Does this look like a lightbulb to you? - Page 1
Forum section: electronics / general

author: amyk
author_rank: Super Contributor
timestamp: December 06, 2015, 05:13:34 am
content: I stumbled across this interesting mystery:https://www.reddit.com/r/whatisthisthing/comments/3vfam4/update_mystery_mercury_bulb_in_the_castle_attic_i/http://imgur.com/a/EkqWtIt doesn't look that old to me, and the base of those bulbs is remarkably similar to that of a standard lightbulb (necked-down base and evacuation pip with tube, and not just a pinched off end); perhaps someone a few decades ago was filling lightbulbs with mercury and leaving them in weird places as some sort of a stupid joke?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: December 06, 2015, 06:13:18 am
content: Speculation totally unsupported by facts:There is a fair amount of fancy glasswork on the "activated" end. The volume of mercury seems about right to fill that up.If the inside and outside layers of glass are heavily leaded, would they be conductive enough to complete a circuit when the mercury flowed in? Not much current, perhaps just enough to run a neon bulb or a small solenoid when powered with a high voltage. This would have required a cable and connector that fit on that glasswork.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 06, 2015, 09:09:27 am
content: I think the posts about it being a mercury whetted contacts float switch are probably right. It's big enough that it floats well. The metal carrier holding it obviously slides along that other rod. If that is more or less upright in the tank but curves over, the bulb will tilt as it goes up/down. Adjusted right it could make/break the mercury contact at water set level.And it would all work fine till the sliding rod corroded enough to jam it.Possibly the wires out the 'base' end corroded away long ago. Both rubber insulation and copper.It might look like a light bulb, because it's manufactured using the same production line as light bulbs? Except the inner wires inside the glass were bent down into the base area, instead of sticking up and having a filament attached.But that leads to the (non)wisdom of having mercury in a thin glass container, in a water tank in a house. Good luck getting all the mercury out of the tank if the glass breaks.More to the point, how many of them did break in the past?

author: SeanB
author_rank: Super Contributor
timestamp: December 06, 2015, 10:20:27 am
content: Lead lined tank, what is the worry of a little extra flavour from mercury, it will be masked by the sweet taste of the lead.

author: amyk
author_rank: Super Contributor
timestamp: December 06, 2015, 04:17:32 pm
content: It's water-treatment snake-oil:https://www.reddit.com/r/whatisthisthing/comments/3vfam4/update_mystery_mercury_bulb_in_the_castle_attic_i/cxosva4That links to abullshit-filled articlewith this unusual paragraph:QuoteSurplus lightbulbs filled with mercury, in other words. I also came upon this:https://en.wikipedia.org/wiki/Barometric_light

author: Deathwish
author_rank: Unknown
timestamp: December 06, 2015, 04:39:21 pm
content: oldest working lightbulb = Livermore CA firestation. Watch the youtube video the lightbulb conspiracy. As for this thing, my guess is its a float of some sort, but I do like the way that tank has some modern pvc clips for the copper piping on it.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: December 07, 2015, 06:56:47 am
content: this sounds more like it was designed to be an oil furnace tank than a water storage tank.

author: G7PSK
author_rank: Super Contributor
timestamp: December 07, 2015, 09:04:55 am
content: The mercury must be in there as ballast, there would appear to be no wires going into the glass container. Either that or it is a re-purposed mercury arc lamp that has burnt it's wires out.

author: Kjelt
author_rank: Super Contributor
timestamp: December 07, 2015, 10:44:30 am
content: Existing gas discharge lightbulbs don't use that much mercury, at most a tiny drop.My guess if it was indeed a switch, it is a level switch, the bulb will float on the surface of the water or oil the mercury will close the switch, if the level is lower then the metal bar it will start to till opening up the switch. Just a wild guess, never seen anything like this.

author: G7PSK
author_rank: Super Contributor
timestamp: December 07, 2015, 11:38:00 am
content: I see no sign of any contact inside the glass bulb, I reckon it worked a mechanical switch and the mercury is just ballast.

author: Kjelt
author_rank: Super Contributor
timestamp: December 07, 2015, 02:28:07 pm
content: Quote from: G7PSK on December 07, 2015, 11:38:00 amThere are much more cheaper and better alternatives than mercury (poisonous and expensive) to use it as ballast such as lead or iron.

author: GNU_Ninja
author_rank: Regular Contributor
timestamp: December 07, 2015, 02:49:32 pm
content: Homebrew version of one of these perhaps:https://victoriancollections.net.au/items/4f72bd8797f83e0308606653Whatever the hell it is or does

author: Maxlor
author_rank: Frequent Contributor
timestamp: December 07, 2015, 03:58:14 pm
content: Quote from: G7PSK on December 07, 2015, 11:38:00 amMechanical hysteresis using mercury? Clever, in a mad way.

author: GNU_Ninja
author_rank: Regular Contributor
timestamp: December 07, 2015, 04:02:39 pm
content: Quote from: amyk on December 06, 2015, 04:17:32 pmThis ^^^^It's a Scalebuoy

author: kc9qvl
author_rank: Regular Contributor
timestamp: December 07, 2015, 11:32:18 pm
content: Looks just like a Glass fire extinguisher

author: calexanian
author_rank: Super Contributor
timestamp: December 08, 2015, 06:13:55 am
content: Its just an old tilt switch. Used to be very common. As somebody mentioned before the leads have corroded away. They were only dumet wire which is steel cored with nickel plating and then copper on top.

author: timb
author_rank: Super Contributor
timestamp: December 08, 2015, 08:12:03 am
content: Quote from: calexanian on December 08, 2015, 06:13:55 amNo. It doesn't fit the timeframe for when electric water pumps would have been used. The first electric water pumps in common use weren't until the early 1900's. They were also manually switched. Large relays for remote switching didn't come around until later.They're Scalebuoyes.

author: wblock
author_rank: Regular Contributor
timestamp: December 08, 2015, 04:12:40 pm
content: One of the references for these things (http://www.waterjournal.org/volume-3/demeoclaimed it produced a "subtle blue-green flash of light" when shaken.The "subtle" might mean it's audiophile territory, only present if you believe in it. And that article is enormously entertaining if you can suspend disbelief while reading it, like a fairy tale.But if that light flash is real, I'm curious to know what effect produces it. Some kind of piezoelectric effect with the glass?

author: Zero999
author_rank: Super Contributor
timestamp: December 08, 2015, 11:50:41 pm
content: Quote from: wblock on December 08, 2015, 04:12:40 pmThe answer was provided much earlier in the thread:https://www.eevblog.com/forum/chat/does-this-look-like-a-lightbulb-to-you/msg815289/#msg815289To simply it even further: as the mercury moves over the glass, it generates static electricity which ionises the surrounding air and mercury vapour, causing flashes of light.