Strange Lighting Event

[Catwatcher]

The items involved are: A duplex remotely controlled by and on-off/dimmer switch. A string of 200 LED Christmas lights plugged into one of the duplex sockets. As string of 60 LED Christmas lights plus a string of 100 incandescent miniature Christmas light plugged into the other duplex socket via an extension cord with an in-line switch.

Now, here's the strange event:.

The dimmer was set to about 90 volts (by accident, forgot to reset when we plugged in the Christmas lights). When the switch on the extension cord is turned off, the remaining set of 200 LED lights dims significantly. Why?

When the duplex outlet operates at full voltage this doesn't happen.

[Edward Reid]

Don't know exactly, but I'd figure it has to do with power factor mismatches.

Wait a minute ...

Are you saying that the remote is a dimmer? Does it do this by controlling dimmer circuitry which is actually in the receptacle? Otherwise it sounds like a neat trick to me. But assuming the actual dimmer circuitry is in the receptacle, the fact that a remote is involved is not relevant.

Most dimmers assume the power factor doesn't matter, which is true for incandescent lighting. But the transformer/rectifier which feeds the LEDs has a strong angle to its power factor. So the incandescent lights absorbed part of the power factor mismatch. When you turned off the incandescents, the power factor mismatch to the transformer became much more significant. Yeah, I'm waving my arms around and haven't figured it out exactly.

When the dimmer is at full voltage, it is essentially shorted and does not alter the power factor.

Edward

[Jeff Thies]

The LEDs draw very little power, apparently not enough for the dimmer to behave "properly". A clue to this is that there are low load dimmers available:

I wouldn't worry about it.

Jeff

[Colbyt]

Dimmer switches should not be used with outlets as you have just learned.

[Catwatcher]

The duplex outlet is about seven feet above the floor and is typically used to power lights above or on the fireplace mantle. The hardwired dimmer is located remotely (a few feet away) at normal switchplate height. During the holidays a couple of Christmas light strings replace the usual mantle lights.

[hrhofmann]

Reread Edwards original comments, he is correct..............

[Catwatcher]

I think that may be the answer. It seems to make sense (to me, at least) that having low load, diode limited light strings in series with a device that truncates the wave form could some type of unusual triggering in the dimmer. It would be interesting to introduce an incandescent light into the arrangement to see what effect the increased load would have. Lest anyone continue to think I'm attempting to dim LED's, that proposal would be just for investigation purposes.

Catwatcher