Pocket Motorcycle Squad (PMS) and we aim to have a techfair booth in early 2013. Here's a picture of Lauren's chopper and future member of PMS!

UPDATE: Here is an instructable for Chiquicycle! It has almost 30k views and it won 2nd place in a "cars and motorcycles" contest winning me a bottle of "water spot remover"

Sunday, May 20, 2012

Tech Dinghy Challenge!

Hey guys!

Last friday was the very first annual Tech Dinghy Challenge at the MIT Sailing Pavilion!

Next House (my old dorm) put together a team for this event full of craziness, sailing and burgers (how could I miss it!?) The competition consisted of getting a team of people and then everyone had to eat at least one burger in 5 minutes time then we had to cram as many people in a boat as possible (modifications were allowed) and then sail to the boston shore and come back! Points were awarded for burgers eaten, people in boat and crossing time.

We modified the tech (sailboat) by adding outriggers with inflatables. We built it desperately in the hours before the competition and honestly I was not sure if it was going to work but PROPS to the designers, they did an awesome job and our modifications were rock solid! Here is a pic of us before putting the boat in the water...

I was fortunate enough to skipper the boat. With so many people on board I had to make use of every resource possible to steer the boat (rudder, sail... even paddles!). IT WAS AWESOME! We had so many sailboats around us taking pictures and throwing water at us! Some incompetent boats even crashed into us which made me extremely mad (why on earth would you crash into a boat with 30 people that is almost sinking?) at some point I was about to jump into the water swim into their boat and pull their rudder out for vengeance. However I desisted...

But my FAVORITE PART was the grand finale, and as videos speak louder than words...

Awesome right? Props to Jeff from the dockstaff who sank us with the wake of his boat! We eventually had to bail the boat to prevent it from sinking into the charles for ever ajajajajja!

I can't wait for next year's challenge! Big shout out to the next house team!


Tuesday, May 15, 2012

Flavorful Borderline Racist Video

So... I'm taking an awesome class called 4.301 - Intro to Visual Arts. And for our first assignment in this class we did a video project. At the start I was not sure of what I wanted to do with my video but with help from my friends and some random inspiration that happens very late at night I decided to do something ridiculous (surprise surprise!)

The video is pretty self explanatory:

So... yeah not self explanatory at all ajaj! The assignment for this video was to think of the theme "Shaping Time" and alto to think about "circuits and systems". I decided to change the name to "Shopping Time" and then to use the supermarket at the system to study, i found the supermarket an interesting system because so many different cultures combine in a small very efficient space. I dressed up with a huge clock to relate to the "shaping time" theme (contrary to public opinion I did not want to emulate flavor flav, actually i did not know who he was when i decided on my outfit). The music was one of my favorite parts because it allowed me to present the different cultures and circumstances via audio and sound.

My prof. really liked the video and even called it "borderline racist", which I am not sure if it is a compliment or not.

Monday, May 14, 2012

Hematocrit Centrifuge


I am sure many of you guys have heard of D-Lab... but just in case I'll explain: D-Lab is a group at MIT that designs solutions to problems in the third world, they try to alleviate poverty and improve people's quality of life thought Design, Dialogue and Dissemination (thus the D in D-Lab).

I took D-Lab Design this semester and out team designed a Hematocrit Centrifuge! A H. Centrifuge is a key tool in diagnosing anemia, you basically spin blood for 5 min and then look at the proportion of red to clear solution (red blood cells to plasma) and from this you can diagnose anemia (a normal human has 40-45% red stuff). Given that most people with anemia live in the developing world, they need rapid ways to diagnose it however industry grade centrifuges cost more than a $1000 and require electricity which is a no-no for a lot of rural clinics out there.

Thus our team designed a centrifuge that could be built for around $40-100 using a power drill transmission. We took apart a drill and used the gear box to provide a good gear reduction for the spinning of blood. Here is a picture of the final design:

Our design has a footprint of about 1' by 1' by < 2', which is a big reduction from our Nigerian Community partner's bike centrifuge. My favorite feature of the centrifuge is that we put in a loose nut in the handle that rattles around when it goes too slow but when the speed is fast enough the centrifugal acceleration overcomes gravity and the nut sticks to the outside. This is how we make sure we are spinning the blood fast enough. Here is some of the math:

wooo! 2.003 in action!

I had my blood drawn at a clinic and then we spun the blood and got pretty good results! We even spun some diluted blood (to simulate anemic conditions):

woooo! I am not anemic!

My group is continuing our communications with Dr. Awojobi (an awesome doctor/designer in Nigeria) to flesh out details on a new design of a centrifuge based on a hand drill. So far he has sent us this picture of his progress so far:

exciting prototype!

Hopefully he can implement this new design successfully in Nigeria and disseminate it around the world! Meanwhile I will try and see if people back home in El Salvador have an interest in the hand crank centrifuge we built! I'll keep you guys posted! Here is a video of us testing out the centrifuge (a big shout out to my awesome teammates (Melvin Salinas, Kwami "The King" Williams, Daisy Chang and Kevin Kung)

(a shout out for my other roomie and lil bro David who I just learned also has a blog!)

UPDATE: 16 May 2012

Dr Awojobi (our partner from Nigeria) just emailed us saying that he has successfully implemented hand drills into his prototype and came up with a model that is about a third of the size of the prototype he has been using for 11 years and costs half as much! Here is a pic:

It is really exciting to see that what we worked on during the semester has had real impact on a someones life!

Stepper Scanner Control

If you know me at MIT, your probably know that I really enjoy controls and mechatronics. Even though my degree says "Mechanical and Ocean Engineering" I have done most of not all my requirements studying control theory and practical applications of control.

This blog post is about the controller design for a lithographic stepper. A "stepper" is a essentially a read head that moves in steps on a silicon wafer while the wafer is exposed to UV radiation. The catch is that the error in position during the half second of UV curing is on the order of tens of nanometers. For my digital controls class, we had to come up with a design for the controller structure.

Although we did not have the opportunity to implement the controller in real hardware, our professor included a lot of non-linearities and real world problems and parameters (he even brought in an old stepper to class) which made the problem incredibly interesting.

Here is a picture of the model for the stepper.

yep... its pretty convoluted! but luckily the professor helped us derive the state space model in class and thus we could focus on the control design of the stage.

We used completely classical control techniques (screw LQR and Kalman filters!) including decoupling and trajectory generations to get optimal performance. Most of the analysis was done is simulink, here is a screenshot of the final simulink model!

The final controller took over 36hrs of work to figure out but it worked great (in theory!) and I learned a great ton about design in controllers and how to be able to compensate for disturbances, noise, saturations and more of those great things that pop up in the real world. 

This was an awesome project to do and hopefully a good intro to my maybe job this summer at ASML!

Thanks to Prof. Trumper and all my controlfreak buddies for the collaboration during 2.171!

Re-Induction of Blog Motion!

Hey guys!
  I have recently (yesterday) decided to restart this blog!

 After being inspired by my awesome roomie Vicky Rodriguez I have decided to revamp my blog and make it a maker blog!

 I'll be posting about stuff I have made/taken apart for classes, for fun, or just random ideas that I have! Please feel free to submit any ideas or comments and I'll definitely take into account your feedback!

For this re-induction post I have decided to talk about a simple Induction Motor me and my roommates made at 2am in September 2011 because we were bored.

Here is a video of the motor running!

 I have recently been really interested in induction motors, ever since I found out about them I cant stop thinking of possibilites to use them (of course, them being such an "old" technology most of their uses have been figured out).

 A induction motor works on the principle of electromagnetic induction (surprise, surprise!), AC is pumped into the stator coils which induces a current in the rotor (a lid in my motor) and this induced current tries to catch up to the changing magnetic field in the stators. Thus we get motion without no mechanical connection whatsoever!

 The motor is classified as a split phase motor, this is because I used one voltage source (a 9V RMS 60Hz sinusoid) and then hooked up one stator coil in series with 220uF a capacitor to create a phase shift which gives the motor self starting capabilities.

 Credits to Nikola Tesla, the real life Tony Stark who invented the induction motor (as well as a myriad of other devices!)

 Thanks for reading guys and please stay tuned to the blog! I'll to try update the website very regularly and document what I do!