The reason and solution of the light still bright after power off

Update:01 Feb 2021

During this period of time, some customers complained t […]

During this period of time, some customers complained that our LED street lights could not be completely turned off after the power was cut off. After the switch was turned off, there was still afterglow on the lights and the power could not be completely cut off. This situation easily made customers think that the lights have quality problems Thereby affecting product acceptance. The following will analyze this phenomenon from several aspects, so that colleagues can explain and solve the problem with customers.

The main reason for the lamp to emit light after turning off is that the lamp is charged after turning off, and the LED chip is particularly sensitive to current. Even if it is a wire without forming a current loop, a small amount of light will still be emitted under various complex sensing states. There are several situations:

1. The switch controls the neutral wire, and the live wire enters the lamp directly
This is the most common cause of luminescence. After turning on the light control zero line, turning off the light only cuts off the power circuit of the LED lamp. The live wire is still connected to the lamp, and the lamp will dim.

Solution: Reconnect the circuit and let the switch control the live wire.

2. The switch has an indicator light or an electronic switch is used
Many switches have indicator lights. If the indicator lights are energized after the lights are turned off, current will flow through the lamps.
Some lamps use electronic switches, such as infrared switches, voice control switches, and remote control switches. This type of switch cannot completely cut off the circuit. It will also cause the lamps to glow after turning off the lights.

Solution: Remove the switch indicator or replace the mechanical switch.

3. Wrong wiring of dual control switch
There are many wiring methods for dual-control switches. If an electrician uses the following wiring method, it will turn off the light and glow.

4. The neutral line is live
If the above problems are solved, the lamp will still be on after turning off the light at night, and it is necessary to consider that the neutral line is live. In theory, as long as the switch disconnects the live wire, there will be no voltage on the neutral wire of the lamp, and no induced current can be formed. In real life, the neutral line is very common. If the neutral line is not well grounded, the line is too long, the wire diameter is too small, or the neutral line current is too large, the neutral line will become charged.

Solution: It is difficult for individuals with live zero line to solve it unless the transmission line is modified. Keeping the lamps away from electrical conductors, such as walls, roofs, and steel keels, can also reduce light emission. But it cannot be solved completely.

5. Using lamp protector can solve various reasons for glimmering

This is a commercially available product. The principle is very simple. It is just a two-way automatic control relay. The control relay is used to completely disconnect the lamp from the entire grid circuit. In this way, even if the switch is connected incorrectly and the neutral line is charged, it will not have any effect on the lamp.