Thursday, December 29, 2011

I Hate Motor Controllers (The Journey of Segboard)

Well, I suppose I kinda failed on the updating more regularly part, but oh well. My apologies. Finals and final projects tend to suck the life out of you. Anyhow, I wanted to give you all an update on Segboard (for which I'll be redesigning the power electronics this winter break).

Here is my first and happiest video of Segboard functioning. 

My friend Charles taped this better version while I was frantically taping a crappy version with my Ipod. Props to Shane for test riding it. Also I super love my tights here. You can get them at Urban Outfitters for $10.

However, there is one catch. This test was done with a commercial motor controller from Pololu. Yup, this is not with my janky home-made motor controller. You see, what I hadn't predicted was the pain and suffering of transforming theory into reality. 

And boy does that pain suck.

Problem 1:

Some of you might know the process of etching printed circuit boards (PCBs) with ferric chloride and toner paper. Some of you might've seen my post about it. Some of you might even think it's a good idea. Well, it is - but mainly for some things. Like small microprocessor breakout shields or something tiny and not high current. DO NOT ETCH SOMETHING HIGH CURRENT OR YOU WILL HATE YOUR LIFE UNLESS YOU ARE A GOD[ESS] OF ETCHING.

You see, etching can be fun in some sense. 

Here are the steps for normal boards:

Step One:
You sandpaper some copper board.

Just as you'd put on primer before applying eyeshadow, sanding your copper is like the same thing. You want a clean copper plate for the toner to stick onto, so sand and acetone that sucker. Also sanding will make your toner stay on more robustly, like preventing eyeshadow creasing. Do this about 5 times. 

Step Two:
You iron your circuit board toner print.

I'm really digging coral right now. I tried this coral nail polish from OPI,  but my skin tone looks weird in this picture. 
This part takes a while. You kind of stand there like a wife from the fifties, except instead of ironing your husband's shirt, you iron your circuit board. Note: Both shirts and PCBs burn, so watch out. 

Step 3:
You somehow remove the paper backing. 

This part is a real pain. The paper doesn't always come off nicely and you have to wait until you can rub it off with your fingers. Also you might rub off the toner, so then you cover up the broken traces with Sharpie (which really works). 

Step 4:
You let it soak in ferric chloride until all the excess copper is eaten away. 

FYI this is one of my worst etchings. The more you make, the better they get.
Step 5:
Drill the component holes and populate the board. Tin the ground plane if so desired.

It looks so innocent, doesn't it?
Theoretically, then you're done!

... (Yeah right)

As I've said before, ETCH HIGH CURRENT BOARDS AT YOUR OWN RISK. DEBUGGING THIS WAS THE WORST EXPERIENCE OF MY LIFE. Want to know why? At high currents these traces have a tendency to pop. THEY WILL LITERALLY EXPLODE. And then you have to look real hard at the back and do all the continuity checks. In addition, solder connections can be weak if you mill out the holes just a little too largely, there can be microscopic breaks in the copper, Gremlins might like your board for some reason, etc, etc. ALL SORTS OF PROBLEMS EXIST IN REAL LIFE. 

Unless you're making a relatively small control board or else have RIDICULOUSLY THICK copper traces, DON'T DON'T DON'T DON'T DON'T etch motor controllers. Just send them out to 4PCB or Gold Phoenix. It's worth the money, I SWEAR.  

Problem 2: 

That ground plane (the big piece of copper that surrounds my traces) was the cause of so many inadvertent shorts and mishaps and UGHHHHHHHH.

If you're doing some sensitive analog controls stuff, having a ground plane reduces the amount of noise on your chips. This is good because you get more reliable logic. However, with something big and clunky like a motor controller, a ground plane is not so great (especially on a homemade board) because when you short your entire board, you blow out a number of things you don't expect. 

I'll alter this statement a bit. If you had your PCB professionally printed, then maybe a ground plane is good, but if you etch your own YOU'RE PRACTICALLY DOOMED. 

Also watch out for ground loops. They will make your controls quite sad. 

Problem 3:
Regenerative breaking is hard. 

Courtesy of "How Stuff Works"
I'm pretty sure a lot of you have heard about regenerative (regen) braking. It's used in a lot of new electric and hybrid vehicles. Essentially, what happens is that when you brake, your wheels are an input of energy (basically a generator) back into your batteries.

I designed my motor controller to use synchronous rectification (basically an H-Bridge) to run my motors. (Note, please looks these up if you don't understand the terms, that's half the fun of learning!) While I thought this was hella-baller, I didn't design anything for the regen that I hadn't really planned, leading to DEATH, DEATH, BLOODY MURDER, DEATH. 

Essentially, this happened each time. 

I would test my motor controllers on the power source with a PWM signal from a micro, it would look fine and work wonderfully. Note, there was no hard braking performed.

I would attach motor controllers to Segboard and then, as I was braking, DEATH OF EVERYTHING AHHHHH WHY ARE MY MOSFETS DYING?????????

Anyway, I figured out why my FETs kept dying. When I was braking, I was regen-ing back into my batteries. However, because my motor controller hadn't been designed to either short out that regen or else somehow bridge it back to battery, my FETs kept avalanching and my voltage regulator died. The voltage regulator (24V to 15V) gave it away. My awesome boyfriend Joe had worked with high-power LED controllers before and had witnessed voltage regulators failing. Apparently they really only die by one thing - the output voltage being greater than the input. This lead to the regen Ah-Ha! moment. This also lead to the fastest and jankiest demo-fix ever as I soldered a diode across my regulator to take the regen braking and them demo'ed a somewhat working Segboard for my power electronics class. Surprisingly, it worked well enough to show it functioning, and that's what really mattered (for that class).

I only kind of hate you. JK! <3

In the end, I've learned a lot. One: theory != reality. Two: Friends are the best thing ever. If they hadn't kept my sanity, I would've just been a lot sadder through this whole ordeal. Anyway, this is just an update of Segboard for now. Like I said, I'm planning a total redesign during winter break (just for fun, not for any class). I can't wait until I ride across campus as MIT's most chic engineer! That should be entertaining. :P

Happy Holidays and Happy New Year!

Monday, December 5, 2011

Victoria's Secret Fashion Show Uses EL Wire

Hey all! Found another example of "high-tech" fashion. I've posted before on Katy Perry's EL peacock tail, and this year Victoria's Secret did a similar thing with their EL Angel wings. While I think they looked overall cute (and were structurally robust, props to whoever mechanically designed them), I was a bit disappointed in their electronic simplicity. I feel like the amount of work for audio processing/visuals isn't that hard. Bright wings that stay on are pretty, but just a little too boring. I would've really like it if Victoria's Secret made their lighting more dynamic (like the beating heart bra worn at 2:00). It's clear that they were technologically sophisticated enough to know how to vary brightness/speed of their lights, but didn't for their wings. At the end of the day, I suppose my main gripe lies with their decision not to. *Shrugs* I'm too judgmental :P

On the bright side, at least I now know of who might want to buy my EL Shutter Shades :)

Wednesday, November 30, 2011

Hunt for the cheapest!

I haven't done any fashion posts for a while and I feel deprived (especially with all the Segboard posts lately). I'm going to show you 2 pairs of shoes that I find similar.

Jimmy Choo Glitter Pumps
Urban Outfitters Glitter Pumps
The question "Am I going to buy an IMU or a pair of shoes?" probably isn't asked by many engineers or fashionistas. I don't meet many people here at MIT who care about fashion. In fact, there's almost an "anti-culture" of dressing up (I'm generalizing, but still). In one sense, practicality drives this trend. You can't wear a chiffon anything while messing with motor grease. However, I try to dress well regardless (just bring another set of clothes or dress differently those days), but most people are either too lazy or too "counter-fashion". Anyway, main point - I like dressing nicely even if a lot of engineers don't and I think it's perfectly fine to be smart and chic.

Nonetheless, I am also really cheap. I almost have to pick between 2 types of tools. Do I buy clothes or parts? The point of the pictures was to show the silliness of price. The Jimmy Choos are $745 and the ones from Urban Outfitters are $49. I'm the type of girl who will go for cheaper if they're similar enough (if you want even cheaper go on ebay). When push comes to shove and you've got to pick between parts for your segway skateboard or nice shoes, the going gets tough :P Basically, always look for the best bargain! 

End rant. 

lolboad frame

Not quite done (needs 2 chains and some trimming on the rod and some shaft collars), but it definitely fleshes the project out :)

It's also entertaining to see a skateboard on the mill (I drilled holes for the motors and wheels). I also got to lathe for once! The spacers from the wheel assemblies were a little too long, so I trimmed them. Lathes are definitely the most scary of all the machine tools. Not sure why though. Probably because it looks like an angry spinning monster of death (and it spews the most coolant on me).

Now for all the code, code, code, cooooooooooooooooooooode............

Tuesday, November 22, 2011

Motor Controller Etching

I'm an h-bridge! :D
Etching is gross and fun :P I've etched a prototype of one h-bridge of Segboard's motor controller to test. I like etching because it's much faster than ordering PCBs (which takes like 2-3 days for shipping and stuff). Also etching is much cheaper. The only problem is that it's pretty messy if you're not graceful (ferric chloride stains your hands and clothes) and your board isn't the nicest looking thing. Oh well, I'm cheap and in college.
I look nice in theory!
I look gross in reality!
Gonna test over Thanksgiving. Yaaaaaaaaaaaaaay!

Tuesday, November 15, 2011

Power Electronics + Segway Skateboard Motor Controller!

Here at MIT, one of our lab classes is Power Electronics (6.131). It's taught by Prof Leeb who's just a bit crazy in the best way. We learn a bunch of basic power management design, (your typical Buck, Boost, and variations) along with some motors. It's my first lab class, and I must say THIS IS MY MOST FAVORITE CLASS SO FAR. Please, please, please if you come to MIT, take 6.131! The thing that bothers me the most about the majority of my classes is that they're all pretty theoretical. I like to make things first-hand, and looking at a bunch of math which doesn't relate to any physical system bores me. 6.131 is the complete opposite. You make the systems you've learned from lecture, which involve lots of building! It's unbelievably satisfying seeing your lecture material turn into a real object you've hand-crafted. But anyhow, I'm getting off topic from what I really want to rant about.

For 6.131 we all have a final project. In fact, it's one of the reasons why I wanted to take this class. I've done more microprocessor projects before, but I've never touched high-power much. For my final project, I'm making *drum roll* SEGBOARD!

You're probably going to see several posts about Segboard soon. Segboard is basically a segway skateboard, based off of the one created by XenonJohn. However, I'm making my own motor controller which changes things up. Not only is my software going to be a bit different, I'm going to have to debug a motor controller. Regardless, physically Segboard should look similar to XenonJohn's.

As some of you might know, my main research deals with wearables (what I like to call fashion engineering), and one might wonder how a segway skateboard has anything to do with that. Well, an addendum to this project is a wearable UI. In order to turn on Segboard, the duty cycle for each motor has to change accordingly, and while this turning mechanism has been implemented with controllers, I want to make a wearable one. My two main ideas for how to do this is through a glove or some kind of jacket, but that's later on (I'll probably first implement Segboard with a hand controller that isn't a true "wearable").  Anyway, I haven't seen many "high-power wearables" (even if through a UI), so I think this could be an excellent example of fashion engineering without LEDs :P This project is legitimately what some might call "hardcore".

I've only the motor controller schematic (below) made now, but I thought I should put it up for fun. Plan for lots of drama, joy, and electronics in the future as I desperately try to finish Segboard before the semester finishes. We'll see if I make it!

Monday, September 19, 2011

Make Magazine Thinks I'm Shiny! :D

This weekend I went to Maker Faire: NYC and got interviewed by Make Magazine! Make sponsors this convention/fair for creative people throughout the US. This year it was hosted in New York. One can register as a maker or as a normal spectator. If you're a maker, you have something to present. I went with the MIT Electronic Research Society (MITERS), and together we had a bunch of modified electronics, and, of course, shiny things.

This was pretty neat as a personal step for electronic fashion!

I also saw lots of other wearables, learned some neat ways to deal with lighting, and had a fun time! Definitely an event worth attending!

Monday, August 22, 2011

Giant Leaf Planetarium?

As some of you know, I've spent the last ~2 weeks working on a giant leaf planetarium! Basically, I walked into IKEA one day and saw these giant leaf canopies for your bed!

They're huge!

The nice thing is that you can attach it to anything! The mount IKEA sells you is made specifically for walls, but with a little ingenuity, you can manage other places as well. You might even be able to use them as a bussle for a dress.

Anyway, this got me thinking about what I could do with them. I mean really, there was no way I wasn't going to somehow hack it. As I was sitting under my leaf one day, I realized, it would make a super awesome planetarium! Plus, it would be a wonderful demonstration of etextiles outside the domain of wearables.

Long story short, 400 ft of fiber optics, 6 power LEDs, and a lilypad arduino later, I present to you, my giant twinkling leaf planetarium.

If you're interested in making one, check out my instructable for it! It was featured by instructables! Also look around the site in general. It's full of awesome projects, from food to microcontrollers. :P


Laser Art is fun. Also yay MIT!

Hope you feel a little more inspired today!

Tuesday, August 9, 2011

Saturday, July 23, 2011

Smart Hood 1.0

This summer I have the best job ever! I'm working at the MIT Media Lab with High-Lo Tech, a cool group that does a lot of e-textiles and electronic craft applications research. Basically I get to do fashion engineering and learn new things, which is always super awesome. Anyway, one of the projects I'm working on is this smart hood that lowers/raises itself in response to light and temperature, and also heats itself up. Not finished yet, but I have a video of it being silly, so hey. :D

3D Pocket Locket!

I've been kinda lazy with blogging ever since the summer started. Sorry! But I do want to share with you my latest full-creation.

For this class I took with Camera Culture from the MIT Media Lab, I made a 3D pocket-sized display. It's based off of a stereoscopic display from Instructables. The difference is mine is about the size of a deck of cards. As this utilizes stereoscopy, you need polarized glasses. If you wanted to be all fancy and make a Nintendo 3DS display, you'll need a fancy lenticular set-up (think of those rulers and stickers you had in grade school that moved if you tilted them from side to side. Lenticular lenses look like that grated plastic). Lenticular lenses are awesome in that they allow you to see 3D without spectacles. They are autostereoscopic displays that basically allow each eye, right and left, to see its specific image due to specific light refraction.

Unfortunately, I wasn't that fancy, so my pocket locket needs glasses, but since it fits into your pocket, I think it's kind of dandy :)

I need to get a real digital camera, but I'm a poor college student :P
If you look at the center lens, it's a 2-way mirror. What happens is that the mirror allows an overlay of 2 images, left and right. When each image is viewed by its respective eye, the right or left, the brain puts the two images together as one 3D picture. Now the 2-way mirror is great in that it reflects one image, the one in front of it, and lets another one through, the one behind. Hence, when you look at the mirror you see 2 pictures. Now, all LCDs are polarized. However, when you bounce an image back, you reverse the polarization. So now on the mirror, you have 2 differently polarized pictures! That means, when you wear your 3D glasses, each eye sees its particular image (and only that particular image due to the polarized light), so your brain sees 3D! Pretty neat! If that was confusing to understand, I suggest looking at that Instructables page. If you want to know how bad my papers are (or want to read it for the lolz), continue down. Either way, hope this spiced up your interest in 3D imaging. :D Now if only someone made some 3D display jewelry. I can see this going in a real locket someday.

Friday, April 29, 2011

Fashion Imaging Applications

Powerpoint on different imaging techniques/applications for fashion. At the bottom are two videos originally in the last side.


Adorable Projector Pattern Demo! [Secretly an ad for Google Image Search lol] 

Thursday, April 28, 2011

Chanel's BAMF-titude

I haven't been able to look at many collections recently, but as I was skimming around, I saw the most awesome shoes.

Dang Chanel, this is just BAMF-tastic. Now I just have to wait until they actually come out. I think they'll be available for sale next month. 

In case you don't have a couple of grand to spend on designer shoes, you can get an equally baller pair of heels with brass knuckles instead of guns for about $50 instead. :D

Now for some more awesomeness. 

Chanel's Fall 2011 RTW has this post-apocalyptic vibe that I love. The whole nonchalance of the baggy shape and tough-textured fabric is It sure has a "Don't Mess With Me" look. I just dig the tomboy twinge.