[William] developed this temperature candle as a tool to help keep babies safe as they sleep. It seems that ambient temperature has an effect on Sudden Infant Death Syndrome (SIDS). This device is meant to alert you when room temperature is outside of the recommended envelope.

The board hosts an eight-pin PIC microcontroller (12F683P), a temperature sensor, RGB LED, and a push button. The round PCB is the same size as a votive candle, which is nice except that you’re going to have to drill a hole in your candle holder to accommodate that barrel jack.

The temperature sensor is read by the microcontroller and used to determine the color of the LED. Red is hot, blue is cold, and just right is somewhere in between. But if you’d rather know the exact current temperature you can press the button and it’ll blink out the Celsius reading using blue for 10 degree increments (three blinks is 30 degrees, etc.) and red for single degrees. Don’t miss the demo of the candle in the video after the break.

Satisfy your need to view some quality machining by looking through this Stirling engine worklog. We’ve seen these engines used a few other times in creating electricity from solar energy, powering a car, and even built from aluminum cans. [David Morrow] built this rendition to push the limits of his machining skills. We’d say he succeeded. The finished piece should run with the help of a heat source such as a candle. There’s no video of this engine, but we’ve embedded a clip of a similar device after the break in order to give you an idea of how this would work.

[Thanks The Ideanator]

Yes, that picture you are seeing is serious. [Roland] needed a chip for a damaged piece of electronics. He was lucky enough to find one on an old board at a local shop. The problem was, he didn’t have the hot air gun to remove the chip the correct way. Instead, he simply cooked the board over a candle to melt the solder. Interestingly, after he cleaned the candle-cooked board, it looked like it survived without damage. The chip worked fine and fixed his problems. Sometimes, we just don’t have the right tools for the job.

[via HackedGadgets]

What you see above is a generator that converts heat to electricity. [Reukpower's] thermoelectric lamp is one of those hacks that makes you scratch your head even though you understand why it should work. The heart of the system uses a Peltier cool, just like the thermoelectric solar generator. When there is a temperature differential from one side of the Peltier to the other a small current is generated.

In this case a candle heats one side and a heat sink cools the other. The tiny voltage picked up from the Peltier’s contacts is then boosted using a joule thief. We’ve seen LEDs powered with a joule thief before, benefiting from their own low power consumption. In this case, the boost circuit is scavenged from an emergency phone charger and probably achieves higher efficiency than if he had built it himself.

We’re barely past Halloween and people are already working on their next LED based holiday decorations. For Hanukkah, Gizmodo pointed out the PCB menorah pictured above. It uses a set of DIP switches to control which LEDs are lit. A couple years ago, Evil Mad Scientist Laboratories put together a tutorial for building a more minimal LED menorah. Each of the nine LEDs are soldered directly to the legs of an ATtiny2313 microcontroller. Every time you power up the device an additional LED is lit. [Ori] liked the project and decided to take a slightly different approach. He used an LM3914 DIP18 LED bar driver. A potentiometer controls how many of the LEDs are illuminated.

Our flickering LED circuit combined two known circuit, and certainly wasn’t graceful because of it. [sprite_tm] saw quite a few areas where the circuit could be reduced. He ended up taking it down to just two LEDs, a battery, and an ATtiny13. The first step was getting rid of the current limiting resistors. The datasheet shows that with a 3V supply the AVR will limit the current well below the maximum current. The light sensor was removed next. [sprite_tm] referenced an earlier post on sensing with LEDs. He measures the voltage across one of the LEDs while it is off to see how much light is hitting it. The current draw while on is 10mA and 50uA while off.

[aballen] wanted to light the jack-o’-lantern this year with something that didn’t actually require fire. After searching for a project that was cheap and yielded decent results, he ended up just making his own. This project utilizes an ATtiny13 and two LEDs, red and orange.  The overall build is quick and simple with some very basic code for the flickering. If you really want it more enclosed, there is this similar project using a cheap electric candle. Of course, not everyone has the time or desire to make one that is this realistic. You could always just go the easy way, no microcontroller required.

Why limit it to just lighting up your pumpkin though? Lets take a stroll through Evil Mad Scientist Laboratories hallways and see the Snap O Lantern or the dark detecting pumpkin and the Cyclonolantern.