Arduino I2C Sniffer

May 21, 2011 by Caleb Kraft 11 Comments

[Johngineer] found himself in need of an I2C sniffer, but didn’t have one available. Necessity is the mother of invention, so he put together this I2C sniffer sketch for Arduino. The arduino will record what is going on for a set time interval, then dump the data via serial as a .csv. You then have to plot it to see what is going on. [Johngineer] recommends Livegraph, since it is portable and easy. As you can see in the code, the time interval is adjustable, but you have the physical limitations of the RAM on the board to consider. This seems like a pretty handy piece of code stored around, effectively giving you a passable I2C sniffer in a pinch.

Bay Area Maker Faire: Hackaday Has Arrived!

May 20, 2011 by Phil Burgess 16 Comments

It’s a madhouse already at the 2011 Bay Area Maker Faire. Though the show doesn’t officially start until tomorrow, Friday is “Education Day”, a special preview for local schools. As makers scramble to set up their displays, a thousand impressionable young minds seek the most cacophonous mixture of taiko drumming, ArcAttack’s musical Tesla coils, and the beeping and booping of the R2-D2 Builder’s Club.

Maker Faire is returning for its sixth year at the San Mateo Event Center, and is shaping up to be bigger and zanier than ever. We’ll do our best to provide some live updates through the weekend. As always, check out the official site for pointers on hours, admission, parking and especially public transit options.

(Photo: Colossus, the death-defying centerpiece of the Midway area of the Faire.)

Send Email, Receive Surveilance Picture

May 20, 2011 by Caleb Kraft 31 Comments

This deathstar like ball is actually an autonomous surveillance camera. [Basil] wrote in to tell us about it. The body is custom designed for the project, then 3d printed. It can be dropped anywhere, as it is battery powered for up to a month, and communicates via cellar networks. It checks an email folder once an hour and responds to any requests with a snapshot of what is going on. In the video, which you can see after the break, he gets an immediate response. You can download the sourcecode as well as the files for the enclosure here.

If you wanted to reduce costs, that case could be done away with, but we suspect it helps with some moderate weather conditioning. We would also love to see a version that rotated around that equator on command for better pictures. Great job [Basil].

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Introduction To The H-bridge Motor Controller

May 20, 2011 by Caleb Kraft 22 Comments

[Chris] sent us this fantastic tutorial, introducing beginners to H-bridge motor drivers. While many of you will consider this stuff basic, those who are trying to expand from building only things the arduino board can handle to bigger more expansive (and powerful) projects will find this quite helpful. [Chris’s] tutorial is very in depth, not only going through the construction of the basic circuit but also showing you how to make your own PCB. Pop on over there and learn some theory and some practice. Then you can build that battle bot you’ve always been dreaming of!

Using An AVR As An RFID Tag

May 20, 2011 by Brian Benchoff 11 Comments

A few years ago, [Beth] came up with the idea of using an AVR as an RFID tag. She’s gotten sidetracked with a few other projects in the meantime but her idea has surfaced again, this time as a duct tape RFID tag. The build is just four components: 0.1 µF and 1 nF capacitors, an ATtiny85 microcontroller, and 100 turns of 40 AWG magnet wire, all soldered together and placed on a duct tape substrate.

Like most RFID tags, the power is drawn from the reader through the coil, but even in low power versions the ATtiny is only rated down to 1.8 Volts. Since the microcontroller is only getting about 1 Volt from the coil, the clock oscillator of the ATtiny won’t work. This isn’t a problem in this build, because the coil is connected to the the clock input – the 125 kHz coming off the reader provides the clock. Very clever.

Of course, the microcontroller is going to need some firmware to send some bits to the reader, so she used the AVRFID firmware (check out the comments in the source for a great walkthrough) to transmit under the HID protocol, itself a derivative of [Beth]’s earlier work with the EM4102 protocol.

Not only are we impressed with this hack, we’re amazed [Beth] is still perfecting her work more than two years after her first post on the subject. That’s dedication and unbridled cleverness.

Via adafruit

DIY Spectrophotometer

May 20, 2011 by Kevin Dady 26 Comments

[Charlie] has been making a DIY Spectrophotometer, and while it is a “shambling mess of information-age technology!” it is still much better than ours. Focused around an arduino, bits of lego, and a flashlight, this creative device rotates a diffraction grating (flake of compact disc) aimed at a photo resistor. As the light spectrum is passed over the sample, the photo resistor measures how much light is reflected and that data is passed back to a pc.

As nothing is as ever easy as it should be, a big problem popped up with using a servo. It was way too course, meaning the entire spectrum would be jumped over in 6 steps. A quick robbery of a gear assembly from a floppy disk drive and the motor movement was smoothed out. A little too well because 120 degrees of the servo is not quite enough to cover the entire spectrum. Oh well there is always room for improvement.

NES Multi-cartridge

May 19, 2011 by Mike Szczys 17 Comments

Here’s a mutlicartridge hack for the original NES that [Callan Brown] put together. He spent some time snooping around the signals on the circuit board seen above until he found the trace that maps the reset signal from the game console. This will be used to cycle through the various games stored on the cart’s memory chip. The ROM images that will be stored on this cartridge are concatenated, then burned to the EPROM. Since the donor cartridge (and the ROMs which were chosen) use memory managment, the hardware can be tricked into reading the ROM from a specific point in the EPROM.

The switching itself is handled by a 74HC161 binary counter chip. The reset signal from the on-board security chip acts as a clock trigger for the counter. Some clever wiring allows the output of the counter to select the starting address for the EPROM. Each time you press the reset button it increments the counter, thereby selecting a different ROM to load. See [Callan] demonstrate the finished hack in the video after the break.

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