There’s a big problem with the Internet of Things. Everything’s just fine if your Things are happy to sit around your living room all day, where the WiFi gets four bars. But what does your poor Thing do when it wants to go out and get a coffee and it runs into a for-pay hotspot?
[Yakamo]’s solution is for your Thing to do the same thing you would: tunnel your data through DNS requests. It’s by no means a new idea, but the combination of DNS tunneling and IoT devices stands to be as great as peanut butter and chocolate.
DNS tunneling, in short, relies on you setting up your own DNS server with a dedicated subdomain and software that will handle generic data instead of information about IP addresses. You, or your Thing, send data encoded in “domain names” for it to look up, and the server passes data back to you in the response.
DNS tunneling is relatively slow because all data must be shoe-horned into “domain names” that can’t be too long. But it’s just right for your Thing to send its data reports back home while it’s out on its adventure.
Oh yeah. DNS tunneling may violate the terms and conditions of whatever hotspot is being accessed. Your Thing may want to consult its lawyer before trying this out in the world.
In the cult classic Dune, there’s this fictional device called the “Pain Box”. If you touch it, you’ll feel like your hand is burning, but in reality, no tissue is being damaged. In the real world this is called the Thermal Grill Illusion, which was discovered back in 1896. Much to our chagrin, [Adam Davis] has just finished building a working prototype.
Sound familiar? We covered a similar project a few months ago — but unfortunately it didn’t work very well. Luckily, and boy do we love it when this happens, [Adam] saw the post, and got inspired to try it himself. He had actually designed a system years back but never got around to building it. Upon seeing the post — and the difficulties in making it work — he just had to figure it out.
So how does it work? The Thermal Grill Illusion uses alternating warm and cool bars which stimulate the temperature receptors in your skin — and confuse them. Neither the warm or cool bars are extreme enough in temperature to do any harm, but your confused little temperature receptors make it feel like you’re either burning or freezing your skin off!
A lot of microcontroller projects out there need some sense of wall-clock time. Whether you’re making (yet another) crazy clock, logging data, or just counting down the time left for your tea to steep, having access to human time is key.
The simplest solution is to grab a real-time-clock (RTC) IC or module. And there’s good reason to do so, because keeping accurate time over long periods is very hard. One second per day is 1/86,400 or around eleven and a half parts per million (ppm), and it’s tricky to beat twenty ppm without serious engineering.
Good RTC ICs like Maxim’s DS3231, used in the Chronodot, can do that. They use temperature correction logic and a crystal oscillator to get as accurate as five parts per million, or under half a second per day. They even have internal calendar functions, taking care of leap years and the day of the week and so on. The downside is the cost: temperature-compensated RTCs cost around $10 in single quantity, which can break the budget for some simple hacks or installations where multiple modules are needed. But there is a very suitable alternative.
What we’re looking for is a middle way: a wall-time solution for a microcontroller project that won’t break the bank (free would be ideal) but that performs pretty well over long periods of time under mellow environmental conditions. The kind of thing you’d use for a clock in your office. We’ll first look at the “obvious” contender, a plain-crystal oscillator solution, and then move on to something experimental and touchy, but free and essentially perfectly accurate over the long term: using power-line frequency as a standard.
CNC machine tools are getting ever more affordable for the amateur machinist, and they’re an enabling technology for many projects. But you’ve got to respect the old school approach to turning hunks of metal into finished parts with no computer control. [Ticktock34] shows off his skills on a WWII vintage manual lathe with a photo album of his .75 caliber miniature black powder cannon build. What starts as a 3″ diameter actuator from a front end loader ends up as a beautiful replica of a full-sized cannon, along with a half-filled barrel of nicely blued scrap metal. Particularly impressive is the nicely proportioned ball end, cut by hand with no more instrumentation than a set of calipers. [Ticktock34] also shares a few tips for getting the trunnions exactly squared and aligned.
Good looking, and functional – stay tuned after the break for a video with the impressive blast from a test firing – with only a quarter charge of powder, mind you.
Want something a little safer for the kiddies and less likely to result in a visit from the police? Perhaps this PVC pirate cannon is more your speed.
One of [Andrey]’s previous designs used a Pololu tracked chassis. But this time he designed everything from scratch. In his first post on the a20, [Andrey] describes the mechanical design of the vehicle. In particular focusing on trade-offs between different drive systems, motor types, and approaches to chassis construction. He also covers the challenges of using open source design tools (FreeCAD), and other practical challenges he faced. His thorough documentation makes an invaluable reference for future hackers.
[Andrey] was eager to take the system for a spin so he quickly hacked a motor controller and radio receiver onto the platform (checkout the video below). The a20s final brain will be a Raspberry Pi, and we look forward to more posts from [Andrey] on the software and electronic control system.
USB power banks – huge batteries that will recharge your phone or tablet – are ubiquitous these days. You can buy them at a gas station or from your favorite online retailer in any capacity you would ever want. Most of these power banks have a tremendous shortcoming; they need to charge over USB. With a 10,000 mAh battery, that’s going to take a while.
We already have batteries with huge capacities, are able to charge quickly, and judging from a few eBay auctions, can be picked up for a song. [Kumar] is working on a device that leverages these batteries – and the electronics inside of them – to build a smarter power bank.
Right now, [Kumar] is working with Dell Latitude D5xx/D6xx replacement batteries that he can pick up easily. These batteries have an SMBus interface, and with a low power ARM microcontroller and a TI BQ24725a, he has everything he needs to efficiently and safely charge these batteries.
[Kumar] says he’s looking for some community suggestions and feature requests for his project. If you have any, be sure to drop them over on his project page.
There’s a lot of talk about CAD software these days, and don’t get us wrong, they’re an essential tool of the trade. But for roughing out an idea, nothing tops paper and a pencil. Even the back of a cocktail napkin will do.
If you’re like us, at some point you may have had an engineering teacher force you to sketch your ideas out on paper, rather than in software. Or maybe you went to a university that required engineering students take a drawing/drafting class, where the first few weeks, you’re only allowed to use paper and pencil.
It may seem silly that in today’s age that one would choose to sketch an idea out by hand, but one simple drawing can communicate an idea quickly and easily – and that’s key. After all, the biggest part of engineering is communication.
If you’re a bit older you may remember a staple in every engineering office was the green graph paper – some people called it an “Engineer’s Notepad.” It’s basically perfect for jotting down an idea. Thick lined graph paper on the back of each page that lets the lines be visible on the front, without being distracting. It’s becoming harder and harder to find at your local office supply place, but if you search for “Ampad Engineering Pad” you’ll still find it. (There is also a “National” brand that this writer prefers.)
If you’re in a pinch, or don’t want to pay for a full pad, we found a wonderful alternative. This online graph paper generator will allow you to make your own graph paper, and even customize it to suit your needs. With things like multi-weight lines, and polar graphs and much more. The result is a PDF file you can download and keep for the future. Or if you’re a bit crafty, you can add your own logo in an vector-type editing program such as Inkscape for free.