asr t1_j2pfp3j wrote on January 3, 2023 at 1:01 AM

Reply to comment by HanzG in How many of these recessed lights can I use on a dimmer switch? by notscammed

That is not worth noting because that's not true.

Older dimmers are NOT variable resistors! That's simply not true.

HanzG t1_j2pnupv wrote on January 3, 2023 at 1:57 AM

"Modern dimmers are built from semiconductors instead of variable resistors, because they have higher efficiency. A variable resistor would dissipate power as heat and acts as a voltage divider. "

Is this quote not true? Were old ones were not resistor types that induce voltage drops?

EliminateTimeZones t1_j2q94xj wrote on January 3, 2023 at 4:29 AM

I have some Luxtrol WBD series variable autotransformers that were removed from residential dining room applications. They are much bigger than your standard wall switch, but designed to fit into a wall cavity.

asr t1_j2q53km wrote on January 3, 2023 at 3:56 AM

Correct, the old resistors based ones were not used in homes, only in commercial applications (theaters).

They were too large and got too hot to be useful in homes.

EliminateTimeZones t1_j2q6h6n wrote on January 3, 2023 at 4:07 AM

I've seen them in homes, typically dining room chandeliers. They are big and got hot, just like you state.

asr t1_j2q6qxc wrote on January 3, 2023 at 4:09 AM

Those are not rheostat (resistor) based though. They use thyristors to chop the electrical current (you can hear them humming if you listen closely).

Basically they are switches that turn on and off very quickly.

EliminateTimeZones t1_j2q8tba wrote on January 3, 2023 at 4:26 AM

Nope. Definitely a thing. Also I'm corroborating your claims that they are too big to fit in a standard electrical box.

I just pulled mine out of basement storage and took a look. Inside is a variable auto transformer. Lookup "Luxtrol WBD" on eBay to get an idea.

EliminateTimeZones t1_j2qb548 wrote on January 3, 2023 at 4:46 AM

Nope no thyristors in these. Just checked. Just a variable autotransformer. (Not a resistor or rheostat).

Fine-Team-4296 t1_j2sr1fj wrote on January 3, 2023 at 6:23 PM

There are 4 general types:

https://brandon-lighting.com/methods-of-dimming/

The only ime I've seen a variable resistor in real life is in a car. It was for the high medium and low select on a fan speed for heater and a/c. I doubt they would have used them in a house because it would be dangerous due to the heat it creates but who knows.