1. LCD usage and troubleshooting:

<1> The use of LCD:

Due to the special principle and structure of LCD display devices, attention must be paid to:

(1) Prevent excessive pressure:

LCD display devices are liquid crystal cells made of two pieces of glass, with only 5-10um between them. The inner surface of the glass is also coated with an orientation layer, which is easily damaged. Therefore, during assembly and use, attention should be paid to:

① The surface of the LCD should not be subjected to excessive pressure to avoid damaging the orientation layer. If the pressure is too high or the middle of the LCD is pressed by hand, it should be left for at least 1 hour before being powered on.

① During assembly, remember to apply even pressure, only on the edges of the components, not in the middle or with uneven force.

(2) Prevent glass damage:

Due to the fact that LCD is made of glass, if it is lost or impacted, it will definitely cause breakage. Therefore, the assembly method, vibration resistance, and impact resistance of the assembly must be considered in the overall design of the machine.

(3) Protection pins:

If it is a pin type LCD, the LCD should be installed at a distance of 2mm or more from the wiring board, and should not be subjected to excessive force or heat to avoid damaging the connection. The maximum temperature resistance at the connection shall not exceed 80 ℃. Do not use detergent at the pins, as under sunlight, the detergent will decompose into Cl2, which forms hydrochloric acid after absorbing water and corrodes the electrode.

(4) Device moisture resistance:

Due to the low voltage, low power consumption, and extremely high resistivity of liquid crystal materials (up to 1010 Ω· cm or more), the conductivity of the glass surface caused by humidity is sufficient to affect the display. There will be "crosstalk" display between segments. Therefore, the overall design of the machine should consider moisture resistance, good sealing of the chassis, and even use sandwich type conductive rubber strips. (8) Use and store within the specified temperature range:

Due to the disappearance of liquid crystal state beyond a certain temperature range, it must be used and stored within the specified temperature range. If the temperature is too high, the liquid crystal state disappears and becomes an isotropic liquid, and the display surface appears black and cannot work. At this time, do not turn on the power. Once the temperature returns to normal, the display surface will also return to normal. If the temperature is too low, the liquid crystal state will also disappear and turn into a crystal. At this point, it is possible to cause permanent damage to the orientation layer during the crystal formation process.

(9) Static interference:

Due to the extremely low operating voltage and high internal resistance of LCD, sometimes there may be a "string" phenomenon when checking with a multimeter (10K range), which is caused by the electrode being suspended and is a normal phenomenon.

<2> Troubleshooting during use:

A qualified display device may sometimes malfunction due to unreasonable use, unsuitable conditions, unqualified accessories, or improper installation methods. The reasons and elimination methods are as follows:

(1) Handwriting exclusion:

After using for a few hours or days, the electrode changes color and black or brown "handwriting" appears, and the LCD box generates bubbles, resulting in inability to display. This is due to the excessive DC component of the driving voltage, which causes electrochemical reactions. Check the circuit, eliminate excessive DC components, and replace with a new LCD. When the "handwriting" first appears, the LCD can be heated to a temperature above the insulation level, that is, when the display surface of the display device changes color completely, the heating should be stopped, and after natural cooling, the "handwriting" can generally be removed.

(2) Vaguely displayed:

The pen segments that should not be displayed after assembly are also vaguely displayed, making it impossible to read. The reason may be:

① The lead wires are not clean, just wipe them with a dry fine cloth.

② The weather is too humid, and the glass surface is conductive. It can be restored after drying indoors.

③ After the common electrode or segment electrode is suspended and reassembled reliably, it can be eliminated.

④ The asymmetric amplitude of the communication square wave causes unclear cutoff when extinguishing. Adjusting the amplitude of the square wave can solve this problem.

⑤ When the conductive rubber stripes are not aligned, parallel, or have poor insulation performance, replace the conductive rubber strip.

(3) Exclusion of poor contrast:

Poor contrast, negative image, chaotic display, or complete display are generally caused by the hanging back electrode, which can be ruled out.

(4) Exclusion of Chaotic Display:

External interference may also cause display confusion, which can be eliminated.

(5) Exclude all displays:

The decoder is normal, but all displays are normal. Generally, it is due to the back electrode not being properly connected or the back electrode experiencing direct current.

(6) Exclusion of missing line display:

The reason for the missing line display may be:

① The electrode lead is contaminated, resulting in poor assembly contact.

② Conductive rubber contamination leads to poor assembly contact.

The above two items only need to be cleaned and assembled. During assembly, do not touch the cleaned parts with your hands.

③ The edge of the glass is damaged and scratches the conductive layer of the external lead.

<2> Troubleshooting of Simple Malfunctions:

(1) Display the elimination of confusion:

1）. Misalignment: The PCB board electrodes and screen electrodes cannot correspond one-to-one, and the reason for the misalignment needs to be analyzed.

① Due to issues with my own assembly techniques, it is necessary to reassemble.

② The installation holes on the PCB board are not in the correct position.

③ The screen cutting edge is not precise.

④ The shell alignment benchmark is not precise.

2）. If the PCB board is damaged, you can use the test board fixture to test the board again.

External interference may also cause display confusion, in which case external interference can be detected and eliminated.

⑵ . Exclusion of missing line display:

1) The PCB board electrodes are contaminated, resulting in poor contact of the zebra stripes.

2) Zebra stripes are contaminated, resulting in poor contact.

3) The conductive electrode is contaminated, resulting in poor contact.

The above three items only need to be cleaned and reassembled. During assembly, do not touch the cleaned parts with your hands.

4) PCB board breakage and virtual soldering. Re test the board and replace it if it is damaged.

5) The screen electrode is damaged or the screen itself is broken or short circuited. Need to replace the screen and reassemble.

6) The shell is not qualified, please replace it and assemble it again.

（3）. Display completely or completely black:

This situation is usually a problem with the PCB board, which needs to be disassembled and retested.

（4）. Uneven and shallow display.

This situation can only be ruled out after careful analysis by him.

① The display of a certain block is uneven, but the wiring is not neat. This situation is usually caused by the screen, which needs to be replaced and reassembled.

② Some items are displayed unevenly. This situation is usually caused by the twisting and deformation of zebra stripes, leading to poor contact. After disassembly,

Lay the zebra stripes flat and assemble them again. If it cannot be ruled out, other reasons need to be analyzed, such as inappropriate height to width ratio of zebra stripes, inappropriate compression ratio, and inappropriate width of conductive bandwidth.