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Wearable Electronics
Published in Muhammad Mustafa Hussain, Nazek El-Atab, Handbook of Flexible and Stretchable Electronics, 2019
Sherjeel M. Khan, Muhammad Mustafa Hussain
A display can be added to a wearable device for a visual representation of data and alerts. The most common type of displays is LCD, LED, and organic LED display. For example, a display can show the heart rate of a patient and show an alert if the patient is detected to be in a chemically hazardous environment. The displays are the most power-consuming components in a wearable electronic system where a small 1.5 inch TFT-based LCD display can consume the power of about 272 mW. The amount of power consumed by a display is directly proportional to the size of the same technology display [61]. Displays are an optional component of a wearable device as we discussed that wireless connectivity has become a necessity for a wearable, and a wearable can use the display on the central node to display relevant data. It is for the same reason that we see smartphones and wearables with displays need to recharge many times a week.
Light-Emitting Diode Displays
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
A light-emitting diode (LED) display manifests itself as a flat panel display that uses LEDs to display video. An LED is a particular solid-state p-n junction diode that gives out light upon the application of a bias voltage. The luminescence process in this case is electroluminescence, which is associated with emission wavelengths in the visible and infrared regions of the spectrum. When a forward bias is applied to the p-n junction diode, carriers are injected into the depletion region in large numbers. Because of their physical proximity, the electron–hole pairs undergo a recombination that is associated with the emission of energy. Depending on the semiconductor band-gap characteristics, this emitted energy can be in the form of heat (as phonons) or light (as photons).
Visual monitoring
Published in Michael Talbot-Smith, Sound Assistance, 1999
VU meters and PPMs have been around for a long time - since the 1930s. In recent years other devices have become available, made possible by advances in technology. There are broadly two types: LED (light emitting diodes). Typically these small light sources are arranged in vertical (sometimes horizontal) columns and appear as a line of green lights, the colour being changed to red above the ‘overload’ region. There is usually associated circuitry that gives a quasi-peak-reading display - the highest LED stays lit for a second or two after the peak has passed. (This is sometimes called a bouncing ball display.)LED displays differ in their resolution: on domestic tape recorders, for instance, the individual LEDs may be 4 dB apart, reducing to perhaps 1 or 2 dB at the top end of the range. On professional equipment the resolution is better, say 2 dB over a wide range. The advantage of LED displays is that they take up very little panel space and are easily observed. The accuracy is never as good as a PPM and for line-up purposes a simple VU meter is a useful addition.Plasma displays. These are much more complex devices and are often to be found on large sound mixers. They appear as a column of light, changing like LED displays to red above a certain level. The column of light in a typical unit is a centimetre or so wide and perhaps 10 cm long. The resolution is good and an accuracy of 1 dB or better is achievable. On some major sound mixers a long line of plasma displays can be used to indicate levels on each microphone channel, switchable to a VU or PPM response.
Precursor sources dependent formation of colloidal CdSe quantum dots for UV-LED applications
Published in Particulate Science and Technology, 2023
Naina Lohia, Shailesh Narain Sharma, D. Haranath
In the current era, futuristic flat panel displays and solid-state lighting have some challenges in the areas of improving efficiency, brightness, color saturation, and thus flexible substrate compatibility (Sekitani et al. 2009; White et al. 2013; Yokota et al. 2016; Kim, Ghaffari, and Kim 2017; Huang, Parashar, and Gijs 2021; Kiprotich, Dejene, and Onani 2022) owing to have their potential application. Current studies on the fascinating optical performance of colloidal nanocrystal (NC) quantum dots (QDs) of compounds in columns II–VI of the periodic table have recommended that QD-light emitting diodes (LEDs) could be a better cost-effective alternative. Particularly, the exceptionally narrow band emission of the monodispersed NCs QD populations resulted in full width at half maximum (FWHM) of ∼18–30 nm (Talapin et al. 2010; Shirasaki et al. 2013). In comparison with the organic LEDs and liquid crystal displays, QD-LEDs produce red and green color emissions with much high spectral purities. Spectral purities of QD-LEDs were observed to be 30% greater than that of the still preferred cathode ray tubes for exhibiting excellent color rendition (Xu et al. 2005; Moeller and Coe-Sullivan 2006; Steckel et al. 2006; Thomas et al. 2021; Mohammed et al. 2022). Since the QD-LED display system have the potential to create a wide range of colors by changing the relative intensities of the three primary colors, i.e., red, green, and blue (RGB) subpixels in each of the screen pixel cell (Moeller and Coe-Sullivan 2006). Thus the superior color purity of RGB-based QD-LEDs will consequently improve the variety of colors that would be displayed in an unprecedented fashion (Rizzo et al. 2007; Talapin et al. 2010; Shirasaki et al. 2013; Chen et al. 2014).