How to choose touchscreen and its components for a China-made tablet or cell phone?


The popularity of smartphones and tablet PCs grows with every next day. The constantly growing demand is simple to explain in terms of the devices' features: compact size, small weight, low energy consumption and standalone operation. The tablets are frequently used in home environment a well as for watching videos, taking photographs, web-browsing, creating presentations as well as other documents. Smartphones took it to the next level! The majority of smartphone owners, after leaving the gadget at home, feel quite helpless without their devices.

Everyone knows that smartphones and tablets with large screens are very delicate devices - the screen is exposed to mechanical damage. Such gadgets need carefull opeartion and proper carrying. The most common «soft-spot» of these are the touchscrens that suffer from fractures caused by dropping on the ground and mechanical from day-to-day opeartion.

China-made multimedia devices are no exception. Their popularity owes to their low price.
Back in the day, in case, the gadget's screen is broken, you would have been recommended to buy a new device. Unlike now, choosing the proper touchscreen for a tablet or a smartphone would become a very complicated task!

GsmServer Store presents the wide choice of touchscreens for China-made smartphones and tablets. Read this article to find out how to choose and identify the proper component (display or touchscreen) compatible with your device.

There are different types of displays and touchscreens. The first task is finding out which component you need.
Nowadays, Chinese tablets and smartphones manufacturers widely use capacitive displays that we shall begin with.

First and easy part — define the dimensions of the touchscreen (or LCD). The first parameter to consider is the touchscreen diagonal. You may try to find its dimensions at the manufacturer's website or in the user manual. However, if that is not possible, take a ruler to measure the touchscreen diagonal size. Put the ruler on the screen and calculate the distance from the bottom left corner to the upper right corner or otherwise.

touchscreen diagonal dimension

If the ruler has no inch scale, you will need to convert the result of the measurment into inches, dividing the number in 2,54 (1 inch = 2,54 cm). Thus, you will obtain the touchscreen's dimensions in inches, according to the standard. For example, after the measurement you might find 22,85 cm of diagonal, that shall be equal to 9”.
Now the other dimensions. Meter the height and the width of the touchscreen (LCD), however, disregarding the frame size.

touchscreen width

touchscreen height

After all you will have obtained the touchscreen width of 233 mm and the touchscreen height of 143 mm. Then use our website filter to input the dimensions known to you, for example:
The models with the diagonal of 9”;
Type – capacitive;
Size – 233*143 mm.
As the result, you approximately will get the following list of the products at your website

However, there is more to come! There are lots of China-made devices available in the market, and, at the first glance, they seem to be absolutely identical, but their componenets appear to be different. Therefore, the tablet shall be disassembled. Simply there are no other options out there, because different factories produce different versions of the devices. After the smartphone or tablet is disassembled, first and foremost it is necessaery to pay attention to the number of contact pins at the flat cable. Here we have 50 pins. Also, in order to find out whether this touchscreen is compatible, we have to compare the marking – TPC0712.

TPC0712 marking

According to the above criteria Item No. 845478 falls under the scope, in particular the Touchscreen for China-Tablet PC 9", capacitive, black, 50 pins, (233*143 mm), (TPC0712).
Now, you have found the necessary component at the website. Then carefully examine the physical form of the touchscreen, in particular, the look of the flat cable and its composition.

China-Tablet PC 9 inch Touchscreen

China-Tablet PC 9 inch Touchscreen

China-Tablet PC 9 inch Touchscreen

Carefully examine the physical form of the touchscreen.

China-Tablet PC 9 inch Touchscreen

Far otherwise scenario shall be used for resistive touchscreens.
What the resisitive touchscreen is? The resistive touscreen is two sheets attached together that measure the resistance caused by the contact point movement. One of the sheets responds to the vertical movement and the other responds to the horizontal. Having recorded initial resistance data at the moment of their contact, we will obtain two coordinates points: the vertical and the horizontal. Then resistance of the sheets is converted to the digital code calculated by CPU.

resistive touchscreen

Here is the equivalent resistive touchscreen scheme:

resistive touchscreen scheme

Sometimes it is hard to find a touchscreen with special chaeracteristics. Though there may be no problem finding the touchscreen according to particular dimensions, however, it may have the different placement or the form of the output wires. In such a case we recommend using suitable touchscreen and check the output wires with tester. Refer to the above equivalent scheme. Finding the output corresponding to the "resistors" shall not be a problem, however, in order to define which of them is horizontal and which is vertical, you will have to measure the electrical resistance of the touchscreen by swiping over it in different positions. Perform the same manipulations to the old touchscreen.

Now, turn on your imagination! You can sold the output wires of the touchscreen onto the corresponding contacts of the motherboard or simply flex the flat cable.
No doubt, these tricks are hard to perform, but you will not have to search and wait for the ideally compatible touchscreen. Of course, all the procedures will take certain time, however, you will have your device working.

Do not forget about the static electricity during the soldering process!!! Getting smartphone down is easy by just touching the motherboard terminals with the soldering iron.

Please do observe the polarity! The touchscreen resistors have positive and negative output. However these are not simply plus or minus. The touchscreen works in any polarity positions. Here we mean the geometric plus and minus.
After having mixed up polarity leads, the point you touched in the upper part of the screen will respond in the lower, or, pressing the point in the right part, you will be shown the response in the left. In order to fix such inconvenience switch the wires atatched to the malfunctioning sensor.

Purchasing the new touchscreen, it is necessary to confirm the touchscreen's physical characteristics. The display dimensions may significantly vary, unlike the touchscreen resistance known to be common. This means, that it is necessary to have the "native" touchscreen measured. Evaluate the dimensions of the width and the height of the sensor sheet, however, certainly not the device's casing. The measurement may be carried out with traditional ruler, of up to +/- 0.5 mm tolerance.

Remove all the protective seals only before you start the device's assembly. Any fingerprints, dust or other traces are unwanted marks on the inner surface. After all the above manipulations are done, calibrate your sensor with respective software function.

We wish correct opeartion to all your devices. GsmServer Store constantly offers wide choice of the touchscreens for tablets and smartphones.

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