Hacking cakes with LEDs, the sequel!

A few weeks back we ran a piece about the convergence of making and baking in an attempt to create a cake festooned with working LEDs. The moral was that not every creative idea ends in victory, but we applauded the spirit it takes to post one’s goofs for the whole internet to see and to learn from.

[Craig]’s LED matrix proved unreliable…and the underlying cake didn’t fare much better, resembling that charred lump in the toaster oven in Time Bandits. The cakes-with-lights meme might have died right there if not for a fluke of association…

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PID Sous-Vide Slow Cooker – Bon Appétit!

In search of a perfectly-cooked brisket, [Aaron] recently completed this DIY  PID-controlled sous-vide slow cooker. Sous-vide (French for “under vacuum”) is a cooking technique in which foods are typically vacuum-sealed and then cooked in a relatively low temperature water bath for an extended period of time. This is done to minimize temperature gradients throughout the food to ensure even cooking. Precise regulation of the water temperature is the key to ensuring that the results are exactly as desired – when cooking for many hours or days, even a few degrees discrepancy can greatly influence the final product.

A few months ago we featured a similar hack that utilized a simple switching temperature controller spliced into an extension cord.  Although probably sufficient for most aspiring “hacker-chefs”, the temperature was not as stable as it could be. The problem is that it takes time for the heat generated in the slow cooker’s heating element to reach the temperature probe (and food) suspended in the water bath.  By the time the probe reads the elevated temperature, the element is already too hot and the temperature overshoots the target. One way to mitigate this effect is to circulate the water to minimize temperature gradients, as is done in many of the expensive commercial units. In order to achieve similar results, [Aaron] instead created a PID controller that uses temperature feedback over time to precisely maintain the desired temperature and reduce any deviations resulting from outside disturbances.

The build is covered in detail and looks great in a custom acrylic enclosure. All of the board schematics, enclosure layout files, and source code are available under Creative Commons licensing at the bottom of his blog page. A good deal of time is also spent addressing the actual PID programming and tuning – something that could be useful for many different hacks requiring precise feedback control.

The end result is a professional looking control box and a slow cooker that is able to maintain temperature within 1°F even while using a DS1820 temperature sensor that is only rated as accurate to 0.5°C (0.9°F). From the pictures it looks like [Aaron] has finally achieved brisket bliss! Now the only question remaining is: what is the best setting for reheating left-over pizza?

PID controlled smoker

[dafonso] purchased a nice 1500W smoker but was somewhat dismayed that it only had one cooking temperature. To compensate he designed his own PID control system which allows him to set the cooking temperature digitally. At the heart of the system is a PICAXE 18 micro which switches the smoker on and off using a solid state relay. Rather than testing the 110V system on the smoker itself (which would have been a pain indoors) he used a lamp instead. To see if he was getting the correct temperature he taped his thermocouple to the light bulb and let the PID switch the lamp on and off. Also be sure to checkout his video which does a good job of explaining how he was able to solder the surface mount components required for the control board.

Refurbishing a refrigerator for fermenting

[Mikey Sklar] wrote in to show us how he refurbished a neighbors useless refrigerator as a fermentation chamber. [Mikey] is a fan of making breads, kemchi, yogurt, and tempeh. To make these, it helps to have a completely controlled temperature for them to ferment in. [Mikey] developed a temp controller for this in the past, but had to either build a control box or use a giant chest freezer.  This is not optimal for limited space, such as a kitchen. He got lucky when a neighbor tossed a wine cooler into the trash. These little coolers are perfectly sized for a kitchen and even have a glass front so you can keep an eye on what is going on inside without having to open it and effect your temps. [Mikey] ripped it open, replaced the peltier cooler with a large heat lamp and his temp controller. Since he was making yogurt with this one, he needed only to heat it. The final product turned out pretty effective.

Roasting Pan Audio Amplifier

When you need a rigid, vibration-free chassis for your amplifier, look no further than a roasting pan. I’ve used cast cement for subwoofers, but using a cooking pan bolted to a heavy wooden chopping board is a cheap way to get a rigid surface on which to build audio gear. The amp circuitry used by [Mark] is not complex, but it gets the job done. The “oxygen free copper cable” and “pure silver wire” are not needed, just make sure you have a solid mechanical connection. In other words, just tin your wires, bend small “u” shapes at each end, hook them together, and apply solder to the heated ends. Alternatively, hold the ends of stranded wires parallel to each other and twist the ends together before tinning, then solder. Test everything with a multimeter while moving wire joints to make sure you have no weak connections. Now you won’t waste your money on hyped-up cabling materials.

Thanks to [Gio] (who seems to have some personal audio projects as well) for the tip.

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