The core components of LED large screens are composed of LED beads and IC drivers. Due to the sensitivity of LEDs to static electricity, excessive static electricity can cause breakdown of light-emitting diodes. Therefore, grounding measures must be taken during the installation of LED large screens to avoid the risk of dead lights.
01 LED display screen power grounding
The working voltage of LED large screens is around 5V, and the general working current is below 20mA, The working characteristics of LEDs determine their vulnerability to static electricity and abnormal voltage or current shocks. This requires us to recognize this in the production and use process, give sufficient attention, and take effective measures to protect the LED large screen. And power grounding is a commonly used protection method for LED large screens.
Why does the power supply need to be grounded? This is related to the working mode of the switching power supply. Our LED large screen switching power supply is a device that converts AC 220V mains power into DC 5V DC power supply for stable output through a series of methods such as filtering rectification pulse modulation output rectification filtering. In order to ensure the stability of the AC/DC conversion of the power supply, the power supply manufacturer has connected an EMI filtering circuit from the live wire to the ground wire in the circuit design of the AC220V input terminal in accordance with the mandatory national 3C standard. To ensure the stability of AC220V input, all power supplies will have filtering leakage during operation, with a leakage current of about 3.5mA for a single power supply. The leakage voltage is approximately 110V.
When the LED screen is not grounded, leakage current may not only cause chip damage or lamp burning. If more than 20 power sources are used, the accumulated leakage current reaches 70mA or more. It is sufficient to cause the leakage protector to act and cut off the power supply. This is also why our LED screens cannot use leakage protectors. If leakage protection is not connected and the LED screen is not grounded, the superimposed current of the power supply will exceed the safety current of the human body. A voltage of 110V is enough to cause death! After grounding, the voltage of the power supply casing is close to 0 for the human body. Indicates that there is no potential difference between the power supply and the human body, and the leakage current is directed to the ground. So, The LED screen must be grounded.
02 The correct method and misconceptions of grounding LED display screens
Users often use incorrect grounding methods to ground LED screens, commonly including:
1. It is believed that the lower end of the outdoor column structure is connected to the ground, so there is no need to ground the LED large screen;
2. It is believed that the power supply is locked onto the box, and the boxes are connected to each other through locking buckles and structures, so structural grounding represents that the power supply is also grounded.
There are misunderstandings in these two methods. Our columns are connected to the foundation anchor bolts, which are embedded in concrete. The resistance of the concrete is within the range of 100-500 Ω. If the grounding resistance is too high, it will lead to untimely leakage or residual leakage. Our box surface is sprayed with paint, and the paint is a poor conductor of electricity, which will cause poor grounding contact or increased grounding resistance in the box connection, and may cause electric sparks to interfere with the signal of the LED large screen body. Over time, The surface of the LED large screen box or structure will experience oxidation and rust, and fixing components such as screws will gradually loosen due to thermal expansion and contraction caused by temperature differences. This will lead to a weakening or even complete failure of the grounding effect of the LED screen structure. Create safety hazards. The occurrence of safety accidents such as leakage current, electric shock, interference and damage to chips.
So, what should be the standard grounding?
The power input terminal has three wiring terminals, namely the live wire terminal, the neutral wire terminal, and the grounding terminal. The correct grounding method is to use a dedicated yellow green dual color grounding wire to connect and lock all power ground wire terminals in series, and then lead them out to connect to the grounding terminal. If there is no grounding terminal on site, it can be connected to buried pipes such as iron water pipes or iron sewage pipes that are in good contact with the ground. To ensure good contact, welding terminals on such natural grounding bodies should be carried out, and then the ground wire should be tightly locked on the terminals without binding connections. However, flammable and explosive pipelines such as gas shall not be used. Or bury grounding electrodes on site. The grounding body can be made of angle steel or steel pipes, buried horizontally or vertically in the ground as a simple grounding point. The grounding point should be selected in a remote area to prevent pedestrians or vehicles from damaging the grounding body. When we ground, the grounding resistance must be less than 4 ohms to ensure timely release of leakage current. It should be noted that the lightning protection grounding terminal requires a certain amount of time for the diffusion of ground current during the discharge of lightning current, which can lead to an increase in ground potential in a short period of time. If the LED screen is grounded to the lightning protection grounding terminal, the ground potential will be higher than that of the LED screen, and the lightning current will be transmitted along this ground wire to the LED screen, causing equipment damage. So the protective grounding of LED screens cannot be connected to the lightning protection grounding terminal, and the protective grounding terminal must be at least 20 meters away from the lightning protection grounding terminal. Prevent the counterattack of ground potential.
Post time: Sep-09-2024
