Tiny Mercury Switches

Thread Starter

Ya’akov

Joined Jan 27, 2019
5,666
I just received these very diminutive mercury switches and thought they might be useful for some of you. I can't say I have ever seen them this small. The seller does not provide specifications so I don't know what the current handling capacity is, but since these are probably destined to pull a GPIO up or down that's not really a concern.

A four wire measurement says they are about 40mΩ closed and the Fluke 287 reads about 0.05nS open. They should find a use where normal microswitch limit switches won't work.


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Approximate Dimensions

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For size comparison, with a 5mm LED
[EDIT: fixed the conductance measurement which was off by an order of magnitude]
 
Last edited:

peterdeco

Joined Oct 8, 2019
481
We stopped using mercury switches years ago when the EU enacted ROHS. We use tilt switches in a similar size metal can with a metal ball inside. I must say the ball switches gave us some trouble at first due to largely increased switch bounce.
 

Thread Starter

Ya’akov

Joined Jan 27, 2019
5,666
We stopped using mercury switches years ago when the EU enacted ROHS. We use tilt switches in a similar size metal can with a metal ball inside. I must say the ball switches gave us some trouble at first due to largely increased switch bounce.
I have some of those switches and I don't like them very much for exactly the reason you mention, bounce. It can be dealt with but they seem a bit flaky in operation when the angle is marginal, or at least the ones I have do. Not as repeatable as I'd like.
 

MrSalts

Joined Apr 2, 2020
1,762
I have some of those switches and I don't like them very much for exactly the reason you mention, bounce. It can be dealt with but they seem a bit flaky in operation when the angle is marginal, or at least the ones I have do. Not as repeatable as I'd like.
Make sure you are not violating any shipping laws if you mail these. There are very strict packaging laws for shipping elemental mercury and all other hazardous materials (a.k.a "Dangerous Goods"). There may be a minimum quantity exception but, is better to check first. Also, if you ordered it from a foreign supplier, you are the responsible party in case there is a spill, contamination, poisoning or unsafe packaging inside the US.
 

MrSalts

Joined Apr 2, 2020
1,762
You know, sometimes I wonder how much smarter I would be if I hadn’t played with lead and mercury when I was a kid. It’s scary!

Bob
Maybe you played with just enough. Like salt, just enough makes food interesting - too much cause osmotic issues. .
 

KeithWalker

Joined Jul 10, 2017
2,354
I used to salvage the mercury by the pound from failed Ignitron tubes as a source of beer money.
It never affected mu..me..me me........
I had a tobacco tin full from a broken U-tube barometer. I played with it and it ate my aluminium Batman ring but it didn't affect me eithth,,,thth...er!
 

Reloadron

Joined Jan 15, 2015
6,585
When my company was paying to have hazardous materials removed I saved them some money.

Precision mercury in glass thermometer standards.
Thermometer Sets.png

I also grabbed the mercury bulb pneumatic thermostats. :)

Never saw mercury switches that tiny. Pretty neat.

Ron
 

KeithWalker

Joined Jul 10, 2017
2,354
I have some of those switches and I don't like them very much for exactly the reason you mention, bounce. It can be dealt with but they seem a bit flaky in operation when the angle is marginal, or at least the ones I have do. Not as repeatable as I'd like.
I have some of those mercury switches too. They make really repeatable tilt switches with a very small hysteresis angle..
 

k1ng 1337

Joined Sep 11, 2020
539
For you older members: Should I avoid playing around with mercury and lead? I got myself some PTH boards and am thinking I should learn to use lead free solder while I'm ahead brain cell wise. The opinion on the internet is small amounts are ok but what constitutes a small amount?
 

Reloadron

Joined Jan 15, 2015
6,585
For you older members: Should I avoid playing around with mercury and lead? I got myself some PTH boards and am thinking I should learn to use lead free solder while I'm ahead brain cell wise. The opinion on the internet is small amounts are ok but what constitutes a small amount?
As an older member I did play with mercury and melted and cast lead as a kid. I still handle lead on a regular basis and like using lead in solder you just take precautions. I handle lead bullets all the time, I also wash my hands with soap and water. You develop and apply good work habits. You don't tempt fate. :)

Ron
 

nsaspook

Joined Aug 27, 2009
9,740
As kids we would remove the sealing lead from old tin roof barn nails to form small bullets, by biting the lead, for bicycle spoke guns (search for the term if curious).
1652911359036.png
Yes, don't tempt fate playing around with mercury and lead.
 

MrSalts

Joined Apr 2, 2020
1,762
For you older members: Should I avoid playing around with mercury and lead? I got myself some PTH boards and am thinking I should learn to use lead free solder while I'm ahead brain cell wise. The opinion on the internet is small amounts are ok but what constitutes a small amount?
The vapor pressure of lead is quite low. Unless you plan to lick each solder joint. You're not getting much lead exposure by soldering.
 
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