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Mercury Wall Switch

No problem here...just thinking about something.

Growing up, my folks had one of those silent mercury toggle wall switches in their bedroom. It was there when we moved in. The regular switches around the house made really loud snaps.

Nowadays, switches are nearly all virtually silent.

I presume the difference was all in the detent action not in the switch contacts themselves (though one might expect the actual contact material having improved).

So they probably could have made the switches silent if they'd wanted to, no?

Did people back in the day actually want switches to make loud snaps like maybe to assure them that the action had taken place?

And when someone did want a silent one, did they not know how to quiet the detent? A mercury switch just seems like a lot of trouble if there was an easier way.

Reply to
Steve Kraus
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The old snap-action switches were a quick-make/quick-break design with heavy springs to move the (brass?) contacts rapidly, to minimize sparking/spark-related metal erosion. You don't erode liquid mercury, it just evaporates a tiny bit and condenses later.

I think the modern switches use a silver alloy button contact, that lasts a long time, and doesn't need to be scraped against other metal to keep it clean.

Personally, I like the mercury switches (am using a few in high-use locations).

Reply to
whit3rd

In the beginning (of electrical service) a given household or area might be fed with DC. Without the regular zero-crossings of AC to extinguish arcs when the switch opens, the snap-action was to get the switch contacts far apart as quickly as possible.

Isaac

Reply to
isw

yeah, they used mercury.

Old switches were made well and lasted forever. New switches at the box stores are complete shit and virtually fall apart just mounting to a box.

My guess here is they didn't want to compromise quality and reliability standards of the tiem to make cheap, short lived crappy swithes like are OK now.

Even places like hospitals get the wrecking ball before they wear out these days.

Reply to
Cydrome Leader

The switches we have are almost all cam-operated, not snap-action. A bump on the handle presses a contact arm onto the other contact. These fail generally by fatigue of the arm, not by burning out of the contacts. They do seem to last 20++ years in residential use. Most of the ones I've replaced are most likely the original ones installed when the house was built, 40 years ago.

Jon

Reply to
Jon Elson

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