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Nimble Dodgebot is Super Skittish


For one of [Aron's] recent robotics modules at college he was tasked with building a small robot. He decided to make project Dodgebot, a cute and extremely quick robot that won’t run into things!

The body is made of perforated steel and supports the motor boxes with wheels (stolen from a toy perhaps?), two IR sensors, and the tidy protoboard on top to contain the electronics — seriously check out the wiring on it!

To control it he’s using an 18-pin dsPIC30F3012 and a SN754410NE driver. The robot works by detecting different states based on the distance measurements from each sensor, and then varying the output to each motor. It’s extremely quick and quite fun to watch as it seems to dodge everything in its path! See for yourself, after the break. 

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WS2811 SPI Driver Using One Transistor and Passives


We love the WS28xx projects because even if we never plan to use them, the signal timing is like the most addictive puzzle game ever. For instance, check out this WS2811A driver which uses hardware SPI to generate the signals.

The WS28xx offerings place a microcontroller inside an RGB LED, allowing them to be individually addressed in very long chains or large matrices (still a chain but different layout). But the timing scheme used to address them doesn’t play well with traditionally available microcontroller peripherals. [Brett] had been intrigued by some of the attempts to bend hardware SPI to the will of the WS2811 — notably [Cunning_Fellow's] work featured in this post. He took it a great step forward by simplifying the driver to just one transistor, three resistors, and a capacitor.

Click through the link above for his step-by-step description of how the circuit works (it’s not worth re-explaining here as he does a very concise job himself). The oscilloscope above shows the SPI signal on top and the resulting timing signal below. You will notice the edges aren’t very clean, which requires the first pixel to be very close to the driver or risk further degradation. But, since the WS28xx drivers feature a repeater which cleans up signals like this, it’s smooth sailing after the first pixel.


Kitchen Computer Hides in Pantry Door


You might look at the images above and think “oh neat” and then go about your business. But you’d be missing a great motorized hidden computer build. We simply must insist that you click on that link and look at all that went into it. Do it. DO. IT.

Still here? Okay, we’ll give you the gist and then you won’t be able to help yourself. First off, [Designforhire] built that door completely from scratch using skills that your average hacker wields. At first glance you’d think it was a retrofit or done with serious woodworking tools (quality table saw, router table, etc.). This actually started with a simple frame out of 2″x3″ pine studs. This is faced with Masonite which was affixed with glue and brads. From there the upper half was outfitted with a dry-erase panel, and trim pieces were added.

Now the hack really starts to get interesting. The opening for the monitor and the keyboard are both motorized. An old cordless drill (borked handle and dead battery) was cannibalized for its motor which is run using the two black switches just above the left corner of the monitor. When closed, a dry-erase calendar covers the monitor and a blank panel keeps the keyboard secret. The computer itself is actually in the basement, with cables running down the hinged side of the door and through a hole in the jamb.

We didn’t see a video showing off the build, but you can satisfy that craving by looking back at the Kitchen HAL installation from a few years back.

GPS For A Graphing Calculator

GPS [Chris], graphing calculator hacker extrordinaire, has seen a few of his projects show up on the front page of Hackaday, mostly involving builds that turn graphing calculators like the TI-84 Plus shown above into something that copies a few features from a smartphone. His latest build, a hardware GPS module attached to the TI-84 Plus, is yet another feather in his cap of awesome and impractical addition to a classic piece of hardware.

There were two major technical challenges behind adding GPS to a graphing calculator. The first of these was powering a GPS sensor. Many a calculator modder has put a lot of work into documenting the USB port on the 84 Plus, revealing it is a USB OTG port, capable of serving as a host or device. It also supplies 5V of power to just about anything, burning through batteries as a result.

The next challenge was reading the data coming off the GPS sensor at 4800bps.The TI-84 Plus series of calculators have a series of interrupts that can fire at fractions of the 15MHz clock. By setting the timer up to fire every 197 clock ticks and dividing again by 16, [Chris] can read data at 4758.9bps. It’s close enough to get most of the data, and the checksum included in the NMEA protocol allows the software to discard bad messages.

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Retrotechtacular: Bakelite Plastics


[ColdTurkey] sent in a really great video for this week’s Retrotechtacular. It’s a half-hour promo reel about Bakelite Plastic. There is so much to enjoy about this film, but we’ve been overlooking it because the first six minutes or so consist of an uncomfortably fake interview between a “Chemist” and “Reporter”. They are standing so close to each other that it’s violating our personal space. But endure or skip ahead and the rest of the video is gold.

Bakelite is an early plastic, and putting yourself in the time period it’s very easy to see the miracle of these materials. The dentures being molded above are made out of phenol formaldehyde resin (to us that sounds like something you don’t stick in your mouth but what do we know?). The plastic pellets take on the shape of the mold when heated — we don’t know if this where the name comes from or if it’s a variation on the name of the chemist who discovered the material: [Dr. Leo Baekeland]. This was the first synthetic plastic, and came at just the right time as it was heavily adopted for use in the electronics and the automotive industry. Both of which were forging new ground at the time.

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A USB Connected Box-o-Encoders


[Colin] loves his PicoScope, a USB based “headless” oscilloscope. While using it he found himself longing for a classic oscilloscope interface. Mouse clicks just weren’t a replacement for grabbing a dial and twisting it. To correct the situation he created his USB-Connected Box-o-Encoders. The box maps as a USB keyboard, so it will work with almost any program.

[Colin] started by finding encoders. There are plenty of choices – splined or flatted shaft, detents or no detents, panel, PCB, or chassis mount. He settled on an encoder from Bourns Inc. which uses an 18 spline shaft. His encoder also includes a push button switch for selection. With encoders down, knobs were next. [Colin] chose two distinct styles. The two knob styles aren’t just decorative. The user can tell which row of knobs they are on by touch alone. Electronics were made simple with the use of a Teensy++ 2.0. [Colin] used a ATUSBKey device running Teensy software, but says the Teensy would have been a much better choice in terms of size and simplicity.

Once everything was wired into the box, [Colin] found his encoders would “spin” when the knobs were turned. They are actually designed to be PCB mounted, and then screwed into a control panel. Attempts to tighten down the panel mounting nut resulted in a broken encoder. Rather than redesign with purely panel mounted encoders, [Colin] used a dab of epoxy to hold the encoder body in place.

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Manual Bitcoin Transactions


For something that’s used for such banal transactions like buying drugs and sending the Jamaican bobsled team to the Olympics, cryptocurrencies such as Bitcoin are actually very impressive pieces of software. It’s a very ingenious solution to the Two Generals Problem, and the fact it made a few Bitcoin early adopters very, very rich doesn’t hurt either. [Ken Shirriff] decided to take a look at the Bitcoin protocol by creating a Bitcoin address and transferring a small amount of bitcoin to that address, manually. It’s a great look at how the Bitcoin protocol actually works, and how ingenious this protocol actually is.

[Ken]‘s first task was to create a Bitcoin address. This is a 256-bit private key is the basis for the Bitcoin wallet private key (after being encoded as ASCII characters), and as the 512-bit public key (after being sent through an elliptic curve algorithm). The 512-bit public key is then hashed with SHA-256 and RIPEM 160 to generate the 160-bit public key hash and the Bitcoin address.

After creating a bitcoin address and wallet, [Ken] set out on manually creating a transaction. The idea was to buy a few cents (USD) from Coinbase and send them to his manually created address. This involved creating a transaction according to the Bitcoin spec and signing the transaction. Signing each Bitcoin transaction is the key to Bitcoin’s security, and is done with a small bit of code written in the Bitcoin scripting language.

With everything written in Python, [Ken] was ready to send his transaction off into the Bitcoin network. This was done by finding a few peers on the Bitcoin network and sending off a few packets. After a little bit of mining on the network, [Ken]‘s transaction went through, confirmed by a deposit into his Bitcoin wallet.

It’s an awesome writeup and impressive achievement to manually send a few Bitcoins from one wallet to another. More impressively, [Ken] provided some amazing insight into how the Bitcoin protocol works, and how much work went into its creation.


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