Power struggle

Originally published 2004 in Atomic: Maximum Power Computing
Last modified 03-Dec-2011.

 

Let's talk about the endlessly fascinating, entertaining and, let's admit it, somewhat arousing topic of power filtering.

Most computer users are vaguely aware that it's a good thing to filter the AC going into your precious multi-gigahertz baby. Surges and spikes can blow it up, slumps and blackouts can shut it down.

Here in Australia, we generally have pretty good AC power. Hook up a fancy RMS voltage and phase meter to the AC supply and you'll see it wandering all over the place from the 230-volt sine wave it's meant to be, but that's cool; things that plug into the mains are made to cope with some degree of input lousiness. PC Power Supply Units are, generally, more tolerant of weird input than most appliances.

But when the guy next door starts playing with his new million-amp welder, or your elderly fridge and freezer both click their squeaky old compressors on at the same time, or lightning strikes a suburb away, it's quite possible for big nasty spikes to appear on the mains. Those can toast PSUs, and possibly other equipment as well. Nearby lightning strikes are particularly nasty, since they can put large currents on phone and cable TV wires, frying computer gear that way.

So you buy a surge/spike protector powerboard and you're fine, right? After all, there are quite a few brands of powerboard that now come with an impressive "Connected Equipment Warranty", offering thousands or even tens of thousands of dollars of insurance if something plugged in through the powerboard gets toasted. How can you lose?

Well, you can lose technically, and you can lose legally.

The technical side is simple enough. No ordinary cheap powerboard ("cheap" definitely includes "a hundred US bucks") actually provides very good protection from line current gremlins. It may protect you once from a big-ish spike, or several times from smaller ones, but it won't last forever.

Cheap surge filters are all based around components called Metal-Oxide Varistors (MOVs). MOVs pass current only when the voltage across them is above a set value, and they react to overcurrent in microseconds. A circuit breaker or fuse can take tens of milliseconds to trip or blow; that's much too slow for spike suppression.

Unfortunately, MOVs will only work a few times, at best. The more work they have to do, the closer to death they come. A surge/spike powerboard with a toasted MOV is now... just a powerboard.

Better surge/spike boards are meant to tell you when their MOV's died via a little light or even a buzzer, but they commonly, actually, don't. A surge/spike filter that's been in use for some years and still reports its MOV as perfectly healthy is, probably, lying.

Better surge suppressors use two other kinds of spike-sinking component. Gas arrestor tubes (also known as gas discharge tubes, or GDTs) are much tougher than MOVs, but respond too slowly to be useful for many applications, including computer protection. But you'll still find them in the better power filters, because they can handle the load of a really big surge, after some other component has (possibly) bravely given its life to intercept the first several microseconds of overvoltage.

And then there are Silicon Avalanche Diodes (SADs), which are between gas tubes and MOVs in toughness, but as fast as a MOV. They're more expensive, though, which is why cheap surge/spike filters never contain them.

The best surge/spike suppressors gas arrestor tubes and SADs, and possibly MOVs as well. Proper "power conditioners" go on to include a great big heavy iron transformer, whose 50Hz resonance (60Hz, in countries that use that mains frequency) and enormous inductance blocks surges and spikes quite well all by itself. This makes the power filter large and heavy and easily as expensive as a mid-range Uninterruptible Power Supply (UPS), but if there's an aluminium smelter down the road from you, this is the kind of filter you want.

In case you're wondering what one of these "ferroresonant" power conditioners looks like - it looks like this.

Heavy object

I picked up this elderly Sola unit cheap on eBay. The price including delivery (by a postman who asked me what the heck this hernia-inducing box contained) was slightly more than a tenth of what newer versions of the same thing commonly cost, even second-hand.

It's got an Institutional Greenish-Beige paint job and a magnificently retro label...

Sticker

...which suggests that this thing may have fed a VAX or something at some point. But, essentially, this relic is very much the same as a modern ferroresonant conditioner.

If you think that probably means that not a lot of innovation has happened in the area of ferroresonant power conditioner design in the last 30 years, you're right. Inside, there's the gigantic transformer (which accounts for most of the thing's roughly 28-kilogram weight - I think the seller knew a guy who slipped this overweight parcel into the postal system...), a bit of wiring, and a couple of hefty capacitors.

That warning label isn't kidding, but the drain resistors across the caps are still working perfectly, so moments after the conditioner's turned off, there's no charge left in the caps.

Eagle-eyed readers will also be able to see, in the full sized version of the above image, that these are "soggy foil" capacitors. Against all reason, that's a real kind of capacitor, and these ones still seem to be OK. The whole conditioner, in fact, still works fine, as far as I can tell; in that first picture of it, it's running a thousand watts of photo lights.

It's possible that this conditioner doesn't have the greatest possible output waveform - old ferroresonant regulators deviated a pretty long way from a sine wave - and I haven't hooked a 'scope up to it to see. But when I plugged a desk fan into the conditioner, the fan motor only hummed slightly louder than it did from ordinary wall power, which is a good sign. And many non-motor devices don't care about power waveform, anyway. Switchmode PSUs like those used by all PCs certainly don't.

You don't necessarily want to have an old-model power conditioner sitting next to your desk, though, for two reasons. One, they themselves hum quite loudly. The strong oscillating electric fields that make a transformer work also make it vibrate, and you can hear the timbre of the sound (and, in this case, probably also the output waveform...) change as the load on the transformer changes. Modern power conditioners have UPS-style warning beepers to tell you if you're overloading them. Old ones like this expect you to keep track of the load yourself. Or, failing that, just know what an overload sounds like.

(The Sola conditioner just cuts out when it's overloaded.)

Ferroresonant conditioners also make a distinctive sound when fired at you turned on, as the simple tank circuit "fills up" with energy. Here that noise is. It's vaguely reminiscent of an engine starting, or twanging a ruler on the edge of a desk. It's not the sort of sound you expect a solid-state device to make.

The other reason why you might not want an old heavyweight conditioner like this is that it's rather inefficient. The Sola draws about 140 watts all by itself, whenever it's powered up. This makes it run rather warm, too.

Fortunately, it's now possible to buy lightweight power conditioners that can run just as much gear as the old monsters. I think they usually don't have the same protection capability as ferroresonant conditioners, but they also only waste a single-digit number of watts by themselves, at most. Some of them are basically just the filtering components from a decent UPS turned into a standalone product; see APC's Line-R products, for instance, or the ones I talk about here.

Anyway, if your local power is crummy enough, or your equipment is valuable enough, that you can justify buying a power conditioner, then rather than faff around buying tons of flaky powerboard filters for all of your electrical outlets, you can get an electrician to install one giant power conditioner at your fusebox. It won't be cheap, but now the whole house should be bulletproof.

You can even get whole-house UPSes, but that's almost certainly overkill. UPSes with moderate filtering capacity just for your computer equipment will do for most users.

That's it for the technical problem with cheap surge/spike filters.

The legal problem has to do with those increasingly popular Connected Equipment Warranties (CEWs).

You can read a sample Belkin Connected Equipment Warranty in PDF format here, or a Panamax one (also PDF) here. I'm afraid they go on a bit, so you might like to skip actually reading them.

I took the time to plough through them, though. So I know that first up, you'd better still have the receipt for your surge protector. The Connected Equipment Warranty probably only covers the original purchaser.

And if you can find a cheap power filter whose CEW covers new-for-old replacement of damaged equipment, I'd like to see it. Normally, they give you blue-book used value for your gear. Blue-book value for a tweaky overclocked "enthusiast" PC with a fast graphics card may be the same as for a bargain-basement Dell with similar basic specs. CEWs also often leave the guarantor the option of having the equipment repaired, rather than replaced. And of making you pay to have your exploded computer shipped to whatever repairer they choose.

If the guarantors really want to weasel out of the deal - which they won't necessarily, but we're talking about the insurance industry now, so anything's possible - they can insist on proof that every wire going into the toasted equipment was protected with their gear. Were you using an extension cord? Were you overloading the surge protector (did you plug your laser printer into it?). Hey, maybe the spike was just bigger than the filter was meant to deal with!

Did the filter protect you from a spike last week, burn out, and so not protect you from a spike this week? If so, then no payout.

Bit of a Catch 22 there, really. If the filter's not burned out then they can say you didn't have it plugged in at all, and if it is then they can say that it was dead already, and you should have stuck your head behind your desk every day to see whether the little orange light had gone out.

The take-home message from all of this is that quality power filtering isn't cheap. Fortunately, though, most people here in Australia don't need quality power filtering.

To Aussies, I therefore say: Go ahead and buy dirt cheap no-CEW filter-boards, and be merry.

Other columns

Learning to love depreciation

Overclockers: Get in early!

Stuff I Hate

Why Macs annoy me

USB: It's worth what you pay

"Great product! Doesn't work!"

The virus I want to see

Lies, damned lies and marketing

Unconventional wisdom

How not to e-mail me

Dan's Quick Guide to Memory Effect, You Idiots

Your computer is not alive

What's the point of robot pets?

Learning from spam

Why it doesn't matter whether censorware works

The price of power

The CPU Cooler Snap Judgement Guide

Avoiding electrocution

Video memory mysteries

New ways to be wrong

Clearing the VR hurdles

Not So Super

Do you have a license for that Athlon?

Cool bananas

Getting rid of the disks

LCDs, CRTs, and geese

Filling up the laptop

IMAX computing

Digital couch potatoes, arise!

Invisible miracles

Those darn wires

Wossit cost, then?

PFC decoded

Cheap high-res TV: Forget it.

V-Pr0n

Dan Squints At The Future, Again

The programmable matter revolution

Sounding better

Reality Plus™!

I want my Tidy-Bot!

Less go, more show

In search of stupidity

It's SnitchCam time!

Power struggle

Speakers versus headphones

Getting paid to play

Hurdles on the upgrade path

Hatin' on lithium ion

Wanted: Cheap giant bit barrel

The screen you'll be using tomorrow

Cool gadget. Ten bucks.

Open Sesame!

Absolutely accurate predictions

The truth about everything

Burr walnut computing

Nothing new behind the lens

Do it yourself. Almost.

The quest for physicality

Tool time

Pretty PCs - the quest continues

The USB drive time bomb

Closer to quietness

Stuff You Should Want

The modular car

Dumb smart houses

Enough already with the megapixels

Inching toward the NAS of our dreams

Older than dirt

The Synthetics are coming

Pr0nBack!

Game Over is nigh

The Embarrassingly Easy Case Mod

Dumb then, smart now

Fuel cells - are we there yet?

A PC full of magnets

Knowledge is weakness

One Laptop Per Me

The Land of Wind, Ghosts and Minimised Windows

Things that change, things that don't

Water power

Great interface disasters

Doughnut-shaped universes

Grease and hard drive change

Save me!

Impossible antenna, only $50!

I'm ready for my upgrade

The Great Apathetic Revolution

Protect the Wi-Fi wilderness!

Wi-Fi pirate radio

The benign botnet

Meet the new DRM, same as the old DRM

Your laptop is lying to you

Welcome to super-surveillance

Lemon-fresh power supplies

A>B>C>A!

Internet washing machines, and magic rip-off boxes

GPGPU and the Law of New Features

Are you going to believe me, or your lying eyes?

We're all prisoners of game theory

I think I'm turning cyborg-ese, I really think so

Half an ounce of electrons

Next stop, clay tablets

A bold new computer metaphor

Won't someone PLEASE think of the hard drives?!

Alternate history

From aerial torpedoes to RoboCars

How fast is a hard drive? How long is a piece of string?

"In tonight's episode of Fallout 4..."

How hot is too hot?

Nerd Skill Number One

What'll be free next?

Out: Hot rods. In: Robots.

500 gig per second, if we don't get a flat

No spaceship? No sale.

The shifting goalposts of AI

Steal This Education

Next stop: Hardware piracy

A hundred years of EULAs

The triumph of niceness

The daily grind

Speed kings

Alt-tCRASH

Game crazy

Five trillion bits flying in loose formation

Cannibalise the corpses!

One-note NPCs

Big Brother is watching you play

Have you wasted enough time today?

The newt hits! You die...

Stuck in the foothills

A modest censorship proposal

In Praise of the Fisheye

Filenames.WTF

The death of the manual

Of magic lanterns, and MMORPGs

When you have eliminated the impossible...

Welcome to dream-land

Welcome to my museum

Stomp, don't sprint!

Grinding myself down

Pathfinding to everywhere

A deadly mouse trap

If it looks random, it probably isn't

Identical voices and phantom swords

Boing!

Socialised entertainment

Warfare. Aliens. Car crashes. ENTERTAINMENT!

On the h4xx0ring of p4sswordZ

Seeing past the normal

Science versus SoftRAM

Righteous bits

Random... ish... numbers

I get letters

Money for nothing

Of course you'd download a car. Or a gun!

A comforting lie



Give Dan some money!
(and no-one gets hurt)