How to solve the problems encountered by liquid Crystal display Module in Anti-static interference of the whole system

- Oct 11, 2019-

I. The interference source is in the system testing phase of the liquid crystal display module, and the anti-interference test is an important project, whether it is a professional instrument test or a long-time running test of the whole machine. The interference is a common and difficult problem for the whole system. When the system circuit is disturbed, a certain frequency, a certain amplitude of the interference wave is generated on the power line or signal line. When this interference wave is applied to the interface line end of the liquid crystal display module, it is necessary to bring an undesirable display effect to the display. The liquid crystal display module is a pure input type component or a passive component for the whole system of the system. The liquid crystal display module itself has no error correction function, that is, the liquid crystal display module can receive any signal satisfying the operation timing relationship without the ability to judge whether it is a non, a pair and a wrong. The wrong signal and the wrong data result in an incorrect control command or an incorrect display pattern, resulting in an incorrect display effect. The primary task of eliminating interference is to find the source of interference and the location where the interference is affected, and then to remove, weaken, or shield, and remedy, with an effective method. 

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II. The anti-interference measure gives some constructive solution to the display problem which is common in the anti-interference test of the whole system of the system or the operation of the copying machine, but the effective method also needs to be groped and verified in the actual test and operation. 1. when the whole machine of the system is in operation or the anti-interference test is carried out, the liquid crystal display module is not displayed, the contrast ratio is not reflected, because the power line of the liquid crystal display module or the/ rese7 signal line is subjected to electromagnetic interference during the operation of the whole machine to generate an interference pulse, Resulting in a reset of the liquid crystal display module. The result of its reset is the internal register of the initialization module, and the display is off. The proposed solution is that, if the interference is applied to the power line, it is recommended that a voltage-stabilizing capacitor (10. mu.f) and a filter capacitor (0.1. mu.f or 0.01. mu.m) be placed between the power supply lines vdd, vss that are closest to the position of the liquid crystal display module. For example, if the interference is applied to the/ reset signal line, it is recommended to select a filter capacitor between the/ reset signal line closest to the position of the liquid crystal display module and the vss, and the capacitance capacity is selected to be 0.1. m u.f or so.01. m u.f. The above-mentioned selection of the capacitance value depends on the effect of the actual test. 2. When the whole system of the system is in operation or the anti-interference test is carried out, the screen produces wrong characters or random points (data error). Or screen translation, upside down, and the like. Sometimes it is not possible to recover, only the screen can be re-written, and even the power-on is required, and the initialization register can be recovered. This phenomenon is mostly due to interference applied to control signals such as/ wr signal,/ rd signal or e-signal or/ cs signal. The interference signal is relatively easy to generate an erroneous waveform on these signal lines, so that the register parameters are mismodified, and the display unit is erroneously written to data or the like. In that operation of the whole system, most program only perform data write operation on the local display area, do not have the write operation of other address, or do not repeat the register which is set only in the initialization, so that the above phenomenon occurs. it is suggested that the interference signal is applied from the space to the transmission line between the mpu and the liquid crystal display module, it is suggested that the shield of the transmission line is made of magnetic ring or tin paper or copper thin, the direction of the transmission line is changed, the interference environment is avoided, the length of the transmission line is shortened, The parallel interface mode: first/ wr (/ rd) signal or e signal, and/ cs signal, and the order of the rs signal is added with a small capacitor of 100-300pf to ground (vss). Serial interface mode: add a small capacitor of 100-300pf to ground (vss) in the order of sclk, sda, and rersreset. 

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