A Bitcoin vending machine

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Accessibility is one of the biggest hurdles facing the Bitcoin revolution, so [Mathias] found a way to give BTCs some market penetration by converting an old condom vending machine. The machine was 30 years old and required some clean up. [Mathias] also worked in a plywood adapter that attaches to the mount on the back so it can install on a wider variety of surfaces. This is an electricity-free alternative to selling coins: the machine is purely mechanical and it vends custom-made vouchers rather than the coins themselves, which you then redeem on the Kondocoin website.

The transaction isn’t as instant or snazzy as the Bitcoin briefcase converter from Defcon this year, but it still provides the advantage of an up-to-date exchange rate, as the vouchers themselves are valued at amount of Euros spent rather than a set amount of coins. The exchange rate is consulted later, when you punch in your voucher key. [Mathias] wants to share the wealth, too, and offers up the server software on github along with a detailed explanation of the process.

Put in pocket change, get bitcoins

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[gbg] put together a neat little project to get people familiarized with Bitcoins. A lot of techies know what Bitcoins are, but the impetus to download the Bitcoin client and start mining is a bit too much for some. [gbg] has a solution for this – a Bitcoin vending machine. Just dump your pocket change in the coin slot, and out comes a QR code that allows you to add Bitcoins to your wallet.

Inside this Bitcoin briefcase is a Raspberry Pi that connects to a local WiFi connection. Every five seconds, the Raspi looks at the current conversion rate of USD to Bitcoins. Once coins are deposited into the briefcase, a receipt complete with a scannable QR code is printed on a small thermal printer.

When [gbg] took this to the latest DEFCON, a lot of people were interested in the project and started shoveling change into the machine. So many people were interested that [gbg] and his compatriots are planning on turning this into a proper open-source device, complete with a bill reader and possibly an ASIC miner so the Pi can sell the coins it produces.

Check out the video below for some more info.

[Read more...]

Raspi Bitcoin miner may just pay for itself eventually

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We’re sure a lot of people out there have a Raspberry Pi or two lying around waiting for a project to come to mind.  [Dave] has an interesting solution to this orphaned hardware – use it to mine Bitcoins and perhaps put a few extra bucks in your pocket at the end of the year.

[Dave] is using a Raspberry Pi, powered USB hub, and an ASICMiner Block Erupter to do Bitcoin mining at 330 Megahashes per second. There are a few ancillary items such as a case and USB fan, but if you already have a Raspberry Pi, you’re only looking at a $50 USD investment to have a dedicated Bitcoin miner.

According to this Bitcoin mining profitability calculator, with a $50 investment that can mine at 330 MH/s, you’re looking at a hardware break even point of about 120 days. You could cut that down to just a few months if you overclock your ASICMiner, but it’s still relatively late in the game for amateur Bitcoin miners to make a substantial amount of money. Think of Bitcoin mining as more of hobby, and you’ll hopefully be more realistic about your goals.

Overclocking your Bitcoin miner

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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.

Trust hacking: How the Bitcoin system works

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[Scott Driscoll] sent us a link to his Bitcoin explanation a couple of weeks ago. We glanced at it but moved on rather quickly. It’s been popping up here and there and we finally gave it the time it deserved. This video is interesting in that it doesn’t just focus on what the Bitcoin actually is, but how the Bitcoin system works when it comes time for money to change hands.

Quite early on in the explanation he mentions that “The Bitcoin system is amazingly designed so that no trust is needed”. That’s a powerful statement. For instance, if you sell your car, one of your friends will probably tell you not to take a check. That’s because a check means you’re trusting that the buyer actually has a balance in their account to cover the transaction. With Bitcoin the transaction carries its own proof that the currency is available by including information about the past transactions through which those Bitcoins were acquired.

If you have some idea of what public/private key pairs are you’re already equipped to understand [Scott's] lecture. After you make it through the 22 minute video maybe you should get down to work doing some Bitcoin mining at home.

Raspberry Pi Bitcoin miner

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Mining bitcoins is becoming a fool’s errand, but there’s always some new piece of hardware coming out that allows those hard-core miners to keep ahead of the curve. One such piece of hardware are new custom ASIC devices that are just as fast as an FPGA while being much less expensive. A lot of these ASIC devices come in interesting packages that look just like a large USB thumb drive. Of course this is the perfect opportunity to show off what the Raspberry Pi can do by mining Bitcoins at rates comparable to the best graphics used in mining today.

The Raspberry Pi simply doesn’t have enough horsepower to mine bitcoins at any worthwhile rate. There are, however, USB ASIC devices that will mine for you at about the same speed as a high-end graphics card. Since multiple ASIC devices can be controlled through a USB hub, it’s simply a matter of plugging a USB hub into a Raspberry Pi, loading up CGminer, and letting your new PiMiner loose on a mining pool.

The Adafruit Pi Miner uses one of their really cool LCD character displays and keypad to display the current mining rate, accepted shares, and enough information for you to calculate how long it will take to break even with your Pi powered mining rig. How long that will be for this four device rig we’ll leave to the comments section.

HDMI color processing board used as an FPGA dev board to mine Bitcoins

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The blue board seen above is the guts of a product called the eeColor Color3. It was designed to act as a pass-through between your television and HDMI source device. It boasts the ability to adjust the color saturation to suit any viewing conditions. But [Taylor Killian] could care less about what the thing was made for, he tore it open and used the FPGA inside for his own purposes.

The obvious problem with this compared to a proper dev board is that the pins are not all broken out in a user-friendly way. But he got his hands on it for free after a mail-in-rebate (you might find one online for less than $10 if you’re lucky) and it’s got an Altera Cyclone IV chip with 30k (EP4CE30F23C6N) gates in it so he’s not complaining. The first project he took on with his new toy was to load up an open source Bitcoin mining program. The image above shows it grinding away at 15 megahashes per second while consuming only 2.5 watts. Not bad. Now he just needs to make a modular rack to hold a mining farm.