Regarding Personal

The Spark Gap

18th December 2014

I don’t often post about other podcasts that I like or that I listen to because I don’t think it’s that interesting a subject. However, every now and then I come across a podcast that I find amazing that I’m really drawn into.

I came across this when doing a vanity search on my own podcast. Thanks to the new Twitter advanced search I found a reference to The Engineering Commons, Pragmatic and something called "The Spark Gap." The show is hosted by Karl Bowers and Corey Lange who are both Electrical and Electrial/Computer Engineers respectively, much like I am.

Love the name too. When I think of a Spark Gap I think of a radio transmitter and I think of Hertz and the early radio experiments of the late 1800s. Already a regular listener to TEC, I gave TSG a shot, and fell in love with it almost instantly.

I started on Episode 21 about PCB layout: a subject near and dear to my heart. I considered doing an episode of Pragmatic about it but I decided it was too niche and decided not to. Thankfully they have, so now I don’t have to…

Their discussion on decoupling capacitor placement had me fist-pumping the air in heated agreement. Not a discussion I’ve had in years and one that annoyed the crap out of me when I did layout in my early career.

One aspect of capacitor use that they didn’t reference that I came across when debugging one of the designs I worked on, was the use of the capacitor as a current tank. The idea is that certain ICs can have high current draw requirements and that draw spikes particularly at high frequencies. The issue is that power propagating across the power plane might not "travel" quickly enough (due to inherent inductance/capacitance between the tracks) to supply power to that supply pin causing the voltage to drop at the input of the IC momentarily. This can then affect the entire ICs performance, and in the cases I was troubleshooting, lead to data corruption on one of the data buses.

We initially used Tanatalums as current tanks due to their low inductance but eventually switched to low inductance ceramics due to reliability issues Tantalums have especially at high temperatures. That, and the fact that their failure mechanism was typcially quite impressive and destructive whereas the newer chip-ceramics were quite stable albeit physically larger. One of the things we tried hard to do in the dependability team was to drive Tantalums out of the boards.

Another issue they discussed was component layout: Single vs Double Sided and so on. At Nortel we restricted most boards to chip caps, resistors and inductors on the backside of the boards as we found the heavier QFPs moved around on the second pass through the reflow oven. That said, epoxy dots would usually keep the bigger components in place on the backside of the board it was still frowned upon as a general practice.

I digress: What they didn’t talk about was the component physical alignment. Cooling profiles and heat loading for ambient air surrounding the components is also a factor for vertically mounted PCBs and we found that with naturally cooled (not forced fan or ACU) had better long term reliability if the components allowed channelled airflow, similar in concept to tall buildings in the middle of a big city, such that air could flow easily between them and rise unimpeded.

There’s no doubt that this podcast is really in-depth, with the double-episode about PCBs delving into Net naming, power and ground planes, vias and stacks more (get it? Uh…never mind…) with so much really good PCB layout advice that those two episodes alone are a must listen for those that want to improve their PCB layout skills.

That said I realise it’s a niche podcast that may well not appeal to many people. For me though: I’m working my way through now from Episode 1. To Corey and Karl: Great stuff guys!

From Coca-cola to Coffee

26th May 2014

You’re never too old to learn a new trick.

Growing up in the tropics meant a predisposition to preferring cold drinks year-round simply because it was hot and the drinks would cool you down from the inside out. Upon moving to Canada I bought a 20oz insulated Aladdin mug and filled it with ice-cubes and cold water even though it was -30 degrees C outside. The comments and looks were unforgettable - yes it was a bit odd now wasn’t it? In my youth I detested hot drinks and drank water almost exclusively with the occasional soda-pop (soft-drink) on special occasions.

Then one fateful month Coca-cola had a competition: enter x20 wrappers from Coke bottles and receive a free Mossimo backpack. Guaranteed. Coke hadn’t been my thing but I wanted a backpack and started on my journey. Along the way I got to liking the alertness and nice feeling that caffeine gave me. In short I became hooked. Congratulations Coca-cola - you got me.

As time went on I drank more and more and although my teeth remained relatively unscathed I began to develop kidney stones in my mid-30s. The colour was unmistakable when the fragments were examined post-op: they were from drinking too many cola beverages. Still I continued to drink them because, well, caffeine and I hated hot drinks!

Here I wrote about my experiences with Weight Loss Surgery. It turns out that after these procedures are done, soda (soft-drink) is extremely painful to drink as the dissolved gases come out of solution and the gas increases the pressure in the stomach/bowel. This pressure stretches the stomach causing pain and in the long term can defeat the purpose of the operation. For these reasons fizzy drinks are advised against and preferably banned from peoples diets post-op.

I said goodbye to my Coca-cola.

And hello to Coffee.

At first I just wanted the caffeine hit but determined to try something new I gave Starbucks, McDonalds, Gloria Jeans and a few different Cafes a shot. We bought an Aldi-brand K-fee coffee pod machine that I learned quickly made disgusting tasting coffee. In a pinch it works I guess but after a few weeks even I can tell the difference. I’ve since switched to Nescafe instant Lattes which aren’t too bad if you have a Stevia tab to sweeten them a little. No substitute for real milk, though.

I’m working my way through flavoured Lattes at the moment with my two favourites both from Gloria Jeans: Caramel and Choc-Mint - neither of which need a sweetener. But I’m eyeing off these Aeropress thingys that people rave about and will give pre-ground coffee a go. The ultimate goal to see if I can make a Latte better than a store bought one. Anyway - I’m only very early on in my coffee journey. Long way to go yet…

You may think then that coffee is the new trick to which I previously alluded. But that’s only part of the story.

I’d been an avid listener of the Build & Analyze podcast from the beginning (well, just after it started and I listened back from the start) and I complained several times about how much Marco talked a lot about coffee. Like here where Marco put my complaint in context for me. (Okay, I had it coming)

Looking back now, what’s interesting about this little exchange is that it has opened my eyes. Don’t criticise today what someday you may become interested in. If it doesn’t interest you at the moment don’t make a big song and dance about it, just move on. Someday, maybe, you might just care.

I’ve now been loading up old episodes and segments that I’d previously skipped of B&A. This time though, I’m listening to an entirely new show. Funny. Looks like an old dog can learn new tricks after all.