Idk if it’s clear but I watched many sports game at night and the spotlights were flickering only during slow motion shots
In: Technology
Mains electricity uses alternating current (AC). Instead of the electricity flowing in one direction (direct current – DC), it goes back and forth 50 or 60 times a second (depending on your country).
For filament bulbs, this doesn’t matter. But a diode is like a one-way street for electricity. This means it only lights up during half of each cycle, when the electricity is flowing in the right direction. When we see it with our eyes, or recorded and played at a normal speed, we don’t notice the dimmer points in time. But when we film this at high-speed and slow it down, those gaps become more obvious.
* LED signs are made up of millions of individual LEDs.
* Each of those LEDs needs to get power.
* However it would be far too costly to have each LED get its own power driver circuit.
* So instead they share them in batches and rapidly switch which batch is getting power.
* To the human eye, the switching is so fast that you would never know that not all the LEDs are getting power at the same time.
* But when played back in slow motion, it’s clear that the LEDs turn on/off in waves.
* Some others have claimed it’s due to AC power changing direction many times a second, but LEDs are driven with DC power so the flickering is un-related.
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