Like some strange manga come to life, you can remove this brassiere with a clap of your hands. Under the red bow is a not-so-small mechanical clasp that replaces the original on the strapless front-clasping undergarment. We hate to criticize, but [Randofo] really went off the deep end of hardware overkill on this project. The clasp itself is the electromagnetic coil removed from the case of a mechanical relay. An ATmega168 listens for a spike in sound pressure from a microphone, then drives the relay to release the feminine support system.

It is Valentine’s day. The question being is this romantic or sleazy? Watch the NSFW video after the break and let us know your opinion in the comments.

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[Eric Friedrich] needed to keep the wort warm enough for yeast to ferment it into beer. To solve the problem he built his own fermentation temperature controler using a microprocessor to turn some heating tape on and off. You can see the heating element embracing that diminutive fermentation bucket in the picture above. This was originally meant for keeping reptile cages warm. It costs less than similar products meant just for brewing and works well for [Eric]. A DS1820 temperature sensor gives feedback to an ATmega168 which then uses a relay to switch the heat on and off. The target temperature can be changed using a potentiometer on the board, with the setting displayed on a character LCD screen on the project enclosure.

If you’ve been lusting after your own glowing display we’re here to help by sharing some simple building techniques that will result in an interesting project like the one you see above. This is a super-accurate clock That uses ping-pong balls as diffusers for LEDs, but with a little know-how you can turn this into a full marquee display. Join me after break where I’ll share the details of the project and give you everything you need to know to build your own.

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When it comes to using servos in projects, there is a definite distinction between the cheap ones and the expensive high power and precision models. The OpenServo project gives you a couple options for enhancing your servo experience. By replacing the control board with a new one based on a familiar microcontroller, a whole new set of features can be attained. For those of you out there with a need for servos like these, you can buy the pre-built replacement board (unfortunately sold out right now), or build your own from the provided schematic, BOM, and source code.

Above you see a solenoid being used as a digital scale. The magnetic field from the coil in the base levitates the platform above, where a load to be measured is place. This floating platform has a permanent magnet in it, hovering above a hall effect sensor in the base. As the distance between that magnet and the sensor changes, the measurable magnetic field changes as well. The hall effect sensor is linear so the measured value can easily be correlated with a weight. In the video after the break [Vsergeev] demonstrates the device using test weights to show off its 0.5 gram resolution. He thinks that with a few hardware improvements he could easily achieve 0.1g accuracy.

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[Alex] ramped up the precision of his timepiece by adding a ChronoDot to the Ice Tube Clock. These two items are among our favorites; the Ice Tube Clock for its old-style multi-digit display, and the ChronoDot for combining a DS3231, battery, and components into a nice small package.

There is a schematic link at the very bottom left of [Alex's] writeup. He mentions that he depopulated the clock crystal and its capacitor pair from the board and patched into the clock input on the AVR. A 100K pull-up resistor is included in the wiring as called for in the DS3231 datasheet. Although not specifically referenced, we assume that [Alex] reprogrammed the ATmega168 clock select fuses to use an external clock signal.

Now he can sit back knowing that the clock will be within 10 seconds per year accuracy.

Welcome back to this fourth and final installment of the series. The first three parts should have been enough to get you off the ground, but a few more learning examples wouldn’t hurt. It’s also a good time to discuss some of the other things these little chips can do. Join me after the break to:

• Expand the sample code, adding features to our simple program while I challenge you to write the code yourself.
• Discuss AVR fuse bits, how to use them, and what to watch out for
• Touch on some of the peripherals you’ll come across in these chips

As a grand flourish to the series, I’ve used the example hardware from this final part to build a bicycle tail light. Hopefully this will inspire you to create something much more clever.

Series roadmap:

• AVR Programming 01: Introduction
• AVR Programming 02: The Hardware
• AVR Programming 03: Reading and compiling code
• AVR Programming 04: Writing code

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[Stan] built this LED matrix using a 16×16 grid of RGB LEDs. He built the hardware and wrote some subroutines to randomize the colors. He’s not using PWM because frame buffering is not feasible for the 1k SRAM limit of the ATmega168 he used. Instead, shift registers drive the lights which can be mixed to achieve eight different colors (including off for black) reducing the framebuffer size to just 96 bytes. After he got done with the build he realized this is sized well for a game of Tetris. We’ve seen AVR tetris, PIC Tetris, and Tetris using composite video but it’s always a pleasure to see a new display build.

After the break we’ve embedded [Stan's] demo video, several pictures, and a schematic. He’s using many of the same principles outlined in our How to Design an LED matrix tutorial.

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