Centimeter-level Precision GPS For $900

[Colin] and [Fergus] have been working with GPS for years now, and like most builders of really cool things, they’re often limited by the precision of off-the-shelf GPS units. While a GPS receiver is usually good for meters of accuracy,  this just isn’t good enough for a lot of projects. What you need is centimeter-level accuracy, something the guys have managed to do with their Piksi GPS receiver.

Where most GPS receivers only look at the data coming from the GPS satellites orbiting overhead, the Piksi uses another technique, real-time kinematics (RTK), to determine the receiver’s location with exacting precision. The basic idea behind RTK is to look at the carrier frequency of the GPS signals at 1575.42 MHz. This frequency has a wavelength of 19 cm, compared to the alternating 1s and 0s of the that are transmitted at around 1 MHz, or about 300 meters between each bit. While centimeter-level precision isn’t possible with only one receiver, two of these Piksi boards – one base station and one on a vehicle, connected via radio link – can make for a very exacting high-accuracy GPS receiver.

Previously, commercial RTK GPS systems have cost thousands of dollars – making a quadcopter or other homebrew project that relies on this level of precision nonsensical. [Colin] and [Fergus] have built hardware that can bring the price of this setup to under $1000. As a bonus, the Piksi board can also receive from other constellations such as Galileo and GLONASS. A very impressive piece of hardware, and we can’t wait to see the applications.

No Computer Ambilight Clone Uses A Computer

It may seem confusing that you’re looking at a Raspberry Pi when this hack is about an Ambilight clone system that doesn’t need a computer. The point here is that this system works no matter what your video source is, where many projects in the past have required the video to be playing from a computer.

This hack follows in the same path of the ARM based custom job we was almost a month ago. Just like that project you use an HDMI splitter to gain access to the feed going to your television. The split signal is fed into an HDMI to composite video adapter. The composite signal is captured by a USB video encoder. The GPIO header drives a strip of addressable RGB LEDs. The whole thing is powered as one using a bit of cable hacking.

It’s slightly convoluted. But all of the components are easy to source and relatively cheap. The one caveat is that it works best if you are already using a hardware HDMI source selector instead of the one build into your TV. That way there is just one HDMI cable going to the television, and this can siphon off of that feed.

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Overclocking Your Bitcoin Miner

The name of the game in mining Bitcoins isn’t CPUs, GPUs, or even FPGAs. Now, hardcore miners are moving on to custom ASIC chips like the Block Erupter, For around $100 USD, you too can mine Bitcoins at 300 MH/s with 2.5 Watts of power and a single USB port. This speed isn’t enough for some people, like [Jeremy] who overclocked his Block Erupter to nearly twice the speed.

[Jeremy] begins his tutorial with a teardown of the Block Erupter hardware. Inside, he found a custom ASIC chip, an ATTIny2313, a USB UART converter, and a voltage regulator for the ASIC. By changing out the 12 MHz crystal connected to the ASIC and fiddling with the voltage with a trim pot, [Jeremy] was able to overclock the ASIC core from 336 MHz to 560 MHz. Effectively, he’s running two Block Eruptors for the price of one with the potential to actually make back the purchase price of his hardware.

It must be noted the 560 MHz figure comes from replacing the 12 MHz crystal with a 20 MHz one, and this mod only lasted about 20 minutes on [Jeremy]’s bench until the magic blue smoke was released. He recommends a 14 or 16 MHz crystal, netting a new speed of either 392 MHz or 448 MHz for a stable mod.

Android Hack Adds Missing Chromecast Button To Netflix App

We finally got our hands on a Chromecast over the weekend and we love it! But it wasn’t without a bit of a speed bump. Including a quick initial setup, we had a YouTube video playing in our living room about three minutes after the package hit our mailbox. But we spent the next twenty minutes feeling like a moron because we couldn’t get the Netflix app on an Android phone to cast the video. Turns out there is a bug in the Netflix app that doesn’t add the Chromecast icon for all devices.

The issue is that the newest version of the Netflix app isn’t pushed to all devices. A fix is on the way, but we’re not good at waiting. We used this technique to trick Netflix into thinking we have different hardware. Notice from the screenshots above that one lists our device as an LG-P769 manufactured by LGE. That’s how our /system/build.prop file originally looked. By using the BuildProp Editor app we changed those settings to Nexus S by samsung. After rebooting several of our apps were missing from the app drawer, including Netflix. But they all still worked hitting the Play Store for reinstallation and we now have no problem casting Netflix.

Hackaday Links: Sunday, August 4th, 2013

hackaday-links-chain

[Craig Turner] shows that simplicity can be surprisingly interesting. He connected up different colors of blinking LEDs in a grid. There’s no controller, but the startup voltage differences between colors make for some neat patterns with zero effort.

Remember the 3D printed gun? How about a 3D printed rifle! [Thanks Anonymous via Reason]

While we’re on the topic of 3D printing, here’s a design to straighten out your filament.

It takes four really big propellers to get an ostrich off the ground. This quadcopter’s a bit too feathery for us, but we still couldn’t stop laughing.

This Kinect sign language translator looks pretty amazing. It puts the Kinect on a motorized gimbal so that it can better follow the signer. We just had a bit of trouble with translation since the sound and text are both in Hebrew. This probably should have been a standalone feature otherwise.

Work smarter, not harder with this internal combustion wheelbarrow. [via Adafruit]

LED Strip Cape Drives Kilometers Worth Of LEDs

led-strip-cape

[Hudson] is looking to drive a lot of LEDs. A driver that effectively addresses kilometers worth of LED strips isn’t an easy thing to come by. So he’s in the process of designing his own BeagleBone Cape to do the work. Above you can see the board layout he’s working with. Notice the set of repeating red footprints in the center? Those are pads for 32 RS485 connectors!

Of course this is all in preparation for Burning Man where the mantra seems to be: he who has the most LEDs wins. Well, unless you’re the sort that likes to work with flames. But we digress. The scaling problem that [Hudson] is dealing with hinges around his desire not to include ridiculous numbers microcontrollers and the need to beef up the 3.3V logic levels of the BeagleBone to travel further on the data bus of the strips. By leveraging the RS485 protocol — which is designed to carry data over long distances — he can get away with a single processing unit by adding an RS485 translator at each remote strip connector. He plans to use the BeagleBone’s Programmable Realtime Units feature to address the eight drivers on the cape. But first he has to solve what looks like a doozy of a trace routing problem