Interview with Sasha Zbrozek

Featured Engineer

Sasha Zbrozek

Sasha Zbrozek - Electrical Engineer at Mission Motors

image: I’m driving the corkscrew at Laguna Seca with half of our 2009 solar car.

How did you get into electronics/ engineering and when did you start?

My parents are both electrical engineers, so you could say it runs in the blood. Growing up I had sworn to myself I would follow my own different path. A series of wonderful chemistry teachers in high school left me thinking I wanted to be a chemist. I was given relatively free reign over the lab and the stock, and my friends owned farms. You can imagine how much fun that was to a set of teenage science nerds.

Dad, the genius opportunist that he is, took the chance to start building a spectrometer for me. It ended up being a father-son project that changed my life. He introduced me to CCD line arrays, optics, flash bulbs, high voltage power supplies, and most importantly microcomputers. For that project I learned how to etch circuit boards at home and how to write code in C. I was never the same again.

Going to college left me a sad emptiness that I would no longer have a proper garage and workbench. My school is inexcusably unwilling to let their students near real tools or work on serious projects; my first few weeks were very depressing. Soon, however, I found my way to the Stanford solar car team and came upon an amazing project with amazing people that has kept me glowing about engineering ever since.

What are your favorite hardware tools that you use?

I’m extremely particular about my hand tools. Between a good set of tweezers, snips, wire strippers, and my trusty old Metcal I can feel at home working anywhere from my work bench to sideways on a motorcycle. Gravity may change direction, but my tweezers will always feel right in my hand.

The bench itself is also surprisingly useful. I can use it to help pry things open, bash things apart, hold up my tools, or slam my boards against to shake holes clean when I don’t have a desoldering gun handy.

What are your favorite software tools that you use?

Free stuff is awesome. It’s amazing what you can get done with LTspice, FEMM, TinyCAD, and FreePCB. Those four tools live on a flash drive in my backpack and travel with me everywhere I go. If we were to suddenly descend into nuclear holocaust, I’d make my way for Minnesota to camp out near 3M and Digikey’s warehouse. From there, empowered by the inventories of industry and the software in my backpack it would be possible to rebuild civilization.

What is the hardest/trickiest bug you have ever fixed?

Goodness, there are so many bugs, it’s impossible to choose one to be the hardest. Figuring out why power supply efficiency is lower than predicted can often be really tricky, but doesn’t usually qualify as a bug. At one point I had designed a DCM boost converter and I was losing a lot of power to eddy currents in the first winding of my foil nearest the air gap. Amateur mistake? Sure, but it was really hard to nail. Similarly, I had a CCM power converter cause my amateur radio to break squelch on all bands when standing within thirty yards of it. It turns out the reverse recovery time of a diode I had chosen was too large to support extreme duty ratios and I was pulsing hundreds of amps for just a few nanoseconds on every switching cycle. That bug made itself more obvious when a diode fell off the board.

What has been your favorite project?

By far it must have been running the Stanford solar car team. It took vastly more time than going to lecture or doing homework, and it put me at odds with many university paper pushers, but the experience was simply unreal. What appealed to me most was the incredible diversity of what had to be done – everything from project management/leadership to fundraising to designing power converters to sanding bondo.

Most of what makes me a good engineer I learned either from my dad or from solar car. What other project has you running over kangaroos in the same day as writing code and reworking boards and getting pulled over by cops who think you’re tailgating a UFO?

Can you tell us some more about the Stanford Solar Car Team Project?

The team size for the Stanford Solar Car varies, but usually we have a core cadre of about 8 and additional 10-14 occasional helpers. My involvement started at the start of my freshman year, five years ago. Each fall the school hosts an activities fair, allowing student groups to advertise to new students. Walking around, the majority of the groups were for some form of social justice or ethnic group. Eventually I stumbled upon this UFO-like car, started asking a bunch of questions, and I didn’t miss a meeting for almost four years.

We use lithium ion batteries – whatever is the highest energy density with acceptable power density at the time. This year that means Panasonic 18650 cells. We design our own packaging and battery management system. For now that’s injection molded plastic housings, patterned nickel plates, and a Linear LTC6803-3 based monitoring circuit.

As for motors, in the past we’ve used an iron-core axial hub motor from NuGen Mobility. The company seems perpetually on the brink of collapse and we’re moving on to the CSIRO-designed ironless dual rotor axial flux machine. It doesn’t offer as much torque or power as the NGM unit, but it’s much lighter and significantly more efficient.

The Australian races happen in late October in odd years. I participated in 2007 and 2009, and plan to participate this year. Dozens of schools participate. Top teams include Nuon from the Netherlands, Umicore from Belgium, and the University of Michigan. Stanford had a reliable, albeit slightly slow car. We scored tenth place overall and fourth in our class. The same car scored fourth overall and second in its class in the American race in 2010. We expect a stronger showing this year; we have pursued an extremely aggressive design.

What are you currently working on?

These days I’m an electrical engineer at Mission Motors, working on motor controllers and battery chargers designed for industry-leading power density. Weekends and evenings still go to the solar car team (I only graduated last spring) helping to prepare our most aggressive entry into the World Solar Challenge ever.

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