Measuring Airflow In An HVAC System

November 4, 2017 by John Baichtal 10 Comments

[Nubmian] wrote in to share his experiments with measuring airflow in an HVAC system. His first video deals with using with ultrasonic sensors. He found an interesting white paper that described measuring airflow with a single-path acoustic transit time flow meter. The question was, could he get the same effects with off-the-shelf components?

[Nubmian] created a rig using a pair of typical ultrasonic distance sensors. He detached the two transducers from the front of the PCB. The transducers were then extended on wires, with the “send” capsules together pointing at the “receive” capsules. [Nubmian] set the transducers up in a PVC pipe and blew air into it with a fan.

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Coffee, Conspiracy, And Citizen Science: An Introduction To Iodometry

October 30, 2017 by Sean Boyce 40 Comments

I take coffee very seriously. It’s probably the most important meal of the day, and apparently the largest overall dietary source of antioxidants in the United States of America. Regardless of whether you believe antioxidants have a health effect (I’m skeptical), that’s interesting!

Unfortunately, industrially roasted and ground coffee is sometimes adulterated with a variety of unwanted ‘other stuff’: corn, soybeans, wheat husks, etc. Across Southeast Asia, there’s a lot of concern over food adulteration and safety in general, as the cost-driven nature of the market pushes a minority of vendors to dishonest business practices. Here in Vietnam, one of the specific rumors is that coffee from street vendors is not actually coffee, but unsafe chemical flavoring agents mixed with corn silk, roasted coconut husks, and soy. Local news reported that 30% of street coffee doesn’t even contain caffeine.

While I’ve heard some pretty fanciful tales told at street side coffee shops, some of them turned out to be based on some grain (bean?) of truth, and local news has certainly featured it often enough. Then again, I’ve been buying coffee at the same friendly street vendors for years, and take some offense at unfounded accusations directed at them.

This sounds like a job for science, but what can we use to quantify the purity of many coffee samples without spending a fortune? As usual, the solution to the problem (pun intended) was already in the room:

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Junkbox Freezer Alarm Keeps Steaks Safe

October 29, 2017 by Dan Maloney 24 Comments

A fully stocked freezer can be a blessing, but it’s also a disaster waiting to happen. Depending on your tastes, there could be hundreds of dollars worth of food in there, and the only thing between it and the landfill is an uninterrupted supply of electricity. Keep the freezer in an out-of-the-way spot and your food is at even greater risk.

Mitigating that risk is the job of this junkbox power failure alarm. [Derek]’s freezer is in the garage, where GFCI outlets are mandated by code. We’ve covered circuit protection before, including GFCIs, and while they can save a life, they can also trip accidentally and cost you your steaks. [Derek] whipped up a simple alarm based on current flow to the freezer. A home-brew current transformer made from a split ferrite core and some magnet wire is the sensor, and a couple of op-amps and a 555 timer make up the detection and alarm part. And it’s all junk bin stuff — get a load of that Mallory Sonalert from 1983!

Granted, loss of power on a branch circuit is probably one of the less likely failure modes for a freezer, but the principles are generally applicable and worth knowing. And hats off to [Derek] for eschewing the microcontroller and rolling this old school. Not that there’s anything wrong with IoT fridge and freezer alarms.

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Dual Direction Gaming/Dining Room Beam Lights

October 22, 2017 by Rich Hawkes 21 Comments

Sometimes, you just can’t find something you want, and that’s when you break out the tools and get dirty with a bit of DIY. Reddit user [JaredBanyard] wanted a nice beam light for the dining room/gaming room. He ended up building one that shone both downward, on the table, and upward, adding some light to the room.

Warm white LED strip lighting was chosen, and two aluminum channels were glued together to hold them. After wiring the four LED strips together a diffuser was placed over them and then they were wired up and turned on to check the amount of light. With two strips per channel, even with the diffuser, there was plenty.

Each pair of channels were set into the main housing, which is made from Sirari hardwood. Two long outside side pieces make for a great looking final product, and the end pieces are sandwiched between the two outside pieces. After a bit of sanding and an application of matte polyacrylic, transformers were screwed inside and then the channels were placed on top. The circuitry was wired to a Z-Wave dimmer to control the lights remotely.

[JaredBanyard]’s put together a bill of materials and there are plenty of pictures. It’s a great, unique, light for the room, which includes a Duchess gaming table from boardgametables.com. For more lighting articles, check out this 2017 Hackaday Prize entry article on modular rail lighting, or this article about adding intelligence to your lighting solution.

[via Reddit]

FruitNanny: The Raspberry Pi Baby Monitor For Geeks

October 21, 2017 by Tom Nardi 14 Comments

Having a child is perhaps the greatest “hack” a human can perform. There’s no soldering iron, no Arduino (we hope), but in the end, you’ve managed to help create the most complex piece of machinery in the known galaxy. The joys of having a child are of course not lost on the geekier of our citizens, for they wonder the same things that all new parents do: how do we make sure the baby is comfortable, how many IR LEDs do we need to see her in the dark, and of course the age old question, should we do this with a web app or go native?

If you’re the kind of person who was frustrated to see that “What to Expect When You’re Expecting” didn’t even bother to mention streaming video codecs, then you’ll love FruitNanny, the wonderfully over-engineered baby monitor created by [Dmitry Ivanov]. The product of nearly two years of development, FruitNanny started as little more than a Raspberry Pi 1n a plastic lunch box. But as [Dmitry] details in his extensive write-up, the latest iteration could easily go head-to-head with products on the commercial market.

[Dmitry] gives a full bill of materials on his page, but all the usual suspects are here. A Raspberry Pi 3 paired with the official NoIR camera make up the heart of the system, and the extremely popular DHT22 handles the environmental monitoring. A very nice 3D printed case, a lens intended for the iPhone, and a dozen IR LEDs round out the build.

The software side is where the project really kicks into high gear. Reading through the setup instructions [Dmitry] has provided is basically a crash course in platform-agnostic video streaming. Even if a little bundle of joy isn’t on your development roadmap, there’s probably a tip or two you can pick up for your next project that requires remote monitoring.

It probably won’t surprise you that geeky parents have been coming up with ways to spy on their kids for some time now, and if you can believe it, some don’t even include a Raspberry Pi.

A Solar Freakin’ Walkway

October 13, 2017 by Dan Maloney 22 Comments

Looking to add a little pizzazz to your back garden? Are those strings of lights hung in the trees looking a little dated? Why not try lighting your garden path with DIY solar-powered pavers?

If [jfarro]’s project looks like a miniature version of the much-touted solar freakin’ roadways concept, rest assured that there are huge differences. For one, these lighted pavers actually work — trust me on this; I live not far from the demo site for the Solar Roadways and the degree to which it underwhelms cannot be overstated. Granted, a garden path is a lot simpler to engineer than a road, but many of the challenges remain.

Using recycled glass blocks that are usually reserved for walls and windows, [jfarro] figured out how to attach Neopixel rings to the underside and waterproof them with a silicone conformal coating. The 12 lighted pavers he built draw considerable current, so a 45-watt solar array with charge controller and battery were installed to power the pavers. An Arduino and a motion sensor control the light show when someone approaches; more complicated programs are planned.

Hats off the [jfarro] for taking on a project like this. We don’t often see builds where electrical engineering meets civil engineering, and even on a small scale, dealing with dirt, stone, and water presents quite a few challenges. Here’s hoping his project lasts longer than the Solar Roadways project did.

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Making Ice Cream With Heavy Metal

October 11, 2017 by Tom Nardi 25 Comments

After his last project left him with an eleven-pound block of aluminum, [Jason] got to thinking of what most of us would in that situation: fresh made ice cream. His mind was on the frozen concoctions of the aptly named Cold Stone Creamery, a mall food court staple where a chilled stone is used to turn fresh ingredients into made to order sundaes.

[Jason] did the math and found that an eleven-pound chunk of aluminum can absorb a little over 67,000 joules, which is over twice the energy required to freeze 100 g of water. In place of water he would be using cream, condensed milk, and strawberries, but believed there was a large enough safety factor to account for the differences between his ingredients and pure water.

His first attempt didn’t go exactly as planned, but with his Flir One he was able to back up his theoretical numbers with some real-world data. He found that he needed to start the aluminum block at a lower temperature before adding his ingredients, and through experimentation determined the block only had enough energy to freeze 30 g of liquid.

In the end [Jason] was satisfied with the frozen treat he managed to make from the leftovers of his radial mill project, but theorizes that an ever better solution would be to use a brine solution and drop the aluminum block all together.

Of course, if putting food on a slab of metal from your workshop doesn’t sound too appealing, you could always go the NASA route and freeze dry it. Either method will probably make less of a mess than trying to print objects with it.