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7.5-inch e-ink display is powered completely by NFC:
NFC (Near Field Communication) is usually only used to for quick text transfers, like a tap-and-pay transaction at a register or a quick data transfer from an NFC sticker. A company called "Waveshare" is really pushing the limits of NFC, though, with a 7.5-inch e-ink display that gets its data, and its power, from an NFC transfer. The $70 display doesn't have a battery and doesn't need a wired power connection.
E-paper (or e-ink) displays have the unique property of not needing power to maintain an image. Once a charge blasts across the display and correctly aligns pixels full of black and white balls, everything will stay where it is when the power turns off, so the image will stick around. You might not have thought about it before, but in addition to data, NFC comes with a tiny wireless power transfer. This display is designed so that NFC provides just enough power to refresh the display during a data transfer, and the e-ink display will hold onto the image afterward.
NFC's power transfer works just like wireless phone charging: the reader (probably your phone) generates an RF field to transfer power to the passive NFC object. NFC stickers (and any other NFC device) have a sizable spiral antenna to harvest the RF signal, just like a wireless charging coil. The amount of power you can transfer over NFC depends on the design of the object and the reader, but Waveshare warns that some phones might not put out enough power. If your phone doesn't work, the company recommends an NFC board that puts out 1.4 watts of power, but Waveshare also shows the device working with a pretty old Android phone, a Samsung Galaxy S7 Edge from 2016.
(Score: 0) by Anonymous Coward on Friday March 20 2020, @03:20AM (2 children)
Thanks... I am still working on HMI for my Arduinos, and am always looking for ways of reducing complexity, connections, and power.
I am quite thankful janrinok ran this one. I will probably buy one of those eval kits and see if there is some way of making a simple way of displaying data from Arduinos graphically without consuming the battery.
Like mimicking a Nextion HMI....
(Score: 2) by dwilson on Friday March 20 2020, @04:08AM (1 child)
I've got a mid-1980's Nissan pickup with an RPi in it, with a bunch of custom sensors feeding data to it. Currently it streams it to an apache page which a smart-phone sitting on the console can display. If you come up with a better plan, I'd love to see it and maybe work to improve on it.
I'm working to modify a stock dash with GM-style stepper motors driven by an Arduino, but haven't gotten very far on that project. What is this eval kit you refer to? Link?
- D
(Score: 1) by anubi on Friday March 20 2020, @11:14AM
Eval kit:
https://www.waveshare.com/7.5inch-NFC-e-Paper-Eval-Kit.htm [waveshare.com]
And I already have another instrument cluster mechanically, although not electrically drop- in, compatible with my van.
It is my goal to rebuild the instrument cluster so it's all driven via I2C, then I can program the gauges to read like I want them to read, and get both tach and speedo known accurate. Also I want my speedo to show me individual glow plug currents during the wait-to-start interval.
Look up the National LM1819 for how to drive the speedo and tach display...however I intend to use DAC (MAX521) driving Howland current sources to do this.
I'd like to repurpose the tach for other things by just telling my Arduino what to route to it, and I'd like to have my software help me in the event someone tries to steal my van, mimic all sorts of odd problems, make it so frustrating no one would want such a mess of problems. Also discourage these businesses that require valet parking. I'll fix it so they will "break" it so I can have some fun with them. Let em drive it six feet, then shut it down. Yeh, I've kinda got a mean streak in me when someone else thinks he can force me to give him my keys.
Also discourages those who try to "be my friend" to get free van rental. Everyone who owns a pickup truck knows exactly what I am talking about. Some people seem to come out of nowhere get their head in front of you, hock up their request, and expect you to hand over the keys. Yeh, the same ones that will give others the finger when the don't need a favor. If anything, I'll get a top off of diesel, as the gauge will read empty.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]