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Comment by akincisor | Hacker News Reader

It would be a good choice to replace tablets that are used outside conference rooms to show the schedule and/or book the room.

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If you could parasitically power the unit from Wi-Fi beacon frames that would be awesome. The idea of a sign that "magically" updates itself over the air gives me a giddy "I live in the future" feeling.

Interesting thought. At that point (or for that fact - at this point) it's is essentially a reusable printable paper. For people arguing about the low resolution of the $70~ model, I would not disregard their argument because we haven't seen it in real life and would love to see how documents scale up on that display.

If you aren't using super-white printer paper, not sure that this is any more eco friendly than printing a sheet of paper off twice a day, every weekday for years. Not sure what the materials impact is for e-ink, and paper is a renewable resource and sourced from trees generally grown specifically making paper as a crop.

We already power our iPads via POE< which is also how you'd power those beacons, so it's not really a great improvement.

BUT the idea that you would "tap in" to book it would be great.

Is there a PoE to lightning adapter?

edit: $28 splitter, https://www.poetexas.com/products/af-lightning

And $100 Belkin Ethernet-PoE adapter.

Use a PoE to USB (female USB-A or USB-C) adapter - variety of models e.g. I saw one for $10 on Alibaba.

I'm talking about radio energy powering the device. 802.1 beacon radio frames, which your access points send out over the air. Configure it via USB, etc, then just hang it on the wall. No cables. Just a passive device.

WiFi -> electric current rectennas announced a year ago[1] were in the range of 40 microwatts, and the blog post says this NFC system runs at 1.4 Watts, that feels a long way away. But years ago LCD calculators could run on a solar cell the size of a finger and powered by ambient room lighting - surely must be some close to crossover level available.

[1] http://news.mit.edu/2019/converting-wi-fi-signals-electricit...

I'm wondering if that was a constant 40 microwatts, and if that could be stored in capacitors so that every 4-5 seconds (the refresh rate of the panel) there would be enough energy accumulated to power the circuitry for an update.

Yes is the answer, but it would be much slower. Assuming 1w for 6 seconds (4s refresh + 2s transfer), it would take about 42 hours for a lossless storage + regulator circuit. 40uw is an incredibly small amount of power.

It doesn't say that the e-Paper requires 1.4 Watts. The board that can be used as an alternative to a mobile device provides 1.4 Watts.

Actually, there are units similar to this that update over Infrared (even non-directionally)

Best Buy use them as price tags: https://www.youtube.com/watch?v=7aVoeDC-7MA

Similar insofar as using e-ink, but they're battery operated (from what I can tell). The "coolness" of what I'm talking about would come from being a completely passively-powered device.

The power density of light is vastly higher than the power density of Wi-Fi almost anywhere. If you can't do it with PV, you definitely can't do it with Wi-Fi.

My employer uses Roomz (https://roomz.io/) which does exactly that.

It has some trade-offs like being very laggy if a meeting is spontaneously cancelled, and it doesn't show double bookings, but besides that, it's pretty attractive.

They're battery powered:

> More than 2 years of autonomy for the ROOMZ Display and more than 4 years for the ROOMZ Sensors. Runs on single Batteries that can easily be replaced.

Still, 2 years is pretty good.

I've seen companies waste some pretty serious time on admin and maintenance of room reservation screens by the doors. Oddly enough they had chose not to go with an iPad based system because of cost

My university replaced some room reservation tablets with pieces of paper on a clipboard.

what were the reasons for doing so? maintenance, theft/vandalism, or worse, bad software?

I assume there was some maintenance cost, but the biggest problem I saw with the tablets was there was nothing preventing anyone from deleting somebody else's meeting and replacing it with their own. There was authentication on the web interface, but nothing if you just directly edited the schedule on the tablet.

At least with the paper-on-clipboard, it's obvious if an existing meeting was crossed out.

The enterprise systems tie in to your Exchange / Outlook messaging for shared calendars. We saw excessive equipment failures with the Steelcase line. This was a few years ago. But like I said, they had the option of using iPads, but went with the proprietary solution instead -- which was NOT reliable for deployment.

With such limited power budget, is there any security circuits for authentication and encryption?

If not, it would be super easy hack.

Even the most basic xor "encryption" would use virtually no power. Define a key and xor all data coming in with it. Given the slow refresh rate of these things, it would provide sufficient security against a bruteforce.

Upload a file consisting of all zeroes (or any other known content for that matter) and now the contents of the screen is the secret used to XOR the input. Surely you meant something a bit more substantial?

You can check for a magic string after decryption and only update the screen if valid.

At this point you might as well just require a plaintext password to update the screen, and forget the XOR.

Most signs are completely insecure already. This exact tech, with no security, is already used for item/price displays in some stores. If you're worried about someone walking up and reprogramming your nfc powered eink sign, I'd love to hear why you need a secure but wirelessy powered sign.

My employer and university have had these on conference/lefture rooms for years. They're ridiculously expensive from what I remember (700€ for the ones at work, I think, the uni ones are larger and older, so probably even more expensive), but compared with not getting the information as easily as they provide it makes them worth it.

$70 for the larger one, I was really surprised at the low cost.

getting larger and the ads displayed in store windows could eventually be replaced. it would be a much better way to display pricing and menus in restaurants than the current fad of large monitors.

there are all sorts of places where information does not need real time updates that this type of technology could eventually satisfy. the best part is reduced energy use and even paper use

Many of the grocery stores in my area actually use e-ink labels[0] on the shelves.

[0]: https://www.displaydata.com/

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