Can the cell phone test light flickering? Is it scientific?

Lighting flicker always make people uncomfortable, which affect our eyes and brain. Especially when children are learning on a tablet pc, the flicker lights make the children refuse to learn, and they feel physically uncomfortable. Nowadays, many families choose LED downlights. Why do some LED downlights or lights flicker? Can flicker free cob downlight solve the stroboscopic problem and how to choose?

Why does the downlight flicker (not only LED lamps)

Because our main electricity is 220V 50Hz alternating current.

First, the current is generated by the conductor moving in the magnetic field in the direction perpendicular to the magnetic line of induction, and the current is generated inside. This principle was discovered by British scientist Faraday in 1821.

In the early days, because people hadn't thought of any particularly advanced methods, they all used the way of converting mechanical energy into electrical energy to make generators, that is, the energy generated by motion was processed into electricity.

But if the magnetic field is made parallel to the positive and negative poles, and the conductor runs from the left to the right, the electricity is gone. Tossing back again is more complicated in mechanical design. So later generations transformed the generator to rotate around the center.

According to the physical structure of the generator, it is determined that the voltage is actually sinusoidal. When the resistance is constant, the current becomes a waveform.

Then the light bulb uses current to convert electricity into light. When the current is large, the light is bright, and when the current is small, the light is small, which causes the flicker of the light.

Is stroboscopic harmful?

Yes it is. The "stroboscopic" problem of LED lights can also cause headaches and eye fatigue, cause photosensitive epilepsy, and cause vision loss.

The 50Hz alternating current is commonly used in our country, that is, the positive and negative changes are 50 times per second. The human brain cannot recognize changes more than 30 times per second, and you seem to be always on. But for sensitive eyes, the effect of the light and dark will make the pupils go up and down, so the muscles that control the pupils are very tired. Easy to cause work-related accidents, for example, toilet bag sewing machine operator, the needle moving up and down at high speed, the illusion of static state, accidentally pricked his finger; the packing of peeled small white taros is prone to visual fatigue, vertigo, migraine headaches, positioning difficulties, etc., parts of piezo injector comprehensive tester and parts of PT pump test bench put wrong; OEM paper perfume packaging box and liquid doy pack flat bottom pouch caused by printing errors rework again and delay delivery.

Can mobile phones measure flicker?

Under normal circumstances, we cannot detect with the naked eye whether there is "stroboscopic". I have seen a piece of news that the mobile phone can measure flicker. The host and related technicians demonstrated on the spot whether the LED light is qualified by using a mobile phone: start the mobile phone camera and aim the camera at the LED light bulb. If there are undulating stripes on the mobile phone screen, it means there is a flicker problem.

Is it reliable to use the mobile phone camera to detect it?

Useful, but unscientific.

At present, CMOS photosensitive elements that can only be used in mobile phones use progressive scanning. That is, the light intensity induced by the first row is temporarily stored in the form of data, and then the second row and the third row are converted and stored. But it takes time to convert and store. When recording the conversion and storing the second line, and in the super short time when the first line is switched to the second line, the brightness of the lamp has actually changed. By analogy, the brightness of each line is different when recording, but the brightness of the light changes periodically, so it causes the phenomenon of light and dark texture in the final image.

There is another factor that can also cause this phenomenon, that is, the shutter speed is less than the period of a light-dark change of the bulb, which is less than 1/50s. Look at the picture below:

In the current smart phones, the default shooting parameters such as the shutter time of the camera app are automatically set according to the brightness of the environment. It is possible that by default, the shutter time is longer than 1/50s.

In fact, as long as AC power is used, there will be stroboscopic flicker, which is just a matter of degree. The evaluation of lamp stroboscopic is generally measured by the percentage of stroboscopic (that is, the depth of fluctuation). Most of the international evaluation standards refer to the IEEE Std1786 version.

We understand that the AC frequency used is usually 50/60Hz, and if the fluctuation depth is less than 8%, it is a low risk;

When the fluctuation depth is less than 3.2%, due to the residual characteristics of human vision, it can be regarded as having no effect on human eyes.

In conclusion

It is unreliable to see the stroboscopic on the mobile phone. Sometimes a slight qualified stroboscopic can also be photographed, and sometimes it is very serious, but it cannot be photographed.

At the same time, even if there is no "stroboscopic" when using a mobile phone to test, the light stroboscopic is still related to various factors such as color temperature, color rendering index and luminous flux.

Whether the LED downlight strobe is qualified or not is by no means a picture of a mobile phone camera to tell. It is reported that in order to meet the conditions of stroboscopic measurement, the most commonly used instrument is a photometer. There is also a way to avoid stroboscopic flicker by means of peripheral circuits.

How to choose high-quality LED lights?

1. High color rendering index

Products with a color rendering index greater than 90.

2. Glare

Buy LED anti-glare gu10 downlight

In normal use, there is no glare, which is anti-glare.

3. Color temperature

The warm white light with a color temperature of 3000K is the warmest light environment in the home;

Too low color temperature is easy to fatigue, too high color temperature will be over-stimulating, and there is a risk of injury.

4. Blu-ray

The blue light hazard is an indicator to detect whether the desk lamp is qualified;

If the brightness of the 400-500 nm blue light band of the light source is too high, the eyes may cause photochemical damage to the retina after looking directly at the light source for a long time;

Only when the blue light component reaches a certain threshold will it cause damage to vision.

5. Structure

Have a reliable and reasonable structure design;

The bracket has a certain length and is easy to stretch and shrink. It is suitable for multi-purpose use such as computers, painting, and piano.

6. Illuminance

Appropriate lighting design ensures the appropriate illuminance for each functional area.

For the above 6 points, you can find that the Chinese national standards, North American standards, and European standards all have mandatory requirements for the status to be allowed to go on sale.

Can flicker free cob downlight really not flicker?

If this product is really a flash-free downlight, then it is true. Because some businesses will recharge the number indiscriminately.

How to choose flicker free cob downlight?

The key point is drive power!

When LED downlights without strobe light, you should carefully check the specifications of the downlights, especially the quality of the driving power supply.

Although flicker will put pressure on the eye muscles, in addition to buying filcker free cob downlights or other lights. In fact, it is more important to maintain good eye use habits, including correct sitting posture and regular eye use habits.