Engineering Your Way To Better Sourdough (and Other Fermented Goods)

Trent Fehl is an engineer who has worked for such illustrious outfits as SpaceX and Waymo. When he got into baking, he brought those engineering skills home to solve a classic problem in the kitchen: keeping a sourdough starter within the ideal, somewhat oppressive range of acceptable temperatures needed for successful fermentation.

A sourdough starter is a wad of wild yeasts that you make yourself using flour, water, and patience. It’s good for a lot more than just sourdough bread — you can scoop some out of the jar and use it to make pancakes, waffles, pretzels, and a host of other bread-y delights. A starter is a living thing, a container full of fermentation that eats flour and has specific temperature needs. Opinions differ a bit, but the acceptable temperature range for active growth is about 60 F to 82 F. Too cold, and the starter will go dormant, though it can be revived with a little love. But if the starter gets too hot, all the yeasts and bacteria will die.

While there are of course commercial products out there that attempt to solve this problem of temperature control, most of them seem to be aimed at people who live in some wonderland that never gets warmer than 80F. Most of these devices can’t cool, they only provide heat. But what if you live in a place with seasons where the climate ranges from hot and humid to cold and dry?

The answer lies within Chamber, a temperature-regulated haven Trent created that lets these wild yeasts grow and thrive. It uses a Peltier unit to heat and cool the box as needed to keep the mixture fermenting at 26°C /78.8°F.

Thanks to the Peltier unit, Trent can change the temperature inside the chamber simply by alternating the direction of current flow through the Peltier. He’s doing this with an H-bridge module driven by a Raspberry Pi Zero. When it starts to get too warm in the chamber, the fan on the outside wall vents the heat away. A second fan inside the chamber pulls warm air in when it gets too cold.

Trent says that Chamber performs really well, and he’s recorded temperatures as low as 60F and as high as 82F. He mostly uses it for sourdough, but it could work for other temperature-sensitive food sciences like pickling, growing mushrooms, or making yogurt. We think it could be ideal for fermenting kombucha, too.

Chamber works well enough that Trent has put further development on the back burner while he makes use of it. He does have several ideas for improvements, so if you want to help, check out his website and Github repo.

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Reading Light Not Quite Powered By Your Favorite Hot Beverage

Thermoelectric devices are curious things, capable of generating electricity via the Seebeck effect from a temperature differential across themselves. The Seebeck effect does not produce a huge potential difference, but when employed properly, it can have some useful applications. [MJKZZ] decided to apply the technology to build a reading light, powered by a hot cup of coffee.

The build is based around four Peltier modules, 40mm x 40mm in size, sandwiched between a pair of copper sheets. The modules are wired in series to create a greater output voltage, and an aluminium heatsink is fitted to one side to create a higher temperature differential. The set-up produces just 230 mV from human body temperature, but over 8 volts when warmed directly with a heat gun. Boiling water in a mug produces a more restrained 2.1V output.

On its own, this voltage is a little weak to do anything useful. Thus, the electricity from the Peltier modules is fed through a joule thief, which helps step up the voltage to a more useful range to run an LED. With a mug of coffee on the copper plate, the assembly isn’t quite able to light the LED enough to allow the user to read comfortably. However, it flickers into life just a touch, demonstrating the basic concepts in action.

While it’s not the most practical build, and it’s likely to cool your coffee faster than you’d like, it’s a fun project that serves to educate about the mechanics of the Seebeck effect and using Peltier devices to generate it. Another fun application is to use them in a cloud chamber. Video after the break.

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Peltier Device Experiments

Once an exotic component, solid state heat pumps or Peltier devices are now pretty mainstream. The idea is simple: put electricity through a Peltier device and one side gets hot while the other side gets cold. [DroneBot] recently posted a video showing how these cool — really cool — devices work. You can see the video, below.

Many things in physics are reversible, and the Peltier is no exception. The device is actually a form of thermocouple, and in a thermocouple a temperature difference causes a voltage difference. This is known as the Seebeck effect as opposed to the Peltier effect in which current flowing between voltage differences causes a temperature difference. It was known for many years, but wasn’t very practical until modern semiconductor materials arrived.

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Process Characterization On The Cheap With A Custom Test Rig

Testing is a key part of any product development cycle. Done right, it turns up unknown bugs and problems, and allows for them to be fixed prior to shipment. However, it can be a costly and time-consuming process. The [Bay Libre] team needed to do some work on power management, but the hardware required was just a little on the expensive side. What else does a hacker do, but build their own?

Enter the Thermo-Regulated Power Measurement Platform. It’s a device designed to control the die temperature of a chip during process characterization. This is where a chip, in this case the iMX8MQ, is run at a variety of temperatures, voltages, and frequencies to determine its performance under various conditions. This data guides the parameters used to run the chip in actual use, to best manage its power consumption and thermal performance.

The rig consists of a Peltier element with controller, a heatsink, and a fan. This is lashed up to a series of Python scripts that both control the chip temperature and run through the various testing regimes. Thanks to this automation, what would normally be a day’s work for an engineer can now be completed in just two hours.

Through a few smart component choices, the team accomplished the job at around one-tenth of the cost of commercial grade hardware. Granted, the average hacker probably won’t find themselves doing process characterization for cutting-edge silicon on a regular basis. Still, this project shows the value in building custom hardware to ease the testing process.

Testing is key to success in production. Custom jigs can make for light work when large orders come in, and we’ve run a primer on various testing techniques, too.

Reon Pocket Keeps You Cool With A Peltier Element

With another summer of heatwaves leaving its mark on our planet, finding a way to stay cool during the day isn’t an easy task. From the morning and afternoon commute in public transport, to busy crowds outside during lunch hour, there are many times when you cannot just find a place inside an airconditioned room to deal with the heat. Exactly for this purpose Sony has successfully completed a kickstarter (in Japanese) on its corporate ‘First Flight’ crowdfunding platform for the Reon Pocket.

Many people probably aren’t aware of Sony’s crowdfunding platform, but it’s a way to gauge the interest from the public for more ‘out there’ products, which do not fit Sony’s usual business model. In this case the Reon Pocket is a Peltier-based device which is placed against the back of one’s neck, from where it can either lower or increase the body’s temperature, reportedly by -13 ℃ and +8.3 ℃ respectively.

Covered in more detail by Engadget and its Japanese sister site, the reported 24 hour battery life refers to the Bluetooth link that connects the device with one’s smartphone, whereas the battery lasts under two hours with the peltier element active. This is probably not too shocking to anyone who knows how a peltier element functions, and how much electricity they consume.

Still, the basic concept seems sound, and there are functioning prototypes. While a 2-hour battery life isn’t amazingly long, it can be just the thing one needs to keep one’s cool during that 15 minute walk to the office in a three-piece suit, without needing a shower afterwards. The device isn’t expensive either, with a projected ¥12,760 (about $117) supplied. Naturally the device will only be on sale in Japan.

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A Stacked Peltier Cloud Chamber Build

Subatomic particles are remarkably difficult to see, but they can be made visible with the right techniques. Building a cloud chamber with dry ice is a common way to achieve this, but coming by the material can be difficult. [The Thought Emporium] wanted a more accessible build, and went for a Peltier-based design instead (Youtube link, embedded below).

By stacking several Peltier coolers in a cascade, it’s possible to increase the temperature differential generated. In this design, the copper plate of the chamber is cooled down to -33 degrees Fahrenheit (-36.11 Celcius), more than cold enough for the experiment to work. Alcohol is added to the glass chamber, and when it reaches the cold plate, it creates a super-saturated vapor. When disturbed by charged particles zipping out of a radioactive source, the vapor condenses, leaving a visible trail.

Cloud chambers are a popular experiment to try at home. It’s a great science fair project, and one that can be easily constructed with old computer parts and a couple of cheap modules from eBay. Just be careful when experimenting with radioactive sources. Video after the break.

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Build Your Own Freezer With Thermoelectric Coolers

Freezers are highly useful devices. You can preserve food, stop a dead animal from stinking out your apartment, and keep your vodka at the optimal drinking temperature. Of course, most of us bought ours from the local whitegoods store, but [Tech Ingredients] set out to build his own (YouTube, embedded below).

Unlike your freezer at home, this build doesn’t use the typical heat pump and refrigeration cycle with a compressor and expansion valve and so on. Instead, this freezer uses thermoelectric devices to pump heat, in combination with a glycol cooling circuit and fan-cooled radiators.

It’s not the most efficient or practical way to build a freezer, but it is functional and the device demonstrably works, making ice cubes over the course of a few hours. Performance can be further improved by moving the radiator assembly outdoors to make the most of the low ambient temperatures.

[Tech Ingredients] has further plans to experiment with a dessicant-based refrigeration system, and reports that initial results are promising. We’re eager to see how that goes; we’re fans of any rig that can cool a beer down in no time flat. Video after the break.

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