Easy Itty-Bitty Blinky LED Jack-O’-Lantern

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Halloween is tomorrow! Do you want to bring a carved pumpkin to work, but aren’t allowed to burn candles in your cubicle? Do you want to carve a mini-pumpkin that’s simply too small for a candle?

Or are you just running late and need to make a procrastinator’s pumpkin?

If you said yes to any of these questions, we just might have the solution that you’re looking for. Here’s an easy way to make a tiny blinking-LED jack-o’-lantern.

The blinking LED circuit is borrowed from a Tirefly, a commonly available type of motion-sensitive light that attaches to the valve stem on the wheel of a bike or car. Our quick modification (less than five minutes and no soldering) defeats the motion sensor so that the LED can blink all day (or all night) for you. (For hardened geeks who want to solder something anyway, we’ll also show you how to mod the circuit to use a higher-capacity battery.)

[Update: (10/2008) A reader wrote in that they have had trouble getting the circuit to blink continuously; the tirefly circuit may have been changed. (Confirmed– It has changed!) Do any other readers have recent success or failure to report?]
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Building a Robotic Dalek Pumpkin

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EXTERMINATE!!! EXTERMINATE!!! EXTERMINATE!!!

We Evil Mad Scientists like Halloween. A lot.

You might have already seen our old-school Cylon Jack-o-lantern. Here is another halloween electronics project, hopefully in time for you to make your own: It’s a radio-controlled robotic Dalek that can move around and turn its head. Oh, and did I mention that it’s a pumpkin?
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Make A Cylon Jack-O-Lantern

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It’s a pumpkin! It’s a Jack-o-lantern! It’s an electronics project! It’s… a Cylon!

Cylons are great. They’re evil, menacing, and shiny. They have glowing red lights, computer-monotone voices, and they aim as precisely as imperial stormtroopers.

For halloween this year, we made Cylon Jack-o-lanterns in both large and small versions.

The design consists of two parts, a pumpkin-carving part and an electronics part. The big idea, of course, is to make the Cylon’s red eye scan back and forth.

How well does it work? Take a look! (Youtube)

This week’s Weekend Projects Podcast at Make Magazine is about making a programmable LED pumkin.

Our Cylon is made with a very different approach. It runs on a 9V battery and uses two cheap integrated circuits (a 555 and 4017) that together control six LEDs (or six groups of LEDs).

Circuits like this are quick, easy, and cheap to build. It’s also fun merely from the standpoint of making something that people might expect to require a microcontroller. For this particular circuit, it turns out to be cheaper and faster to do it without one.

If you’re handy with a soldering iron, you can build this circuit for less than ten dollars, in less than two hours, without any programming at all.
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The story with a thousand comments

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Rob Cockerham, the genius behind cockeyed.com,(and one of the few, the proud, the Honorary Mad Scientists) decided to assemble an “Elite Comment Strike Force!!!” and auction off 1000 blog comments.

Watching this auction on eBay, one of the things that surprised me was the set of “Similar Items on eBay”; Rob wasn’t alone– and the other guys are serious! There are titles like “100,000 US BLOG Visitors to your BLOG! Real Traffic,” and “200 Articles To Boost Your Article Directory/Blog #3.” I hadn’t really appreciated that there was a market for this sort of mercenary blog traffic. I’ll have to keep that in mind next time that I’m a sleazy scum-of-the-internet spam-blog operator!

Do we need to buy hits for our web page? Well, no. It’s not like we have any advertising on this page with which to make money. But we are indeed willing to pay for the privilege of being the web site that was the victim of Rob’s “Elite Comment Strike Force!!!”

Naturally, I bid, along with 23 other eager folks. The final price was $90. (Hey, free shipping!)

So, here it is: This is the story with one thousand comments. Strike force, do your worst!!!
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Nuclear test in North Korea

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My friend Dave wrote me tonight: “That North Korean nuclear test claim? I checked the USGS website. Within an hour of the claim, they had posted data consistent with a nuclear test – 4.2 magnitude (too big to fake easily), depth 0 km, location pinned to a hillside in NE North Korea that has surprisingly good aerial coverage on the crosslinked Google Earth map – given that it’s a site long noted as a possible test facility. There is a road leading straight up to the base of the mountain, then disappearing.”

That’s pretty convincing!

Edit 2014: corrected links to usgs.gov and maps.

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Homopolar motor exhibit at the Exploratorium

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A couple of weeks ago, we visited the The Exploratorium, where we saw this giant homopolar motor, labeled “Daisy Dyno.” This is a classic demonstration of a homopolar motor. There’s a giant permanent magnet. In its jaws sits a big copper disk that is free to spin. A low-voltage but high current power supply is provided, where the positive end is hooked to the bearing in the center of the copper disk.

To run the motor, you touch the loose lead from the negative end of the power supply to the edge of the copper disk. A neat little arrow shows you exactly where to touch. The electric current flows from the center of the disk to that point of contact, which is in the direction perpendicular to the magnetic field, which creates a force in the correct direction to cause the disk to spin. In order to help the electric currents move in a fairly straight line between the edge of the disk to the center, the disk has a lot of radial slits cut through it, giving the disk the appearance of a daisy (hence the name) when it’s at rest. In the photo here, it’s moving pretty quickly.

We, of course, are quite fond of motors and magnets and things that spin, and have (so far) written up three under-one-minute science projects that are related: How to build a homopolar motor, how to make the version that spins water instead of a metal disk, and how to make a super-simple directional compass.

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