Lights Flicker - AC vs DC

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#electrician #electrical #electricity

[kalebjohns]

The flickering could be fixed by slapping a capacitor between the rectifier and the LED

[paulrozinski]

If you are old enough and unfortunate enough to have been on the NYC Subway System back in the late 60’s and 70’s, you would have noticed the station lighting visibly flickering. Back then, the subway system generated their own AC power that was 30Hz instead of the standard 60Hz and the incandescent bulbs hung down from the station ceilings. If you looked at an illuminated bulb from a peripheral view, you could see the flicker.
BTW: The bulbs were left- handed thread to discourage thieves from stealing them, it didn’t work!!😫😫

[ScottGrammer]

Okay, one. Incandescent bulbs don't flicker because the thermal mass of the filament keeps it hot and bright in between cycles of AC. Two, not all LED lamps flicker. If they have a filter capacitor after the rectifier they will not flicker.

[JMGilberto]

Dimmed LEDs are also subject to pulse-width modulation in order to dim them, thus further increasing perceived flicker.

[Youhaveaname]

I tell my wife I can see the flicker in the cheap christmas lights we have. She cannot and thinks I'm crazy.

[andrewstradley]

I always thought of pulsingDC as cleanedDC. But it’s actually dirty lol. Awesome to learn how that actually affects the lights! Thank you

[tbone]

I’ve noticed working in maintenance. Electrical engineers would wired a 6v lantern battery in series with office lighting. Seemed to me it makes no difference but I agree this video sums up why they did it.

[rachelmichaels]

The forcing on us of LEDs is already backfiring. As a handyman I’ve seen a lot of them flickering so bad they had to be replaced. ‘Oh sure, lasts for years’ is Bull.

[MrKen]

Flicker has more to do with temperature and brightness than rectified AC. Full wave rectifier doesn’t pulse as bad as half wave and filters smooth out the dips. The incandescent is like a picture tube in a TV where the element takes longer to cool than the short dip.

[ervivekchoubey]

The LED isn't directly using the rectified DC but it is being driven by an SMPS circuit to maintain the efficiency and safety these are known for.

[tylercgarrison]

Leds also turn on and off rapidly, called PWM, or pulse width modulation. Same concept to how computer fans work

[sc]

More noticeable in Europe than North America due to the lower 50Hz frequency

[DeathracerXD]

You see this with led but the lovely incadesant bulbs can have a smoothing of the flicker if built right

[shaunclarke]

It's because they're built to a price and omitted any filtering on the DC output.

[andrewfischer]

i miss in the ny subway when i was young they still used incandesants(left handed) and every few min they would go out as you hit a cross track

[andreyavery]

Thank you for the information. Just want to comment on the connectors which seems like not rated for those type of conductors 😉

[bernsfindsandmore]

I have noticed this pulsing on LED bulbs that are dimmable. I thought it was my eyes playing with me until I got annoyed and got non-dimmable LEDs and problem solved. Funny is that the cheaper Home Depot branded fix the expensive GE or Phillips bulbs I had when I moved into my house.

[NoName-OG]

If any LED is “dimmable” it is in Pulse Width Modulation — PWM. Even if on 100 that plus is still occurring. To dim the light the width between off and on increases.

[brianjmortensen]

Sawtooth or Ripple DC. Most LEDs have trim caps, but are usually only effective up to what is considered perceivable to the eye. This keeps costs of manufacturing reasonable.

[thinking-laaf]

Unless the LED light has a switching PSU and the capacitor is big enough to keep the voltage fairly consistent