Sciencemadness Discussion Board

metal vapor lights

Magpie - 23-6-2007 at 12:43

For those interested in aquiring metal vapor lights I thought I would show off my semi-ghetto equipment. The 1st one I made is a reassembled 35W sodium vapor light. It came as a security light with a huge clunky housing and lens. I discarded all but the ballast and socket, remounting them to a wooden box. The holes are for ventilation to prevent heat buildup. Main purpose for this is for use with my Cenco polarimeter.

The second and very recent construction is a 100W mercury vapor light. This also is a security light. I kept the housing as it provided a good solid mounting for the heavy ballast. The socket I remounted remotely in an effort to have a more user friendly light for use in my hood. This will be used for chlorinations and such. It also can be used, I understand, to attract moths, as they are partial to the blue wavelengths.

It is interesting to note that the mercury vapor light was priced at $37 whereas if you try to buy just the ballast I could not find one cheaper than about $75.

Below is a picture of the two lights. After dark I will take a picture of them lit and post it.

metal vapor lights.jpg - 72kB

chemkid - 23-6-2007 at 16:37

Is it plausible to condense mercury or sodium from one of theese lamps? Not so sure about ordering an ounce of sodium from Unitednuclear, much rather make some myself.

Chemkid

Jdurg - 23-6-2007 at 16:46

You would need a lot, and I mean a LOT of these lamps in order to accumulate any visible amount of sodium or mercury. The amount of metal inside these tubes is next to nothing. Just enough to conduct a current and emit light. A single tube won't give you any visible amount of metal at all.

not_important - 23-6-2007 at 18:55

by this patent

http://www.freepatentsonline.com/4075530.html

the amount of sodium is less than 0.05 milligrams of sodium and less than 0.6 mg mercury per cc of lamp volume. Note that volume is <u>not</u> of the bulb that you see, but rather that of the alumina tube at the center, which for typical lamps has a volume of 4 to 8 cc.

[Edited on 24-6-2007 by not_important]

Magpie - 23-6-2007 at 20:33

Here's the picture of the lights lit, 35W sodium vapor on the left and 100W mercury vapor on the right. I'm going to leave the mercury vapor light on for awhile and see if any big moths show up.

lights lit.jpg - 43kB

chemkid - 26-6-2007 at 15:43

I went to wikipedia and found this:

"It has two inner borosilicate glass U-pipes that hold solid sodium and a small amount of neon and argon gas Penning mixture"

I checked several other sources as well. Solid sodium metal is contained in low pressure sodium vapor lamps (however not high pressure). ANd i would bet if you have a friend in the town goverment then you can get them for free. I would bet that if you could get some old used ones there would still be some recoverable sodium metal. Furthermore, barium is used as a getter in these lamps to make a vaccum, so you get some of that too. or if you can afford it just order one for forty dollars with fresh sodium in it.

Chemkid

[Edited on 26-6-2007 by chemkid]

[Edited on 26-6-2007 by chemkid]

not_important - 26-6-2007 at 18:36

Low-pressure sodium vapor discharge lamp
United States Patent 4401914
"The lamp contains neon and approximately 30 mg of sodium. "

Although some of the large older models have up to a gram of sodium in them. But $40/gr sounds a bit pricey to me. The low pressure lamps are less common, because of their narrow band light output which trashes colour rendition and makes depth perception difficult.



Barium getters - remember that the getter is heated to cause barium to vapourise and form a very thin mirror on part of the interior of the tube or bulb, it's not sitting there as a lump.
While these are CRT getters, you can get a feel for how much barium would be in a street light, as that is proportional to the volume to be scrubbed.

http://www.saesgetters.com/default.aspx?idpage=460

indigofuzzy - 26-6-2007 at 21:36

Quote:

It also can be used, I understand, to attract moths, as they are partial to the blue wavelengths.


I thought the moths (and many other flying insects) liked the longwave near-UV though, which mercury vapor lamps produce in abundance. And I know this is nitpicky, but the closest to a blue line in a mercury vapor discharge is the indigo/violet line. But your color perception may vary. ;)

Eclectic - 27-6-2007 at 05:09

If you can run the mercury lamp with the outer glass shell removed, you can get lot's of long and short wave UV. I think the inner pressure tube is made of fused silica to be able to withstand the heat and pressure. I had one set up to erase UV erasable E-proms, back in the day when that was the only technology in use. No 15-20 minutes with a UV lamp to erase my E-proms. Mine were zapped in 30 seconds.

[Edited on 6-27-2007 by Eclectic]

MagicJigPipe - 22-6-2011 at 08:39

@JDurg:
Quote:
You would need a lot, and I mean a LOT of these lamps in order to accumulate any visible amount of sodium or mercury.


I disagree. I saw a 175 W Hg vapor lamp at a famous US home improvement store the other day. The outside glass had no phosphors so you could see the actual Hg vapor lamp inside. I could see easily visible droplets of Hg on the sides. In fact, I was shocked at how much mercury was in there. There were at least 5 drops with a diameter of about 1 mm.

I think you are thinking of common fluorescent bulbs. That is true for those (except for some tanning bulbs, which can contain visible droplets of Hg).

[Edited on 6-22-2011 by MagicJigPipe]

Rogeryermaw - 22-6-2011 at 17:32

Quote: Originally posted by Eclectic  
If you can run the mercury lamp with the outer glass shell removed, you can get lot's of long and short wave UV. I think the inner pressure tube is made of fused silica to be able to withstand the heat and pressure. I had one set up to erase UV erasable E-proms, back in the day when that was the only technology in use. No 15-20 minutes with a UV lamp to erase my E-proms. Mine were zapped in 30 seconds.

[Edited on 6-27-2007 by Eclectic]


light sensitive e-proms are crazy. not so long ago i installed high-end security equipment and occasionally after the install, upon photo-documenting our work, the camera flash would ruin the programming in the chip. took a while for us to figure out why. putting vinyl tape over the chip solved the problem.

Intergalactic_Captain - 23-6-2011 at 00:33

Shot in the dark, but I'm guessing that you're working with magnetic rather than electronic ballasts - Being salvaged and "heavy," they sound old-school. As such, you should be able to find ballast set-ups in the $50 range for anything up to about 500 watts - Believe it or not, when I built my projector, the smaller the ballast the more expensive it was - Opposite for the bulbs.

Which brings this up - Say you want to design a system around a bulb - The following is not complete and will be poorly explained, but it took me quite a while to figure out just how the hell a ballast works and this will probably help someone...


I wanted a 150 watt system. It was the perfect balance and I had a couple of cheap MH bulbs to work with. I got lucky and found the perfect ballast/ignitor pair for $50, an unused NOS service kit on ebay. IMO, it is much easier and cheaper to build around a bulb than around a ballast than to go the other way or to buy something complete - Of course, the dumpster-diver will toss in some caveats...

Essentially, the ballast system is nothing more than a large inductor and HV capacitor wired in such a way as to provide a high-voltage spark to strike the arc and a controlled current source to maintain it. The inductor serves only one purpose - limiting the current to the bulb. The bulb itself is essentially a contained lightning bolt - It will happily consume as much current as can be delivered to it, until either it melts and breaks the arc or overdraws the current source.

...That said, when designing a system, one must think opposite the way one would design any other power supply - Take my 150 watt bulb for example - It's designed to work at 150 watts. Intuition would say that a 200 wat ballast would give a good safety margin, but that's the direct opposite of what you want to do. In reality, the bulb will see that 200 watts are available and use it all until catastrophe strikes - It is much better, if one cannot find the perfect match, to use a smaller ballast than bulb - Say you have a 175 watt bulb and can only find a 150 watt ballast... It won't work optimally, but on the other hand it won't overdraw.

Another note, sodium and mercury systems are for all intents and purposes interchangeable - You can use a sodium bulb in a mercury system and vice versa - MH is where it gets tricky, as the strike and restrike procedures are a bit different. Also, I'm not familiar with the type of spectrometer you're building, but for something wide-spectrum MH would be the better way to go, much more so with the wide variety of "color temperatures" available.

watson.fawkes - 23-6-2011 at 10:42

Quote: Originally posted by Intergalactic_Captain  
Essentially, the ballast system is nothing more than a large inductor and HV capacitor wired in such a way as to provide a high-voltage spark to strike the arc and a controlled current source to maintain it. The inductor serves only one purpose - limiting the current to the bulb. The bulb itself is essentially a contained lightning bolt - It will happily consume as much current as can be delivered to it, until either it melts and breaks the arc or overdraws the current source.
All true insofar as it goes. I want to elaborate on two points.

An arc is like a very low value resistor that doesn't obey Ohm's Law. In one sense, it's like a short circuit; it offers little resistance to electrical flow. In another, it's definitely a resistor, as it dissipates heat and generates a voltage drop. Regardless, it's the inductor in a traditional magnetic ballast that limits current flow, not the arc. Also, while it's physical possible to run an arc on DC, regulating it quite difficult. By contrast, the AC impedance of an inductor limits current flow without big losses.

The second point is that if you're scratch-building one of these systems, it's useful to use a push-to-start button in them. This connects the starting circuitry up only when manually starting and leaves it out of the circuit at other times. This alleviates stress on the parts and allows smaller (and cheaper) components. These aren't well-suited for building lighting, because there you want a single light switch. For a piece of lab gear, push-to-start is just fine.