Overthinking Solenoid Control

May 11, 2016 by Elliot Williams 65 Comments

No circuit is so trivial that it’s not worth thinking hard about. [Charles Wilkinson] wanted to drive a solenoid air valve that will stay open for long periods of time. This means reducing the holding current to prevent wasting so much power. He stumbled on this article that covers one approach in a ridiculous amount of depth.

[Charles] made two videos about it, one where he debugs the circuit and learns things live on camera, and another where he sums it all up. We’ll be walking you through the long one, but feel free to skip around.

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Solar FPV Plane Flies Forever

May 10, 2016 by Elliot Williams 69 Comments

We love solar power. Not only is it environmentally friendly, but it’s relatively lightweight and involves fragile high technology. Just the sort of thing that we’d want to strap onto the wings of a large model aircraft.

Solar power on a remote-controlled plane would get you unlimited cruising range. Now, a normal land-and-swap-battery process might be good enough for some people, but judging from [Prometreus]’s YouTube channel, he’s a fan of long flights over the Alps, and of pushing long-distance FPV links to the breaking point. For him and his friends, the battery power is definitely the limiting factor in how far / long he can fly.

All of the information we have is in the video, but that’s plenty. [Prometreus] didn’t bother with maximum-power-point tracking, but instead wired up his solar cells to work just about right for the voltage of his batteries and the level of sun that he’s seeing. So it won’t work nearly as well on cloudy days. (Check out this MPPT build that was submitted for the Hackaday Prize.)

He could switch the solar cells in an out remotely, and it’s pretty gratifying to see the consumed current in the battery go down below zero. In the end, he lands with a full battery. How cool is that?

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Minimal MQTT: Building A Broker

May 9, 2016 by Elliot Williams 49 Comments

In this short series, we’re going to get you set up with a completely DIY home automation system using MQTT. Why? Because it’s just about the easiest thing under the sun, and it’s something that many of you out there will be able to do with material on-hand: a Raspberry Pi as a server and an ESP8266 node as a sensor client. Expanding out to something more complicated is left as an exercise to the motivated reader, or can be simply left to mission creep.

We’ll do this in four baby steps. Each one should take you only fifteen minutes and is completely self-contained. There’s a bunch more that you can learn and explore, but we’re going to get you a taste of the power with the absolute minimal hassle.

In this installment, we’re going to build a broker on a Raspberry Pi, which is the hub of your MQTT network. Next time, we’ll get an ESP8266 up and running and start logging some data. After that, we’ll do some back-end scripting in Python to make the data speak, and in the last installment, we’ll explore some of the useful frills and fancy bits. Let’s get started!

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X-Ray Everything!

May 9, 2016 by Elliot Williams 24 Comments

We’re not 100% sure why this is being done, but we’re 110% happy that it is. Someone (under the name of [The X-Ray Playground]) is putting interesting devices under an X-ray camera and posting videos of them up on YouTube. And he or she seems to be adding a few new videos per day.

Want to see the inner workings of a pneumatic microswitch? Or is a running pair of servo motors more your speed? Now you know where to look. After watching the servo video, we couldn’t help but wish that a bunch of the previous videos were also taken while the devices were being activated. The ball bearing wouldn’t gain much from that treatment, but the miniature piston certainly would. [X-Ray Playground], if you’re out there, more working demos, please!

How long the pace of new videos can last is anyone’s guess, but we’re content to enjoy the ride. And it’s just cool to see stuff in X-ray. If we had a postal address, we know we’d ship some stuff over to be put under the lens.

We don’t have as many X-ray hacks as you’d expect, which is probably OK given the radioactivity and all. But we have seen [MikesElectricStuff] taking apart a baggage-scanner X-ray machine in exquisite detail, and a DIY fluoroscope (yikes!), so we’re not strangers. Who needs Superman? We all have X-ray vision these days.

Thanks [OiD] for the tip!

Running A Hackerspace Is Hard: Egypt Edition

May 8, 2016 by Elliot Williams 16 Comments

It’s no secret that it’s difficult to run a hackerspace. Different personalities, different material requirements, and often constrained spaces can require continual negotiation. But if you think that having the metalworking types getting their shavings on your electronics bench is a problem, try having your entire hackerspace demolished on short notice.

The situation in Cairo is far from normal at the moment. The building that Cairo Hackerspace had recently moved to was raided, closed for two months, and then re-opened under strict surveillance in February.

All was well until a part of the building unexpectedly collapsed. Then they got a demolition order, followed by postponement, followed by armed police entering anyway and breaking stuff, followed by a further declaration of the building as safe, and now a heritage site. And all of this over a week’s time. While some of the art studios in the Townhouse were saved, the Cairo Hackerspace’s space is gone.

The good news? Nobody got hurt in all of this, and the Cairo Hackerspace crew were able to get their gear out after the initial demolition notice. They’ve been working on a mobile hackerspace-in-a-van approach lately, so hopefully they’ll be able to keep on hacking.

So when you’re bickering over who didn’t clean up the hackspace’s coffee machine, or the proper location of your favorite soldering iron, think kindly about the Cairo crew and get back to doing what you do best — projects.

How about you? What hackerspace tales do you have? Contact us through the tips line — we’d love to hear.

Smallest MIDI Synth, Again!

May 8, 2016 by Elliot Williams 17 Comments

Not content with fitting a tiny square-wave MIDI synthesizer into a MIDI plug, [Mitxela] went on to cram a similar noisemaker into a USB plug itself.

Besides being physically small, the code is small too, as well as the budget. It uses V-USB for the USB library running on an ATtiny85, and a couple of passive parts. His firmware (apparently) takes in MIDI notes and spits out square waves.
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Gyroman Walks With Just One Motor

May 8, 2016 by Elliot Williams 11 Comments

For some reason, we seem to really want our robots to walk on two legs like we do. And this despite how much the robots themselves want to be made out of motors, which match up so naturally with wheels. The result is a proliferation of inventive walking mechanisms. Here’s another.

Gyroman is a 3D printed gyroscope with legs. The gyroscope is geared down to lift one leg and then the other. First-semester physics, that we still find a little bit magical, makes the gyro precess and the robot turns a bit. Time these just right and it walks. See the video below for a demo. (Admittedly, Gyroman looks like he’s had a bit too much to drink as he winds down.)

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