A dark detecting circuit for your jack-o’-lantern

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Here’s an inexpensive electronic circuit that you can build to put in your Jack-o’lantern. It provides power to drive a few LEDs at night, and automatically turns them off during the daytime. It’s a simple and automatic dark-detecting circuit that you can use to for your very own photosensitive pumpkin.

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Easy high-power LED blinking circuit

Clear overview

Often times when people get started in electronics, they want to blink LEDs. This is this a great idea, and we really like blinking LEDs, so we’re happy to help. In the last year or two there’s also a growing chorus of people that want to drive high powered LEDs. That’s not always as easy, but it can be done.

Now by the time that you start talking about blinking the high power LEDs– you shouldn’t be surprised if people start whipping out the heavy artillery: 555 timer chips, transistors, boost converters, microcontrollers, solid state relays, and/or dedicated LED driver chips. While each of those does have its place, sometimes it’s nice to have a simpler and much less expensive alternative.

Here we describe what is possibly the simplest and cheapest circuit for driving and blinking high-power LEDs. The secret ingredient? Our good old friend the blinking incandescent light bulb.

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Tiny portable AVR projects: Business card breakout boards

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For all of our different AVR microcontroller based projects, we seem to find ourselves continually wiring up minimalist target boards; little circuit boards that fit both the AVR and a 6-pin header for connecting to your in-system programmer. And, when you find yourself hand-wiring the same circuit over and over again on a protoboard, that’s really just life’s way of telling you “just lay out a damn printed circuit board already.”

Coincidentally, we needed a new business card.
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Weekend Projects with Bre Pettis: Make a Joule Thief

Weekend Projects Podcast!
In this week’s Weekend Projects video podcast, Make Magazine’s Bre Pettis and I show you how to make a Joule Thief. The PDF file that goes with the podcast is here (450 kB PDF file).

So whatsa Joule Thief? It’s a little wisp of a circuit that allows you to drive a blue or white LED from a low voltage. Normally, if you want to light up a blue or white LED you need to provide it with 3 – 3.5 V, like from a 3 V lithium coin cell. But a 1.5 V battery like a AA cell simply will not work. But using the Joule Thief, it works like a charm. Not only does it work with a brand new battery, but it works until the battery is nearly dead– down to 0.3 V. That’s well below the point where your other toys will tell you the battery is dead, so it can steal every last joule of energy from the battery (hence the name). To learn how to make one, watch the video, which is available in a variety of formats.

The original site where we learned about the Joule thief shows you how to make a miniature version of this circuit, such that you can fit it in a tiny flashlight. However, in the video we show you how to make it big, large enough (1) to make with clumsy hands and (2) that you can see what we’re doing.

After the jump, some detailed photos of how the coil is wound in case you need more detail than in the video.

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More circuitry snacks

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My old friend Kevin sent in these pictures of a massive array of tasty electronic treats that he and his family made for a group picnic at Los Alamos National Laboratory. (Nice work!) If your diet is short on precision op-amps and instrumentation amplifiers, these just might hit the spot.

You can read our own article about circuitry snacks (dated July 11, 2007) here.

Laying out printed circuit boards with open-source tools

There has historically been, and still is, a lack of good, free MacOS native EDA (electronic design automation) software. The situation has somewhat improved in the past few years because the X11 layer in Mac OS X allows graphical unix applications to run natively on the Mac, concurrently with other programs. I recently learned to use some of these tools in the gEDA suite to lay out printed circuit boards. These (loosely, if at all, organized) notes should be helpful to anyone that wants to get started making PCBs using a mac, linux, or other unix-like system.
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Vintage Remote TV-B-Gone Case Mod

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Turn off that television in classic style!

Here we show you how to hack a TV-B-Gone into the case of a vintage television remote control, such that the original on/off button instead activates the TV-B-Gone. We also modify the power supply so that it runs off of a regular 9 V battery, instead of a set of lithium coin cells.
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