The Genius Design of Light Switches

In this video, we'll use a 3D-printed model of a light switch to explain its ingenious use of a bistable mechanism. What happens if the switch is left in the middle position?

Thanks for watching!
-Steven

[qualitydirtmoving]

This is not actually how the switches look inside but thats how they work

[Elriuhilu]

When I was at primary school there was a light switch in one of the toilets that if you held it halfway would buzz, while visible sparks and wispy smoke came out of the gaps in the cover. When you're eleven years old it's a fun, consequence free toy, but at the same time I was educated enough to use the back of my hand to operate the switch just in case.

[ThantiK]

This is what's known as an "over-center" mechanism; which is also bistable.

[BohumirZamecnik]

Maybe the most important part: You don't want the contacts to be close but not touching, to prevent an electric arc at high enough voltage.

[AmandaPandaPowell]

Techconnections did a great video on this topic

[ziggyzoggin]

You didn't even explain how the mechanism translates to metal contacts touching?

[Hobypyrocom]

this is just the basic mechanism of how the light switch works, not even close on how it actually works tho...

[exja]

Would like to see the inside of a real one though

[ralfbaechle]

Circuit breakers are even more interesting. An overload will break the circuit even if the lever is being held.

[heronimousbrapson]

For a time in the 1960's, there were switches that made no "click". I guess manufacturers considered it annoying.

[TS_Mind_Swept]

I wonder how long until that 3D printed spring gets a hole in it 🤔

[Zeero]

It's also important that when the contacts connect, they don't bounce, which can cause arcing, which itself can cause a fire and/or potentially weld the contacts together.

[timinwsac]

When you put it between on and off time will stand still.

[Chris-opyt]

a safer switch is a relay. here in australia many brands of cheap light and power switches are pretty bad, where the tiny crappy parts (on 240 volts) can break and create shorts or easily expose contacts to human hands. the race to the bottom.

[dam]

lever consistently stays on either side
*adds spring*
lever now stuck in the middle
*visible confusion*

[nsqwhdy]

how about showing us a real light switch?

[BA]

I was just wondering how these worked. I was like I bet that’s a bistable mechanism.

[TheEgg]

No. You didn't explain what happens if its stuck in the middle. You can hold a switch slightly open. Electricity will jump the gap to make the connection and that is very bad.

Bad video. Thumbs down.

[davidt]

The reason for such a bistable mechanism is the high speed at which it goes from middle unstable position to either stable position, thanks to the mechanical force of a spring-like object. Especially for opening the contact: any current (electric or water...) does not want to stop brutally (imagine some inertia), so when the gap starts opening, there's an electric arc forming. If you open it slowly, the arc stays on the air and increases so that current continues flowing through the ionized gas, which is the opposite of switch-off. With a fast contact blade, the arc is not able to follow the fast evolution of electric field, thus it stops.
Similarly, when closing contact, reducing the gap fast limits the time between arc starting and metal-metal contact (no more arc).
Side note: there is always a small hot arc on closing and opening, so such switches are prohibited in ATEX (explosive) environments if nothing prevents arc formation (capacitor / shock coil...).

[elebeu]

This 2:54 minute video was 2:50 minutes longer than it had to be.