Determining Kibble Level Via Time-of-Flight

August 26, 2017 by John Baichtal 12 Comments

[WTH] is building an IoT kitty food dispenser. There are a few of these projects floating around that measure out portions very sensibly — some use screws to dispense a set amount of food at a time, some measure the weight of the remaining stockpile. This build is definitely not that. This kitty food monitor uses a time of flight sensor to determine the remaining level of food in a hopper. [WTH]’s feeder lets the cat eat all the grub it wants, then alerts the hooman when kibble levels drop below a certain level.

The project starts with one of those pet food dispensers that consist of a hopper that gravity feeds into the food bowl. As the animal eats that food, more dispenses into the bowl. Attached to the lid is an ESP8266 connected to an Adafruit time of flight sensor. This reports the kibble level in centimeters, which is good enough for [WTH]’s purposes. Sensor data is logged to a Google Drive spreadsheet, published as a graph through M2X (AT&T’s IOT service), and texted to [WTH]’s smart watch via IFTTT.

Look for a plethora of Tweeting, Instagramming, and otherwise automated feeding of the cat overlords right here on Hackaday. Check out automatic cat feeder dispenses noms, wants cheezburger, and a cat feeder made with laminator parts.

Custom Cut Pinwheel Makes A Useful HVAC Duct Flow Meter

August 25, 2017 by Dan Maloney 12 Comments

Everyone is familiar with pinwheels, and few of us haven’t crafted one from a square of paper, a stick, and a pin. Pinwheels are pretty optimized from a design standpoint, and are so cheap and easy to build that putting a pinwheel to work as an HVAC duct flow meter seems like a great idea.

Great in theory, perhaps, but as [ItMightBeWorse] found out, a homemade pinwheel is far from an ideal anemometer. His experiments in air duct flow measurements, which previously delved into ultrasonic flow measurement, led him to try mechanical means. That calls for some kind of turbine producing a signal proportional to air flow, but a first attempt at using a computer fan with brushless DC motor failed when a gentle airflow couldn’t overcome the drag introduced by the rotor magnets. But a simple pinwheel, custom cut from patterns scaled down from a toy, proved to be just the thing. A reflective optosensor counts revolutions as the turbine spins in an HVAC duct, and with a little calibration the rig produces good results. The limitations are obvious: duct turbulence, flimsy construction, and poor bearings. But for a quick and dirty measurement, it’s not bad.

Looking for an outdoor anemometer rather than an HVAC flow meter? We’ve got one made from an old electric motor, or a crazy-accurate ultrasonic unit.

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A 3D Printed Junction Transistor Model

August 25, 2017 by Adil Malik 10 Comments

Transistors are no doubt one of humankinds greatest inventions. However, the associated greatness brings with it unprecedented complexity under the hood. To fully understand how a transistor works, one needs to be familiar with some Quantum Mechanics! As perhaps any EE undergraduate would tell you, one of the hardest subject to fathom is in fact semiconductor physics.

Take your pick: Mathematical equations governing the various currents inside a BJT

A good place to start to comprehend anything complex is by having an accurate but most importantly, tangible model at hand. Semiconductors are hard enough to describe with elaborate mathematical tools, is a physical model too much to ask?

[Chuck] has designed, printed and explained the workings of a BJT transistor using a 3D printed model. We really like this model because it goes a long way to shed light on some of the more subtle features of BJT transistors for beginners.

For example, the simplest “electronic switch” model completely ignores the application of a transistor as a linear amplifier and cannot be used to explain important transistor parameters such as hfe (DC current gain Beta) or the VBE (voltage to forward bias the base-emitter junction). [Chuck’s] model on the other hand certainly offers better intuition on these, as the former can be linked to the length of the levers arm and the latter to the minimum force needed to rotate the lever. The Tee structure even signifies the combination of base current with the collector current during operation!

If physical models are not your thing, the classic pictorial depiction, the “Transistor Man” in the Art of Electronics might be of interest. If you’ve even outgrown that, its time to dig into the quantum mechanics involved.

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Credit Card Sized Spacecraft Poised To Sail To Alpha Centauri

August 21, 2017 by Dan Maloney 77 Comments

As a space-faring species, we’ve done a fair job of exploring and exploiting our local neighborhood. We’re pretty good at putting people and machines into orbit, but our galactic-scale signature is pretty tiny. Our radio signals are no more than 100 light-years away, and our farthest physical artifact isn’t even a light-day away from us 40 years after it launched.

Clearly we need to do a better job of getting out there, and that’s the goal of Breakthrough Initiatives’ Starshot program, which aims to launch a nano-spacecraft to Alpha Centauri and get it there fast. The program aims to build solar-powered credit card-sized spacecraft with sensors, cameras, communications, and even MEMS thrusters for attitude control. Motive power will come from solar sails catching laser light shined onto it from Earth, eventually accelerating the craft to 20% of the speed of light and reaching its destination within a generation.

The thought that we could start spreading ourselves out into the galaxy within the lifespan of most of the people on Earth is intoxicating. Sure, a wafer of silicon is a far cry from a sleek starship with powerful warp engines and all the finest appointments, or a gritty star freighter that can make the Kessel Run in less than 12 parsecs. But the laws of physics and the limits of engineering conspire to keep us mostly stuck at the bottom of a deep gravity well, and if this means sending fleets of nanobots across the galaxy in our stead, so be it.

And no matter what form our first galactic spacecraft take, you can bet that the Deep Space Network will be supporting the mission. For now, you can listen in on the program’s test satellites currently in orbit if you tune to 437.240 MHz.

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Embiggen Your Eclipse 2017 Experience With A Sun Funnel

August 19, 2017 by Dan Maloney 7 Comments

As exciting as Eclipse 2017 is going to be this Monday, for some folks it might appear a bit — underwhelming. Our star only occupies about half a degree of the sky, and looking at the partial phase with eclipse glasses might leave you yearning for a bigger image. If that’s you, you’ll need to build a sun funnel for super-sized eclipse fun.

[Grady] at Practical Engineering is not going to be lucky enough to be within the path of totality, but he is going to be watching the eclipse with a bunch of school kids. Rather than just outfitting his telescope with a filter and having the kids queue up for a quick peek, he built what amounts to a projection screen for the telescope’s eyepiece. It’s just a long funnel, and while [Grady] chose aluminum and rivets, almost any light, stiff material will do. He provides a formula for figuring out how long the funnel needs to be for your scope, along with plans for laying out the funnel. We have to take exception with his choice of screen material — it seems like the texture of the translucent shower curtain might interfere with the image a bit. But still, the results look pretty good in the video below.

Eclipse 2017 is almost here! How are you planning to enjoy this celestial alignment? By proving Einstein right? By studying radio propagation changes? Or just by wearing a box on your head? Sound off in the comments.

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Fool Giants With Novelty-Sized Gold Bricks

August 18, 2017 by John Baichtal 25 Comments

If you ever wondered how to make a giant-sized gold bar out of sheets of pink household insulation, well, there is a video showing you the steps. YouTube workshop guru [Jimmy DiResta] built oversized prop gold bricks out of foam. He cut sheets of 1.5″ Owens Corning foam insulation on his Saw Stop, making angled edges onto each piece so they could fit together in the trapezoidal ingot shape we know and love.

The pieces were put together with Great Stuff insulating foam sealant, the sort of spray foam used for filling up gaps in your house’s insulation, but here serving as glue. [Jimmy] created lettering by lasering out the shapes in what appears to be cardboard, then gluing the letters in place, using the leftover material from the laser cut to place the letters in neat rows. He then sanded down the edges, priming and painting the bars with gold paint–but there were too many imperfections visible so he re-sanded and repainted.

We have been inundated in foam projects recently, like this ultralight built out of foam insulation and a foam cutter built with a 9V battery.

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Catch The Eclipse With A Wearable Pinhole Camera

August 18, 2017 by Dan Maloney 18 Comments

You say you didn’t have enough warning to order eclipse glasses, and now they’re too expensive to buy? Or maybe you did order some but they ended up being those retina-combusting knock-offs, and now you’ve got nothing to protect you during the partial phase of Monday’s eclipse? Don’t dump a ton of money on unobtainium glasses — just stick your head in a cardboard box.

You may end up looking like a Box Troll with the aptly named [audreyobscura]’s box on your head, but it really is a safe and effective way of watching the eclipse, or for gazing at our star anytime for that matter. It’s nothing more than a large pinhole camera, with a tiny hole in a scrap of aluminum soda can acting as an aperture. The pinhole in one end of a box casts a perfect image of the sun on a paper screen at the other end of the box. A hole for your head with a proper gasket around your neck — maybe the neck of an old T-shirt would be a bit more comfortable and light tight? — and you’re ready for the show. The bigger the box, the bigger (and dimmer) the image will be, so you’ll want to cruise the local home center for long boxes. Because walking around with a water heater box on your head is totally cool.

Really, though, Hackaday readers can’t say they didn’t know this was coming. We started covering this in January, we’ve got hundreds of eclipse meetups across the country, and we’ve even covered some citizen science opportunities you can partake in on Eclipse Day. If you don’t have your head in a box, that is.

Thanks to [Roger Guess] for the idea on this one.