Interview with Jeff Keyzer

Featured Engineer

Jeff Keyzer

Jeff Keyzer - Electrical Engineer, Freelance Circuit Designer, Blogger, Author

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

I have pretty much always been interested in electronics. When I was five or six years old I would collect and play with extension cords (much to my parents’ dismay). By the time I reached the 6th grade I could solder and had a modest electronics lab in the basement. I remember the day my father brought home a Radio Shack 160-in-one electronics kit – the kind with the springs that hold the wires – I had been begging for one for months! I think that was a turning point for me and pretty much guaranteed that electronics would always be a part of my life.

What are your favorite hardware tools that you use?

My stereo zoom microscope. It’s an American Optical scope from the late 70s. It’s built like a tank, has great optics and was super cheap on eBay. I couldn’t do surface mount work without it. I also couldn’t live without my homebrew PID-controlled soldering hotplate. It’s amazing how useful a big chunk of aluminum at just the right temperature can be. I’ve used it to do other things, like cure epoxy, and it also makes a great coffee warmer.

What are your favorite software tools that you use?

Cadsoft Eagle, LTspice, the avr-gcc toolchain, Virtualbox, Wordpress

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

I worked as an RF designer for several years, designing power amplifiers for cellular and wireless networking applications. In that time I dealt with a few amplifiers that really wanted to be oscillators. The worst offender was a paralleled amp I worked on – two die in one package. It was unstable into VSWR at some combinations of phase angle and temperature. I went crazy trying to stabilize this circuit. Usually I could fix oscillations by playing with bypass/decoupling caps but this one required a re-spin of the PA chip, which was stressful because I had a deadline to meet and this kind of stuff never simulates. How do you know if you have fixed the problem? I have a few grey hairs thanks to this one but I fixed it eventually.

What is on your bookshelf?

The Art of Electronics (Horowitz and Hill) – Every engineer should have a copy of this book!
Getting Started in Electronics (Forrest M. Mims III) – I have a really tattered copy of this that I have had since I was a kid, along with a few of his mini notebooks. I really love his style and illustrations.
Microwave Transistor Amplifiers (Guillermo Gonzales) – I learned enough “old school” microwave circuit design from this book to design a 24GHz low noise amplifier while I was an undergraduate, before I had taken any RF classes. An excellent resource.
Every issue of Make: magazine from volume 1!

Do you have any tricks up your sleeve?

I like to use my fingers. I poke traces and components to start or stop oscillations, check if ICs are too hot (ouch!), look for loose connections and cracked chip caps, and see the effect of some lossy capacitive loading on the circuit. Is that pin floating? Let’s find out! Another tip from my years in RF design – the best capacitor (the one with the lowest ESR) isn’t always the best one for your design. Crappy caps (X7R, Y5V) can damp oscillations and stabilize an otherwise unruly circuit. Of course, the value matters too. Watch that self resonant frequency!

What has been your favorite project?

My first big contract after becoming a freelancer was to design a complex power supply and communications board for a small startup company. The schedule was very aggressive and I only got one pass at the PCB design. The PCB was a monster, at least for an IC designer who didn’t have much PCB design experience – 4 layers, over 200 SMT components, lots of high speed, phase-matched differential signals, etc. The boards worked. Maybe I was lucky, but I really pushed myself on that project and it was hugely rewarding.

Do you have any note-worthy engineering experiences?

I’ve been shocked a few times but I am generally pretty careful. I think the worst shock I have ever received was from a laser power supply I was working on. I’m not sure if it was the 10kV starting pulse or the 1.5kV operating voltage that got me, but I let go really quickly.

What are you currently working on?

I’m writing a book with Mitch Altman about how to make cool things with microcontrollers (for complete beginners). We just released a sneak preview – a comic book that will teach anyone how to solder. You can download it for free here.

You can see more of my latest projects on my blog. I’m also on Twitter.