On Thu, 20 Dec 2018 17:13:52 -0000, trader_4 wrote:

On Thursday, December 20, 2018 at 12:07:40 PM UTC-5, William Gothberg wrote:
On Thu, 20 Dec 2018 16:25:22 -0000, trader_4 wrote:

On Thursday, December 20, 2018 at 7:29:53 AM UTC-5, William Gothberg wrote:
On Thu, 20 Dec 2018 11:57:01 -0000, whisky-dave wrote:

On Wednesday, 19 December 2018 16:35:05 UTC, William Gothberg wrote:
On Wed, 19 Dec 2018 16:21:41 -0000, Mark Lloyd wrote:

On 12/19/18 6:01 AM, William Gothberg wrote:

[snip]

They probably are fairly crude. I know they flicker, for example if I
use my cordless drill, the chuck appears to spin the wrong way under the
LED lighting.
I remember seeing that with a washing machine (under fluorescent
lights). As the tub was slowing down, the row of holes around the tub
would appear to reverse direction. Same thing with (spoked) wagon wheels
in movies.

It looks absolutely ridiculous with modern cars with LED headlights in films. How hard can it be to put a smoothing capacitor on the output of the power supply?

It's easy but that isn't the point. The most efficient way of driving to make maximium power into the LED means yuo have to pulse the LED's. Using a capcitor to smooth out the DC is yet another mode of inefficincy as it would get warm due to current flow. Indictors in series might be better but then you run the risk of 'radio' interference.

Being inefficient would presumably make it impossible to get enough brightness out of LEDs that fit into the lamp holder. The LEDs would get too hot trying to give out enough brightness for a car headlight.

However cars vary a lot, some are easy to detect flickering, some difficult, and some impossible (with the naked eye). Perhaps they just use a higher frequency?

Taillights are pretty bad on a lot of cars, as they dim the brakelights by deliberately flickering them.

Either you have eyes that are way more sensitive to this or you're in a
country that uses different car lights than here in the USA. There
are a lot of cars with LED lighting, headlights and rear lights, and
I've never noticed this flickering, nor have I ever heard it mentioned
before this thread. I haven't noticed flickering from any LED lights
I've used either.

I can see flicker on a 60Hz CRT monitor, but not on a 90Hz one, so that'll give you an idea on how good my eyes are.

Can you see flicker on tailliights if you scan your eyes across the scene?

Like I said, I haven't noticed it in the driving I've done. Nor have I
heard anyone else mention it. Next time I come across a car that has
LEDs I'll look more closely and see if I can see anything. If just
scanning reveals it, you;d think a lot of people would be noticing it.
Scanning is a part of driving.

I'd estimate about 1 in 5 people can see it, similar to how many can see flicker on a 60Hz CRT computer monitor.

Don't most cars have LEDs now? Or does your area have a lot of older cars? People (stupidly) around here seem to like cars that are no more than 10 years old. I don't think many cars after 2008 had bulbs.

Searching for "LED tail light flicker" without the quotes in google produces 4.5 million results!