When people use LCD display
devices, they are not only affected by the earth's magnetic field, but also more or less by other equipment and communication equipment, which is also called electromagnetic disturbance. When these devices are in operation, they will become an electromagnetic source, forming a magnetic field around them and radiating electromagnetic waves outward. The size of the magnetic field and the intensity of radiation are determined by the power of these devices.
LCD display screen is a pure input component or passive component for the whole system. LCD display screen itself has no error correction function, that is, LCD module can receive any signal that satisfies the timing relationship of receiving satisfactory operation without judging right or wrong. The wrong signal and wrong data will produce wrong control instructions or wrong display pictures, which will lead to the wrong display effect. The first task of eliminating interference is to find the location of the interference source, and then use effective methods to eliminate, weaken or shield and remedy it.
1. LCD display screen does not display, and contrast adjustment does not respond. This phenomenon is due to electromagnetic interference on the power or signal lines of LCD display screen during the whole operation period, resulting in interference pulse, resulting in the reset of LCD display module. The result of reset is to initialize the internal register of the module and turn off the display at the same time. The recommended solution is: if the interference is applied to the power line, it is recommended to merge a voltage regulated capacitor (10uF) and a filter capacitor (0.1uF or 0.01pF) between the power line VDD and VSS nearest to the LCD display module. If the interference is applied to the signal line, it is suggested that the signal line nearest to the LCD display screen be merged with the VSS. Enter a filter capacitor and choose 0.1uF or 0.01uF. The selection of the capacitance values mentioned above depends on the effect of the actual test.
2. The picture produces erroneous characters or random points (data errors), or the picture translation, upside down and other phenomena. Sometimes it can't be restored. It can only be cleared and rewritten. It even needs to be powered on again to restore the initialization register. This phenomenon is mostly due to interference applied to control signals such as / WR signal, / RD signal or E signal, or / CS signal. It is easy for the interference signal to produce wrong waveforms on these signal lines, which makes the register parameters modified and the display unit written into the data by mistake. When the whole system runs, most programs only write data to the local display area, no other address writing operation or no repetitive settings to some registers that are only set up after initialization, so the above phenomenon occurs.