3 articles were written in August 2013:

2013-08-28

A self-powered battery tester with an EFM32

I like to participate in electroics design contest. Its always interesting to apply skills within a given timeframe, most times also within a given frame of what to do. Many times its also a chance to get your hands on interesting hardware one would never buy otherwise. Most times I have participated so far was because the theme of the contest (or the hardware to be used) gave me the idea for an interesting project - so its most times just an excuse to build something for fun…

The same happened when Energy Micro announced, last september, their EFM32 Giant Gecko design contest. The theme was, as one would expect from Energy Micro, energy efficency. When I read about it, there came two recent events to my mind. First I had, a couple of weeks ago, disassembled a defective car temperature sensor, which left me with a single AA-cell battery holder still lying around. Second, I had many times before (and with an increasing rate) the problem to find whether some particular battery from the child toys in out household still have some energy in them or not. Until then I always I used a cheap multimeter for that which had a “battery measurement” range, but it gave only a number betwen (typically) 20 and 40, and I never knew whether that was supposed to be good or not.

So the idea hat came to my mind was: why not build a proper battery meter which can give real and accurate numbers. That can’t be so complicated! And since the EFM32 is so low-power, why not make it powered from the battery I’m currently measuring? Drawing some additional microamps from it can hardly change the results…

So I applied with this idea (and second one to, but this will be another post), and got accepted for the next round in the contest (only 40 ideas were accepted overall). So some weeks later I got a STK3700 with a EFM32GG on it my mailbox:

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