All posts in category Technical

Using MOSFETs as blocking diodes

Connecting a battery backwards to an electronic circuit can rapidly do a lot of damage — current will flood through (and destroy) many integrated circuits when powered up the wrong way, and electrolytic capacitors have a famous tendency to explode. For this reason, it’s common to use a blocking diode in a circuit to provide […]

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Deriving magnetism from electrostatics and relativity

Imagine a world where there was no magnetism at all — just electrostatic forces. It turns out that by adding Einstein’s laws of special relativity to that world, and looking at the effects that special relativity has on moving charges, the laws of magnetism appear — just by mashing electrostatics and relativity together. In other […]

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Where’s the North Pole on Google Maps?

I’ve seen several posts on the internet asking about the North Pole on Google Maps: where is it? Why isn’t there any snow there? Where’s Santa’s house? There’s a couple of reasons why the ice around the North Pole is not shown on Google Maps.

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The Galaxy Nexus PenTile display: a reasoned take on the debate

There has been a lot of discussion on the ‘net about the infamous PenTile display. Lots of sites are throwing numbers around, comparing the ‘subpixel resolution’ of competing phones such as the Galaxy Nexus and iPhone 4/4S. Some commentary has been insane, comparing apples with oranges and declaring PenTile an abomination regardless of resolution. Others, […]

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Rattling Nikon MH-18a charger: how to fix/prevent

During my holiday in Thailand, I was silly enough to drop my Nikon MH-18a battery charger on the floor from a height of a metre or so. As soon as I picked it up, I heard a rattle. When I looked inside, this is what I found: The core of the inductor had broken into […]

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Setting up gmail as a relay host in postfix (without creating certificates)

When your linux box needs to send email (e.g., mail sent by a webpage, cron job output, etc), postfix can normally send the email directly to the recipient. However, if your ISP blocks port 25 outbound, or you want to keep a nice log of all outgoing messages, or want replies to arrive in your […]

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