# Tag Info

## Hot answers tagged touchscreen

64

Title of question: Is there a technical reason why most touch screens use glass rather than plastic? Note the word "technical" and not "marketing" What are the reasons that most modern portable touch devices come with a glass panel on their fronts, rather than plastic or something else? Glass (as a cheap and common material) has a good dielectric ...

40

When decisions about consumer electronics are made, many reasons beyond technical come into play. There is no valid reason for a phone to be disassembled in 7 pieces in order to replace a battery, yet that's how one of the most popular phones is made. Mobile phones are as much a product of marketing as they are of electronics, and many design decisions ...

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You mention cracking as a downside to using glass, but most touchscreens will encounter far more potential scratch-causing events than crack-causing events. Glass is highly scratch-resistant: at a Mohs hardness of 5.5, it's harder than anything else in your pocket (steel is around 4). Synthetic sapphire is even more scratch-resistant: at a hardness of 9, ...

28

I generally resist analogies, but since you're a software-only guy, and since everyone else insists on talking to you about capacitance, I'm going to go for the story. Imagine you are firing paint balls at a wall. Everywhere you hit the wall, there's a splat of paint. Except there's one place you fire at, and when the paint hits it, it makes a little mark ...

16

Glass is hard, and therefore brittle, so it shatters. Plastic (acrylic or polycarbonate) is softer, so more prone to scratches. It's certainly a possibility and some cheap phones have plastic touchscreens. But the underlying LCD behind the transparent touchscreen has to be made of glass, due to high temperature parts of the process. So that's still ...

12

Touch screens have transmit (Tx) and receive (Rx) electrodes which are drawn in transparent indium tin oxide (ITO), forming a matrix of crossed traces with each Tx-Rx junction having a characteristic capacitance. The human finger is basically a ground that alters the mutual capacitance between the RX and TX electrodes. This network is very sensitive to ...

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No. The edges of a resistive touch overlay are important. They carry the conductors that connect to the resistive layers. Those white traces around the edge are conductors, and are necessary for the overlay to work. If you look carefully, you can actually see which wire corresponds to which axis and side. Keep in mind that you can always use an overlay ...

9

so that means that I should be able to interact with it as long as I can bring a small current to the screen where I want to touch. No. You don't "bring" current to the device. These devices measure capacitance, not current or voltage. The additional capacitance thru your body back to ambient or circuit ground is detected by looking at how the capacitive ...

8

Power consumption is a function of many factors, besides resolution. So, I don't think your question is answerable, in the general case. However, I think it's fair to say that most of the power of an LCD screen goes into the backlight. So as a first order approximation, screens of similar size will have similar power requirements. But also consider other ...

5

I'd use an analog multiplexer in combination with a 2D matrix. An example: Matrix of 64 sensors in an 8*8 configuration An eight-channel analog multiplexer with three-bit address input, each input channel connected to a row of the matrix A means of applying a voltage to each column in turn (for example, an 8-bit shift register and some transistors) A ...

5

Yes, this is quite possible to do. Simply place a small piece of copper foil on the screen. Connecting the foil to ground will simulate a finger press. You can use an N-channel FET to switch the foil between connected and not connected. The gate of the FET goes to your microcontroller.

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How does the tinted film only filter in one direction? That is an OLED screen, not LCD, so the structure is a little different. Instead of having just the top polarizer, an OLED screen has the top polarizer attached to the top of a quarter waveplate: When oriented the correct way, the polarizer converts incoming ambient light to be linearly polarized. ...

4

Capacitive sensors react to the polarization of a conductor or dielectric that touches (or is close enough to) its surface, so the size or connection to the water should be taken into account. An isolated drop might not affect it, while a stream of water will. I have a large trackpad for my computer, and an app that visualizes its input. I put a fairly large ...

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I realize I'm late to this, but perhaps this answer may be useful to future viewers. This will also be off topic because it is more Stack-Overflow or Super User related and less EE related. It also sounds like you care mostly about having an interface to the touch screen and you are not dedicated to your current method. I'm also going to assume you have and ...

4

They basically aren't interested in a flow of current, at least not from your actual body, that is why it works through a plastic or glass insulator. It measures the capacitance on several sensors, generally by charging them with a constant current and time, then measuring the resulting voltage. It registers a capacitance change because your body works to ...

4

I expect the high-resolution display to use slightly more, but roughly the same amount of power as the lower-resolution display. Most of the power consumed by the display in a tablet like this goes to two primary components: the backlight and the LCD. Typically the backlight consumes very roughly 75% of the energy going to the screen. Most tablets like ...

4

Most touch screens are capacitive - meaning they detect the change in capacitance that is introduced by touching them. Insulators generally do not introduce a large enough change in capacitance to trigger the touch screen. So if your fingers are turning to papery stumps somehow, you wont be able to trigger it. This has nothing to do with the temperature of ...

4

Some data as what the excitation signals for the screens are would help. But even without that you could design a powered stylus with a fine tip. The basic setup would be a simple metal wire connected with one end to a voltage source. The other end of voltage source should be insulated. Now you have a artificially generated electric field around the wire. ...

4

I was about to file a query to Samsung Support. To ask better questions, I re-study the webpage again, and I came across this post having the table below: In the row of "Sub-Pixels Per Inch", we can see that only green pixels are having 432 ppi. Both red and blue pixels are at only 305 ppi. Doing a few maths:  Closest\ (inclined)\ distance\ between\ red\...

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There is really no way to do what you ask. Each copper plate is a single electrode. You therefore have a single capacitor. Something disturbing the field or coupling to the plates can be detected as a change in capacitance of the capacitor, but there is no way to tell where on a plate. You can only measure a single value. How do you suppose you get the ...

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First, is your pen well-shaken, so the ink is silver-laden? If not, the ink may be barely conductive. The ink will settle out to form a silver clot inside the pen, and the your circuit-lines are mostly the solvent, not the silver. These pens contain weighted beads to stir up the silver and distribute it in the ink. (Like the metal beads inside an aerosol ...

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Capacitive touchscreens are designed to react to the capacitance of a human body, which is about 100 pF according to Wikipedia. So when a regular user touches it with their finger, the equivalent schematic might look something like this: simulate this circuit – Schematic created using CircuitLab Now, when you made your tweak to your head stick, you ...

4

Chargers use the same frequencies in performing their voltage conversions as touch screens use to sense the user touching the screen, these frequencies are usually a in the range of a few hundred kHz. This means that the charger can interfere with the device. Because most chargers are two pin devices the USB output is floating (i.e. not connected to ground)...

4

Your questions requires a bit more specification as to the technology behind the touch detection. Touch detection techniques vs. Materials Typically, plastic surfaces are resistive touch panels placed in-front of glass or plastic LCD screens. They have to be made from plastic (as opposed to glass) because they detect touch by deforming. The user's finger ...

4

A capacity touch screen really needs no force at all, so these kind of actuators are all horribly overpowered. In fact, capacitive touchscreen actually do what their name says: measure the capacity between screen matrix and ground. When you put your finger on a screen, it forms a capacitor. So you don't have to build a mechanical actuator at all. You just ...

4

I don't think any one color will be more "easy" on your display. The circuit and structure for a LCD monitor are the same for each color, they just have a color filter in front of them. There are other ways to do it with color changing backlights or color wheels, but that doesn't change the advice that the color doesn't matter. --Edit @Trevor made me look ...

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In general, glass front panels are near optimal because they conduct electric fields almost twice as easily as plastic panels. This means is Glass ($\epsilon _R =4.7$) has twice the relative permittivity of plastic ( $\epsilon _R =2.3$ ) in the materials preferred here. This applies to both mutual and direct capacitance. What is free space permittivity ...

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Your best bet it to find an OLED panel with a controller that has an eDP (embedded display port) interface. There are plenty on alibaba.com, and you can either bodge yourself a cable [quite hard to get right], or use one of the many available DP (Display port) to eDP adapter boards that exist [much easier as it'll do the pre-emphasis for you]. Most of those ...

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Most of capacitive touch screens are constructed as X,Y array of capacitive sensors. Once You drill the hole in the middle You will open circuit some connection and might loose possibility to properly sense the touch in the rest of the touch screen. See example below: It would be better to design custom capacitive Sensing board, that has connection the ...

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