Computers, bikes and things I’d like to remember.

Ur Thowa

March 29th, 2008 Posted in General

There’s the TV advertising, there’s the print media, there are quite a few blogs, and there was even an email to all staff at work about it. Earth Hour 2008 is happening today.

I’m sure there is a rich and nuanced debate to be had around the usefulness or otherwise of switching stuff off for an hour, but that’s not what’s on my mind.

Y’see, I have more experience than I care to remember in the area of fixing electronic stuff that’s gone ‘boom.’ Years and years sitting at a workbench with a ’scope, various meters and a hot soldering iron, chasing down elusive failures in all things electronic. In among the many wondrous ways in which stuff can stop working, one particular sort of failure comes to mind.

Most modern pieces of electronics make use of a switchmode power supply. Everything from TVs and DVD players, to computers and kitchen appliances are likely to have one, and in general they are a wonderful thing. Small, light, cheap and able to run from the mains power in most parts of the world without caring whether they’re plugged into 110, 115, 150, 230 or 240 volts. They (mostly) just work.

In some circumstances though, they can be problematic. If you have something like a VCR, a DVD player or a TV that is plugged into a power outlet and only ever switched on or off via a remote control, then there is always a small part of the switchmode power supply ticking over, even when the device is switched ‘off.’ It needs to do this so that there’s a trickle of power available for the remote receiver to keep going, waiting for you to press the ‘on’ button on the remote control.

If you have this device plugged into power all the time, a small part of its switchmode power supply - the part responsible for kickstarting it from completely off - never gets used. And this part almost always contains a handful of tiny electrolytic capacitors that play no part in the running of the device until it’s disconnected from the power outlet, and then connected again. Then it’s their job to get the power supply started. These little beasties don’t like heat very much, but they usually live in a hot place (the switchmode power supply) and so as the months and years go by, the heat slowly kills them. They can die completely and you’ll never know. Unless you unplug the device or switch off the power outlet.

So I’m wondering what will happen if thousands or millions of people switch off everything at the power outlet all at once. I think that there’s an excellent chance that quite a lot of stuff won’t come back to life when the power goes back on. Sure, it won’t happen to everyone and in fact it will probably only happen to a very few. Still, I reckon that on Monday of next week, the electronics repairers of at least this nation will have cause to be grateful to the Earth Hour organisers. Or is it the retailers who’ll be delighted? Do people get stuff fixed any more?

My other thought on the subject is this. The electricity suppliers have their systems set up to expect a certain minimum load that never goes away. While I’m sure that their systems are designed to cope safely with the sudden loss of load when everyone switches off, I can’t help but wonder just when they tested this.

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