On Thu, 20 Dec 2018 04:22:39 -0000, Clare Snyder wrote:

On Wed, 19 Dec 2018 19:36:51 -0000, "William Gothberg" "William
wrote:

On Wed, 19 Dec 2018 17:47:17 -0000, trader_4 wrote:

On Wednesday, December 19, 2018 at 11:35:06 AM UTC-5, 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?

I've never noticed that. Any films come to mind?

A lot of Top Gear programs showing the DRLs of cars fitted with LEDs. With a feature film, they might take the time/trouble/money to do something to stop it.

It seems especially
weird, since cars have a 12V supply with a big battery to smooth
anything out. I guess the power supply that reduces that to whatever
the LED headlights use though might have a switching power supply these
days too.

AFAIK it's deliberate, making the LEDs operate brighter than they are capable of, but only 1/4 of the time. Our eyes just see the brightest part of the cycle, so we think they're four times brighter than the LED is really capable of, without overheating itself.

That is PWM Overdrive. Peak junction current is over the nominal
rating, but the average power consumption is below nominalmaximum
current - and the peak lumen output is significantly enhanced without
reducing the junction life appreciably.
THIS would definitely cause flicker as there is a "significant" dead
period between the "strobe flashes"

Agreed, although Rod thinks only freaks can see it.

I wonder why none of my houselights use this? Do car lights have to make more brightness from a smaller area? Or would flickery houselights annoy people more?

If it's the extra brightness, I don't understand - because I have a torch with a single LED and parabolic reflector that gives out 20W equivalent without overdrive. Simply have three such lamps with their own little (only 1.5 inches across) reflector next to each other to make the headlamp.