A Random USB… Hourglass

December 21, 2009 by 20 Comments

[Peter] thought of a creative, way to generate random entropy for under $100.

The USB Hourglass combines a sand timer with a rotating mechanism and an optical beam through the center of the timer to observe the falling sand. The amount of light reaching a detector is digitized at frequent intervals and processed by a microcontroller to determine when to rotate the hourglass. The digitized light levels are also sent by USB to a host PC where they can be used as a source of random entropy. Power is supplied over the USB cable.

With the USB Hourglass, the user can look at the sand falling through the center of the hourglass and monitor the randomness in the USB output data. And one can read the code line-by-line, compile it, and upload it to the microcontroller using only open-source and widely supported tools.

Advent Wreath From Parts You Have On Hand

December 20, 2009 by 9 Comments

Here’s an advent wreath made from six parts and a paper clip. Powered by a CR2032 3v button cell, the circuit has been free-formed using a paper clip as the conductor. We love the “dead bug” style of construction used with the ATtiny13 microcontroller because it adds an extra level of intrigue for the uninitiated. This project build on the flickering circuit we saw last year and uses the LEDs as light sensors, only turning on when a certain darkness level has been reached.

We used a tiny13 with our Menorah project last year and still have some lying around that we can use for this. We’re sure you’ve got at least a couple of low-pin-count micros on hand. If you don’t, you should!

New AVR Simulator For Linux

December 20, 2009 by 29 Comments

simavr is a software simulator for the AVR line of microcontrollers. You might be asking why anyone would write this sort of thing considering the simulator provided with AVR Studio is a wonderful tool? Well, a lot of folks don’t run Windows and don’t wish to use that development environment even if Wine or Virtualbox could make it happen.

We haven’t tried it out ourselves yet. There is a discussion thread going that reports some positive results of using simavr with GDB and AVR Eclipse. It’s a new package, but so far it seems to have put its best foot forward. Currently there is support for ATtiny25/45/85, ATtiny13, ATmega48/88/168, andATmega164/324/644 chips. Several of the common on-chip peripherals are already supported with the others on the way.

Have you tried it out? Let us know what you think in the comments.

[IC Photo]

Sarrus Linkage 3d Printer

December 20, 2009 by 21 Comments

[fdavies] has been working on his own 3d printer. He is using printed parts, but unlike the RepRap he’s purposed Sarrus linkages in his design. If it works, this should remove the need for precision rods in building these types of CNC based machines. He’s also recovered DC motors and optical encoders from some inkjek printers. Given that many retailers require you to take junky inkjets home when you purchase a computer we’re betting you’ll find friends happy to part with their unused hardware. We’re impressed with the motion of the prototype seen after the break. Let’s hope this leads to the next generation of affordable 3d printers.

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Don’t Point That At Me

December 20, 2009 by 10 Comments

Some things are made to look steam punk but others are steam punk. This example of the later is a camera made mostly of brass. The body has been soldered together with only a shutter and lens being purchased for the project. There is a viewfinder and separate range finder to determine the proper focus for pictures as this is not a single lens reflex.

It should be obvious by now that this is a film camera. It relies on the photographer to turn the winder until an arrow on the knob lines up with a mark on the body for proper alignment. If you set out to make one of these, perhaps you should also manufacture your own film for it.

[via Dvice]

Better Resistors From A Pencil

December 20, 2009 by 37 Comments

Many of us here in the office (myself included) can’t tell the difference, but the audiophiles out there who want the best sound from their resistors should check out [Troel’s] write-up for making your own non-inductive graphite resistors. Graphite resistors have the traits for being non-inductive, have a negative temperature coefficient, and supposedly sound better. We liked the detail of his tutorial and how he gives many examples for making your own graphite resistor.

[Thanks Maxime]

Bluetooth Based Pseudorandom Number Generation

December 19, 2009 by 19 Comments

[MS3FGX] has done an interesting study about using Bluetooth adapters as a source for Pseudorandom Number Generation (PRNG). As it turns out, the Bluez package has a function that calls a remote Bluetooth adapter to return a random number. He picked up 10 compatible adapters for about $30 from DealExtreme and set about assembling some numbers to see how this compares to an OS-based PRNG.

Because millions of samples are needed for an accurate comparison, time became a problem. The adapters are a little bit slow responding to a request, sending just 4800 numbers in the first 30-second test. This can be overcome with multiple adapters being accessed by multiple computers for hours at a time. What can this be used for? Your guess is as good as ours, but [MS3FGX] has done a great job of writing up his tests. He’s also made a set of 20.7 million randomly generated values available if you want to generate your own statistical analysis.