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Published on: September 26, 2013 / Comments: None

Building a noise generator with transistors

Believe it or not, it’s actually quite difficult to generate random numbers on computers and microcontrollers.  I’m talking about true random.  A lot of the randomness computers use isn’t random at all, it’s predictive (or pseudo random).  Difficult, but still predictive.   It’s important when doing cryptographic functions to use a good random source.

So f4grx decided to build a random circuit and do some analysis on it.  The circuit design is built around the idea of using an open collector on a transistor.  What’s essentially going to happen is tiny electrical noise in the air is going to cause the circuit to produce 1′s and 0′s which then can be used to plot random.

Interesting read.  Check out f4grx’s experience.

Published on: September 22, 2013 / Comments: 2

Lazy Sunday Links – 9/22/2013

It’s Sunday again, time to take a break from watching your favorite NFL team lose and learn something somewhat productive.

First up, you should fire up your 3D Printer and make yourself a set of these cool 8bit video game coasters.

Not in the mood for some video game coasters? Well did you know there are more places to get 3D models to print for your 3D Printer other than Thingiverse ?  There’s Defcad which commonly has all those items that people are forced to take down other places, and Yeggi which seems to just scour the web hunting models.  If you are making industrial designs like PCB layout, there’s 3dcontentcentral.  That should get you going.

You’ve obviously heard of FFT or Fast Fourier Transform, you have it on your trusty O’Scope and when you look at it, you think you see valuable information.  But what exactly is a Fourier Transform?  Check out the interactive guide to Fourier Transform so you can learn something.

Looking for somewhere to host your software project, not a fan of GitHub?  Srchub is just starting out, but offers subversion, git, mercurial, wiki, issue tracker.  Lets you assign multiple collaborators and also make private repositories.  Not a bad gig for free.

You JavaScript/Node.js guys have probably seen the Espruino microcontroller.  A micro that can be developed using JavaScript.  But did you know there is another one ?  The Tessel.  This one’s got on-board wi-fi.

Published on: September 15, 2013 / Comments: None

Lazy Sunday Links – 9/15/2013

Sunday is a good lazy day. Time to learn stuff and bang out some easy hacks.


Chirp is a Javascript toolkit for creating chiptunes.  Only works in Google Chrome but sounds retro-tastic and actually sounds pretty good.

Voltage dividers are an essential skill to learn when building circuits. Go learn some voltage diviers.

Transmit data serially without a Microcontroller.  Uses a specialized IC by Holtek to transmit and receive, but really quite useful if you have some data you want to move and don’t feel like adding a Microcontroller to your project!

The gMax is a pretty large 3D Printer on kickstarter.  It boasts a 16″ x 16″ x 9″ print volume.  Wow that’s some large prints!

Don’t understand how hobbyist FDM 3D Printers work ?  Here’s a writeup on how they work.

The illustrated guide to crypto hashes.  Informative

Tuning an RTOS can be daunting to pick the right scheduling algorithm. How to select the right algorithm using system modeling.

If you’re not a VIM guru, you’re probably using the nano text editor.  Here’s some tips to make your nano experience a little more pleasurable.  Works on the Raspberry Pi too.


Published on: September 6, 2013 / Comments: None

555 Timer Chip Music Player

Steve posted a detailed video showing off his entry for the 2013 Ottawa Mini-Maker Faire.  A 555 Timer Chip Music Player. The beauty of the project is its simplicity.

As paper passes over individual copper plates any number of wires can drop through the holes to make contact. The length of the holes determine how long a note is played and the resistors attached to the copper plates adjust the frequency of the square wave which generates the tones.  This is the perfect project for getting your kids excited about electronics. Check out the schematic and additional build photos after the break.


Published on: August 30, 2013 / Comments: None

Can’t get enough Raspberry Pi CarPuter’s

Title says it all, we can’t get enough of people doing cool car stuff with their Raspberry Pi’s.  Each one is a little bit different and have a little different purpose.  So up is Keith’s Toyota Echo.  Keith is going green, he wants to watch the environment and his wallet.

So he’s got his Raspberry Pi, an OBD-II sensor, and a Nokia LCD.  He’s written an app in python that reads his vehicle speed and mass air flow sensor.  From that he is able to calculate his estimated fuel consumption at that specific point in time.   He’s logging this data in a SQLite database and displaying it in real-time on the LCD.   Nice job Keith.

Source code and build here.

Published on: August 24, 2013 / Comments: None

Monitoring your filament’s strain with a load cell

Mark is on a quest for that perfect 3D Print.  On his journey he came up with a cool idea to design an extruder with a load cell built-in.  It’s a bowden style extruder and as the filament is pushed into the hot end it records the extra load.

He’s been actively testing different variables such as feed rates, temperatures, and retraction speed.  While doing so he’s been recording and graphing how each variation performs.  Typically when you calibrate your printer settings, you mainly just look at the output of how it’s performing.  Having this inside knowledge has let Mark gain optimal output settings by identifying problem areas (without looking at the leftover stringy plastic hairs).

Mark believes (and I agree) that what he has uncovered is just the tip of the potential of his filament force sensor design and has numerous possibilities.

Check out his entire write-up as well as his collected data here.

Published on: August 6, 2013 / Comments: None

Enabling hardware random numbers on your Pi, and explore randomness

Recently a driver has been released for the Raspberry Pi that enables the hardware random number generator on the Pi’s processor.  The numbers are generated by tiny thermal fluctuations in the processor.  On the linux side after the driver is loaded a new /dev node appears.  Once installing the rng-tools rngd it will seed your /dev/random with entropy from the hardware random number generator.

Some cool things are to visualize your random data, or to listen to it.  Check out the article or complete instructions and a little theory.