Projecting Video Directly Onto The Retina

April 9, 2012 by Brian Benchoff 30 Comments

With the head-mountable, augmented reality Google Glass capturing tons of attention in the press, it was only a matter of time before we saw a DIY retina projector. This isn’t a new build; [Nirav] has been working on it for a few months, but it might just be time for this information to be useful to someone.

A retina projector focuses laser light though beam splitters and concave mirrors to create a raster display on the back of your eye. There’s an incredible amount of research into this field, but not many DIY projects. To make this project a reality, [Nirav] picked up a SHOWWX laser video projector and mounted it in a 3D printed frame along with a few pieces of optical equipment.

[Nirav]’s build isn’t without its drawbacks, though. The exit pupil, or the apparent size of the image, is only about 1.5 mm wide and much too small to be of any real use. Also, commercial retina projectors have an output of a puny 2 microwatts, where [Nirav]’s laser projector puts out 200 millwatts. This is more than enough to permanently damage your eye.

Build An Induction Heater And Become A Metalsmith

April 8, 2012 by Brian Benchoff 84 Comments

If you’ve ever wanted to forge, cast, or smelt metal, this project is right up your alley. It’s a 30 kVA induction heater built by [bwang] over on Instructables. It gets hot enough to melt and forge steel, iron, and aluminum.

An induction heater operates by surrounding the object to be heated with a coil carrying high frequency AC current. Basically, the entire setup acts like a huge transformer with a shorted secondary. To get these currents into a workpiece, [bwang] used a TL494 PWM controller as an oscillator. The output of the TL494 is filtered and amplified a few times to generate a huge amount of AC current.

Larger versions of [bwang]’s induction heater are found in foundries and forges all across the land; even though this small version sucks down 50 A out of a dryer or stove outlet, induction heating is very efficient. We’re actually wondering why we don’t see many home blacksmiths using induction heating, so we’ll leave that for our readers to discuss in the comments.

[sessions] reminded us of this induction heater from a few years ago. A little smaller, but still usable.

GSM Modem Means Wireless Serial Connections

April 6, 2012 by Brian Benchoff 33 Comments

By now, most of us have seen have seen one of those GSM to wi-fi hotspot bridges. They’re interesting devices, and being able to carry a small wireless router with you at all times is very handy. Surprisingly, we haven’t seen many builds featuring these portable wireless hotspots, something probably due to the effort in breaking out a serial connection on these devices. The people at Open Electronics decided to build their own small serial-enabled cell phone modem, a boon to someone wanting a serial connection to any place with a cell tower.

The Open Electronics GSM/GPRS/GPS modem includes a header for an FTDI USB serial chip and a GSM module. Plug one into your computer and after a few short commands into a terminal, you’ve got a serial connection to nearly anywhere in the world.

The cost of the setup is a little high – around 80€ or $100 USD – and you probably should buy more than one so you can also receive data. While it is more expensive than the XBee wireless boards we see often, this GSM modem isn’t limited to the 300 foot range of the XBee. We’ll probably see this in a high altitude balloon before too long.

Reverse Engineering A Futaba SBUS Remote Control

April 5, 2012 by Brian Benchoff 18 Comments

In the world of model aircraft, Futaba’s SBUS system is a big deal. Instead of having one servo per channel, the SBUS system allows for 16 proportional controls and two digital channels for each receiver. Basically, if you’re building an awesome plane with retracts on the landing gear and bomb bay doors, this is what you want to use. [Michael] wanted to use a few SBUS servos for a project he’s working on, so of course he had to reverse engineer this proprietary protocol.

Each SBUS servo operates over a single 100kbps serial connection with a few interesting twists: the signal is transmitted as big endian, but the individual bytes are little endian, something [Michael] figured out after stumbling across this month old mbed post. [Michael] used a serial library written by [fat16lib] and was able to change the parity and stop bits along with a simple hex inverter. Everything worked perfectly when the servo was connected to a an Arduino Mini.

Even though the SBUS system requires special Futaba servos, we can easily see how useful [Michael]’s work would be to outrageously complex robots or cnc machines. Check out the video after the break for a quick demo of [Michael]’s breadboard controlling one of these SBUS servos.

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Building A Combination Lock With Logic Chips

March 30, 2012 by Brian Benchoff 10 Comments

The component gods must have smiled on [Darrell], because he recently ran into a cabinet full of 7400-series logic chips for sale at his local college surplus. All the regulars were there – flip-flops, logic gates, and SRAMs – in DIP packages. the 7400-series of logic chips gets very esoteric as the numbers increased, so when [Darrell] found a 74ALS679 address comparator, he didn’t quite realize what he had. After a quick review of the relevant datasheet he had a fairly good idea of the actual function of this chip and decided to make a combination lock.

From the datasheet, [Darrell] figured out how this small logic chip can compare two 12-bit addresses with only 20 pins: each of the 12 address pins are hardwired to match a single four-bit value. If the four-bit ‘key’ is set to 0110, the first six address pins are tied low, and pins 7-12 are tied high. After wiring up his address comparator to a trio of Hex dip switches, [Darrell] had a combination lock that used the word ‘FAB’ as a key.

In the 7400-series of logic chips, there are some oddballs; the 7447 seven-segment display driver is useful, but the 74881 ALU and 74361 bubble memory timing generator aren’t exactly something you would find in a random component stash. If you’ve got a weird logic chip build (there’s a 300-baud modem, you know), send it on in. You can check out an animated gif of [Darrell]’s lock after the break.

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Press Play On Tape For Your Fignition

March 26, 2012 by Brian Benchoff 13 Comments

[Julian Skidmore] has been busy improving the Fignition, a tiny AVR-powered educational computer, to support loading programs from a cassette tape.

We first saw the Fignition after the BBC decided to cover an old-school hacker dedicated to improving computer education with a simple ‘bare-metal’ computer. [Julian]’s Fignition harkens back to the days of very simple computers like the BBC Micro and the TRS-80, and encourages students to work with PEEKs and POKEs instead of the decades of cruft that have accumulated on our laptops and desktops.

Because the Fignition is designed to hacker and student-friendly, it’s entirely possible to build a keyboard, or even build a Fignition on stripboard. Now, these students have much improved hardware that allows for saving and loading programs to tape (or any audio recorder) , and even a graphic video mode with 160×160 resolution.

We know it seems a little weird, but kids graduating High School this year were born in 1994, and in all probability have never laid their eyes on a Commodore 64, Sinclair Spectrum, or the other 1980s microcomputers an entire generation learned on. The Fignition is an attempt to stem the tide of ignorant masses unaware of how far the computer has progressed in the last 30 years, and we love it for that.

SimpleCortex, For When An Arduino Is Too Wimpy

March 25, 2012 by Brian Benchoff 46 Comments

Sometimes, an Arduino just doesn’t have enough horsepower. Whether you’re gathering loads of sensor data and sending it over the web via Ethernet, or just trying to build a home-brew video game, it’s very easy to run into the limitations of the Arduino platform. [Rik] and his fellow classmates may have a solution to this problem with their SimpleCortex development board.

The SimpleCortex began as an answer to the Arduinos [Rik] and his classmates had to use at school. The SimpleCortex gets its name from an ARM Cortex M3 microcontroller running at 120MHz; more than fast enough to do some very interesting things, and 512kB of Flash to hold much larger programs.

The Arduino IDE is admittedly terrible, and big projects are a pain in the butt with a tiny 8-bit micro. SimpleCortex improves upon this development environment by using the free CoCenter IDE put out by CooCox. The CoCenter IDE supports debugging and code completion, standard features on any serious desktop programming environment.

The SimpleCortex has Arduino-compatable header pins, so it should be easy to use existing shields, like the 3G modem we saw this week and the NTSC video IO shield that can do object tracking. While the specs of the SimpleCortex put it in a distant second to the Raspberry Pi, sometimes you just don’t need Linux, but a standard AVR or PIC isn’t quite enough.

There’s no word on when this board will be available, but the team is working with ITead Studio to officially release boards into the wild.