Crystal display (LCD) tester

Posted on Aug 16, 2012

Liquid crystal displays are currently available in several versions and various sizes. The wide variety of features, has resulted in there a little chaos in the provision of the pin. So that even when, after much effort, we can find a screen that fits our needs, we are rather difficult to use it. And because most likely we can not find technical manuals to describe all that remains is for us to try to locate the pins by making successive trials. For this work the circuit described below is particularly useful and convenient. An LCD consists of two thin sheets of glass are few among them.

Crystal display (LCD) tester
Click here to download the full size of the above Circuit.

On inside surfaces of the two sheets have been developed various shapes that are electrically conductive. When looking at the 'sandwich' of two glass sheets perpendicular to the surface, the conductive patterns are, usually consist of parts or places dots are invisible. If we look in a corner, we can distinguished as pale shadows. The gap between two sheets of an organic liquid in which when imposed electric field changes the polarization of light passing through it. In this manner the conductive patterns can appear transparent or dark, depending on whether or not they require in these voltages. In ieriptosi we have in our hands a screen is very easy to identify the parts which form the digits of an alternating voltage of a few pins that correspond to them. It is important to be the alternating voltage is not constant, since in the latter case the screen will suffer irreparable damage. The reason of the disaster has to do with the displacement of the conductive material forms, which as noted above aiioteloun parts of digits. The alternating voltage causes and that the same phenomenon, but the displacement caused by the positive half, called from that caused by the negative, so a visual basis of no observed deterioration. Most of the oscillators, which could be used for producing such a waveform, is unfortunately not able to provide 'clean' symmetrical waveforms. Instead, they produce a rectangular ground time to time (DC) ranging around 50%. Contrary to these, 4047, chosen for this application, provide the requested using an internal splitter. As a result we have two additional outputs with DC = 50%. The operating frequency of the oscillator is equal to 1 kHz, while the voltage required for operation can be any between 3-9 V. Most often, the power of the oscillator would a normal battery, but in some cases it may be better to resort to an adjustable laboratory power supply. So, if you resort to the second option, you will also find the voltage at which the screen antspokrinetai better or the tendency that for which the angle iaratirisis is the best. The current circuit absorbs the total reaches 1 mA. The control voltage should in all cases be between the common pin, which most often is the pin backplane, and the pin corresponding to the section want to locate. If you do not know the pin backplane, you can connect an output oscillator section, and the other to turn it the other pins. Once the department become dark, the same time you know and what is the pin backplane. If it happens and the Board does not 'tan' having stimulates all other pins, then you most likely have to display two different backplane which each can controls and a different group.

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