Dan's Data letters #174
Publication date: November 2006.Last modified 03-Dec-2011.
Hot under the cooler
In relation to your CPU cooler tests, you use a wire wound resistor to produce heat. Do you have more instructions or extra tips on building your hot-CPU emulation device, or is it WYSIWYG per the web page? My main question is this: What voltage and current do you apply to the resistor to emulate a normal "hot" CPU? Are we talking mains (240VAC here in Sydney), big DC voltage, or what?
Ben
Answer:
It's not really rocket science to build a CPU simulator. Getting the fake socket right is much trickier than the
electronic part.
Just cut a channel in the flat face of your standard aluminium-encapsulated wirewound resistor, stick a thermal probe in there with the thermally-tolerant glue of your choice (metal-filled epoxy is good - "Devcon" is the most common brand, but any aluminium-filled epoxy will do, and be about 400 times as strong as you need for this application), and then stick the resistor onto the CPU-shaped plate.
You can stick the resistor on with more of the glue (a thin layer, by preference). I did it a bit more elegantly by drilling and tapping mounting holes in the plate and screw-mounting the resistor, with ordinary thermal compound between it and the plate.
You can get a lot fancier than this, with custom-made inserts to represent different CPUs (I just used different-sized copper rectangles that I sat on top of the plate with thermal grease on either side), cut-outs to get the heat source more realistically close to the heat sink, and so on.
If all you need is something that'll give you a good idea of the relative performance of different coolers, though, a gimcrack solution like mine will do. If you expect to be testing hundreds of different coolers, though, a bit more effort in the first place could be a good investment.
The voltage and current you need to apply depend on the resistor value. This is a simple DC circuit, so V=IR applies.
If you've got a one-ohm resistor and want to be able to wind it up to 75 watts, then R=1 and VI=75 (voltage times current equals power), thus V=75/I, and so, from V=IR, 75/I=I*1, so 75=I^2, and I and V must both be 8.66 (amps and volts, respectively).
You don't even have to do this much algebra if you've got your power supply and resistor options in front of you already. You can just quickly figure what you'll get from each combination.
If, say, you elect to use a cheap high-current 12-volt power supply (like a PC PSU), and so you've got 12V and plenty of amps to play with, then if you decide to use a 2.2-ohm resistor V=IR works out as 12=I*2.2, thus I=12/2.2, or 5.45 amps, and 12 volts times that is 65.45 watts.
If you want an off-the-shelf power supply, 13.8V high-current units made to run CB radio gear and such outside vehicles are quite cheap. But you could use an old rusty car battery charger, as long as it's got a decently constant output voltage.
A voltmeter across your resistor will tell you what voltage it's actually seeing, so you can compensate for any drift in your power supply and for loss in the cables (measure the resistor's exact value first, or you won't have accurate values for all of the variables; big low-value power resistors may or may not have a resistance very close to the figure printed on them). Between them, PSU drift and cable loss can add up to a significant power difference for this sort of low-resistance, high-current application, and with cheap PSUs there can be a bit of output drift from minute to minute. Though, thankfully, probably not nearly enough for the drift to outweigh the noise in the rest of the system.
All of this requires you to find low value high wattage wirewounds, which are fairly rare beasts. Most big resistors have values that're too high for simple DC heater applications, and the low-value ones can be hard to find here in Australia.
Fortunately, this place has 'em.
Note that you don't need a resistor that's rated for anything like the power you'll be using it at here, since you will by definition be hanging great big coolers off the thing all the time. The power rating is all about heat; you can vastly exceed the rating if you keep the resistor cool. Just don't decide to see how hot your "10W" resistor will actually get if you run it at 100W without a cooler. You might not actually let the smoke out, in this situation, but you probably will let the sand out.
Fish power
Before going on vacation I was considering installing a UPS for my girlfriend's aquarium systems. But I realized I am not sure it is feasible, because:
* Medium-low-end consumer (500VA or such) UPSes have a runtime of about one hour at 50 watts. The pump and heater only draw about 15W. Still, would such a UPS have enough capacity to run the rig for any useful time?
* There's a pump in there - does its working depend on having a decent sine wave input?
Florian and the Gourami team
Answer:
Whether a given UPS has enough run-time for a given task depends on how long a power cut you're expecting. If the
power goes out for a whole day then you could indeed be in trouble if your UPS could only run the aquarium gear for
a couple of hours, but that doesn't happen often in most places. And, of course, it's not like we're talking about
a heart-lung machine, here; fish don't drop dead instantly if you turn off their bubbler/heater/whatever.
(If you've got a tank heater, by the way, it's likely to draw quite a lot more power than a pump. Buy yourself a power meter to get some idea of how much energy you're actually using.)
UPSes have a fixed power overhead, so you can't expect one that'll run a hundred-watt load for one hour to run a one-watt load for a hundred hours. But an ordinary cheap-ish consumer UPS certainly would run aquarium gear for a decent length of time - I think basic UPSes are actually quite popular among fish-fanciers.
It's not hard to find UPSes with factory extended battery options, either. Or you can, of course, do the car-batteries-in-the-corner thing, if you're a bit handy.
(Now you're going to tell me that two parts per billion of sulfuric acid vapor in the air will kill every fish for a ten block radius, aren't you.)
Note that if you got a UPS for the fish-tank room, you could also hook it up to anything else there that loses its brain annoyingly when the power goes out. I now live in a town where the power's a bit flaky, so as well as thoroughly power-conditioning all of my computing gear, I've got a small UPS in my bedroom connected to the clock radios, and to a compact-fluorescent-globe lamp, so I can at least read a book in comfort when the power's out.
An aquarium pump will very probably work OK from the modified-square-wave output of a modern cheap UPS, but most AC motors run louder, and hotter, when they don't have sine-wave input.
This may or may not be a problem. If the motor runs warm normally then it might get hot enough to have problems from UPS power, if it has to run from it for a long time. Or it might not. The motor windings very probably won't be water cooled, on account of how fish don't like breathing what dissolves out of electric motors, but there will probably be some minor cooling to the water through the casing of the pump, as well of course as ordinary air cooling.
I'd guess that there wouldn't actually be a problem with running any half-decent aquarium pump from a UPS, but you'd have to test it - with an aquarium containing no creatures you very much want to keep - to be sure.
Usually, for low-power motor applications (i.e. not running a hammer-drill for hours), modern modified-square-wave inverters are fine. They (should) have much better output than the earliest examples of the breed (some of which are still around...), and those in turn were much better than the earliest square-wave inverters, which were the ones that really toasted motors.
Of course, you can get around this problem entirely if you use a shiny true-sine-wave UPS (note: "quasi sine wave" and "modified sine wave" are just fancier ways of saying "modified square wave"), but those do cost a bit more. If you're only looking for one with a modest power rating, though, you may be surprised at how cheap they've become. Only the gold-standard dual-conversion (inverter always running) UPSes are still really expensive, and practically nobody needs one of those.
Apparently, some fish-tank pumps have vapour lock problems, or something, when a UPS switches over to inverter power. I'm not too sure about the accuracy of this, because the switchover time is very short for even basic modern UPSes. If tiny power hiccups like this freak the system out, you'd expect it to be stalling all the time anyway because of normal minor power glitches.
A dual-conversion UPS definitely will deal with all such problems, though. It has no switchover delay, because it doesn't have to switch over.
Teeny tanks
I have to ask about the tiny DigiQ tanks from Konami (I need an office timewaster), because they look like tremendous fun: Are they still available?
I haven't been able to find them; I can find something called Vs. Tank, which looks similar but seems much cheaper, on the internet. The controller in particular looks junky.
Any thoughts on these battling bantams?
Gary
Answer:
Unfortunately, Konami have done the usual Japanese hobby thing and just stopped making DigiQ tanks. There were versions
with rotating turrets available not very long after I wrote my review, but they're all
off the market now and so attract a large price premium when they occasionally show up on eBay.
Hang around a while and Konami will probably re-release their mini tanks. In the meantime, though, you're out of luck.
The VsTank or "Vs Tank" or whatever versions are, as you say, inferior Chinese knock-offs. Often the knock-offs are quite good value, if not as good in absolute quality as the original, but from what I've heard from people who've played with both, the VsTanks aren't worth bothering with if you're not willing to tinker with them a lot.
They're also, in case you were wondering, incompatible with the DigiQ versions. No controller compatibility, no IR-combat compatibility.
There are bigger 1/24th scale VsTanks, though; they might be OK. Note also the similarly large "Commando Challenge" tanks, which are cheap, still available, and pretty decent.
Or, y'know, just get a few Tamiya 1/16th scale tanks with their Battle System installed.
That shouldn't cost you much more than $US700 per tank, if you shop carefully!
Dan's Travel Advice
I'm coming to Australia in a few weeks and, as part of it, I'll of course be seeing Sydney. Are there things that are Best Not Done there?
For example, I know that there are two different wildlife preserves/zoos near/in Sydney. Are they good zoos? That is, do they treat their animals well (unlike others nearer me...)?
Also, it seems (if you believe Michael Moore) that Australia is, on a per capita basis (and in terms of absolute numbers as well) pretty damn safe. That said, are there places in Sydney that I Just Shouldn't Go with my Fancy New Camera? (I finally went digital - got me an EOS 5D!)
Any and all answers you may provide will be very gratefully received.
Patrick
Answer:
As is always the case in places like Sydney, there are some standard tourist things that aren't actually all that
interesting. But there's nothing that's likely to end with a knife in your neck.
Regarding zoos, Taronga Zoo (the one in Sydney proper, and the only big zoo for a long way) used to have the classic grim concrete enclosures with some poor large animal stuck in there - the old Elephant House was a ghastly prison with Indian decorations. But they've been much better for, oh, 10 or 20 years now. There's only so much you can do with an enclosure for elephants if your zoo isn't the size of a large farm, of course, but Taronga is still a good place to visit, and you can pack another tourist staple in and get a ferry to Taronga from Circular Quay.
(Note that just catching a ferry to Manly from Circular Quay and sitting on the thing until it comes back again is a very cheap way to get a picturesque day or night tour of the Sydney waterfront. It's been a while since I did it, but I'm pretty sure the payment gates only operate for people who get off or on at Manly, so this trip is actually free if you're only sightseeing. I'd still buy a ticket if I were you, though.)
On the other hand, Taronga's for Australians as much as it is for tourists, so a lot of the animals there aren't Australian. If you're interested in getting close to Australian animals - wallabies eating out of your hand, kookaburras and native owls sitting on a twig right next to your head, and also koalas and wombats within poking distance (neither of those is actually a very "pattable" creature, but all they're likely to do is look grumpy and stomp away if you try to molest them), I can highly recommend Featherdale Wildlife Park (Pictures! More pictures!). It's out in western Sydney, but only about a half-hour drive from the middle of town. That's down a toll road, but not a very expensive one, and it's not one of the few Sydney tollways that requires you to have an electronic tag on your windscreen or else do some complicated thing involving phone calls.
There are emus at Featherdale. They come close. Feel free to try to pat one if you're courageous.
(For a real emu experience, Western Plains Zoo [same Web site as Taronga] way out in Dubbo probably still has 'em wandering around loose and stealing people's sandwiches. Unless you've decided to drive to Lightning Ridge or something, though, or have a burning urge to get yourself some of those vast-expanse-of-not-much views for which Australia is well known, I contend that the Zoo is not enough reason to go to Dubbo.)
Featherdale also has non-Aussie wildlife, including peacocks wandering all over the place (presumably because they're good crowd-pullers - there are a few albinos, to match the collection of albino native beasties), and various random creatures in a petting-zoo area whose main purpose appears to be to escape and cause small ornamental chickens to be found all over the Park. But it's well worth the trip and admission price, and will give your camera a workout.
Other touristy stuff that I have actually done and which is worth doing:
* Going up Sydney Tower (often referred to as "Centrepoint Tower", with or without American spelling, though corporate sponsors have changed its name twice since then). Go to the (revolving!) buffet restaurant for lunch. Queues for the plain observation deck can be horrifying, and the a la carte restaurant is stunningly expensive.
Problems with this: Restaurant has hilarious 70s-time-warp decor (perhaps they can't get a redecoration crew up there in the small and unreliable high-speed lifts...), and frankly bad food, and it's still not cheap. If this experience was in a ground-level restaurant and cost the same, you'd be threatening someone with bodily harm to get your money back. Sydney and Melbourne residents tend to have very high value expectations from restaurants, because that's usually what we get, but this deal is just ridiculous in anyone's language.
Reason why you should do it anyway: The view is exactly as spectacular as the ads promise.
Obviously, you will feel robbed if you do this on a day when there's low cloud.
* Taking a day (at least) to wander around the Royal Botanic Gardens, around the Opera House (don't eat there unless you have to - the food's OK, but the price premiums are large), and maybe over the Harbour Bridge as well. All of this is free (doing one of the over-the-top "Bridge Walks" is not, but there's an ordinary footpath at road level that is. Enjoy the fun of finding the stairs to get onto it!).
If this view had a portrait aspect ratio, you'd see all of the Gardens as well as the Opera House and the Bridge. Circular Quay is the distinctly non-circular wharf area between the House and Bridge - actually, Google Maps now has good road maps for Sydney that point stuff like this out, which is nice.
Once you've gone north over the bridge, by the way, you can either go to Luna Park and do some pretty generic amusement-park things, or you can just walk back. There's nothing else exciting in North Sydney (IMNSHO), except the usual selection of good restaurants.
* If you've got the time, the good beaches are not the city beaches. The city beaches are somewhat dirty and quite crowded (especially Bondi, of course). There are lots more beaches north and south of the city. I wrote this a while ago, and it still applies. Except now I live in Katoomba too - I suppose I should update it.
(Woo! Good maps all the way down there, too!)
If you just want to eat fish and chips while sitting on a genuine Australian beach, of course, the city ones will do fine. Try the cleaner and less crowded Coogee or Maroubra (at least some of which Google currently think is called "Marboubra"; fair enough, since Australia is the Land Of Ridiculous Place Names That Aboriginal Tribes Probably Just Made Up To Make The White Men Look Silly).
As far as Dangerous Parts Of Sydney go, there really aren't any. There certainly are a few sketchy neighbourhoods, notably Redfern if we're talking inner-city, but anywhere you'd actually be likely to want to go is likely to be safe enough. (Redfern is a scathing indictment of our handling of the problems of indigenous Australians, et cetera, but that also means it's what Australians commonly call "a hole", and not at all interesting. A small part of it is the actual below-the-poverty-line stuff, and the rest is boring gentrified terrace houses.)
Sydney doesn't turn into a lawless cesspit after dark. Most of it just dies. You could shoot a cannon down any street adjacent to Centrepoint at 2AM on a weekday and hit nobody. That also means, however, that you can wander through the well-lit Hyde Park at midnight and see lots of possums scurrying around, which is neat.
(The rustlings in the underbrush that sound like rats are, by the way, rats.)
There are distinct areas of nightlife, though. If you tried the cannon trick on Oxford Street at the same time you'd kill plenty of people. Different Australians have varying opinions about how many of those people would have deserved it.
Actually, speaking of Gay Sydney, that's another thing worth doing - start at the city end of Oxford Street and walk until you run out of interesting stuff, or have eaten at least three meals. Oxford Street down to the area around Taylor Square is fairly described as "Sydney's main gay district", but that just means "you see a lot of men holding hands there". Anybody's welcome anywhere, unless they've got an urge to take a bullhorn into a nightclub and start preaching.
[Patrick's had his Australian trip, now:
"I just want to say thanks for your extensive advice about stuff to do/not
do in Sydney; I had a great time there, at least partly because of the advice you gave. You're right, by the way,
about Sydney Tower: The food and the decor are both laughable (don't you just love the low-pile red carpeting?), but
the view (just after sunset, when I went) was spectacular."]
And finally, on a heartwarming note
Not Everclear, but pretty close is Polish Pure Spirit by Polmos, the company that also brought us "Wodka".
80% alcohol, available from some bottle shops.
James
Answer:
Yeah, I know about that one. It's what's often quoted as the strongest hooch there is, if you don't count repackaged
medical alcohol like Everclear.
(I love the Shrine to Spirits, too. I never would have been turned on to McLintocks Vanilla Fridge Wipe if it hadn't been for them.)
I hadn't looked for PPS in Australia for a while, though, and just noticed this dealer, who's selling it for $AU56.99 for 500ml. 40%-alcohol vodka of moderate quality can actually cost a bit more than that, per unit of alcohol; 700ml of Stoli, for instance, is $AU35.99 from the same dealer. You can save if you shop somewhere cheaper, of course, but it's still interesting to see Pure Spirit (which is not actually what you'd call a "premium" vodka, I think) without a monster price premium.
That dealer's got quite affordable shipping, too, especially if you buy enough bottles to fill a fixed-price carton.
I don't think I'll be buying a whole carton of PPS, though.
