[pocketstar]

The new batteryless wireless sensors coming out of uw are incredible. Dr. Smith is leading some great work. My interest started when I heard of the WISP [0]. The RF power harvesting design is so simple and elegant. It is amazing what can be done with uW of power!

[0] https://sensor.cs.washington.edu/WISP.html

[tootie]

Is this thing operating on the same principle as wireless charging? It can convert RF to power? And power consumption is so low that something like a wifi router can produce enough RF to satisfy it?

[pocketstar]

Same principle in that they both use electromagnetism, yes. But Qi and similar wireless charging using inductively couples coils. WISP power is generated from radio waves absorbed by the antenna generating a small current then boosted to a usable voltage for a low power microcontroller. The microcontroller can control the impedence of the antenna, changing the backscatter of the antenna, measure the change in backscatter you can get your 1s and 0s out of the sensor!

edit: wifi router could power these sensors, just a limited range.

[rasz]

Indeed, its _so amazing_ it has potential of replacing $.2 watch battery some day.

[edoloughlin]

It is amazing. With this approach, you wouldn't have to change the battery every 10 minutes.

[icoder]

Although I don't recognise myself in the style of the comment you're responding to, I would like to point out a (watch) battery will not die in 10 minutes when drawing microwats only. I think we want to separate low energy usage, which is a cool feat by itself, and RF harvesting (which goes well with low energy usage, but so might a small, cheap, battery).

[edoloughlin]

I'm not an RF engineer, but the video mentioned that the 'traditional' WiFi component would draw 1W. I assumed that, if you add a battery, it's to power this part.

[rasz]

No, backscatter is the only legit part of this writeup, everything else is made up.

"we simulate an ASIC, which achieves 60 fps 720p and 1080p HD video streaming for 321 µW and 806 µW, respectively" simulate, how convenient!

"Our inter and intra-frame compression algorithms reduces total bandwidth requirements by up to two orders of magnitude compared to raw video" so they also invented mpeg4 level of compression 1mW codec.

You might wonder how such an amazing compression codec works? its middle-out. They transmit "fullhd" by transmitting ~100x50 resolution intra frames ":). Everything is Simulated, Estimated, Planned, Theorized, Calculated and Faked. That cool 1080 YT clip of them walking around the corridor just after showing you face mounted camera models? Never happened, prototype is BW 112×112, "simulated" again. Their setup can do 1080@60 of a static picture, there is only enough bandwidth to sustain ~2fps without dropping data. They even conveniently kept all the calculations ignoring color (3x the data).

Reminds me of energy harvesting wristwatch crowdfunding HN was raving about few months back, conveniently ignoring particular design including battery able to power it for couple of years.

[rasz]

>10 minutes

try 10-20 days if you believe in their simulated 800uW ASIC with magic middle out compression. Assuming everything works according to their predictions and simulations (nothing was actually build to confirm that) you have to pump 1W from your cellphone to power 1mW wearable camera. Your cellphone will run out of battery after 4-6 hours.

Think about that for a second, they want you to recharge your phone every 6 hours to "save from inconvenience of recharging your wearable". This is they main proposed design, right there in YT presentation.

[pocketstar]

It really is. The bottom line is these sensors can scale to small sizes unlike watch batteries enabling remote sensing and integrated manufacturing. Think temperature sensors inside that watch battery. Strain sensors in existing and future infrastructure to monitor uninspectable areas for >50 years. There are a lot of novel applications.