Computing stuff tied to the physical world

It’s been a year

In News on Oct 6, 2014 at 13:10

It’s been a year since the last post on this weblog. A year is a long time. The world has changed in many ways, and technology has advanced in just as many, but completely different ways. I have also progressed, in the sense that I’ve been exploring and learning about lots of new things in the world of electronics, software, and physical computing.

Some things have solidified, such as my main laptop, which is still the same as three years ago (an 11″ MBA), because the shiny big fast one went to my daughter Myra, who has a far bigger need for that sort of hardware – for her photography and video work. Another solidifying trend has been my touch typing, which is now at the point where I do so 95% of the time (editing code still makes me go for the hunt-and-peck mode, occasionally).

Other things have stagnated, such as most notably the work on writing The Jee Book. There are pages and pages with words and images on my laptop, but I don’t like them one bit, and will not publish these as it is today. There is not enough direction, passion, focus, and fun in those draft pages. It would diminish the excitement and joy this deserves.

I’ve given a few presentations and workshops in the past year, but nothing of substance has come out of it all with respect to the JeeLabs site(s). My goal for this month is to get back into higher gear in public. Writing has always been very fulfilling and its own reward for me – I’m looking forward to finding my voice on the web again, in some form or other.

Now the hard part… I could use your help.

A year in solitary confinement (just kidding!) has made it harder for me to understand what you’d like most from JeeLabs. Just to get this clear: I don’t think I can restart the daily schedule of the weblog, as it was up to a year ago. This isn’t only about the effort and energy involved, or the lack of material, but the fact that the resulting stream-of-conscience website that it leads to is a bit hard to navigate through. Also, the resulting collection of articles is really not very practical as a resource – there are too many bits and pieces of information in there which are outdated and at times even misleading by now.

What sort of topics would you wish to see covered? My own interests still tend to gravitate towards long-lasting autonomous wireless sensor nodes. What frequency and size of posts / articles do you like? Should the topics be spread out broadly, or rather focus on some very specific problems? How simple or deep-diving should the information be? Do you want more science and maths, or rather some detailed construction plans? Do you prefer a personal and conversational style (such as this), or more a factual information source?

As always, I will make my own independent choices, but I promise to listen carefully and respectfully to each and every comment you send my way (email to jc@wippler.nl).

Wrapping up

In AVR, Hardware, Musings, News, Software on Oct 6, 2013 at 00:01

I’m writing this post while one of the test JeeNode Micro’s here at JeeLabs is nearing its eighth month of operation on a single coin cell:

DSC_4507

It’s running the radioBlip2 sketch, sending out packets with an incrementing long integer packet count, roughly once every minute:

Screen Shot 2013-10-04 at 15.44.58

The battery voltage is also tracked, using a nice little trick which lets the ATtiny measure its own supply voltage. As you can see, the battery is getting weaker, dropping in voltage after each 25 mA transmission pulse, but still recovering very nicely before the next transmission:

Screen Shot 2013-10-04 at 15.45.45

Fascinating stuff. A bit like my energy levels, I think :)

But this post is not just about reporting ultra low-power consumption. It’s also my way of announcing that I’ve decided to wrap up this daily weblog and call it quits. There will be no new posts after this one. But this weblog will remain online, and so will the forum & shop.

I know from the many emails I’ve received over the years that many of you have been enjoying this weblog – some of you even from the very beginning, almost 5 years ago. Thank you. Unfortunately, I really need to find a new way to push myself forward.

This is post # 1400, with over 6000 comments to date. Your encouragement, thank-you’s, insightful comments, corrections and additions – I’m deeply grateful for each one of them. I hope that the passion which has always driven me to explore this computing stuff tied to the physical world technology and to write about these adventures, have helped you appreciate the creativity that comes with engineering and invention, and have maybe even tempted you to take steps to explore and learn beyond the things you already knew.

In fact, I sincerely hope that these pages will continue to encourage and inspire new visitors who stumble upon this weblog in the future. For those visitors, here’s a quick summary of the recent flashback posts, to help you find your way around on this weblog:

Please don’t ever stop exploring and pushing the boundaries of imagination and creativity – be it your own or that of others. There is infinite potential in each of us, and I’m certain that if we can tap even just a tiny fraction of it, the world will be a better place.

I’d like to think that I’ve played my part in this and wish you a lot of happy tinkering.

Take care,
Jean-Claude Wippler

PS. For a glimpse of of what I’m considering doing next, see this page. I can assure you that my interests and passions have not changed, and that I’ll remain as active as ever w.r.t. research and product development. The whole point of this change is to allow me to invest more focus and time, and to take the JeeLabs projects and products further, in fact.

PPS. Following the advice of some friends I highly respect, I’m making this last weblog post open-ended: it’ll be the last post for now. Maybe the new plans don’t work out as expected after all, or maybe I’ll want to reconsider after a while, knowing how much joy and energy this weblog has given me over the years. So let’s just call this a break, until further notice :)

Update Dec 2013 – Check out the forum at jeelabs.net for the latest news about JeeLabs.

Flashback – Anatomy of a transmission

In Hardware on Oct 5, 2013 at 00:01

One of the really fun things I always like to work on, is to push the envelope on power savings in the JeeNode.

It all started long ago, but over the years, I did refine the measurement process as my insight and instruments both got better. Here’s the most primitive approach, inserting a multimeter in series with the power supply to measure the static current consumption:

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The big problem with this is that a multimeter is far too slow to really see what’s going on. Only static idle current can be measured this way.

Another approach was to use a second JeeNode as power consumption tracker with some extra circuitry, to measure the voltage drop repeatedly:

Screen-shot-2009-12-19-at-16.27.09

This design can capture spikes by performing lots of repeated measurements, and in this particular case it even had a fairly large measurement range of 1 µA to 60 mA. This was done by using two separate sensing circuits and switching between them as needed.

But the real breakthrough came mid 2010, when Jörg Binkele sent me an oscilloscope snapshot of the voltage over a small series resistor. Here is one of the last ones, after lots of power saving techniques had already been applied:

detail_power_use1

As you can see from the annotations, there is an incredible amount of information one can glean from such oscilloscope traces.

This was one of the main reasons for me to learn more about oscilloscopes and eventually to buy a modern one myself – as described in a couple of posts, such as this one.

The capabilities of a modern digital storage oscilloscope (DSO) are truly phenomenal – and much of it is not even that much affected by the actual price range, although their cost does tend to keep them out of reach for occasional hobby use.

After many days of tinkering, it became possible to produce a very detailed map of the current consumption of a sensor acquisition + packet transmission cycle, as seen here:

annotated-room-packet1

The “haircomb” is the power consumption while sending individual bytes over SPI to the RFM12B module (and the received ACK after that), whereby the ATmega is even going to sleep between those bytes. For reference: the entire trace on this last screen is similar to the little blip marked “RFM12B transmission” on the previous screen. It’s not only considerably more detailed, but actually calibrated in 5-mA steps on the vertical axis.

Fascinating stuff, and no doubt a major reason why JeeNodes can perform so well nowadays in terms of ultra-low power consumption. If you had asked me this in 2008, I honestly would never have thought such a level of insight and performance to be attainable by anyone without access to a big research lab!