Dan's Data letters #179Publication date: 27 November 2006.
Last modified 05-Sep-2015.
Make a game of it!
Being that you're a fellow owner of cats, I'm hoping you've maybe got a solution to my problem.
My wife and I have two cats, and one of them in particular likes to come and sit next to my monitor (a slightly aging Compaq 1725 monitor rescued from a garage sale), and rub up against it. As a result, this leaves a lot of fur and dander all over the screen and happens several times a day. I figure after a week I've removed enough fur and dander from the screen to cover said cat a couple of times over, and this is despite the fact that both cats get brushed regularly.
So what I'm wondering is this: is there something I can do to cover/treat my monitor screen so it won't attract fur etc so readily?
Thanks in advance for any advice you can pass along.
Not really. You could try anti-static sprays made for LP records and such, but none of those actually work very well. The old polonium-bearing radioactive antistatic brushes for LP records work very well (it's only alpha radiation, so it's safe if you don't eat the brush), but the polonium in "vintage" brushes will have decayed away to nothing, since polonium-210 has a one step "decay chain" straight to lead, and a half-life of only 138 days. And, furthermore, a CRT will just charge straight back up after you stop brushing it.
Upgrading to a newer CRT is likely to help, though, and upgrading to an LCD should solve the problem entirely.
Older CRTs - computer monitors and televisions - are famous for having very high electrostatic charges on the screen. You might have noticed that old TVs used to crackle very noticeably when you turned them off (well, if the local humidity wasn't 90% or something, anyway), but modern CRTs aren't nearly as dramatic.
The reason for the crackling is simple enough - CRTs work by shooting electrons at the inside of the tube, and that inescapably means a large charge builds up on it. This charge will attract any lightweight stuff in the vicinity - dust, fluff, cat hair and so on. It'll also repel said crud away again after it's sat on the screen for a moment and accumulated the same charge, but it doesn't repel hard enough to get rid of all of it (there's some mechanical adhesion there), and there's always new crud to take its place.
The reason why modern CRTs don't do this as dramatically is that the coatings on the outside of the glass now include a somewhat conductive layer, which is earthed and drains the charge.
LCDs don't have any electrostatic charge at all, though. They won't pick up any more crud than would a piece of plain glass sitting in the same place.
On the plus side, the more static-y a CRT is, the more suitable it is to be used as a charge source to power electrostatic gizmos!
Hi Dan, I'm trying to convince a friend of mine not to be taken in by these shysters. Think you can help out?
This is what professionals refer to as a lie.
Which is just as well, because otherwise either no car would come within 1000% of passing modern exhaust emissions tests, or everybody's catalytic converter would be white-hot all the time. Unburned fuel has to go somewhere; either you combust it in the converter or you spray it out of your exhaust pipe and into the air.
Cre8tec then go on to claim, among other things, that putting their... I don't know, is it meant to be a voltage regulator or something? Where does it get the power from?... across your battery terminals will cause your small-engined car to no longer lose power when you turn the air conditioning on.
Practically all car air conditioners are driven directly by the engine, via a belt. If the magic Cre8tec device can compensate for the loss of drive power from increasing the load on the engine that way, it can presumably also compensate from the loss of drive power caused by... anything else. It's all just load on the engine, after all, whether you're running an air conditioner, climbing a hill or pushing against wind resistance on the highway.
So, logically, their device enables your car to travel at the speed of light.
I'm surprised they don't mention that. It sounds like a pretty big selling point to me.
Here comes the feedback
I assume you've seen this, but just in case...
Yeah, they're just a fountain of fun, aren't they?
(Machina Dynamica are also the guys who sell the magic chip that you put on top of things to make them sound better. Until the chip wears out and you have to buy a new one, of course.)
Note that you can also get audiophile outlets to put under the covers!
That's less insane, of course, but only as much less insane as it is to believe the CIA put tiny radios in your teeth, compared with the belief that it was Emperor Palpatine that did it.
Another correspondent also pointed this out to me, in which it is discovered that old PlayStations are, allegedly, superb incredible audiophile CD players.
You'd think anybody would be able to just look at the 6moons site and see that those guys are completely out of their trees... but no, people who write for real sites happily quote 6moons as if they're a real source of information.
(Needless to say, 6moons think Machina Dynamica's mystic rocks are great.)
It really is like a religion, where everybody says "oh, yes, the Illuminated Master really is able to levitate and walk through walls" and gets very offended when someone asks whether he's ever actually been proven to do it.
When crazy audiophiles promote cheap gear, though, it's hard to complain. There's no harm in it. I've now got one of the little Sonic Impact amplifiers that 6moons like so much, and I'm perfectly happy with it. It's a little amp. It works. Is it amazing and incredible and life-changing? Of course not. But it's not as if it's some $30,000 object I had to import from France, either.
I have a question about ground loop hum for you. After moving into my new apartment, my stereo started emitting an annoying hum as soon as I connected my Media Center computer up to it. After some research (including your page), I found out about ground loop isolators and bought one. Problem solved, or so I thought. My difficulty is that after buying two different audio isolators (one for the computer itself, one for the MP3 player hooked up to both the computer and the stereo), I find that I still get the annoying hum when I hook up the secondary video output from my computer to my stereo (and then to my TV). Worse, I now get image distortion on the TV.
A Jensen video isolator (necessary because of the differences in the video signal vs the audio signal, meaning that the audio isolators I tried won't work with a video signal) will cost me about $100 Canadian (a shock, as the audio isolators were less than 10$ each on eBay), but I'm wondering if perhaps I should be looking more closely at the computer itself. This is a problem I have not had before, in about 8 years of using my computer to listen to music and play movies on the TV.
In your opinion, do you think there might be something seriously wrong with the PSU from my computer (which I can replace)? If so, can you recommend a PSU that will eliminate ground loop hum? Or is the problem somewhere in the wiring for my new apartment (and therefore out of my control entirely)?
Earth loops are only a problem because the "earth" potential at different points in the various circuits in your house is not the same. This is mainly because of coupling - inductive and/or capacitive - between energised wires and earth wires, which puts a small AC potential on all of the earth conductors which differs depending on which active conductors each earth wire runs next to, and for how far.
When the earth potentials of two components are different, and you connect their earth planes together through a second conductor - like, classically, a shielded audio cable - you complete a circuit, and current flows through it. This current can, in turn, induce current in the very low level signal conductors of the cable. You'd never notice it if it happened to a high level signal, like a speaker cable, not that speaker cables have an earth wire anyway. The induced current in low-level signal conductors, though, produces hum or video interference, or various other problems.
The Jaycar primer also discusses the really diabolical low level loops you can get with only signal cables involved, but those need not concern us now (thank goodness).
Your video cable is just another shielded connector, so when you plug it in between your computer and receiver, you create yet another bloody loop.
There are three ways to defeat earth loops. Well, three safe ways, anyway.
The first, and often the easiest, is to get the offending components' earths closer together. If they're plugged into separate outlets, plug them into the same outlet instead, with the help of a powerboard. When their plugs are separated by less house wiring, there's less opportunity for them to develop different earth potentials.
This, of course, isn't practical when you've got lots of interconnected equipment - even if you can hang a whole big home theatre system off one wall plate without blowing a fuse, you still shouldn't. But if you've only got two components that're still causing a problem and everything else is already isolated, then just shuffling power plugs and powerboards certainly can solve the problem.
Another solution is to physically break the loop, which is what the various isolators do.
One form of breaking the loop is an unsafe solution to the problem - if you just cut the earth conductors on the power cord of all but one participant in each loop, the problem is solved. But those un-earthed components may then, one day, try to kill you.
If you remove the earth conductors from all but one of the devices and then connect all of their chassis together you have the fairly safe version of this solution, but it's only practical in situations like professional recording studios. Apart from the inconvenience of doing this with home gear, it's bad practice to have devices that depend on another device for their safety earth sitting around your house.
Less alarmingly, you can often break an earth loop by cutting the shielding of the offending signal cables. They'll still be well enough shielded if they're only earthed at one end, or even if one half of them is connected to one component's earth and the other half is connected to the other. In domestic situations the amount of current flowing through an earth loop should be quite small, so this option is perfectly safe - it's quite possible for earth potential differences in home equipment to be large enough to give you an exciting little tingle, but it's only in situations where people decide to run earthed data cables between different buildings that there's likely to be enough potential difference between earths for things like electrocution or fire hazards to develop.
To separate earths when you're dealing with simple coaxial cables, you just take to the cable with a sharp knife (usual disclaimers apply) and "ringbark" it. Remove a "bracelet", a few millimetres long, of the insulation and the shielding foil or braid under it, wrap the area with ye olde electrical tape to protect the conductor underneath, and you're done.
The problem with doing this with a computer "VGA" lead is that it has its own earth wires, which are all tied to the earth of the device they plug into, if not tied to the shield-earth inside the plug as well. There are five ground wires in the standard VGA pinout; if you ringbark the shield and leave those wires in the cable then the loop will still exist. If you cut the earth wires in the cable as well, then the receiving device won't have the same earth reference as the sending one, so I suppose it might get the signal levels wrong. But this doesn't seem to happen when people just ringbark separate coaxial video leads, or when they use one of those expensive VGA balun doodads that you're trying not to buy (the primary purpose of those things is to allow you to run video a long way on cheap network-type cables, but they provide ground loop isolation as well). So I'm guessing that it's not actually a problem.
Cutting the wires isn't actually that hard if you can take apart the plug at either end of the cable. If it's one moulded lump, you might like to just bust the relevant pins off the connector at one end. A reversible version of this is painting nail polish or something on those pins, though you could still end up with capacitive coupling that way.
I get a lot of article-announcement e-mails from various sites. Today, I got this one:
BlueTomorrow.com has posted a new article. A news post on your website would be most appreciated. If you have news, please send it to email@example.com and we'll be happy to post it (assuming your site has news regarding Bluetooth technology).
Title: Motorola Bluetooth - No Wires, No Limits
Quote: "As consumers look for new and convenient ways to stay in touch via mobile phone, headset, laptop or car, Motorola's Bluetooth easily offers communication options through a diverse collection of Bluetooth enabled products. By consistently anticipating and fulfilling the needs of on-the-go users, Motorola has become the leader in the Bluetooth industry, all while continuing to modernize communication in both business and entertainment."
Direct link: http://www.bluetomorrow.com/content/section/340/461
I replied to Scott as follows:
So that's what passes for an "article" on your site, is it? I'd call it a big slobbery suck-job, myself, but I suppose opinions differ.
Remove me from your mailing list, immediately.
One would think that this would cause Scott to retire, appropriately chastened, as normally happens when someone absent-mindedly promotes a piece of paid advertising material - and not very well-written paid advertising material, either - as an actual article.
And perhaps he did.
But someone called Peter Manzella (firstname.lastname@example.org, but I am no longer calling upon the Horde to make a nuisance of themselves upon him), also on the editorial staff of BlueTomorrow, had this to say:
We will gladly remove you from our mailing list. In fact, that is all you had to say. Your comments were unnecessary and quite frankly inexcusable when you consider the website your operating. Your site is simply one big advertisement; you don't offer any ounce of valuable content to read. So, before you start criticizing others, maybe you should stop and really take a look at how to improve your site.
Frankly, I think I was a bit mild about the strap-on-the-kneepads quality of that article, every single word of which is a blissful paean to the unlimited gosh-darned excellence of all things Motorola and Bluetooth.
I'm sure my faithful readers can come up with a better review of the article, while we all wait for Peter to substantiate his claims about this site.
I mean, not to blow my own trumpet or anything, but there are almost a thousand pages on Dan's Data now. He's read them all, and not found any content? Anywhere?
Well, darn - I thought I was doing so well, these last eight years!
Anyway, I'm sure Peter will be very glad to
hear from you all. (He's mellowed out now, so I'll
stop inviting you all to wee in his inbox.)
CC: me, if you think you've come up with something especially witty.
Or if Peter loses what remains of his mind in an entertaining way.
Pete's replied to me again, now. His attitude may be summed up as "Bring it on!"
But wait - ANOTHER reply, only an hour after the last one!
Big brave Peter has now changed his mind, and is threatening to sue me for defamation, for printing what he sent me and invited me to print, and my honest opinion about it.
Unfortunately for Peter (and most of the other people who've threatened to sue me over the years), he's in the United States of America, where I believe there's still a reasonable amount of enthusiasm about freedom of speech.
He could still sue me there, and probably even get a default judgement since I'm not crazy about heading to the USA, but that wouldn't affect me much.
I suppose he could menace my most excellent and reliable hosting company, SecureWebs, who are in the USA. But every time someone tries something like that, the page they're trying to suppress does indeed disappear, but the content spreads all over the Web, as outraged Netizens voice their feelings on the subject.
Oh, and my blog is hosted in Ireland.
So I kind of hope he tries it. It'll be hilarious.
Interestingly, Peter's now revealed himself to be in some way associated with an actual law firm. He says that's where he's getting his legal advice, and he e-mailed me from an address there. He didn't seem to be on their list of "attorneys and other professionals", though, so I'm not sure what his connection with the firm was. He didn't sound very lawyerly in his previous correspondence, but not all lawyers do.
I, meanwhile, am joyously bereft of scary legal connections, and am located in New South Wales, Australia. Where our defamation law was recently changed to, quite sensibly, permit truth by itself as a defence in most defamation actions. Not that Peter's likely to bother flying to Australia to file a suit against me, anyway.
Peter's now clarified his legal threat as not having actually been one at all, and apologised nicely.
So stop sending him goatse.cx pics, you dorks.