The other night I picked back up playing with insulated gas discharge tubes (IGDT), better known as plasma globes. The basic idea is to pump a sealed chamber filled with a noble gas (or air, in a pinch) down to low pressure (1s to 10s of Torr), and apply electricity at high voltage (a few kV) and frequency (a few kHz) to ionize the gas. Depending on the gas(es), pressure, voltage, and frequency, the results should range from a diffuse eerie glow to a bunch of lightning-like plasma streamers dancing around inside the chamber. The most well-known example are the Eye of the Storm novelty globes and their knockoffs.

[Photo Album]

Here are some pictures from tonight’s initial playing, using a scavenged fridge compressor as a vacuum pump and a cleaned-out glass pasta sauce jar as the globe. The effect inside the jar was generally unimpressive over a wide range of pressures, but the effect on the clear PVC tubing and the white plastic hose barb I used to attach it was certainly interesting! The hose barb connector glowed brightly and the plastic tubing lit up like a flexible neon sign, with a glow that crawled through the hose several feet toward the compressor as the pressure dropped. Nice poor-man’s neon effect, but I suspect air will outgas and/or leak through the walls of the PVC tubing rapidly (days?), ruining the vacuum and the effect. This calls for further study :-)

I didn’t play too much with additives except to revisit the combination of plasma globe and discrete mini Neon lamps. This looks much cooler with the neon lamps actually inside the evacuated chamber with the glowing plasma (and finally with a decent camera!). Everything so far has used plain old air.

Fridge Compressor as Vacuum Pump

The short story is yes, you can use the compressor from a refrigerator or dehumidifier as a quick & dirty vacuum pump (or light duty air compressor), provided the refrigerant has all been vented/leaked before you get to it (unless you have facilities to safely capture and recycle the refrigerant, which few do). The design of these things seems pretty universal, as well as ingenious: the “in” tube leads to a piston, which is driven by a big electric motor in the center of the compressor via a crankshaft. The output of this valved piston vents directly to the inside of the case, which is sealed and in facted welded shut, with the “out” tube being the only escape. The bottom 1/4 inch or so of this mechanism is submerged in a pool of light oil, which is sucked up by a cone on the bottom of the crankshaft mechanism, sucked through the shaft and flung out the top and against the outer walls of the compressor by centri[whatsit] force – providing simultaneous lubrication and transfer of heat from the pump mechanism to the outside case, which acts as a heatsink. This page has a very cool teardown of one of these compressors, complete with videos of the oil-slinging mechanism in operation.

As a side effect to this design, small amounts of oil are sometimes ejected from the outlet along with the air, necessitating some kind of primitive oil recovery/trap mechanism. For mine I attached a small length of vinyl tubing to the outlet, made a sort of drip loop in it, and attached the other end to a piece of plastic pipet taped vertically to the side of the compressor. The width of the pipet prevents oil from being blown out all the way to the top, while the drip loop in the tubing (intentionally seeded with a couple drops of oil) provides a simple but highly effective visual flowmeter, good for indicating the end of effective pumping (or a leaky system). A loosely fitting cap taped over the pipet helps reject dust.

It’s probably a good idea to eyedropper out occasional oil from this catcher and feed it back into the inlet to keep the piston lubed up. (I had to drain all the oil out of mine to transport it, then refilled it with an equal volume of some SAE 30 motor oil I had on hand. No ill effects thus far, but I’m pretty sure the original oil was a lot lighter.)

But how good is it? I have no actual meter that will deal in these pressures, so it’s hard to say. On this pump a jar of water would–just barely–start to boil at room temperature. According to this calculator, that approximates to roughly 20 Torr (.026 atmospheres). Not bad for free!

Possible sealing approach (haven’t gotten around to trying it yet)

Professional globes are all-glass affairs of a complex shape, with the glass fill tube(s) heated and melted shut while under vacuum to seal the globe. This is not really an option for hobbyists, since it must be connected to a live vacuum during sealing and a typical “globe” has a nonglass base (plastic or Plexiglas) where an equally nonglass fill tube emerges, since glassmelting is not compatible with the typical vinyl tubing connecting it to the live vacuum system in the process. Some just leave a small length of tubing and a closed valve permanently affixed. But good valves aren’t cheap, and cheap valves aren’t good. The approach I’d like to try is to epoxy a hose barb into the base with a very thin piece of hollow metal tubing (needle) epoxied inside of it, making the tube the only gas path into or out of the globe. This is connected via a short piece of vinyl tubing to one of two matching hose barbs on a small lidded jar (e.g. baby food – something with a “magic button” style rubberized lid), such that the needle snakes through the center of the tubing and just reaches the bottom of the jar. A small discardable “bucket” (e.g. soda cap) of 5-minute epoxy would be mixed up and placed inside the jar, the lid screwed on, and the needle sunk into the epoxy. The jar, and thus globe, are then evacuated via the 2nd barb in the babyfood jar lid. When the pump is switched off, the normal small leakage (maybe introduced via valve, if the pump setup is just that good) will allow the vacuum to relax slightly, forcing liquid epoxy up the metal needle, where it is allowed to cure and permanently seal the globe. The excess epoxy-filled metal needle and hose barb can then be cut off. Extending this setup to multiple flush/fill hoses on the globe would be easy enough, other than trying to hand-align these multiple needles at once.

I was there to demo my self-powered wireless brake health monitoring system at the FRA’s Advanced Concept Train booth. Despite the final assembly of this and the other 29 units occurring only a couple days before (and passing through the TSA’s loving hands), everything went perfectly! (Murrphy’s Law might have a surprise or two for me on back-order.)

The train show wasn’t all that exciting to me (not a train nut), but the food was good, and I got to visit the fam back home for a bit. :-)

And the winner goes to… The Terms & Conditions for use of the Hampton Inn’s complimentary WiFi. Weighing in at 47.4KBytes* and a whopping 90 screens (scrunching it all into a tiny browser text box did not help in this regard), this is quite possibly the longest, and most unilaterally evil, user agreement I have ever read.

(I would start here with a list of definitions of usage information (‘hereinafter … referred to collectively as the “Information”‘) gathered by the service, but man is it lengthy. Basically, your IP, lists of websites visited, transactions and purchases on 3rd-party websites, you name it.)

You agree that HHC shall own all Information.

By using the Service, you voluntarily, expressly and knowingly acknowledge and agree with all of the foregoing and further agree to each and all of the following: (I) such Information belongs to HHC and is not personal or private proprietary information; (ii) such Information, wherever collected, may be processed, used, reproduced, modified, adapted, translated, used to create derivative works, shared, published and distributed by HHC in its sole and absolute discretion in any media and manner irrevocably in perpetuity in any location throughout the universe without royalty or payment of any kind, without, however, any obligation by HHC to do so

I’m guessing the main “[iI]nformation” they’re interested in is clickstream data, but the definition of this [iI]nformation includes any piece of data transmitted through or “relating to” or “describing” the service (even prior to being presented with this contract), presumably including this blog post. (*Starts lawsuit clock*) So you might not want to use this service to email your just-finished Great American Novel manuscript to your publisher. Also, this is the first legal agreement I’ve ever seen explicitly covering the entire Universe.

Also, when you submit information (including the Information) to us in your use of the Service, you thereby (i) represent and warrant that such information is complete, truthful, and accurate, that you own all rights in such information, that the information, if applicable, is entirely your own original, unpublished work, is not based in whole or in part upon any pre-existing work or work of any other person,

Again, ass-uming they’re mostly after clickstream data, this makes it a legally-actionable offense to surf in such a way as to provide non-unique clickstream data, i.e. surfing the same sites you surfed yesterday. And apparently, you are forbidden from transmitting already-public data through the WiFi connection (even if you own it…err, would have owned it until the moment you sent a copy through Hampton Inn’s WiFi connection)…maybe they are fishing your packets for saleable manuscripts, leakable memos and not-yet-submitted patents after all.

Because we are not involved in the actual transaction between buyers and suppliers, if applicable, in the event that you have a dispute with one or more users, you also on behalf of yourself, your predecessors, if applicable, and each of their present and former officers, employees, directors, shareholders, parents, subsidiaries, alter egos, affiliates, partners, agents, attorneys, accountants, heirs, executors, administrators, conservators, successors and assigns, as applicable, hereby fully and forever releases and discharges the Indemnified Parties, from any and all claims, demands, liens, actions, agreements, suits, causes of action, obligations, controversies, debts, costs, attorneys’ fees, expenses, damages, judgments, orders and liabilities of whatever kind or nature in law, equity or otherwise, whether now known or suspected which have existed or may have existed, or which do exist or which hereafter can, shall or may exist, based on any facts, events or omissions occurring from any time on or prior to the execution of this Agreement which arise out of, concern, pertain or relate in any way to this Agreement or the Service.

Synonymania! Oh yeah, that is ONE SENTENCE.

Notwithstanding such provisions, this release shall constitute a full release in accordance with its terms. You knowingly and voluntarily waive the provisions of Section 1542, as well as any other statute, law or rule of similar effect. In connection with such waiver and relinquishment, You acknowledges that you are aware that you may hereafter discover claims presently unknown or unsuspected, or facts in addition to or different from those which you now know or believe to be true, with respect to the matters released herein. Nevertheless, it is your intention, through this Agreement, and with the advice of counsel, fully and finally settle and release all such matters, and all claims relative thereto, which do now exist, may exist, or have existed between and among the parties hereto, including the Indemnified Parties. You hereby acknowledge that you have been advised by your legal counsel, understand and acknowledge the significance and consequence of this release and of this specific waiver of Section 1542 and other such laws.1

Hereby, the party of the first part registers a parse error on Line 1. The remainder of this section has you agree to an end-run around a California law protecting you from getting screwed over by an omission from the contract or other omitted facts which, if known, would have materially affected your decision to enter the contract.

If there is any place that runs a “Worst User Agreements” contest, I saved a copy…

* This is about 15% of Pride and Prejudice by weight, according to Project Gutenberg, and >100% as dull, according to the party of the first part myself.

So, a week-and-change ago Kr* and I picked up some basic homebrewing stuff and started a batch of English brown ale. Since this is our first ever beermaking attempt, we purchased a ready-made ingredient kit with all the stuff pre-selected and measured into labeled baggies, idiot-proofing the process as much as possible. This Sunday we cracked the fermenter open and bottled the (almost) finished product. It has to sit in the bottles a few more weeks to carbonate and condition, and then we can drink it! Naturally, we documented the entire process ;-)

Clear your calendars for about a month from now; our yield was about 45 bottles and we’re going to need help consuming it…

Notes: There was a bit of a scare when we added the yeast, sealed up the fermenter and watched as nothing happened for a good few days. We thought we royally screwed something up. While I was down there checking on it at about the 3rd day, I noticed a faint beery smell on one side of the bucket. When I ran a wet finger around the airlock seal (it easily passed visual inspection) to check for bubbles/leaks, this completed the seal and the airlock suddenly started bubbling furiously (“furiously” being one big bubble every 2-3 seconds). Everything was fine, we just couldn’t see it.

Another bit of weirdness is that we got a very low initial specific gravity reading. This is an important measurement to determine when fermentation has stopped and how much alcohol is in your brew. According to the kit we used, the starting gravity should have been within the range 1.040 ~ 1.048; our initial reading was a lowly 1.034. Final gravity was measured at 1.012, the top end of the recipe’s specified range. If taken as accurate, this would mean our beer has 2.9 ~ 3.1% alcohol, which is far lower than expected (according to the recipe it should be 4.0 ~ 5.0% ABV). It’s likely that the initial measurement is way off due to not stirring up the mixture after adding cold water to the hot, slightly viscous wort before the measurement, so the top layer we measured may have been uncharacteristically watery. (This internets sez: In a malt extract beer when less than 5 gallons is boiled , the problem usually stems from not adequately mixing the top-up cold water with the wort. Typical results will be very low (or very high) hydrometer readings. Cold water and hot wort are a little like oil and water, and must be vigorously mixed for at least a minute to blend the hot sugars into the cold water.) We’d heard somewhere that agitation/aeration = bad, so we held off any mixing until it was absolutely necessary – a slow gentle stir when adding the yeast, which was after the IG measurement.

As you probably know, a Web cookie is a small bit of information (typically a server-generated ID number) a Web site can store on your computer to read back on any subsequent visits, even years later. Currently, the major browsers support making all cookies “session-only” (even if the site sends them with an expiration date 200 years into the future), where a session is defined as the time from when you open your first browser window to when you close the last one (i.e. terminate the browser completely). In my book, this is the best thing to happen to browser privacy settings in years. With this setting, when you close the browser at the end of the day, all the tracking cookies used by marketing sites, etc., go away. Every logon is a fresh start.

Google Chrome and IE add a tab-grouping feature, in which the browser maintains awareness of the path you took to get to a particular page (shown in a tab) – if you click a link from one page to another and open it into a new tab, the tabs are grouped next to each other. If you created a new tab from scratch for some unrelated surfing, it’s not grouped with any existing tabs. This makes sense.

It also begs a logical extension. If the browser can now differentiate between related and unrelated “threads” of surfing, it could also allow enhanced privacy by preventing sites from sharing information between threads. (By “thread”, I mean an uninterrupted stream of link clicks in a single browser window/tab or its parent tabs.) Typing a new URL into the address bar, being diverted to a different site via non-click means (e.g. Javascript tricks), or closing the window/tab, ends the current thread and begins a fresh new thread. In this proposed feature, ending a thread destroys any information (cookies, etc.) it contains, at least from the Web site’s point of view. (This is the exact opposite of Chrome’s current “incognito mode” behavior, which prevents history and other data from being saved on your machine, but doesn’t do anything to limit 3rd-party sites from cross-service and cross-domain sharing.)

Currently, any Web site can store and retrieve any cookie data (as long as it originated from its own domain), at any time. A common scenario: The first thing you do in the morning is open a browser and log into your GMail account. Throughout the day, you’re performing various unrelated Google searches, all in different windows/tabs. You could have even read 1 email and then closed the mail window/tab early in the day. All of your search history is now permanently tied to you via your GMail account (if you have a login for GMail or other Google services, have a look at http://www.google.com/history/?hl=en). Persistent user data is tied to the browser as a whole, not the browser window. In other words, the page loaded in window #2 can see what you’re doing in window #1, so long as the domain-access rules are met. Remember, any *.example.com page/site/service can retrieve data (e.g. a uniquely identifying cookie) set by any other *.example.com page/site/service – and if it can tie any one of these bits to a more stable form of identification (in this example, your email login), all of it now can be tied there. It’s entirely possible that you don’t want all these unrelated bits of information collected permanently, in a trivially subpoena-able form, securely notarized (via your login/password and most likely SSL) as uniquely and provably your own. Anymore, many sites absolutely require cookies to function, so blocking them outright is not a solution.

2nd example: You’re reading an article on some medical site about some arbitrarily embarrassing personal malady. The site has ads, which are embedded into the page from a large 3rd-party ad conglomerate (say “evilclick.net”). You close this window and go about your daily surfing. Three hours later, you’re showing a cluster of co-workers something you found on Spamazon.com and still all the ads being served up are for embarrassing personal cremes and lotions. Spamazon.com, like 90% of web sites, uses evilclick.net as its ad provider. Since the ads themselves all come from the same place (regardless of all the different sites they actually appear on), evilclick.net has permissions to read/write cookies and track the user’s movement across all these sites. The proposed approach would help curtail such cross-site sharing.

This concept, although not foolproof, would provide enhanced privacy and deniability for Web usage data. A service would then be limited to trying to correlate data to a user’s IP address, which is harder to hide, but also is much less reliable at identifying a specific user. Currently, via proxy servers and proxy-based anonymizers (such as Tor) a user’s IP could change on every request, and thousands of users could share the same IP (e.g. through an ISP’s caching proxy, or any NAT such as a home wireless router, etc.). A service could at best “guess” an x% probability that various requests might come from the same user, but could not verify it.

I’m contemplating picking up some homebrewing equipment this week. Anyone else interested in making (+ drinking) some homebrew beer?