Jan 24, 2014

Ten years and rolling

posted by Dick Selwood

Ten years ago today the Mars Rover Opportunity bounced its way on to the surface of Mars, at the start of a three month mission. In that time, as well as driving 24 miles, the little machine has added enormously to our understanding of the history of the planet.

And this is a huge endorsement of the team who put together the electronics. The development process started nearly twenty years ago, and by the time the mission launched most of the electronics used was, to put it kindly, mature. The central processor is a 32 bit Rad 6000 microprocessor, a radiation-hardened version of a Power PC that was launched in around 1965.

Just look around- how much of the electronics you own is ten years old and still functioning? What software are you using that ceased development around 15 years ago.  That is a little unfair since the software on Opportunity has undergone several upgrades.

That in itself is quite mind-boggling. When did you last do a major software upgrade and how easily did it go?

This week there was another space event that was a tribute to system designers. The Rosetta mission to investigate comet Churyumov-Gerasimenko woke up after 31 months in hibernation mode the latest stage in journey that started almost ten years ago.

So It is possible to create systems that last for years- you just have to work hard at it.

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Jan 23, 2014

TSensors Roadmap Takes Shape

posted by Bryon Moyer

Last fall, an effort was started to drive the MEMS business (or sensors in general) to the point where a trillion sensors are shipped yearly. We covered the TSensors event, and we promised to update.

As a quick recap, the approach here is to identify high-yield applications and then focus in on those to remove barriers (largely, but not exclusively, cost). So the current process is to establish what those applications are going to be, and then have a chairperson for each application driving the writing of a chapter, to be contributed by various people.

The topics selected are as follows:

  • Noninvasive fitness-wellness-health monitoring (possibly to be expanded to include animal health)
  • Noninvasive chronic disease detection and monitoring
  • Minimally invasive fitness-wellness-health monitoring (possibly to be expanded to include animal health)
  • Personal imaging
  • Computer sensors (smell, taste, color, biometrics, etc.)
  • Environment sensing
  • Sensors for food production
  • Smart grid/Energy/Harsh environment sensors
  • Energy harvesting
  • Ultralow power wireless communication
  • Network infrastructure for Internet of Things

That’s a lot of stuff, covering a lot of ground.

One thing that’s clear is that there is room for more contribution by authors and even chapter chairs, at least as of the last update I saw. So if anyone is interested in participating, contact information is available on the TSensors website.

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Jan 23, 2014

Harvesting Microwaves

posted by Bryon Moyer

We have just looked at an approach to wireless power transfer using low MHz electromagnetic field oscillations. But such a concept is only “power transfer” if the whole reason for the signal in the first place is to transfer power. If such a signal exists for some other reason – like communications – then doing the exact same thing wouldn’t be power transfer: It would be energy harvesting.

And indeed folks are trying to harvest energy out of all of the waves running rampant through our environment. The issue is efficiency, however, and you don’t really see a lot of practical discussion of this type of harvesting as being on its way to commercialization.

But there are some interesting things going on. And they involve “metamaterials” – artificial matter that can achieve characteristics – like a negative index of refraction or negative permittivity – that aren’t possible in nature. We took a look at some of these a couple years ago.

I have tended to think of metamaterials as the careful stacking and arranging of materials at the nano level; apparently that’s not always the case. Some folks at Duke University created a microwave energy harvester using a macro-sized metamaterial.

The fundamental unit of this “material” is the split-ring resonator. These can be very small, and would need to be on the order of 10s of nanometers across to respond to optical wavelengths, but the one Duke used was not that small: the outer diameter was 40 mm, and the gap was 1 mm. It was tuned for 900-MHz resonance.

Split_ring_resonator.png

 

Image courtesy 吴艺(Wikipedia contributor)

My initial thought was that these were made out of a metamaterial, but no: they’re made out of copper, and an array of these becomes the resonator. They used five of them (5x1 array) in their experiments.

It’s interesting to me that one of these rings bears a remarkable resemblance to the structure that WiTricity uses as source and capture resonators, albeit at lower frequencies. I suspect that’s no accident.

While simulation suggested they might get into the 70% efficiency range, their results were closer to 37%. There wasn’t really an explanation of that discrepancy; I’m going to assume that will be the focus of more work.

You can read more details about their work in their paper (PDF).

Late update: there's another "out of thin air" technology that's more than harvesting. It will be the topic of a future piece...

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