Tuesday, May 31, 2022

Drawing on a plasma display with a laser pointer

An orange plasma display will retain an image caused by incident near-UV light. This is an interesting visual combination of photoelectric, hot carrier injection, plasma, and charge trapping effects.

Correction: The orange display is running at 700Hz, 130V in the video.
  I realize that I may have conflated the issues of one-resistor-per-pixel and the display's ability to maintain an image throughout row scanning. They are separate problems that are both addressed by designing the panel to work on AC. Each pixel can maintain its state (on or off) by being supplied constantly with a lower "sustaining" voltage, and can be set or cleared by giving it a momentary higher or lower amplitude. The sustaining voltage allows the pixel to be emitting light or not, and its state remains because of its own impedance until updated on the next scan. In color plasma displays, separate electrodes are used for sustaining and addressing pixels, and the discharge may be sustained between coplanar electrodes instead of plane-to-plane, as in this display.

It's also a possibility that the dielectric and MgO layer only exists on one electrode (the metal), and the ITO is bare. I don't know. On this display, if all rows are electrically connected together, and all columns are connected together, and AC is applied to rows and columns, this effect does not work -- no light is emitted at all! At least some of the electrodes (ie every other column) must be left floating to emit any light, and to show this memory effect. So, driving AC plasma panels requires more waveform tricks that I do not fully understand.

Prior art patents: https://patents.google.com/patent/US7283301B2/en https://patents.google.com/patent/US20060132716A1/en

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Saturday, April 9, 2022

Silver nanoprisms grown into structural colors by high power LEDs

How to chemically synthesize silver nanoparticles, then grow them into triangular nanoprisms with light from a variety of LEDs. Each color LED creates a different size nanoprism, which has its own characteristic color.



CMDITR video: https://www.youtube.com/watch?v=agD5jfXua-o 
Multispectral LED driver on Github: https://github.com/benkrasnow/MultiSpectLED 
Chemicals sourced from Amazon/eBay 
20ml glass vials with PTFE lined cap (do not use metal-lined): Environmental Express APC1675P Already gone from Amazon 
pH pen (this cost more than I remember, but it works really well, and has lasted many years. Cheaper pH pens are often pretty bad) https://www.amazon.com/gp/product/B01ESYG6B0/ 
Comparison of CD, DVD, Blu-ray discs with electron microscope: https://twitter.com/BenKrasnow/status/615327472909840385 
Great way to find related papers: https://www.connectedpapers.com/ 

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