Led array display

This guide will walk you through connecting the LED array and using some code examples to make those LEDs light up. 5e was used to dynamically display Arabic numbers by controlling the driven circuit, validating the potential of self-emissive micro-PeLEDs in practical display applications. Oct 30, 2023 · a SiO 2 passivation of InGaN dual-color micro-LED array. 29. Apr 22, 2020 · In the experiment, the LED array has 64 × 64 pixels resolution with the size of 88 mm × 88 mm. Gallium nitride (GaN) micro-light-emitting Controlling LED Matrix Array With Arduino Uno (Arduino Powered Robot Face): This instructable shows how to control an array of 8x8 LED matrices using an Arduino Uno. Because of this, it is compulsory to utilize mass transfer technology for large area micro-LED displays by shifting the LED array to a receiver substrate. LED. com: HJHX 2pcs Ws2812b LED Matrix 16x16,256 Pixels RGB 5050SMD Full Color Individually Addressable Digital Led Array,Programmable Flexible Led Screen Panel Display for Arduino, Raspberry pi,etc DIY Project : Electronics The concept of these LED array displays is straightforward, but implementation is quite challenging if the goal is to develop high-resolution 3D volumetric 3D display systems. The Full-Array LED Display uses a two-layer system to reduce electrical loss and increase the light output. Fabrication of a vertically-stacked passive-matrix micro-LED array structure for a dual color display. The good news is that the display is pre-white balanced with nice uniformity so if you turn on all the LEDs it's not a particularly tinted white. Buy Multicolour LED Bar Graph Arrays. · Transparent Displays: See-through screens that find use in retail, automotive, and more. The HAT takes care of level conversion and power distribution so you can just plug in displays and go. Micro-LED displays take advantage of the exceptional luminance of LEDs by spreading the generated photons over a larger area than the area occupied by the micro-LEDs themselves, either by distributing the LED elements spatially or by Aug 1, 2011 · An auto-stereoscopic display is a device that can render 3D images for viewers without the aid of special headgear or glasses. Nov 1, 2016 · An array of micro-LEDs makes up a micro-LED display, which ranges in size from fractions of an inch up to 70 in. To achieve higher pixel density, the luminous pixels of panchromatic micro-LED arrays have been gradually reduced. Consider your budget, usage, room lighting, and viewing angle requirements before making your decision. Oct 19, 2020 · The rapid development of display technologies has raised interest in arrays of self-emitting, individually controlled light sources atthe microscale. 16mm. visible light communication and display. 84mx7. Deep-UV Micro-LED stimulated quantum dots display obtained 121% of the Rec. Jun. Mar 24, 2023 · A squeegee photopatterning method was employed to obtain a patterned PQD array with thermal stability and uniform dispersion during the patterning process for a full-color PQD micro-LED display. Prepare 8 LEDs with cathode legs trimmed to around 10mm. It is extremely important to be diligent in this process. The device has combined vertically stacked blue and green passive-matrix LED array chips sandwiched by a transparent bonding material. To focus on serving our overseas customers with the most durable, functionalized, and intelligent LED display system, LEDARRAY was established in 2014 by its two co-founders who were formerly have had working experiences in leading LED display manufacturers, are experts in LED display engineering since 2009. 7M colors to ensure that the picture super three-dimensional sense. No. Typically arranged in grid pattern with either the positive or negative terminal of the light emitting diode tied together as a common circuit node. In this study, we proposed a super multi-view 3D display with 170 viewpoints based on rotating OLED display columns. Dec 26, 2022 · We developed a prototype of full-color micro-LED display by patterning the optimized QD-PRs on a large-area micro-LED array (20 × 20 pixels) after the metal interconnection process (Supplementary 2pcs Ws2812b LED Matrix 16x16,256 Pixels RGB 5050SMD Full Color Individually Addressable Digital Led Array,Programmable Flexible Led Screen Panel Display for Arduino, Raspberry pi,etc DIY Project. 1 The micro-LED array structures are divided into those with active and passive matrices, and both of them have advantages and Sep 1, 2011 · A new design of an auto-stereoscopic swept-volume display (SVD) system based on light-emitting diode (LED) arrays based on a combination of PC software, field-programmable gate arrays (FPGAs), and supporting circuitry is presented. disclosed a three dimensional video display device with rotating LED array in their patent, as shown in Fig. The improvements are achieved by choosing a chromatic LED chip with a small size (SMD18 Apr 14, 2021 · Over the past 20 years, considerable research effort has been focused on the development of flexible displays, including light-emitting diode (LED) arrays integrated into flexible substrates, thin Specifically, the role of integration technology in micro-LED display manufacturing is reflected in the following 3 aspects. In this paper, we present a new design of an auto-stereoscopic swept-volume display (SVD) system based on light-emitting diode (LED) arrays. 8 to 4 V (nominally 1. There are 20 pins, 10 on each side, with 0. LED displays can be networked together to form a Jun 4, 2019 · Passive matrix GaN-based micro light-emitting diode (LED) arrays with two resolutions of 32 × 32 and 128 × 64 are designed and fabricated, and a micro control unit is used to drive the devices and display Chinese characters. It is realized by bonding the GaN epi with the pre-defined anode pad array to the specific pixel driver on the IC backplane, followed by laser lift-off and ICP BRAVIA Mini LED backlight. LED Bar Graph Array, Green, 20 mA, 2. 1 spacing so you can easily plug it into a breadboard LED circular arrays are packages of multiple LEDs used to create luminaires (combined light sources). This would be a nightmare to drive with plain RGB LEDs, even with cunning multiplexing, but luckily you can buy indexable Oct 10, 2023 · As technology continues to advance, LED displays are poised for exciting developments. 2020 standard in the CIE 1931 color space. and is The device exhibited a minor blue shift phenomenon as the current density increased. The CXB1310 incorporates Cree's SC5 Technology Platform in the 6mm LED array which delivers the most lumens in the industry for the light-emitting surface (LES) size. Step 3: Arranging the LEDs. This tightly packed LED array allows for new and differentiated The example code in listing 1 is a simple LED dot matrix display driver that uses column multiplexing to display a pattern. Apr 12, 2023 · Firstly, full-color display requires integrated micro-LED array with polychromatic emission (red, green, blue [RGB]), or integration of monochromatic micro-LED with color convertors [31,32]. However, this results in an extremely high level of pin usage on either a microcontroller or a latch integrated circuit (IC). This system can be electrically converted between 3D and 2D modes by using different combinations of LEDs in the LED array without any mechanical movement. Feb 5, 2024 · The LED lights of full array displays are smaller in size, which gives more control and freedom to master the display. Full-array TVs have a similar LED placement, but the number of LEDs is significantly more, and these LEDs are divided into different zones. You can buy a pre-built multiple-block LED Matrix (e. Power Requirements. 8-bit micros are going to struggle if they work at all. Step 3. 2015. This system is constituted of a display device and a graphics control sub-system. Use the circuit figure below to connect the Arduino LED matrix together. 6 V for blue, and as high as 4. We report a color tunable display consisting of two passive-matrix micro-LED array chips. Learn how to control multiple LEDs with Arduino, using the array + function combination. The HDSP-4850 is a 10-element Bar Graph LED Array designed to display information in easily recognizable bar graph form. 18µm CMOS technology to be integrated on a 512x512 microLED array by using the KlettWelding hybrid interconnection technique forming a microLED display of 1411 ppi with 10kfps working speed. 1 The micro-LED array structures are divided into those with active and passive matrices, and both of them have advantages and Display Modules - LED Dot Matrix and Cluster units are Devices that use a light emitting diodes arranged in a matrix layout to provide visual graphics. Feb 12, 2016 · We recommend the 3 x 4-1/4″ Solderable Perf Board model: 64-8934. Many kinds of research have been done to explore how to combine the lighting and data transmission and how to increase Jan 11, 2018 · Visible light communication (VLC) is being explored as an alternative form of wireless transmission due the increasingly crowded radio frequency spectrum. Stereoscopic, or multi-view, display systems are considered as better alternatives to conventional two-dimensional (2D) displays, since such systems can provide Large 8x8 LED Matrix Assembly Part 1 - jolliFactory. g. 1. Processing and characterization of high resolution GaN/InGaN LED arrays at 10 micron pitch for micro display applications. b InGaN blue/green dual-color micro-LED display with Si growth substrate removal. 5mm drill for 1. 2 comentarios Facebook Twitter Flipboard E-mail. 1, the thermal behavior study can be simplified into a 10-LED in line array. B03. 5in x 3. 1 V, 1. Just like with Full Array, Mini LED TVs control areas of the backlight so both dark and bright subjects are presented clearly. Enhance the grayscale to 22bit. System Design VLC system with LED array cube is usually low-data-rate, which is suitable for the indoors positioning and other Internet of things application. The following are the main steps to take to build the 8x8 LED Matrix: Step 1. This ultra-wide color gamut indicated it as a competitive candidate for future display technology. 00 with coupon. 8 V for a red LED, moving up to 2. Using a microcontroller, and a whole lot of LEDs this tutorial walks through the concepts behind making this 24×5 display possible on only a single microcontroller chip. Feb 6, 2017 · We report a color tunable display consisting of two passive-matrix micro-LED array chips. As a result, this configuration requires 28 pins for 4-segment displays. 3. 2023. Jan 18, 2023 · Micro light-emitting diode (micro-LED) display, mainly based on inorganic GaN-based LED, is an emerging technique with high contrast, low power consumption, long lifetime and fast response time Jan 22, 2009 · This video outlines how to build your own large LED Array that can be used to display patterns, simple preprogrammed messages, or even scroll data from your PC. First, the deep However, the core technology of VR, near to eye display technology, is still hard to attain people's expectations [1,2]. Oct 9, 2023 · High level of grayscale control, LED display can be used 1024 ~ 4096 level of grayscale control clearly and realistically show more than 16. 3sqm (3. Then on the bonnet: Unscrew the small screws at the top of the terminals. The emergence of micro-LEDs which have significantly higher modulation band-widths compared to conventional larger area LEDs is important as it not only enables VLC links with higher data rates but also opens up the possibility of VLC being Apr 7, 2022 · [67-69] Normally, in inorganic LEDs, the dimension of developed wafers is usually 4, 6, and 8 in. Because there are 8 sets of 10-LED arrays and the LED array arrangement is symmetrical, shown in Fig. You can use the solder dot prototyping board for soldering the LEDs on it. 2013. Jun 25, 2022 · VA monitors commonly have contrasts of 3,000:1, while a typical IPS comes in at 1,000:1. 2 V for yellow, 3. Each of the OLED display columns is composed of OLED display units and optical lenses, which generate 170 viewpoints. Oct 1, 2017 · Micropixelated blue (470 nm) and ultraviolet (370 nm) AlInGaN light emitting diode ('micro-LED') arrays have been fabricated in flip-chip format with different pixel diameters (72 microm and 30 Jun 12, 2018 · Step 3: Matrix Theory ! If you don’t know what a LED matrix is here is a very simple explanation for it, If we connect the cathode of a LED to –ve of supply and anode to +ve of supply this will be a 1X1 matrix. Article CAS Google Scholar Kang CM, Kong DJ, Shim JP, et al. In this paper, a VLC system with LED array cube will be introduced. To change the message in microcontroller we have to reprogram it every time we can outplay this scenario by integrating it by new wireless IoT RoHS. Aug 1, 2019 · Passive matrix GaN-based micro light-emitting diode (LED) arrays with two resolutions of 32 × 32 and 128 × 64 are designed and fabricated, and a micro control unit is used to drive the devices and display Chinese characters. During an emergency, they immediately display pre-programmed messages as needed. Feb 9, 2018 · Driving arrays of 7-segment LED displays can involve connecting each control pin to a dedicated output. 9 mcd, 10 LEDs, 25. Our Mini LED TVs have highly accurate backlight control that's unique to Sony—XR Backlight A full‐color micro‐LED display can be achieved by red, green, and blue (RGB) chips or by a blue/ultraviolet (UV) micro‐LED array to pump downconverters. This display is bright, beautiful, and funky with nice diffused rectangular lenses for a striking look. They should also be square to the face. Size: 55. Some of the emerging trends and innovations include: · Flexible Displays: Displays that can be bent or curved for unique applications. Based on different full-color schemes, the integration method is either transferring RGB onto an assembled package or growing RGB together into a same chip. 1. Features of full-array LED display . The pattern to be displayed is stored in the array mBuf. Pixels were driven at a constant current with pulse width modulation to achieve sixteen levels of gray. the first 1100, second 1200, and third micro-LED panels 1300emit light of different wavelength bands. Dec 28, 2023 · Full Array LED offers superior contrast, enhanced picture quality, and improved viewing angles, while LED TVs are thinner, lighter, and more cost-effective. the voltage applied on the LED is larger than the threshold 2. IPS Black displays, which started coming out this year, claim to double the contrast of typical IPS led 1 blinking led 2 blinking led 3 blinking led 1 blinking led 2 blinking led 3 blinking led 1 blinking led 2 blink ended led 3 blinking led 1 blinking led 2 blink May 2, 2024 · Unlike traditional display devices that might use fluorescent lamps or incandescent light bulbs, an LED display employs a vast array of LEDs, providing unparalleled brightness and color accuracy. Watch on. Farnell UK offers fast quotes, same day dispatch, fast delivery, wide inventory, datasheets & technical support. FREE delivery Tue, Apr 23 on $35 of items shipped by Amazon. In parallel to mass transfer technology, pick and place, selective release and transfer, and MicroLED. Jan. Ideally, the LEDs have replaced the traditional cold cathode fluorescent. $2888. Make your code much more readable and scalable. These arrays are called circular because they combine to form a circle of light engines (known as a family) that work as a singular light output. The first step is to wire up the LED bar graph display to the Arduino board. Push the LEDs through the adjacent holes on the board. An analysis of array luminance uniformity is Recent years, visible light communication (VLC) has become popular technology to implement radio frequency technology, because of the security, safety, no electromagnetic radiation, and so on. This way you might display letters, numbers or custom animati… The LED Array (8x7) is a set of 56 LEDs arranged in a nice 8x7 grid. In addition to many problems faced by the optical fiber bundle display, there is an issue of voxel occlusion due to the opaque nature of LEDs themselves. The micro-display has the pixel pitch of 30 μm and the size of micro-LEDs is only 8 μm. Visible light communication (VLC) is being explored as an alternative form of wireless transmission due the Apr 1, 2021 · Micro-LED array device is of broad interest in the VR display [1], neuronal stimulation [2], optical wireless communication [3], LIFI [4]. The QNED90 has a 120Hz panel in front of its mini-LED Full Array Local Dimming arrangement, while the QNED85 makes do with a 60Hz A 400×240 monochromic micro-LED micro-display based on GaN vertical-LED structure is presented. Our main products are LED flexible strip, LED neon strip, magic LED strip, IP68 LED strip, LED flood light, and LED highbay. Feb 25, 2014 · A single LED requires drive current between 20 and 60 mA, and has a voltage drop of 1. These big displays might be impressive, but there remains significant room for innovation and interest in arrays at far smaller scales. Make a small linear display with a glowing red color using this elegant LED bar graph only 1 long. Firstly, full-color display requires integrated micro-LED array with polychromatic emission (red, green, blue [RGB]), or integration of monochromatic micro-LED with color convertors [ 31, 32 ]. Slide the exposed copper from the cables into the terminals. 312023. Dec 30, 2022 · This LED displays are becoming primary need in heavy crowded places such as malls, railway stations, educational institutions to display information regarding offers, platforms or important notices. Apr 21, 2023 · Guo W, Tai J, Liu J, et al. 10 LEDs are contained in the plastic body. The scanning method is based on static latching to guarantee high-intensity bright light. Insert these 8 LEDs to the leftmost column of holes of jig #4 (see photo above for orientation of LED). 5 V for green, 3. Jan 7, 2020 · Edge LED, Direct LED y Full Array: diferencias entre los diferentes tipos de iluminación para televisores LED . In the display device, a rotating LED unit has a left-eye LED array and a right-eye LED array. The process began with the growth of a bilayer MoS 2 thin film (thickness, ~1. Available in a variety of sizes and colors Feb 5, 2024 · The LED lights of full array displays are smaller in size, which gives more control and freedom to master the display. Silicon nitride (SiNx) is the main component of dielectric protective layer as a mask layer in the . But LEDs of Mini LED backlight are much smaller and denser, so they need far more precise control. A LED matrix can be composed of a single block or multiple blocks in a daisy-chain. This display does best with a high speed, high RAM microcontroller like a SAMD21, SAMD51, ESP32, etc. We demonstrate that vertically stacked blue and green micro-pixels are inde … The important factors on this are: A) the holes should be a tight fit for the PMMA fiber, in this case I used a 1. Similarly now if I take 2 LEDs and short their cathodes this will make 1X2 Matrix and If I add Feb 1, 2023 · Ludovic, D. Oct 1, 2017 · The relationship between the LED structure and driving architecture in an integrated active matrix micro-LED system is discussed andSimulated results show that an NMOS active matrix driving circuit is able to achieve 4 times the modulation bandwidth of an equivalent PMOS circuit. 4mm x 10. As the name suggests, these screens use light-emitting diodes (LEDs) to form images. However, such a color‐converted micro‐LED system usually suffers from color crosstalk and low efficiency due to limited optical density of Apr 4, 2022 · Figure 1a presents a schematic illustration of the stages in the fabrication of a full-colour micro-LED display. When in non-emergency mode, they can display time and date, or any other message as desired. There's a lot of LEDs! The LEDArray Series Indoor displays are LED message centers designed for light industrial, commercial and office use. J Elec Materi, 2019, 48: 5195–5201. First, the deep Jun 6, 2022 · Micro-light emitting diode (micro-LED) is an emerging display technology with excellent performance of high contrast, low power consumption, long lifetime, and fast response time compared with the current display (e. The LED array can display binary patterns with red, green and blue at a maximum rate of 2. avicena. ShenZhen Arraystarled Limited specialized in commercial lighting and industrial lighting products manufacture and development. Jan 11, 2023 · The 5 × 5 array in Fig. 4 nm the micro-LED array display device capable of achieving full colorincludes a first micro-LED panel 1100, a second micro-LED panel 1200, and a third micro-LED panel 1300, each of which includes a plurality of arrayed micro-LED pixels. The left-eye LED array displays a left-eye image and the right-eye LED array displays a right-eye image. Gallium nitride microLEDs transferred onto a silicon backplane - these optimized for high speed data connections (from Avicena - www. A LED circular array has an integrated LED driver (electronic control gear) that protects the Introduction. B) the hole spacing should be fairly accurate to match the LED array, so that the light couples to the fiber. The high efficiency, contrast and color quality of such direct-image LED displays result in excellent performance, although the products remain more expensive than traditional backlit LCD displays. Before you get started you'll want to be familiar with LED matrices and the Raspberry Pi by reading these guides: 16x32 and 32x32 RGB LED Matrix Guide. c Al(Ga)N buffer etchback to open the window regions on Nov 28, 2019 · Hidefumi et al. Because we’ve opted to use the common-row cathode arrangement in our matrix, we will be inserting the pins of the LEDs into the perf board in a particular fashion. Each element in mBuf contains a value that indicates whether the corresponding LED in the matrix display should be on (1) or off (0). As the light source of the VLC, LED has two main functions, lighting, and display. tech) MicroLED, also known as micro-LED, mLED or μLED is an emerging flat-panel display technology consisting of arrays of microscopic LEDs forming the individual pixel elements. It relies on Charlieplexing to control individual LEDs, which means less GPIO pins are used (as opposed to a traditional grid format ). 2m double side) led display, led screen Introduction to LED Technology. SPIE 10104, Gallium Nitride Materials and Oct 1, 2018 · An optimized array process of micro light-emitting diode (LED) display is descripted as follows. Then tighten the screws to secure them. Micro-LED array has great potential in VR display due to the advantage of small size, high brightness, high resolution, low energy consumption, and good monochromaticity compare to the other display technologies. LED array drivers, with accurate constant current regulation and embedded serial interfaces, offers a solution that is suitable for most of the Jul 21, 2022 · Amazon. 5 MHz, which is a significantly improved device of our previous work . You will declare the size of the LED matrix you use in the ESP32 code. Apr 13, 2023 · Example1: how to use led bar graph display with Arduino without an analog input. 5mm fiber and the fit was good. et al. This involves connecting each LED in the bar to a digital pin on the board, as well as connecting each LED to a resistor to limit the current flowing through it. 9-inch model comes with a “2D backlighting system with 2596 full‑array local dimming zones Jan 4, 2022 · Mini-LED is a type of screen tech found mostly in TV displays. Aug 20, 2013 · – with 512 LEDs lit (ie all LED on each board) it drew from 140mA (0) to 1760mA (15). An auto-stereoscopic display is a device that can render 3D images for viewers without the aid of special headgear or glasses. display (LCD) and the organic light-emitting diode (OLED) display technologies on the market, micro displays based on micro-LED array technology have fast response, active illumination, high contrast, long lifetime, etc. 1in LED Matrix Flexible FPCB Full Color Works with K-1000C,etc Controllers Image Video Text Display DC5V : Tools & Home Improvement Apr 23, 2024 · The Adafruit LED matrix HAT also makes it easy to connect RGB LED matrices to the Pi. LED Distribution Nov 4, 2021 · A larger matrix like this 16 x 16 x 16 LED build, has a total of 4096. BROADCOM. With technological advantages, micro-LED holds promise to be widely applied in augmented reality (AR), flexible screens, etc. But unlike both direct-lit and full-array TVs, edge-lit TVs have LEDs on the perimeter, and depending Aug 3, 2023 · In this work we present an in-pixel driving circuit designed in a 0. High driving power. Apr 16, 2019 · The Journal of the Society for Information Display publishes original works dealing with the theory and practice of information display. Oct 13, 2023 · As the name suggests, direct-lit TVs feature a panel of LEDs placed directly behind the display stack. LED Distribution The LED arrays consisted of 240 columns 2 144 rows (u0018VGA/8) with pixels on a 20-u0016m pitch and were driven in a column major matrix addressing mode at 60 frames per second for image display. com: BTF-LIGHTING WS2812B RGB 5050SMD Individually Addressable Digital 8x32 256 Pixels 12. Opt Express, 2017, 25: 2489 Feb 21, 2021 · Volumetric 3D displays that allow the viewing of full 3D images without special glasses are not unknown in our community, usually taking the form of either a 3D LED matrix or a spinning rotor eithe… May 1, 2012 · The conventional LED flat panel display consists of an 80-LED chip array in line used for the bottom lighting. It is the LEDs that form pixels, play an integral role in backlighting, and subsequently help in the image or video display. This guide might be used to create a simple (and relatively cheap display) for your own projects. May. 0 V for amber, 2. Driving LEDs means that designers must shift their thinking from the more-common voltage-sourcing supply Sep 28, 2023 · Depending on the exact panel you purchase, you will likely need to cut and strip the red and black wires. The use of LEDs in applications like displays, information and advertising panels, signs, traffic signals, automotive lighting and architectural lighting is becoming more and more common. With the rapid advancements in TV display technology, there’s no doubt that the Welcome to visit our booth at Hall 17. The 18V Cree XLamp® CXB1310 High Density (HD) LED arrays are the next generation of high lumen density LED arrays. 4-in-1, 8-in-1) You can also buy multiple blocks and wire them to form a LED matrix with the desired size. Which consist of 1 Row and 1 Column. Step 2. This technology spans a wide spectrum of applications, from the immersive experience of large-format digital signage in public spaces to the personal Mar 10, 2015 · You need to connect all the positive leads of the LEDs in columns and the negative leads in rows. Save $3. Abstract A high-efficiency organic light-emitting diode (OLED) microdisplay has been developed with some new technologies including microlens array. 0 V for white). 2020-01-07T11:22:39Z . Use of this bar graph array eliminates the alignment, intensity and colour matching problems associated with discrete LEDs. This technique provides 3D images to the viewers with Mar 23, 2016 · Amazon. The device has combined vertically stacked blue and green passive-matrix LED Apr 23, 2021 · According to the iPad Pro tech specs, the mini-LED-powered Liquid Retina XDR display in the new 12. The latter helps relieve the burden of epitaxial growth of tri‐color micro‐LED chips. A better way to lower the pin count is to We propose a two-dimensional (2D) to three-dimensional (3D) convertible display technique using a light-emitting diode (LED) array based on the principle of modified integral imaging. , liquid crystal and organic LED (OLED)). Feb 6, 2017 · A dual color micro-LED array with a vertically stacked subpixel structure is realized and the color of each pixel is tunable in the entire wavelength from the blue to green region by applying pulse-width-modulation bias voltage. If you power the array from the Pi and the array draws too much current (eg because you’ve attempted to display some text or patterns that needs too many LEDs lit), your Pi will of course cut out. Large-screen display system with rotating LED arrays. Process optimization of passive matrix GaN-based micro-LED arrays for display applications. In Proc. The process of the micro-LED display arrays is systematically optimized, where emphasis has been put on solving two specific technical problems. uw ny qf xx rz pd vi pa sd de