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I have tried to look online but I have no idea what this is so its like spotting a needle in a haystack. It would be really helpful if someone could tell me what this is (see pic). It has a "silver oval shaped blob" inside of it...Also are there any general voltage specs I should know about before connecting it to a breadboard circuit because no specifications were included...

enter image description here

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2 Answers

up vote 9 down vote accepted

Does the "silver oval shaped blob" move around inside of it? If so, it is a mercury switch. Depending on how the thing is oriented, the mercury makes an electrical contact between the two leads. You'd use one as a tilt sensor or something.

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yeah it does move around. Upon doing a google image search it does seem like that's what it is. thanks! – rrazd Jul 30 '11 at 4:56
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looks like a neon light bulb to me. If you want to light it you'll need around 70V and about 22k of resistance in series to protect it. It'd be easier to connect it (with the series resistor) to the 110V or 220V on the bench instead. :-)

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A hg switch does look like a neon bulb, but the blob ( of hg ) pretty much seals the case ( which is a good idea as hg is Toxic ) – russ_hensel Jul 30 '11 at 12:48
I've played with a good amount of mercury switches as a child (without knowing of the health issues it presents) -- the device very well could be a mercury switch, although I haven't seen a glass bulb for a mercury switch quite that same shape. As @rrazd mentions in David's answer, though, the blob moves. It's indeed a switch. – Andrew Kohlsmith Jul 30 '11 at 13:42

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