Disposable Rocket Stove Keeps You Fueled In The Wild

June 1, 2021 by Kristina Panos 55 Comments

Don’t know about you, but we can’t start the day without coffee and a shower. If you were to drag us on some overnight trip into the wilderness, we could probably forego the shower for a day, but we will be a grumpy trail mate without some kind coffee, even instant.

Yes, if you were to get us on an overnight outdoor adventure, we would insist on bringing along a couple of these little disposable, self-destructing rocket stoves, if for no other reason than that we can have some coffee without having to forage for a bunch of firewood and build a whole regular-sized campfire. Don’t worry — we’ll share the water because there’s plenty of time built in. Per [smogdog], these Swedish torches will boil water in 20 minutes and burn for 60 — that’s enough time to make a coffee, a bowl of soup, and toast a single marshmallow before the fire consumes the scrap wood.

We love the use of bike chain as a burner to raise up the pot for fire ventilation. But our favorite bit has to be the dual-purpose packaging. It’s nice-looking, it’s informative, and it’s paper, so you can use it as a fire starter. Failing that, [smogdog] has a backup fire starter system — rubbing alcohol in a small spray bottle. Unwrap a protein bar and check out the demo video after the break.

Tired of the same old, boring trail foods? How about flat-pack pasta that morphs into fun shapes when you boil it?

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3D Printing Espresso Parts

May 15, 2021 by Bryan Cockfield 28 Comments

Virtually any hobby has an endless series of rabbit holes to fall into, with new details to learn around every corner. This is true for beekeeping, microcontrollers, bicycles, and gardening (just to name a few), but those involved in the intricate world of coffee roasting and brewing turn this detail dial up to the max. There are countless methods of making coffee, all with devout followers and detractors alike, and each with its unique set of equipment. To explore one of those methods and brew a perfect espresso, [Eric] turned to his trusted 3D printer and some compressed gas cylinders.

An espresso machine uses high pressure to force hot water through finely ground coffee. This pressure is often developed with an electric pump, but there are manual espresso machines as well. These require expensive parts which can withstand high forces, so rather than build a heavy-duty machine with levers, [Eric] turned to compressed CO2 to deliver the high pressure needed.

To build the pressure/brew chamber, he 3D printed most of the parts with the exception of the metal basked which holds the coffee. The 3D printed cap needs to withstand around nine atmospheres of pressure so it’s reasonably thick, held down with four large bolts, and holds a small CO2 canister, relief valve, and pressure gauge.

To [Eric]’s fine tastes, the contraption makes an excellent cup of coffee at minimal cost compared to a traditional espresso machine. The expendable CO2 cartridges only add $0.15 to the total cost of the cup and for it’s simplicity and small size this is an excellent trade-off. He plans to improve on the design over time, and we can’t wait to see what he discovers. In the meantime, we’ll focus on making sure that our beans are of the highest quality so they’re ready for that next espresso.

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Coffee Cupping Is A Grind — Spectroscopy Could Brew Better Beans

May 1, 2021 by Kristina Panos 18 Comments

If you’ve ever bought whole coffee beans, chances are good that there was all kinds of information on the bag that led to your decision, like the origin, the roast type, and the flavor notes. Traditionally, coffee grading — that’s judging the aroma of both dry and wet grounds and slurping the coffee evenly across the tongue to determine the flavor profile — is done by humans in a process called cupping. To call it a process is too clinical — it’s really more like a ceremony performed with the grave sincerity that coffee deserves.

A traditional cupping ceremony. Image via Kaldi’s Coffee

There’s an industry standard coffee flavor wheel, so why not leverage that to make a robot that can remove the human bias and possible error of doing things the traditional way? That’s exactly what Demetria, a Columbian-Israeli company is doing.

They’ve developed an AI platform that can determine bean quality as judged by handheld scanners that were born on Kickstarter. The scanner uses near-infrared to look for biochemical markers in the bean, which it uses to match up with a profile backed by the all-knowing coffee flavor wheel.

Demetria is using SCiO scanners and a custom app to judge beans before they’re even roasted, which greatly speeds up the process but makes us wonder how green bean spectroscopy stacks up against roasted beans as judged by humans. You may remember the SCiO, a pocket-sized, connected spectrometer made by Consumer Physics that finally started delivering the goods a few years after funding. If you got your hands on a SCiO, you might like to know that there’s an open project out there to hack them. Sparkfun did a nice, thorough teardown, and it seems to be a well-engineered piece of hardware.

On the one hand, cupping is a tradition and thus may people feel that robbing coffee of this tradition will rob coffee of its soul. On the other hand, cupping is wasteful, as the coffee must be roasted and ground immediately prior to the ceremony and it requires the availability of Q graders who have been trained in the ways of coffee grading.

Want to know more about coffee production? Might as well learn the Retrotechtacular way.

[Main and thumbnail images via Demetria]

Keep Coffee Warm Through Induction Heating

April 11, 2021 by Bryan Cockfield 13 Comments

Transformers have an obvious use for increasing or decreasing the voltage in AC systems, but they have many other esoteric uses as well. Electric motors and generators are functionally similar and can be modeled as if they are transformers, but the truly interesting applications are outside these industrial settings. Wireless charging is essentially an air-core transformer that allows power to flow through otherwise empty space, and induction cooking uses a similar principle to induce current flow in pots and pans. And, in this case, coffee mugs.

[Sajjad]’s project is an effort to keep his coffee warm while it sits on his desk. To build this special transformer he places his mug inside a coil of thick wire which is connected to a square wave generator. A capacitor sits in parallel with the coil of wire which allows the device to achieve resonance at a specific tuned frequency. Once at that frequency, the coil of wire efficiently generates eddy currents in the metal part of the coffee mug and heats the coffee with a minimum of input energy.

While this project doesn’t work for ceramic mugs, [Sajjad] does demonstrate it with a metal spoon in the mug. While it doesn’t heat up to levels high enough to melt solder, it works to keep coffee warm in a pinch if a metal mug isn’t available. He also plans to upgrade it so it takes up slightly less space on his desk. For now, though, it can easily keep his mug of coffee hot while it sits on his test bench.

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How To Cobble A Wobble Disk Roaster Together

March 14, 2021 by Kristina Panos 9 Comments

As with anything else, once your knowledge of coffee expands, the more attractive it becomes to control as much of the process as possible. Buying whole beans and grinding them at home is one thing, but you’re not a real coffee geek unless you’re buying big bags of green beans and roasting them yourself in small batches.

[Larry Cotton] has made an even more portable version of the wobble disk roaster we saw last summer. Beneath the housing made of aluminium flashing is the guts of a $15 Harbor Freight heat gun pointing upward at a metal strainer. A large metal disk mounted at a 45-degree angle to the spinning axis tosses and turns the beans as they get blasted with heat from below. [Larry] used a 12 VDC motor to run the wobble disk, and an an adapter to change the heat gun from 120 VAC to 12 VDC. This baby roasts 1½ cups of beans to city plus (medium) level in 12-15 minutes. Grab a cup of coffee and check it out after the break.

Roasting beans isn’t rocket science. Even so, there are some things you would benefit from knowing first, so here’s our own [Elliot Williams] on the subject of building DIY roasters.

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Our Curious Relationship With Caffeine

March 10, 2021 by Jenny List 109 Comments

If you were to paint a few stereotypes surrounding our community, where would you start? Maybe in apparel habits: the t-shirt from a tech conference, or the ubiquitous hoodie. Or how about leisure pursuits: gaming, or even D&D? There’s one thing I can think of that unites most of us, we have a curious affinity for caffeine. Is it a propensity for working into the dark of the night that’s responsible, or perhaps those of us with ADHD find the alertness helpful, but whatever it is we like our coffee and energy drinks. Rare is the hackerspace without a coffee machine and a fridge full of energy drinks, and I have lost count of the times I have been derided by the coffee cognoscenti among my peers for my being satisfied with a mug of mere instant. Deprived of my usual socialisation over the festive period by the pandemic, and contemplating my last bottle of Club-Mate as I drank it, I took a while to ponder on our relationship with this chemical.

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Tired Of Popcorn? Roast Coffee Instead

February 25, 2021 by Al Williams 17 Comments

We’ve seen a lot of coffee roaster builds over the years. [Ben Eagan] started his with a hot-air popcorn maker. If you think it is as simple as putting beans in place of the popcorn, think again. You need to have good control of the heat, and that requires some temperature monitoring and a controller — in this case, an Arduino. [Ben’s] video below shows how it all goes together.

With the Arduino and the power supply strapped to the sides, it looks a bit like something out of a bad post-apocalypse movie. But it looks like it gets the job done.

In addition to the Arduino, a thermocouple measures the temperature and that takes a little circuitry in the form of a MAX31855. There’s also a relay to turn the heater on and off. There are other ways to control AC power, of course, and if a relay offends your sensibilities you can always opt for a solid state one.

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