28.02.2014|Articles & Video

How to choose the touchscreen for a Chinese tablet or cell phone?

Nowadays tablet PCs are becoming more and more popular. There are quite a lot of reasons for such a change in demand. First of all - tablets are compact, light, consume less power and operate in offline mode much longer. Tablets are also very convenient for outdoors usage. You can view video and photos, check web sites, look through presentations and other documents, read e-books and even play games. The important part of every tablet is its touchscreen both as place and functionality are taken into consideration.

Unfortunately, not everyone can handle a device with a large touchscreen easily. Very often the sensor breakage is caused by its fall or drop, sometimes mechanical damage occurs while carrying or handling the tablet in public transport. Sometimes touchscreens stop working due to a not careful usage.

Chinese multimedia devices are not exceptions. They are quite popular due to their low price. Recently it was very difficult to choose an appropriate touchscreen. So facing any problems with you tablet you were usually advised to throw it away and to buy a new one. Now things are different. A versatile choice for a wide range of touchscreens for Chinese tablets, phones and GPS navigation systems is offered in our online store.
How to choose a touchscreen for your device learn below.

There are different types of touchscreens. First let's determine what exactly touchscreen you need. Today, in most Chinese tablets and phones capacitive touchscreens are used, that's why we'll start with them. There are no common standards for spares identification, so it is necessary to start with the simplest – defining the dimensions of the touchscreen. The first characteristic that we need to know is the length of diagonal. The easiest way is to find the description in the manual or on manufacturer w site. If this is not possible we can measure dimensions by means of a ruler. Attach the ruler to the working area of the screen and measure the distance from the lower left corner to the upper right or vice versa.

 Diagonal

If there's no inch scale on the ruler just divide the measurement by 2,54 ( 1 inch = 2,54 cm) and you'll receive the screen dimensions in common measures. In our case the diagonal of screen is 22,85 cm, that means the diagonal equals 9".
Now let's define the external dimensions. It is necessary to measure the height and width of a sensor ignoring framing of the housing.

Sensor width

 Sensor height

In our case, we obtain sensor width: 233 mm, height: 143 mm. Using filters on our site we see the following characteristics:
Models with diagonal: 9";
Type – capacitive;
Dimensions – 233x143 mm.
As a result we'll receive such a list of goods:

There are many Chinese devices on the market. Tablets that are identical by appearance turn out to be absolutely different inside. Therefore, it is necessary to disassemble every tablet. It could not be identified in any other way because each of 2 billion Chinese manufacturers makes its own version. Pay attention to the number of pin on a flat cable. In our case it's 50 pin. Next we check for labeling – TCP0712.

 Labeling – TCP0712

By all the criteria mentioned above, we can conclude that we will approach product code 845478, the Touchscreen for China-Tablet PC 9", capacitive, black, 50 pin, (233*143 mm), (TPC0712).

 Touchscreen-for-China-Tablet-PC-9

 Touchscreen-for-China-Tablet-PC-9

 Touchscreen-for-China-Tablet-PC-9

Note the appearance of the touchscreen.

 Touchscreen-for-China-Tablet-PC-9

With touch screens of resistive type the situation is completely different.
A resistive sensor consists of two films that change their resistance when touched. One film reacts to vertical shift of touch point and the other film changes its resistance in response to horizontal shift of touch point. Having data on the initial resistance of both films and the resistance changed after being touched, we can get two coordinates: one - "vertical" and another - "horizontal". Then the resistance of films is converted into a digital code calculated by a processor.

 Touch screens of resistive type

Here's the scheme of the resistive sensor:

 The scheme of the resistive sensor

Sometimes it's quite difficult to find a particular sensor with specific characteristics. It is much easier to find a screen that fits the dimensions, but with different location or configuration of pin. In such situations we recommend the following: take a sensor with a relevant dimensions and make a continuity test using a tester. Please check the scheme above. It is very easy to find a pin corresponding to two resistors. You can find out which one is vertical/horizontal by measuring the resistance of sensor to touch on various points. The same manipulations are to be conducted with the old sensor as well.

And then try to find a solution! It is possible to solder the sensor pin to the appropriate contacts on the board by means of thin wires or try to bend the flat cable somehow. Of course, all these manipulations are quite difficult and troublesome, but on the other hand, you do not have to search or wait for the sensor which is ideal for you. You'll spend several hours and receive a working device as a result. Do not forget about static electricity when you solder!!! One touch of a soldering-iron to the pads on a board can "kill" the phone.

Remember the polarity! Resistors of every sensor have a positive-negative pin. But this is not plus/minus in the usual sense. Touchscreen works when connected either polarity. We are talking about the geometric plus/minus. If you reverse the polarity, it will be something like this: when you touch the icon at the bottom of the screen an icon in upper part will work; or by pressing the left mouse button the right button will work. To resolve these problems, it is enough to swap the wiring to the appropriate sensor.

Also, when buying a new sensor you need to know its measurements.If resistance of a new sensor is the same, the dimensions of the screen may differ significantly. So, it is necessary to measure your own sensor very carefully. You should measure the length and the width, but not the housing cover and the sensor itself (film). It can be done by means of a ruler and its accuracy should be +/- 0.5 mm.

And one more tip. Remove all protective films only before you start assembling the device. Fingerprints, dust and other trifles look ugly on the inside surface of the screen. After all manipulations are done it is necessary to calibrate the sensor in the corresponding menu.

In our online store you will find a wide range of touchscreens.


 
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