Battleships Over BGP

June 7, 2018 by 14 Comments

The Border Gateway Protocol (BGP) is one of the foundations of the internet. It’s how the big routers that shift data around the Internet talk to each other, passing info on where they can send data to. It’s a simple protocol, with each router sending text messages that advertise the routes that they carry. The administrators of these routers create communities, each with an individual code, and this information is passed between routers. Most top-level ISPs don’t spread this data far, but [Ben Cox] realized that his ISP did. and that he could use this as an interesting way to transmit data over the Internet. What data to send? He decided to play battleships.

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Pocket Projector Uses Raspberry Pi

June 6, 2018 by 51 Comments

Who doesn’t want a pocket protector projector? Nothing will impress a date more than being able to whip out a PowerPoint presentation of your latest trip to the comic book convention. The key to [MickMake] build is the $100 DLP2000EVM evaluation module from Texas Instruments. This is an inexpensive light engine, and perfect for rolling your own projector. You can see the result in the video below.

If you don’t need compactness, you could drive the module with any Rasberry Pi or even a regular computer. But to get that pocket form factor, a Pi Zero W fits the bill. A custom PCB from [MickMake] lets the board fit in with the DLP module in a very small form factor.

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Stars Looking A Bit Dim? Throw Some Math At Them.

June 6, 2018 by 16 Comments

As the cost of high-resolution images sensors gets lower, and the availability of small and cheap single board computers skyrockets, we are starting to see more astrophotography projects than ever before. When you can put a $5 Raspberry Pi Zero and a decent webcam outside in a box to take autonomous pictures of the sky all night, why not give it a shot? But in doing so, many hackers are recognizing a fact well-known to traditional telescope jockeys: seeing a few stars is easy, seeing a lot of stars is another story entirely.

The problem is that stars are fairly dim; a problem compounded by the light pollution you get unless you’re out in a rural area. You can’t just brighten up the images either, as that only increases the noise in the image. A programmer always in search of a challenge, [Benedikt Bitterli] decided to take a shot at using software to improve astrophotography images. He documented the entire process, failures and all, on his blog for anyone else who might be curious about what it really takes to create the incredible images of the night sky we see in textbooks.

In principle it’s simple: just take a lot of pictures of the sky, stack them on top of each other, and identify which points of light are stars and which ones are noise artifacts. But of course the execution is considerably more difficult. For one thing, unless the camera was on a mount that was automatically tracking the sky, the stars will have slightly moved in each image. To help with this process, [Benedikt] used a navigational trick that humanity has relied on for millennia: mapping constellations. By comparing groupings of stars in each image, his software is able to accurately overlay each image.

But that’s only one part of the equation. In his post, [Benedikt] goes over the incredible amount of math that goes into identifying individual stars in the sea of noise you get when a digital image sensor looks into the black. You certainly don’t need to understand all the math to appreciate the final results, but it’s a fascinating read for those with an interest in computer vision concepts.

This kind of software is precisely what you want to pair with your 3D printed star tracker, or even better a Raspberry Pi sky monitoring station.

[Thanks to Helio Machado for the tip.]

Classifying Crystals With An SDR Dongle

June 6, 2018 by 4 Comments

When it comes to radio frequency oscillators, crystal controlled is the way to go when you want frequency precision. But not every slab of quartz in a tiny silver case is created equal, so crystals need to be characterized before using them. That’s generally a job for an oscilloscope, but if you’re clever, an SDR dongle can make a dandy crystal checker too.

The back story on [OM0ET]’s little hack is interesting, and one we hope to follow up on. The Slovakian ham is building what looks to be a pretty sophisticated homebrew single-sideband transceiver for the HF bands. Needed for such a rig are good intermediate frequency (IF) filters, which require matched sets of crystals. He wanted a quick and easy way to go through his collection of crystals and get a precise reading of the resonant frequency, so he turned to his cheap little RTL-SDR dongle. Plugged into a PC with SDRSharp running, the dongle’s antenna input is connected to the output of a simple one-transistor crystal oscillator. No schematics are given, but a look at the layout in the video below suggests it’s just a Colpitts oscillator. With the crystal under test plugged in, the oscillator produces a huge spike on the SDRSharp spectrum analyzer display, and [OM0ET] can quickly determine the center frequency. We’d suggest an attenuator to change the clipped plateau into a sharper peak, but other than that it worked like a charm, and he even found a few dud crystals with it.

Fascinated by the electromechanics of quartz crystals? We are too, which is why [Jenny]’s crystal oscillator primer is a good first stop for the curious.

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Roll A Black Box For Your Wheels

June 6, 2018 by 22 Comments

Telemetric devices for vehicles, better known as black boxes, cracked the consumer scene 25 years ago with the premiere of OnStar. These days, you can get one for free from your insurance company if you want to try your luck at the discounts for safe driving game. But what if you wanted a black box just to mess around with that doesn’t share your driving data with the world? Just make one.

[TheForeignMan]’s DIY telematics box was designed to pull reports of the car’s RPM, speed, and throttle depression angle through the ODBII port. An ODBII-to-Bluetooth module sends the data to an Arduino Mega and logs it on an SD card along with latitude and longitude from a NEO-6M GPS module. Everything is powered by the car’s battery through a cigarette lighter-USB adapter.

He’s got everything tightly wrapped up inside a 3D printed box, which makes it pretty hard to retrieve the SD card. In the future, he’d like to send the data to a server instead to avoid accidentally dislodging a jumper wire.

If this one isn’t DIY enough for you to emulate, start by building your own CAN bus reader.

32 Shades Of Gray

June 6, 2018 by 16 Comments

The ATtiny85 is an incredible piece of engineering. In just eight pins, you get a microcontroller with just enough oomph to do some really heavy lifting. You get an Open Source toolchain, and if you’re really good, you can build your own programmer. It does have its limits though; there isn’t a whole lot of Flash, and of course you’re always going to need a few extra pins.

For his Hackaday Prize entry, [danjovic] is pushing whatever limits are left with the ‘tiny85. He’s using it as a test pattern generator, pushing out pixels to any old TV. The entire circuit is powered by a coin cell, and the entire thing fits in a Tic-Tac box.

The heart of the project, as you would expect, is a resistor ladder using all six available pins, using five for luminance and one for the sync. That is thirty-two shades of gray, if you’re keeping track. The trick is using the internal PLL and a bit of math to calculate the proper resistor values. The result is just a test pattern, yes, but [danjovic] managed to get a test pattern that has a resolution of 850 pixels across. That’s not bad by any measure.

Of course, if grayscale isn’t your thing, you can also use the ‘tiny85 to send Never The Same Color over the air or even push out the jams over a VGA port.

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The Hacky Throttle Repair That Got Me On The Road Again

June 6, 2018 by 82 Comments

Old cars are great. For the nostalgia-obsessed like myself, getting into an old car is like sitting in a living, breathing representation of another time. They also happen to come with their fair share of problems. As the owner of two cars which are nearing their 30th birthdays, you start to face issues that you’d never encounter on a younger automobile. The worst offender of all is plastics. Whether in the interior or in the engine bay, after many years of exposure to the elements, parts become brittle and will crack, snap and shatter at the slightest provocation.

You also get stuck bolts. This was the initial cause of frustration with my Volvo 740 Turbo on a cold Sunday afternoon in May. As I tried in vain to free the fuel rail from its fittings, I tossed a spanner in frustration and I gave up any hope of completing, or indeed, starting the job that day. As I went to move the car back into the driveway, I quickly noticed a new problem. The accelerator was doing approximately nothing. Popping the hood, found the problem and shook my head in resignation. A Volvo 740 Turbo is fitted with a ball-jointed linkage which connects the accelerator cable to the throttle body itself. In my angst, the flying spanner had hit the throttle body and snapped the linkage’s plastic clips. It was at this point that I stormed off, cursing the car that has given me so much trouble over the past year.

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