Hackaday Prize Entry: Open Sip And Puff

A sip-and-puff device is an assistive technology used by people who cannot use their hands. Being a quasi-medical device, you can imagine this technology is extremely expensive, incapable of being modified, and basically a black box that can’t do anything except what it was designed for. For his Hackaday Prize entry, [Jason] is building his own sip-and-puff interface that’s cheaper and more capable than the available commercial versions.

Sip-and-puff devices can be mapped to control a wheelchair, click a mouse, or press a key on a keyboard. You can do a lot with USB, so for this open sip-and-puff device, [Jason] is using the ever-popular ATmega32U4 microcontroller.

USB is only one part of the problem, and to measure the sips and puffs of air through a plastic hose, [Jason] is using a pressure sensor from Freescale/NXP. While this is very similar to what would be found in the off-the-shelf version of a sip-and-puff device, it’s rather hard to interface with. The current version of the board is using an instrument amplifier, and the mechanical connection between the pressure sensor and the board is slightly bizarre. [Jason] has a few ideas for a better sensor, and for the rest of the Hackaday Prize he’s going to work on redesigning this device with simplicity in mind.

Filed under: The Hackaday Prize

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Antenna Rotation Arduino Style

Back in the days when you didn’t pay for your TV programming, it was common to have a yagi antenna on the roof. If you were lucky enough to have every TV station in the area in the same direction, you could just point the antenna and forget it. If you didn’t, you needed an antenna rotator. These days, rotators are more often found on communication antennas like ham radio beams. For terrestrial use, the antenna only needs to swing around and doesn’t need to change elevation. However, it does take a stout motor because wind loading can put a lot of force on the system.

[SP3TYF] has a HyGain AR-303 rotator and decided to build an Arduino-based controller for it. The finished product has an LCD and is able to drive a 24 V motor. You can control the azimuth of the antenna with a knob or via the computer.

[Waldemar Lewandowski] built a variant of the rotor (taking some additional ideas from [SQ9OUB]) and made a video of the device in operation (see below). The video is a little quiet, but you’ll get the ideas and you can see the original [SP3TYF] version’s code and documentation.

If you want to work satellites, you need an additional rotation axis. And if you think about it, rotating an antenna and moving a solar panel, probably have a lot in common — the sun is floating around in space, too.

Filed under: Arduino Hacks

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Next-gen DTV platform runs Android on quad-core Cortex-A53

The “Poplar Board,” based on HiSilicon’s quad-core Hi3798C V200 SoC, is the first SBC to implement Linaro’s “96Boards Enterprise Edition TV Platform” spec. The “under $100” Poplar Board is aimed primarily at Internet connected TV set-top box (STB) developers, but it also targets hobbyists and the open-source community, according to HiSilicon’s announcement. The SBC, which […]

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Internet Of Things Woodworking

Woodworking is the fine art of building jigs. Even though we have Internet-connected toasters, thermostats, cars, and coffee makers, the Internet of Things hasn’t really appeared in the woodshop quite yet. That’s changing, though, and [Ben Brandt]’s Internet of Things box joint jig shows off exactly what cheap computers with a connection to the Internet can do. He’s fully automated the process of making box joints, all with the help of a stepper motor and a Raspberry Pi.

[Ben]’s electronic box joint jig is heavily inspired by [Matthias Wandel]’s fantastic screw advance box joint jig. [Matthias]’ build, which has become one of the ‘must build’ jigs in the modern woodshop, uses wooden gears to advance the carriage and stock across the kerf of a saw blade. It works fantastically, but to use this manual version correctly, you need to do a bit of math before hand, and in the worst-case scenario, cut another gear on the bandsaw.

[Ben]’s electronic box joint jig doesn’t use gears to move a piece of stock along a threaded rod. Stepper motors are cheap, after all, and with a Raspberry Pi, a stepper motor driver, a couple of limit switches, and a few LEDs, [Ben] built an Internet-enabled box joint jig that’s able to create perfect joints.

The build uses a Raspberry Pi 3 and Windows IoT Core to serve up a web page where different box joint profiles are stored. By lining the workpiece up with the blade and pressing start, this electronic box joint jig automatically advances the carriage to the next required cut. All [Ben] needs to do is watch the red and green LEDs and push the sled back and forth.

You can check out [Ben]’s video below. Thanks [Michael] for the tip.

Filed under: Raspberry Pi, tool hacks

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The Evolution of a DIY Circuit Board Plotter

In this three part video series we watch [Dirk Herrendoerfer] go from scraps to a nice 3D printed assembly as he iterates through the design of a pen plotter for making circuit boards.

[dana] mentioned [Dirk]’s work in the comments of this post which describes a different process. Many permanent markers stick to copper well enough to last through the chemical etching process. While hand drawing definitely produces some cool, organic-looking boards, for sharp lines and SMDs it gets a bit harder; to the point where it becomes advisable to just let a robot do it.

Of course, [Dirk] was aware of this fact of life. He just didn’t have a robot on hand. He did have some electronic detritus, fishing line, an Arduino, scrap wood, brass tubes, and determination.  The first version‘s frame consisted of wooden blocks set on their ends with holes drilled to accept brass rods. The carriage was protoboard and hot glue. Slightly larger brass tubing served as bushings and guide. As primitive as it was the plotter performed admirably, albeit slowly.

The second version was a mechanical improvement over the first, but largely the same. The software got a nice improvement. It worked better and had some speed to it.

The latest version has some fancy software upgrades; such as acceleration. The frame has gone from random bits of shop trash to a nicely refined 3D printed assembly. Even the steppers have been changed to the popular 28BYJ-48 series. All the files, software and hardware, are available on GitHub. The three videos are viewable after the break. It’s a great example of what a good hacker can put together for practically no money.

Filed under: Arduino Hacks, cnc hacks

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Simple Arduino-Controlled, No-Pump Plant Watering

noPump_1Make this computer-controlled plant watering system that doesn’t use a pump.

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The post Simple Arduino-Controlled, No-Pump Plant Watering appeared first on Make: DIY Projects and Ideas for Makers.

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NES Light Gun Fires Awesome Laser Effect

[Seb Lee-Delisle]’s NES lightgun gave us pause as the effect is so cool we couldn’t quite figure out how he was doing it at first. When he pulls the trigger there erupts the beam of light Sci Fi has trained us to expect, then it explodes in a precision sunburst of laserlight at the other end as smoke gently trails from the end of the barrel. This is a masterpiece of hardware and trickery.

seb-lee-delisle-nes-zapper-trick-thumb
Demo video posted by @seb_ly

The gun itself is a gutted Nintendo accessory. It looks like gun’s added bits consist of two LED strips, a laser module (cleverly centered with two round heatsinks), a vape module from an e-cigarette, a tiny blower, and a Teensy.  When he pulls the trigger a cascade happens: green light runs down the side using the LEDs and the vape module forms a cloud of smoke in a burst pushed by the motor. Finally the laser fires as the LEDs finish their travel, creating the illusion.

More impressively, a camera, computer, and 4W Laser are waiting and watching. When they see the gun fire they estimate its position and angle. Then they draw a laser sunburst on the wall where the laser hits. Very cool! [Seb] is well known for doing incredible things with high-powered lasers. He gave a fantastic talk on his work during the Hackaday Belgrade conference in April. Check that out after the break.

So what does he have planned for this laser zapper? Laser Duck Hunt anyone? He has a show in a month called Hacked On Classics where this build will be featured.

Filed under: laser hacks, led hacks, nintendo hacks

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Circuit Design? Spread the Joy

Accountants and MBAs use spreadsheets to play “what if” scenarios with business and financial data. Can you do the same thing with electronic circuits? The answer–perhaps not surprisingly–is yes.

Consider this simple common emitter amplifier (I modeled it in PartSim, if you’d like to open it):

In this particular case, there are several key design parameters. The beta of the transistor (current gain) is 220. The amplifier has an overall voltage gain of about 3 (30/10). I say about, because unless the transistor is ideal, it won’t be quite that. The supply voltage (Vcc) is 12 volts and I wanted the collector voltage (VC) to idle at 6V to allow the maximum possible positive and negative swing. I wanted the collector current (IC) to be 200mA.

Design by Math

So how do you select the values of  the resistors? Start with R3 at the collector. I specified that VC=6V and Vcc=12 V so R3 has to drop 6 V. If VC had been, say, 9 V then the drop would be 12-9 or 3 V. I also said that the collector current, IC, had to be 0.2 A. Ohms law, then, says R3= 6/0.2 = 30 ohms.

The gain in this configuration is going to be R3/R4. So if the gain is 3 and R3 is 30, it stands to reason that R4 is 10. The current through R4 is almost the same as IC. It is actually related by the alpha of the transistor which is related to the beta. In a transistor like this, the alpha will be nearly 1.0. That means the emitter current will be equal to slightly more than the collector current. For a quick calculation, let’s assume they are the same so the voltage at the emitter is going to be 0.2 times 110 or 2 V.

The voltage at the base, then, needs to be about 0.7 higher or 2.7 V. Because the transistor model is accurate and it models a real transistor, I actually want to set the base voltage to about 0.8 V higher than the emitter and that’s 2.8 V. The base will look like the emitter resistor times beta in ohms (2220 ohms). So the voltage divider of R1 and R2 really has 2200 ohms in parallel with R2. To get the 12 V knocked down to 2.8 V needs R1=202 ohms and R2 to about 64 ohms. That’s it! You now know all the values and PartSim (or another circuit simulation tool) will show that it works. The 1 kHz signal is just for testing and you can see you get roughly a gain of 3 from input to output (along with a 180 degree phase shift):

screenshot_246

Spread the Joy

While those steps aren’t very complex, it is tedious. Why not use a spreadsheet (download amp.xlsx from GitHub) to capture the algorithm? Then you can easily make changes and see the results instantly. Here’s an example:

What happens if you change the IC to 0.1 A? Or the gain to 5? Or the input voltage to 24 V?

There are two cells that you probably won’t change much, so they aren’t under inputs, but they do affect the overall design. The first is the Vbe drop. For a normal silicon transistor, this should be about 0.6 or 0.7 volts, dependant on temperature. If the real circuit or an accurate simulation shows a different voltage drop between base and emitter (for example, the base is at 2.8 V and the emitter is at 2 V), use that difference (0.8) in the parameter and you’ll get a better result.

The second cell is the current in the voltage divider (R1 and R2). The total current through R1 is equal to the current through R2 and the base of the transistor. The base looks (more or less) like the emitter resistor multiplied by the beta of the transistor (which isn’t a very stable parameter). In theory, you could use a lot of different values of the voltage divider resistors to get the correct ratio. The spreadsheet assumes that the total current will be a fixed multiple of the expected base current. If you set this multiplier too low, you’ll get a negative resistance, so you’ll have to raise it.

In general, if you set the total current to, say, four times the base current, then R2 will get three times the base current through it. A reasonable value is 10 which ensures that changes in the base current won’t affect the divider output very much.

Of course, the spreadsheet won’t pick standard resistance values. That’s fine for simulation, but if you are really going to build, you might want to get close values. For example, to use a 47 ohm collector resistor, you could adjust the quiescent voltage or the collector current. For example, try the example with a collector current of 0.127. That results in values of 47 ohms and 16 ohms, both standard 5% resistors. For the dividers, you can play with the current multiplier. Continuing on the example, setting it to 11 puts the divider in range of a 1.5K resistor and a 510 ohm resistor, both standard values. Remember, device parameters will vary along with part tolerances, so getting close is good enough (and if it isn’t, then you have a problem anyway because of variations due to the manufacturing of the transistor, temperature, and other effects).

Speaking of tolerances, it is easy to look at the effect of tolerance ranges using the spreadsheet. With a little work you could even repeat the math on a single spreadsheet to catch all the end cases.

Solve Your Problem

Many spreadsheet programs can also solve optimization problems. Next time, I’ll show you how you can use that in conjunction with models of your circuit to easily find component values.

Filed under: how-to

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New X-Carve CNC Router Bulks Up for Advanced Usage

Screen Shot 2016-08-31 at 8.44.33 AM copyLast May, we spotted what looked like an updated version of Inventable’s X-Carve. The company has now made it official.

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The post New X-Carve CNC Router Bulks Up for Advanced Usage appeared first on Make: DIY Projects and Ideas for Makers.

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Big Brother and Others Are Watching Your Car

We are all (hopefully) aware that we can be watched while we’re online. Our clicks are all trackable to some extent, whether it’s our country’s government or an advertiser. What isn’t as obvious, though, is that it’s just as easy to track our movements in real life. [Saulius] was able to prove this concept by using optical character recognition to track the license plate numbers of passing cars half a kilometer away.

To achieve such long distances (and still have clear and reliable data to work with) [Saulius] paired a 70-300 mm telephoto lens with a compact USB camera. All of the gear was set up on an overpass and the camera was aimed at cars coming around a corner of a highway. As soon as the cars enter the frame, the USB camera feeds the information to a laptop running openALPR which is able to process and record license plate data.

The build is pretty impressive, but [Saulius] notes that it isn’t the ideal setup for processing a large amount of information at once because of the demands made on the laptop. With this equipment, monitoring a parking lot would be a more feasible situation. Still, with even this level of capability available to anyone with the cash, imagine what someone could do with the resources of a national government. They might even have long distance laser night vision!

Filed under: digital cameras hacks

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