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Published on: October 8, 2013 / Comments: 18

NEST Thermostat torn down and analyzed

Daniel has a curiosity that most hackers like him share.  And let’s face it, we like to take stuff apart.   Some time ago, Daniel seen a previous teardown of the NEST thermostat by the ifixit guys.  Inside there is an 802.15.4 radio transceiver that isn’t mentioned anywhere in the documentation this radio is commonly used in zigbee/xbee/mesh networks.

Daniel even went as far as to ask them what the radio was for, and got stonewalled.  So Daniel decided to do his own teardown and probe at the inner workings of the thermostat even further.  One of the goals was to see if the 802.15.4 radio was ever used without them saying so.

He notes at the end that the NEST guys have announced some new products like a smoke detector, and they have in the specs the 802.15.4 radio so it makes sense that the radio is there for future upgrades for the other devices to be able to talk, but I recommend watching the teardown video, it’s long but entertaining.

Check out the video after the break.  Also more info over at Daniel’s site.


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 5, 2013 / Comments: 2

Build your own wireless modem using a 555 timer and 565 PLL

This build uses good old FSK (frequency shift keyring) technology sending 1′s and 0′s through the air.  Although its applied using infra-red, the same concept is used for RF.  Also Infra-red is still technically wireless (lol).  So on to the build.  Just in-case you want to brush up on your FSK I recommend just straight up hitting wikipedia.   (If not, here’s the TLDR version;  A steady pulse is used to represent a 1, and a variation in the pulse width is used to represent a 0)

On the transmitter side a 555 timer is set up as a Astable Multivibrator, the digital input (fed from say a microcontroller) pulls down the transistor which modifies the frequency of the 555 timer, causing a 0.  Leaving the pin high (representing a 1)  leaves the 555 timer alone.  The data is transmitted via infra-red led.

On the receiver side, a 565 PLL (Phase Lock Loop) IC locks on to the frequency of the 555 timer and outputs a 1 or a 0 when the signal alternates between the 2 frequencies.

This is a great project but mostly as an educational one.  Full post up on gadgetronicx.

Published on: August 29, 2013 / Comments: 4

How to figure out the pinout of a NPN or PNP transistor

Ever pick up a transistor without being able to read the part number to look up ?  Or can’t find it when you look it up ?  Well grab a multimeter and with a little know-how you might be able to figure it out.

First thing is to find the base, this can be done by measuring the resistance.  Once you have the base figured out, then with the tip of your finger touching the base (acting like a switch) you can determine which one is the collector, and which one is the emitter.  Sounds cool right ?

Check out the full instructions here. (fixed link)


Published on: August 26, 2013 / Comments: None

Data into smart phones and tablets via audio

You have probably seen those little dongles that let people swipe their credit card on their smart phone or tablet.  These little dongles transmit data to the device via the microphone jack.  The audio recorded is then examined and the data is either a one or a zero.

In the example described by the article, they are using a PIC and the data is encoded via manchester encoding.  A resistor and a pot are used to tweak the output level.  This is a great way to send data to a smart phone or tablet without making any crazy custom dongles but you are limited in capabilities.

Schematic and example source code is included in the post.

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 15, 2013 / Comments: 2

Run your LEDs on AC power


Dealing with mains voltage is no joke, please be careful

Running your LEDs from AC voltage is pretty efficient, you can light up a whole lot of LEDs with little effort.  Most Christmas lights you buy nowadays already do this, but as Matt points out in the video they flicker a lot.  Matt decided to set up a bridge rectifier, and a capacitor to smooth out the flickering.  As shown on the oscilloscope those simple modifications make a huge improvement!

Of course you can’t just plug the LEDs into the wall and expect it to work (and not catch fire).  A little planning is needed.  By calculating the collective voltage drop of the LEDs in series you can run a lot of LEDs with very little current limiting.  Cool hack Matt.