Hi. The OLED displays should be powered using 5V. Do you get any address after running the I2C scanner sketch? Regards, Sara

The model we’re using has four pins and communicates with any microcontroller using I2C communication protocol. There are models that come with an extra RESET pin or that communicate using SPI communication protocol.

hello i have an idea for an project for myself but i dont understand coding that good i would ask if you could help me to get the code i need. if this is ok for you, i would like to talk further via email

Microlenses are a topic of considerable interest in applications ranging from biomimetic optical systems1 to security printing2 and solar concentrators3. The most commonly-used solid microlenses are made through delicate fabrication processes4, 5 and require mechanical adjustments to focus the image. In liquid lenses, the focal length is varied by electrowetting6,7,8,9,10. Liquid crystals (LC) can also be used to make lenses either by filling11 or imprinting LCs in curved substrates12, 13; by using a LC film with constant thickness, but spatially-varying refractive indices14,15,16; by creating focal-conic defects in smectics17, 18 and by using short pitch cholesteric liquid crystal polygonal textures19. The common feature of all these microlenses is the requirement for delicate fabrication processes. Thus, a simpler means of forming well-defined microlenses is highly desirable.

Analysis of the height profile of an N* LC microlens: (a) Plot of the square of the position of the minima with respect to their number, with m = 1 corresponding to the outermost ring. The linear dependence shows that the height profile is spherical. The lower inset shows the microlens viewed using a pair of circular polarizers and a green filter λ = 0.55 ± 0.02 μm. The length of the white arrow is 100 μm. The upper inset shows the intensity profile along the white arrow; (b) Cartoons of the directors within the cell: the upper images shows the cross sectional profile with relevant geometric and surface tension parameters, while the lower image shows the top view of the director configuration.

More than two years too late, but I found this when searching for the same problem. The missing step, which is shown in the image but not the text, is to set the Preset to Monochrome from the dropdown menu, before setting the type and scan direction.

I have tested this on an ESP32 WROOM DA and a Wemos lolin32 using Arduino IDE/ I have tried using older versions of the libraries, pulling down the reset button pin. all to the same result.

After understanding the optics of our N* LC lenses, what is left to explain is the reason for the formation of the lensing shape under water. The equilibrium shape of the film can be obtained by minimizing the free energy density with respect to the height h of the spherical cap.

10.1 Inch Screen Monitor 1024x600 Small Portable HDMI Monitor w/Stand, IPS Screen Display 1024x600px USB Capacitive Compatible with Raspberry Pi 4B

The different textural features might each have several origins. First consider the slow background variation in color: the observation of three distinct orders for the larger grids confirms that this is due to birefringence. The variation of the optical path difference \(\xi ={\rm{\Delta }}n\cdot {\rm{\Delta }}D\) with Δn ~ 0.15 provides \({\rm{\Delta }}D \sim \frac{0.3\,\mu \,m}{0.15} \sim 2\,\mu m\) for the smaller grids with a = 0.1 mm and \({\rm{\Delta }}D \sim \frac{1.2\,\mu \,m}{0.15} \sim 7\,\mu m\) for a = 0.22  mm. The height h = ΔD/2 and radius a of spherical caps can be related to the curvature radius R of the sphere as \({a}^{2}=h(2R-h)\approx 2Rh\) when h ≪ a, i.e., R = a 2/ΔD. This yields R~5  mm for a = 0.1  mm and R ~ 6  mm for a = 0.22  mm size grids.

rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT) configsip: 0, SPIWP:0xee clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00 mode:DIO, clock div:1 load:0x3fff0030,len:1184 load:0x40078000,len:13160 load:0x40080400,len:3036 entry 0x400805e4

The twist term does contribute to W w due to the uniform homeotropic anchoring at the wall that is incompatible with the helical structure far from the walls. The positive energy related to the unwinding of the helix near the wall is decreased by reducing the thickness of the LC-wall contact area by ΔD = h (taking into account the fixed volume of the lens; see Fig. 4(d)). Taking into account that the depth of the unwound region is proportional to the width of the LC-wall contact area b = D-h, \({W}_{w}=-\frac{{K}_{22}}{2}\cdot {(\frac{2\pi }{{p}_{0}})}^{2}\cdot 6a\cdot (D-h)\cdot h\). For a = 0.1  mm and D = 20  µm experiments indicate that h~1  µm, which gives W w  ~ 10−13 J, i.e., three orders of magnitude larger than W LC .

Litestar bietet Ihnen jetzt die OFC-Serie Outdoor P6.67 / P8 / P10 Front Service 10.000 nits Helligkeit SMD Digital Led Board Display mit abnehmbarem IP68 ...

Saad, S. M. I., Policova, Z., Acosta, E. J. & Neumann, A. W. Range of validity of drop shape techniques for surface tension measurement. Langmuir 26, 14004–14013, doi:10.1021/la1020675 (2010).

The interfacial tension between the nematic liquid crystal, with and without CD1, and water were measured with a homebuilt liquid droplet tensiometer: a droplet of the liquid crystal was extruded from a Hamilton syringe, fitted with a J-shaped needle, within a cuvette (borosilicate glass supplied by Wale Apparatus PA) filled with water. The droplet shape is determined by the balance of gravity and LC/water interfacial tension through the Laplace equation. The droplet shape was imaged by a CCD camera (PixeLink PL-B776F) with a light source (ThorLab) and diffuser (ThorLab). Before forming the droplet, the set-up was cleaned with methanol to remove any organic residues. The syringe and needle were each rinsed three times with chloroform. The cuvette was cleaned using KOH solvent (164 g MeOH, 24 g H2O and 25 g KOH), and rinsed with first deionized water and then ultra-pure water, a minimum of three times each. The drop shape was analyzed to determine the interfacial tension with Axisymmetric Drop Shape Analysis (ADSA) software provided by Applied Surface Thermodynamics Research Associates (ASTRA) from the Neumann group23. Interfacial tensions for oil/water interfaces agreed well with values found in the literature. For the liquid crystal droplet in water, the Bond (Eötvös) number was 0.3, within the range that this technique is valid; the uncertainty in the density difference between water and the liquid crystal was the main source of the measurement uncertainty. We found γ = (9.4 ± 1.6) mN/m for pure 5CB, consistent with literature values24, while for the 5CB/CD1 mixture γ = (7.2 ± 1.4) mN/m.

When the liquid crystal filled all the grids, no light path bypassed the microlenses and the marking could not be imaged directly [see Fig. 3 (a’)]. However, one inverted image appeared for each cell in the grid [see Fig. 3(c’)]. This is similar to image formation by the compound eyes of insects, except that the grids are flat in our case. The image of the suspended liquid crystal lenses are shown in Fig. 3(b’) using left and right circular polarizers and a green filter to clearly show the presence of the microlenses. The geometric optics are sketched in Fig. 3(d).

However, we have demonstrated both that equation 3 is in agreement with the observed shape and that it is in qualitative agreement with the observed variations in shape with grid size and with pitch. However, h increases more than expected with grid size and less than expected with the concentration of chiral dopant. This discrepancy may be in part due to the fact that all other parameters (K 22 , n and γ) depend on the chiral dopant. However, we expect that the model needs to be refined based on a more in depth analysis.

Public Service Announcement I had an “A HA” moment yesterday. Sometimes simply pasting in code into the IDE isn’t enough. Just typing in libraries using the #include command doesn’t cut it. I’ve had more success when I use the IDE method of including libraries (Sketch->Include Libraries). This way, additional dependant libraries also get added.

Screen size is nothing but the physical measurement of the screen in inches, while screen resolution is the number of pixels on screen.

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128×64 Serial.println(F(“SSD1306 allocation failed”)); for(;;); } delay(2000); display.setFont(&FreeSerif12pt7b); display.clearDisplay();

Then, you define your OLED width and height. In this example, we’re using a 128×64 OLED display. If you’re using other sizes, you can change that in the SCREEN_WIDTH, and SCREEN_HEIGHT variables.

Xiao, W. & Hardt, S. An adaptive liquid microlens driven by a ferrofluidic transducer. J. Micromechanics Microengineering 20, 55032, doi:10.1088/0960-1317/20/5/055032 (2010).

The actual focal length is due to the combination of the geometric and Pancharatnam lenses; if we approximate the combined effect as due to two closely-spaced lenses, the focal length is the geometric mean, \(f={f}_{G}\cdot {f}_{p}/({f}_{G}+{f}_{p}) \sim 2.2\,mm\). This value is slightly larger than what was estimated from the image and object distances. This could be due to the ~20% measurement uncertainty, and because Eq. (2) is strictly valid only for half-wave plates, which is not fulfilled in our case, thus modifying f P .

Although the model should be further tested experimentally and may need refining, the dependence of the shape on surface parameters means that presented lens array has a potential to detect the presence of nanoparticles or biologically relevant materials, similarly to other LC biosensors31,32,33.

Here, we demonstrate assembly-driven microlenses with size controlled by the grid in which chiral nematic liquid crystal films are suspended. Upon immersion in water, the suspended films spontaneously form converging spherical microlenses, which operate primarily as Pancharatnam lenses. We characterize the geometry and imaging properties of such lenses, and show that the lens shape is induced by molecular chirality and is driven by the liquid crystal-grid interaction.

Pishnyak, O., Sato, S., Lavrentovich, O. D., Oleg Pishnyak, S. S. & Oleg, D. L. Electrically tunable lens based on a dual-frequency nematic liquid crystal. Appl. Opt. 45, 4576–4582, doi:10.1364/AO.45.004576 (2006).

Krupenkin, T., Yang, S. & Mach, P. Tunable liquid microlens. Appl. Phys. Lett. 82, 316–318, doi:10.1063/1.1536033 (2003).

A similar configuration was suggested for the corneal lenses of fireflies and June beetles28,29. These lenses are composed of lamellae, where different levels of laminae create spiraling ribbons in the thickness of the section. This spiraling structure is very similar to the centrosymmetric structure shown in Fig. 4(b), except at the center where spirals will avoid defects, whereas the concentric structure should lead to defects at the center. Based on the fact that no defects are seen in our experiments (see Fig. 2(d–k)), we conclude that the azimuthal rotation of the director is not completely centrosymmetric, but closer to the spiraling structure of the corneal lenses.The similarity between the structure of the corneal lenses of bug eyes and our cholesteric lenses suggest the self-assembly of the bug eyes is also driven by chirality.

Hello, Is there a way to print the string from input1 of the web from on a 0.96 oled display?? I’ve tried so many things but without success. I followed your other great tutorial about esp32 and oled displays and tried to combine the two scripts but with no luck..

After specifying the font, all methods to write text will use that font. To get back to use the original font, you just need to call the setFont() method with no arguments:

Our optical studies reveal that the suspended N* films immersed in water act as microlenses, i.e., can be used for image formation with visible light. This lensing effect is illustrated in Fig. 3.

Brake, J. M., Daschner, M. K., Luk, Y.-Y. & Abbott, N. L. Biomolecular interactions at phospholipid-decorated surfaces of liquid crystals. Science (80-) 302, 2094–7, doi:10.1126/science.1091749 (2003).

The Adafruit library for the OLED display comes with several functions to write text. In this section, you’ll learn how to write and scroll text using the library functions.

Zakharov, A. V., Tsvetkova, M. N. & Korsakov, V. G. Elastic properties of liquid crystals. Phys. Solid State 44, 1795–1801, doi:10.1134/1.1507268 (2002).

HI Sara, thank you for your reply! I uninstalled and reinstalled Arduino IDE. After a few fiddly attempts, I got this Adafruit example to run ONLY WHEN I COMMENTED OUT this part of the sketch:

🔥 Learn LVGL: Build GUIs for ESP32 Projects​ » Learn how to build Graphical User Interfaces (GUIs) for ESP32 Projects using LVGL (Light Versatile Graphics Library) with the Arduino IDE.

This work was financially supported by NSF DMR-0907055 and DMR-1506018. We acknowledge Philip Westerman and Don Diehl for the synthesis of the chiral dopant CD1. We also thank Phil Bos and István Jánossy for fruitful discussions.

Image

Demonstration of lensing using an N* microlens array. (a–c) micrographs seen when only the middle cell is filled with LC and the others are empty; (a’–c’) micrographs when every grid cells are filled with LC. (a) Direct image of a “50” marking on a microscope calibration slide, using light that travels through the empty cells. (b) Direct image of the N* microlens surrounded by empty cells. (c) Inverted image of the marking produced by N* microlens, using circular polarizer. (a’) “Image” seen at the equivalent position to (a), with all the grid cells filled with microlenses. (b’) Direct image of the array of microlenses as seen using a pair of circular polarizers and green filter. (c’) Array of inverted images of the marking produced by the N* microlens array, using circular polarizers. (d) Illustration of the geometric optics and the imaging setup for a single microlens, with the relevant parameters. Blue parts illustrate water medium, white part at the bottom illustrates the inverted microscope used to focus on the object, grid and image by changing the position of the objective. The different components are not to scale.

Figure 2 (b–f) shows textures of 5CB + 5 wt% CD1 (p ~ 3 µm). When the LC in N* phase is held in air, which provides homeotropic anchoring (molecules tend to align perpendicular to the film surfaces on both sides), a so-called “fingerprint texture”25 forms [see Fig. 2 (b)]. When the LC films in N* phase are put in contact with water from the bottom side (planar alignment) only, a hybrid alignment occurs resulting in a “ripple-like” fingerprint texture (see Fig. 2(c)). When the N* film is fully immersed in water (planar alignment on both sides), the fingerprint texture disappears and is replaced by colored circular patterns as seen in Fig. 2 (d). Note that the background birefringence color slowly changes between pale orange at the edge to green at the center. The Michel-Levy chart indicates a change of an optical path difference (Δn · d) of about 300 nm. Alternating bright and dark rings stand out when a green filter is inserted after the light source [see Fig. 2(e)]. The rings are visible even without polarizers [Fig. 2(f)].

This is a truly comprehensive guide to interfacing the 128×64 0.96” OLED display with ESP32. Super useful – especially the code to check the I2C address! It makes life much easier, because I wasn’t sure if my display was even working in the first place.

Hello, I got the OLED to function on my Nano and Uno. Now that I’m moving up to the ESP32, I’m seeing this error: fatal error: util/delay.h: No such file or directory I can actually track down the util/delay.h file and folder. It’s buried way down in the ProgramFiles(x86). There is a delay.h file within the util folder… but maybe its path is all wonky? argh.

Use the the drawTriangle(x1, y1, x2, y2, x3, y3, color) method to build a triangle. This method accepts as arguments the coordinates of each corner and the color.

Studied materials and details of the experimental set-up. (a) Chemical structures of the host liquid crystal 5CB and chiral dopants CD1 and CD2, respectively; (b) Depictions of the configurations of the liquid crystal when bounded by air on both sides (homeotropic), water on one side and air on the other (hybrid), and water on both sides (planar); (c) Sketch of the experimental setup including the light beam, circular polarizers, a grid containing the LC film, and image acquisition using a CCD camera mounted on an inverted microscope.

Popov, P., Mann, E. K. & Jákli, A. Accurate Optical Detection of Amphiphiles at Liquid-Crystal–Water Interfaces. Phys. Rev. Appl. 1, 34003, doi:10.1103/PhysRevApplied.1.034003 (2014).

Very Small Lcd Screen(496+).

I was having zero luck getting fonts to work. An hour later, after searching through .cpp files, .h files, Googling error codes, etc, I added the GFX library by the Sketch->Include Libraries method, and 4 other necessary libraries were included also. The font specification worked, and the font universe has opened to me!

This situation is similar to imaging by smectic lenses. In that case, the focal length was dominated by the lateral variation of the refractive index18; in our case, the refractive index is basically uniform, equal to the extraordinary refractive index of the liquid crystal. On the other hand, due to the varying film thickness and the degenerate planar anchoring of water, the azimuthal angle of the director varies radially by β/2 = 2πΔD/p from the edge to the center and by β over the diameter of the lens, Fig. 4(b).

The I2C address for the OLED display we are using is 0x3C. However, yours may be different. So, make sure you check your display I2C address using an I2C scanner sketch.

The free energy W related to the shape change can be divided into three terms: W = W LC  + W i  + W w . W LC is the distortion energy density taking account the director deformation (splay, twist and bend) related to the shape change; W i is related to the energy increase of the interface; and W w is the decreased wall energy due to a decrease of the film thickness in the immediate vicinity to the grid.

Lin, Y.-H., Chen, H.-S. & Chen, M.-S. Electrically Tunable Liquid Crystal Lenses and Applications. Mol. Cryst. Liq. Cryst. 596, 12–21, doi:10.1080/15421406.2014.918243 (2014).

The OLED display doesn’t require backlight, which results in a very nice contrast in dark environments. Additionally, its pixels consume energy only when they are on, so the OLED display consumes less power when compared to other displays.

The chiral mixtures were suspended in one half of a d = 20 µm thick 50/100 mesh nickel double grid from Ted Pella, Inc. Before each experiment, the grid and microscope dish were cleaned in methanol with an ultrasonic cleaner (Branson B200).

McUmber, A. C., Noonan, P. S. & Schwartz, D. K. Surfactant–DNA interactions at the liquid crystal–aqueous interface. Soft Matter 8, 4335, doi:10.1039/c2sm07483d (2012).

2) i had to take (cut and paste) all the functions and placed them before the setup() function since in platformio, it is true C++ and not a .ino file (that declare functions in the background).

Hi. That’s weird. Did you install all the required librarieS? Do you have the ESP32 add-on updated in your Arduino IDE^? Regards, Sara

Typical POM textures under white light illumination for various configurations of hexagonal grids with a = 0.1 mm sides are shown in Fig. 2. When the pure 5CB film is fully immersed in water and viewed between circular polarizers, one sees a nearly uniform color as shown in Fig. 2(a), demonstrating a uniform film thickness.

I think when good libraries update, their dependencies also update. Going forward, I’m not going to just type in library includes, I’ll make sure they’re attached by this method.

The drawRect(x, y, width, height, color) provides an easy way to draw a rectangle. The (x, y) coordinates indicate the top left corner of the rectangle. Then, you need to specify the width, height and color:

The library also provides methods to displays rectangles with round corners: drawRoundRect() and fillRoundRect(). These methods accepts the same arguments as previous methods plus the radius of the corner. For example:

whenever i try and upload the example sketch “ssd1306_128x64_i2c” to an ESP32 I get this error message whenever i press the reset button:

Carefully patterned LCs have been used to form Pancharatnam lenses. Unlike conventional phase or amplitude gratings, Pancharatnam phase20 devices operate by locally modifying the polarization state of light waves passing through them. Recently, the unique optical properties of Pancharatnam devices have been utilized in making high efficiency compact optical lenses by providing an appropriate profile across an aperture21, 22. In such lenses the optical axis is in the plane of the film with an azimuthal angle β that spatially varies along the radial direction.

Use the drawLine(x1, y1, x2, y2, color) method to create a line. The (x1, y1) coordinates indicate the start of the line, and the (x2, y2) coordinates indicates where the line ends. For example:

where λ = 0.55 µm is the wavelength of the light passing through the green filter and n is the refractive index of the lens (n = n ⊥ ≈ 1.7). This shows that r 2 is proportional to m and the slope s of the line is \(s=\frac{\lambda R}{2n}\). A plot of r2 vs. m is shown in Fig. 3(a). The fit to the line give s = 954 µm2, which provides R = 5 mm in agreement with the estimation from birefringence. This agreement confirms that the rings are due to interference between the water and the biconvex liquid crystal lens.

Then, click OK. Finally, in the main menu, go to File > Convert. A new file with .c extension should be saved. That file contains the C array for the image. Open that file with a text editor, and copy the array.

Popov, P., Honaker, L.W., Mirheydari, M. et al. Chiral nematic liquid crystal microlenses. Sci Rep 7, 1603 (2017). https://doi.org/10.1038/s41598-017-01595-6

I’m fighting this, too. Still having the same issue after reloading the libs thru the Sketch menu. Hello World works, but can’t change the fonts (but they DO exist in the Adafruit_GFX lib).

Polarizing optical microscopy pictures of LC films suspended in d = 20 μm thick hexagonal grids with various boundary conditions above and below the plane with 100 µm (a–i) and 215 µm (j,k) edge length. All pictures except for in (f and k) are taken between left-, and right-handed circular polarizers under white light illumination. (a) Pure 5CB between with water on both sides; (b) N* with 5% CD1 with air on both sides; (c) N* with 5% CD1 with air above and water below; (d–f) N* with 5% CD1 with water on both sides; (e) is the same as (d), but viewed with a green filter, and (f) is the same as (d) but without polarizers; (g) N* with 2.5% CD1 with water on both sides; (h) the same as (d) but with 3% CD2; (i) racemic mixture containing 1.5% (S)-CD2 and 1.5% (R)-CD2. (j) 5% CD1 in large grid between circular polarizers; (k) 5% CD1 between crossed linear polarizers. Bars correspond to 50 µm, while the circles in the lower-left hand corners indicates that the sample was between left and right handed circular polarizers while the crossed arrows in the same position indicates that the sample was between crossed polarizers.

Oct 17, 2021 — Initialization clean: 1. Press the Windows + R keys, type MSConfig and click Ok. 2. On the Services tab, click Hide Microsoft Services. 3. Click ...

Also, maybe as a reminder to everyone, this isn’t the only SSD1306 library available. In the interim, I tested and had immediate successful test example results with “ESP8266 and ESP32 Oled Driver for SSD1306 display” by ThingPulse. It has some cool advanced examples on its own. Its setup has a bit more options, and is fiddly-er than Adafruit’s, but worth checking out.

The molecular structures of the studied materials and the experimental arrangements are shown in Fig. 1. Chiral nematic LC (N*) materials were obtained by adding chiral dopants CD1 or CD2 to the nematic LC (NLC) material 4-cyano-4′-pentylbiphenyl (5CB) obtained from Sigma-Aldrich and used without further purification. The nematic phase of 5CB is observed from 21.5 °C to 33.2 °C. Chiral dopant CD1 was obtained from Kent Displays, Inc., and (S)- and (R)-CD2 (code: ZLI 811 and ZLI 3786, respectively) were purchased from Merck.

We’ll program the ESP32 using Arduino IDE, so you must have the ESP32 add-on installed in your Arduino IDE. If you haven’t, follow the next tutorial first:

The library provides an additional method that you can use with shapes or text: the invertDisplay() method. Pass true as argument to invert the colors of the screen or false to get back to the original colors.

For R ~ 5  mm and p ~ 3  µm we get f p  ~ 3  mm.

#include #include #include #include #include

The other parameters in equation 3 are more difficult to vary independently. To vary the anchoring (surface tension) on the grid, one either need to change the LC (which then will also change n and γ) or the grid material. We tested copper grids and found qualitatively similar behavior. However the copper grids were found to have very rough cell edges that introduced many defects. We also tested gold grids, which were difficult to hold with tweezers and would require a new type of sample holder. It would be interesting to coat grids with, for example, a hydrophobic layer; this technology is well-developed for gold, and is an interesting future direction. The remaining other parameter is the elastic constant, K 22 , which can in principle be varied with temperature. To do so requires a liquid crystal with a wider nematic temperature range and a new setup with precise temperature control. Of course, as the temperature and varies, so will n and γ, which should then be measured separately. All of these tests would therefore require a completely new set of measurements, which is beyond the scope of this paper.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Struggling to get any display. I am using I2C display module and using ESP32. I2C scan returns 0x3C. Don’t get any error but still no display.

Popovic, Z. D., Sprague, R. A. & Connell, G. A. Technique for monolithic fabrication of microlens arrays. Appl. Opt. 27, 1281–1284, doi:10.1364/AO.27.001281 (1988).

The Adafruit GFX library allows us to use some alternate fonts besides the built-in fonts. It allows you to chose between Serif, Sans, and Mono. Each font is available in bold, italic and in different sizes.

2022213 — The most common screen resolution in 2023 will most likely be 1920×1080. This is because it is a resolution that is currently being used by the ...

If you get the “SSD1306 allocation failed” error or if the OLED is not displaying anything in the screen, it can be one of the following issues:

For symmetry reasons, and because of the density of LC is almost equal to that of the water, we can assume that the curvature radii of the spherical caps of the biconvex lens are basically equal at the top and bottom.

The (-1) parameter means that your OLED display doesn’t have a RESET pin. If your OLED display does have a RESET pin, it should be connected to a GPIO. In that case, you should pass the GPIO number as a parameter.

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My OLED 128×32 screen is not getting ON, as the connection was proper. For debugging, purposes where the OLED is damaged or not I have run i2c_scanner to check the i2c address of OLED. What is the issue even after following the all steps in this?

Equation (3) shows that h (and therefore the curvature radius R = a 2/2  h) depends on the twist elastic constant K 22 , the helical pitch p, the interfacial tension γ, and the size of the grid a.

Next consider possible origins of the rings (particularly distinct as bright and dark rings under a green filter). They have some similarity to defect lines in Grandjean-Cano wedge cells26 marking jumps in number of half-pitches that can fit in the spatially-varying thickness. For this mechanism, the number of lines m is determined by the variation of the film thickness ΔD as \({\rm{\Delta }}D=m\cdot \frac{p}{2}\). For grids with a = 0.22 mm, we found m = 45 [see Fig. 2(j)], which would mean the lens would be h ~ 80  µm thicker in the middle than at the edges. Such an h is an order of magnitude larger than we estimated from the birefringent color and the constant volume requirement would result in negative thickness at the edge, i.e. they would not be stable. Additionally, due to the degenerate planar anchoring, the azimuthal angle of the director varies smoothly, which would be seen only between polarizers in contrast to rings that are visible even without polarizers (see Fig. 2(f)).

202471 — Arduino vs. Raspberry Pi · Arduino is a microcontroller motherboard. A microcontroller is a simple computer that can run one program at a time, ...

Kim, J. W. & Kim, H. Lee Myoungbae & Magda, J. J. Interfacial tension of a nematic liquid crystal/water interface with homeotropic surface alignment. Langmuir 20, 8110–8113, doi:10.1021/la049843k (2004).

Accordingly, W LC can be neglected, and the height of the spherical caps can be determined by the condition \(\partial ({W}_{w}+{W}_{i})/\partial h=0\). This yields

First, use an imaging program to resize a photo or picture and save it as monochrome bitmap. If you’re on a Windows PC, you can use Paint.

Hi. There shouldn’t be any conflict between that. If you’ve bought the Web Servers course, please post your issue on the RNTLAB forum: https://rntlab.com/forum/ It is easier to help there. Regards, Sara

The microscope calibration slide with a “50” marking placed between the light source and the N* microlens array (immersed in the water) was imaged by an inverted microscope. When only one of the grid cells was filled with LC (empty adjacent cells), the light could travel from the “50” marking to the microscope either through the lens or through the empty cells. Clear images of the marking were observed when light along either path was properly focused on the camera. The “50” marking of the slide could be seen with and without polarizers while its inverted image produced by the chiral nematic LC film could be seen only between polarizers (see also video in SI.) The objective lens must be in different positions to focus properly in these two cases. In one position, the direct marking was in focus [Fig. 3(a)]. Then, the N* LC lens itself was imaged by moving the objective by a distance l o  = 4.9  mm [Fig. 3(b)]. The inverted image of the “50” marking produced by the microlens was in focus after further moving the objective by l i  = 1.9  mm [Fig. 3(c)], with a 15% uncertainty. Assuming that l o and l i are the objective and image distances of the lens, the magnification of this lens would be M = l o /l i  = 1/2.6. This matches well with the apparent magnification of Ma = 1/2.7 obtained by comparing the sizes of “50” in Fig. 3(a) and (c). Small differences are expected since during focusing on the object, grid and image, the objective eyepiece length slightly varies, thus complicating the optics. Assuming that this complication is not significant, we estimate the focal length of the geometric lens with object and image immersed in water as \({f}_{G}=\frac{{l}_{o}\cdot {l}_{i}}{({l}_{o}+{l}_{i})}\approx 1.4\,mm\).

Present address: Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg, Grand Duchy of Luxembourg, Luxembourg

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins) Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

To draw a pixel in the OLED display, you can use the drawPixel(x, y, color) method that accepts as arguments the x and y coordinates where the pixel appears, and color. For example:

We hope you’ve found this guide about the OLED display with EPS8266 useful. Now, you can integrate the OLED display in your own projects. Proceed to the next tutorial to learn how to display sensor readings on the OLED display:

To measure the helical twisting power (HTP) of the chiral dopants, a concentration gradient was created by putting the pure 5CB in contact with a c = 5 wt% mixture of CD1 or CD2 in 5CB. Only integer numbers of the half pitch (p/2) can be accommodated within the cell thickness, d, so that bands with half-pitch jumps in twist form between the region with no dopant and the region with the full 5 wt%. Counting the number, k, of these bands yields the \(HTP\equiv \frac{1}{p\cdot c}=\frac{k}{2d\cdot c}\,\). We found that HTP (CD1) ~ 6  µm −1 and HTP (CD2) ~ 8  µm −1. These mean that 5CB + 5% CD1 has a pitch \(p={(c\cdot HTP)}^{-1} \sim 3\,\mu m\), with uncertainties of about 20%.

You can use the fillRect(x, y, width, height, color) to draw a filled rectangle. This method accepts the same arguments as drawRect().

display.setTextSize(1); display.setTextColor(WHITE); display.setCursor(0, 20); // Display static text display.println(“Hello, world!”); display.display(); }

Tang, T.-T., Wu, H.-Y., Lin, C.-J. & Pan, R.-P. A Simple Method of Determining the Pitch of a Chiral Nematic Liquid Crystal. Mol. Cryst. Liq. Cryst. 478, 143/[899]–150/[906] (2007).

The OLED display that we’ll use in this tutorial is the SSD1306 model: a monocolor, 0.96 inch display with 128×64 pixels as shown in the following figure.

Upload the following sketch that implements each snippet of code we’ve covered previously and goes through all the shapes.

Experimentally, the lateral size dependence is the easiest to check as other parameters can be kept constant. We found that h ~ 1 μm for a = 0.1 mm and h ~ 3.5 μm for a = 0.22  mm grids, whereas Eq. (3) would predict an increase in h that is smaller by about 50%.

Thank you so much for the I2C scanner sketch! I was looking for the error in my former running code for hours. This time I just got a display with a different address. And thanks for the rest of the article. I’m sure, it will help a lot of people with their projects. Best regards, m.

Kim, Y. H. et al. Fabrication of two-dimensional dimple and conical microlens arrays from a highly periodic toroidal-shaped liquid crystal defect array. J. Mater. Chem. 20, 6557, doi:10.1039/c0jm00910e (2010).

Sato, S. Liquid-Crystal Lens-Cells With Variable Focal Length. Jpn. J. Appl. Phys. 18, 1679–1684, doi:10.1143/JJAP.18.1679 (1979).

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Thanks for this great tutorial. Two comments for people who may want to use this tutorial with platformio in place of arduino IDE. I had to change two few things in the code in order to make it works with platformio. 1) I added this line: #include in the main.cpp since platformio had difficulty to locate it in the adafruit BusIO folder

An Olympus CK40 inverted polarizing optical microscope (POM) was used to observe the N* films. A QICAM Fast1394 CCD camera was mounted on the microscope to capture images and videos. The sample was held either between circular polarizers with opposite handedness (see Fig. 1(c)) or between crossed linear polarizers. The intensity profiles of the N* films were analyzed by ImageJ™.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Hi. Search for the board pinout and see what are the default I2C pins. Use those pins and make sure you select the correct board in Tools > Board and you won’t need to change anything in the code. Regards, Sara

The interfacial contribution to the energy has two terms. W i1 is due to the replacement of LC-wall interface by water-wall interface on an area of 6a·ΔD = 6ah. Denoting γ LC/N  − γ N/w  = Δγ, where γLC/N and γN/w are LC-nickel and nickel-water interfacial tensions we get \({W}_{i1}=6{\rm{\Delta }}\gamma \cdot a\cdot h\). Utilizing that \({\rm{\Delta }}\gamma =-\,\gamma {\rm{c}}{\rm{o}}{\rm{s}}\varphi =\gamma {\rm{s}}{\rm{i}}{\rm{n}}{\rm{\Delta }}\phi \), where γ = γLC/w is the liquid crystal-water interfacial tension [see Fig. 4(b)] and taking into account that \({\rm{s}}{\rm{i}}{\rm{n}}{\rm{\Delta }}\phi =a/R=2h/a\), we get W i1 = 12γh 2. The second term of Wi is due to the increase of the LC-water interface area. Using spherical caps Wi2 approximated as W i2 = 2γπh 2. Using the value for γ = γLC/w ~ 10 mN/m as discussed in the methods section, we find Wi  ~ 10−13 J, which is similar to the magnitude of the wall energy.

Lee, J.-H. et al. Switchable reflective lens based on cholesteric liquid crystal. Opt. Express 22, 9081–6, doi:10.1364/OE.22.009081 (2014).

Li, F., Chen, S., Luo, H. & Gao, Y. Curved micro lens array for bionic compound eye. Optik (Stuttg). 124, 1346–1349, doi:10.1016/j.ijleo.2012.03.063 (2013).

The sizes are set by the actual font. So, the setTextSize() method doesn’t work with these fonts. The fonts are available in 9, 12, 18 and 24 point sizes and also contain 7-bit characters (ASCII codes) (described as 7b in the font name).

The Adafruit OLED library provides useful methods to draw pixels, lines and shapes. Let’s take a quick look at those methods.

Set your monitor to its native resolution · Tap or click to open Display. · Tap or click Adjust resolution. · Tap or click the Resolution list and find the ...

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additionally, could someone advise me / share a link on how to diagnose / solve future issues like this? Im not finding useful links for this issue.

First, you need to import the necessary libraries. The Wire library to use I2C and the Adafruit libraries to write to the display: Adafruit_GFX and Adafruit_SSD1306.

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Bayon, C., Agez, G. & Mitov, M. Lab on a Chip liquid crystal microlenses †. Lab Chip 14, 2063–2071, doi:10.1039/c4lc00152d (2014).

To check the prediction of Eq. (3) for the pitch (which should be inversely proportional to concentration) we can compare Fig. 2(d) and (g) that show m = 9 rings for 5% CD1 and m = 5 rings for 2.5% CD1. Assuming the refractive index n does not significantly change with the concentration, we find that h(5%)/h(2.5%) = m(5%)/m(2.5%)~2. On the other hand, from Eq. (3), assuming K 22 and γ do not vary with the concentration of the chiral dopant, we would get h(5%)/h(2.5%) = p 2(2.5%)/p 2(5%) ~ 4, which is about twice as large as the value obtained experimentally. Even if we take into account the 20% uncertainty of the determination of the concentration of the chiral dopants, this exceeds the experimental uncertainty.

Error log: ***** begin Build options changed, rebuilding all /home/avp/src/sketchbook/ESP-OLED_HellowWorld/ESP-OLED_HellowWorld.ino: In function ‘void setup()’: ESP-OLED_HellowWorld:34:20: error: ‘FreeSerif12pt7b’ was not declared in this scope display.setFont(&FreeSerif12pt7b); ^~~~~~~~~~~~~~~ /home/avp/src/sketchbook/ESP-OLED_HellowWorld/ESP-OLED_HellowWorld.ino:34:20: note: suggested alternative: ‘FreeSerif9pt7b’ display.setFont(&FreeSerif12pt7b); ^~~~~~~~~~~~~~~ FreeSerif9pt7b exit status 1 ***** end

Dong, L., Agarwal, A. K., Beebe, D. J. & Jiang, H. Adaptive liquid microlenses activated by stimuli-responsive hydrogels. Nature 442, 551–554, doi:10.1038/nature05024 (2006).

Just a heads up for anyone struggling with LCD image converter, it doesn’t seem to play nicely with Inkscape PNG images. I just ended up with solid blocks of either black or white upon actual conversion.

After initializing the display, add a two second delay, so that the OLED has enough time to initialize before writing text:

The lens shape deduced above implies a focal length given by (since the lens is much thinner than its radius) the Lensmaker equation27 \(\frac{1}{{f}_{G}}\approx \frac{{n}_{l}-{n}_{m}}{{n}_{m}}\frac{2}{R}\). Here f G is the focal length determined by the geometric optics; n l is the average refractive index of the lens and n m is the refractive index of the surrounding medium (water). With n m  = 1.33 and n l  ~ 1.7 (here, we assumed the extraordinary refractive index of 5CB + 5% CD is very close to that of the pure 5CB), we get \({f}_{G}=\frac{5\,mm\cdot 1.33}{2\cdot 0.37} \sim 9\,mm\). This is about five times larger than what we estimated from the imaging geometry. Additionally, microlens image formation could be detected in our experiments only between polarizers, indicating that the focal length is determined by the director configuration as well as the shape of the lens.

The LC-filled grid was manipulated by holding the unfilled half of the grid by tweezers and positioning it horizontally inside a dish that later was filled with water (Fig. 1c). The 35 mm glass-bottom microscope dish was obtained from Azzota. The water was purified by a PureLab Plus system (18.2 MΩ·cm). The presence of air or water sets the boundary conditions for the liquid crystal (Fig. 1b).

In this example, we’re using I2C communication protocol. The most suitable pins for I2C communication in the ESP32 are GPIO 22 (SCL) and GPIO 21 (SDA).

I have an ESP32 development board (the same as what is shown in this tutorial) and trying to interface a ssd1306 OLED display with it. I installed the Adafruit libraries (both ssd1306 and GFX). When I download the example file (ssd1306_128x64_i2C), my board keeps rebooting no matter the OLED display is connected or not. I tried powering up the display both through the USB internally or through a 5V external power supply. It is apparent that the power supply is not an issue since the board keeps rebooting even if the lcd is not connected.

Hello, your descption about Display Bitmap Images in the OLED is very interesting. But my problem is, how you get so a nice monochrome picture of this colored picture. My monochrome’s are mostly black, so I can’t recognize my face.

There are several libraries available to control the OLED display with the ESP32. In this tutorial we’ll use two Adafruit libraries: Adafruit_SSD1306 library and Adafruit_GFX library.

To draw a circle use the drawCircle(x, y, radius, color) method. The (x,y) coordinates indicate the center of the circle. You should also pass the radius as an argument. For example:

Since a water surface promotes degenerate planar alignment, the helical axis is expected to be perpendicular to the water/LC interface and the birefringence should be uniformly \({\rm{\Delta }}n={n}_{\parallel }-{n}_{\perp }\), where n ‖ and n ⊥ are the refractive indices along and perpendicular to the director. Such a film with uniform film thickness D would have uniform optical path difference \(\xi ={\rm{\Delta }}n\cdot D\), and consequently uniform birefringence without the observed concentric rings. Thus, the rings must be due to varying film thickness, in contrast to the flat surfaces observed for the pure 5CB and the N* with homeotropic or hybrid alignments (Fig. 2(a–c)). The inverted image provided by the lens suggests that the effective lens shape is double convex and nearly spherical.

Because the OLED display uses I2C communication protocol, wiring is very simple. You can use the following table as a reference.

P. Popov did measurements on chiral liquid crystals and analyzed the results, L.W. Honaker did experiments on racemic liquid crystals, M. Mirheydari did surface tension measurements, E.K. Mann co-directed the work and analyzed the results, A. Jakli co-directed the work, analyzed and interpreted the results. All authors contributed to paper writing.

In case you’re using a different OLED display, you may need to change the OLED address. In our case, the address is 0x3C.

Gao, K., Cheng, H.-H., Bhowmik, A., McGinty, C. & Bos, P. Nonmechanical zoom lens based on the Pancharatnam phase effect. Appl. Opt. 55, 1145–50, doi:10.1364/AO.55.001145 (2016).

Such a Pancharatnam-type phase lens has a focal length of f P  ≈ πa 2/(2λβ)22, where a is the radius of the lens, and λ is the wavelength of the light (in our case analyzed in, λ = 0.55  µm). Using the relations β = 4πΔD/p and ΔD = a 2/R we can express the Pancharatnam focal length as

display.setTextSize(1); // Normal 1:1 pixel scale display.setTextColor(SSD1306_WHITE); // Draw white text display.setCursor(0, 0); // Start at top-left corner commented out this line –> display.cp437(true); // Use full 256 char ‘Code Page 437’ font

If this address doesn’t work, you can run an I2C scanner sketch to find your OLED address. You can find the I2C scanner sketch here.

In summary, we have demonstrated the spontaneous formation of converging spherical microlens arrays by immersing a chiral nematic liquid crystal suspended in sub-millimeter size grids into water providing an extremely simple method to make microlenses. We have also demonstrated the imaging capability of the microlenses and showed that the focal length is influenced by the combination of geometric optics and a spontaneously formed Pancharatnam optics. Finally, we have proposed a theoretical model that can explain the lensing effect and predict the dependence of the lens shape on material parameters (twist elastic constant and surface tension), and on sample geometry (thickness and lateral size of grids).

Hi, is there a way to switch off the display with a touch button and wake it up again when button pressed in ESP32 TTGO oled ssd1305/06 ?

Please make sure that you have the SDA and SCL pins of the OLED display wired correctly. In case of the ESP32, connect SDA pin to GPIO 21 and SCL pin to GPIO 22.

Patel, J. S. & Rastani, K. Electrically controlled polarization-independent liquid crystal Fresnel lens arrays. Opt. Lett. 16, 532–534, doi:10.1364/OL.16.000532 (1991).

Serra, F. et al. Curvature-Driven, One-Step Assembly of Reconfigurable Smectic Liquid Crystal ‘Compound Eye’ Lenses. Adv. Opt. Mater. 3, 1287–1292, doi:10.1002/adom.v3.9 (2015).

Gao, K., Cheng, H., Bhowmik, A. K. & Bos, P. J. Thin-film Pancharatnam lens with low f-number and high quality. Opt. Express 23, 26086–26094, doi:10.1364/OE.23.026086 (2015).

I was trying to implement the same project on esp32 S2 and S3 but they don’t have any GPOI22. Can you help me out how can I change the pins, I tried initializing wire.begin in the setup with my desired pins but I did not see any output on the display and on the serial monitor as well

Copy your array to the sketch. Then, to display the array, use the drawBitmap() method that accepts the following arguments (x, y, image array, image width, image height, rotation). The (x, y) coordinates define where the image starts to be displayed.

For these reasons, the rings are likely to be due to the interference between the liquid crystal film and water, as illustrated in Fig. 4(a). The position r m of the mth dark Newton ring of a biconvex lens with volume a 2 π·D, height h and curvature radii R of both spherical caps can be approximated as

Hi. I guess you need to start with a high-quality picture and increase the contrast if needed. I just used my picture as described in the tutorial and it turned out pretty well. There are no hidden steps. Regards, Sara

Define the position where the text starts using the setCursor(x,y) method. In this case, we’re setting the text to start at the (0,0) coordinates – at the top left corner.

The energy due to the distortion of the liquid crystal director can be expanded as W LC  = W splay  + W twist  + W bend , where \({W}_{splay}=\frac{{K}_{11}}{2}{\int }^{}{(\overrightarrow{\nabla }\cdot \overrightarrow{n})}^{2}dV \sim \pi {K}_{11}{({\rm{\Delta }}\phi )}^{2}{D}_{avg}\), \({W}_{bend}=\frac{{K}_{33}}{2}{(\overrightarrow{n}\times \overrightarrow{\nabla }\times \overrightarrow{n})}^{2}6{a}^{2}{D}_{avg} \sim \frac{3{K}_{33}}{2}{(\frac{\Delta \phi }{{D}_{avg}})}^{2}{a}^{2}{D}_{avg}\), and \({W}_{twist}=\frac{{K}_{22}}{2}{(\frac{2\pi }{p}-\frac{2\pi }{{p}_{d}})}^{2}6{a}^{2}{D}_{avg}\). Here, \({D}_{avg}\cong 20\,\mu m\) is the average thickness of the convex N* film and \({\rm{\Delta }}\phi =\varphi -\pi /2\) is the change of director angle due to the splay and bend deformations associated with the lens shape with contact angle ϕ [see Fig. 4(a)]. Assuming the elastic constants of the doped 5CB are similar to those of the pure 5CB, i.e., K 11 = 6.4 pN 30, K 22 = 5.4 pN 30, and K 33 = 13.8 pN 30, we get that W LC  ~ 10−16 J. In fact, the twist term is exactly zero since the pitch does not need to be deformed (pd = p) due to the degenerate planar anchoring.

(1) The primary component (the screen) in an LCD monitor or TV. The term panel is widely used in the LCD manufacturing industry.

This guide shows how to use the 0.96 inch SSD1306 OLED display with ESP32 using Arduino IDE. We’ll show you how to write text, set different fonts, draw shapes and display bitmaps images.

I have an issue that is a bit confusing to me. I took the tutorial from your ESP32 server book and modified the web page to send back a string of characters through the web socket. I then connected up a 1306 128×32 OLED display and modified the code to render the results on the display. The result when rendered on the display is corrupt. Is there an issue when using I2C with the web socket library? Have you tried this? I’m using Visual Studio IDE if that makes a difference. Thanks

Figure 2(g–i) show similar ring patterns for two different CD1 concentrations and for another chiral dopant, CD2. The number of rings (i.e., the curvature) decreases with decreasing dopant concentration (i.e., with increasing helical pitch; Fig. 2(g)). The number of rings for 5CB with 3 wt% (S)-CD2 [Fig. 2(h)] with similar pitch is comparable to that of 5 wt% CD1, indicating that only the helical pitch, and not the specific chiral dopant, is important. Figure 2(i) shows the film when a nearly equal percentage of the (S) and (R) enantiomers of CD2 are added to 5CB, i.e., when the mixture is racemic. One sees no fringes, thus showing that an enantiomeric excess of chiral dopant is necessary for lensing.

Chronis, N., Liu, G., Jeong, K.-H. & Lee, L. Tunable liquid-filled microlens array integrated with microfluidic network. Opt. Express 11, 2370–2378, doi:10.1364/OE.11.002370 (2003).

Typical POM textures between circular and crossed linear polarizers for 5CB + 5 wt% CD1 liquid crystal suspended in hexagonal grids that are twice as large (edge length a = 0.22 mm) are shown in Fig. 2(j and k). In this case, the number of fringes is much larger (about 40) and the background birefringence varies over about three full bands (estimated change of optical path difference is about 1200 nm). In addition to the concentric stripes, off-centered Moiré-type stripes are also visible, especially when the sample is viewed between crossed linear polarizers.

Bouligand, Y. Twisted fibrous arrangements in biological materials and cholesteric mesophases. Tissue Cell 4, 189–217, doi:10.1016/S0040-8166(72)80042-9 (1972).

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Nematic liquid crystals (NLCs) of achiral molecules and racemic mixtures of chiral ones form flat films and show uniform textures between circular polarizers when suspended in sub-millimeter size grids and immersed in water. On addition of chiral dopants to the liquid crystal, the films exhibit optical textures with concentric ring patterns and radial variation of the birefringence color. Both are related to a biconvex shape of the chiral liquid crystal film; the rings are due to interference. The curvature radii of the biconvex lens array are in the range of a few millimeters. This curvature leads to a radial variation of the optical axis along the plane of the film. Such a Pancharatnam-type phase lens dominates the imaging and explains the measured focal length of about one millimeter. To our knowledge, these are the first spontaneously formed Pancharatnam devices. The unwinding of the helical structure at the grid walls drives the lens shape. The relation between the lens curvature and material properties such as helical pitch, the twist elastic constant, and the interfacial tensions, is derived. This simple, novel method for spontaneously forming microlens arrays can also be used for various sensors.

After wiring the OLED display to the ESP32 and installing all required libraries, you can use one example from the library to see if everything is working properly.