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William Gothberg William Gothberg is offline
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Default Do switch mode power supplies flicker in time with mains?

On Thu, 20 Dec 2018 17:09:00 -0000, Sir Gaygory's Owner's Owner 🐶笛 wrote:


On Thu, 20 Dec 2018 08:34:35 -0800 (PST), LO AND BEHOLD; trader_4
determined that the following was of great
importance and subsequently decided to freely share it with us in
:
On Thursday, December 20, 2018 at 7:51:32 AM UTC-5, William Gothberg
wrote:
On Thu, 20 Dec 2018 04:31:31 -0000, Clare Snyder
wrote:
On Wed, 19 Dec 2018 13:03:19 -0500, "Clark W. Griswold"
wrote:
On 12/19/2018 11:36 AM, William Gothberg wrote:
On Wed, 19 Dec 2018 16:18:29 -0000, Mark Lloyd wrote:

On 12/19/18 5:23 AM, William Gothberg wrote:
Do switch mode power supplies flicker in time with mains? Specifically
LED power supplies in commercially available domestic lamps. By in time,
I don't mean at the same 50/60Hz, but anchored to it. I.e. if you have
several such lamps each with their own built in supply, will they all
flicker in time, using the mains frequency to keep them in time, or
will they be random, making the room overall not flicker due to them
all being random? And is there any way I can test this? I tried
taking photos of them, but my camera only goes as fast as 1/2000th of a
second, which shows all the lights at the same brightness each time, I
suspect the flicker is above 2000Hz.
I once had an audio amplifier with a solar cell rather than a microphone
for the input transducer. This made it possible to listen to light. The
sun is steady, incandescent lights (AC powered) hum. That was 40 years
ago. Maybe something like that would work today.
The trouble is I want to compare 2kHz+ from one light with 2kHz+ from a
neighbouring light and see if they're in sync.
Maybe use a dual trace oscilloscope? Since this landed in
alt.home.repair, I gotta ask. Do you have single-phase or two-phase?
No such thing as "2 phase" -
Perhaps he meant split phase, like in the USA - centre tapped 240V.
Which could conceivably mean I could have some lights on each circuit,
and if they were fed by half wave rectification, flickering at 50Hz,
they could be out of time with each other and make the whole room
flicker at 100Hz, filling in each other's gaps. Mind you the same can
happen by just putting the bulb in the other way (in the UK bayonet cap
fittings allow you to connect live/neutral the other way at random with
bulbs).

They won't be out of time with each other as each circuit is reaching
it's peak value at exactly the same time. That's how you get 240V,
120+120 = 240.

it's actually not technically that the phases reach their peak values at the same time, as they are 180 degrees out of phase. phase a is reaching its peak at the same time as phase b is at its lowest point. voltage potentials are calculated as the difference in potentials between two conductors.

120 - (-120) = 120 + 120 = 240


Only half wave rectified LED PSUs would help each other out when connected to the other half of the phase.