A Lesson In Blind Reverse Engineering – Signals Intelligence

spread sheet of binary data

In a fit of desperation, I turned to data mining tools and algorithms, but stepped back from the horror of that unspeakable knowledge before my mind was shattered. That way madness lies.

–[Rory O’hare]

Wise words. Wise words, indeed. Who among us hasn’t sat staring into the abyss of seemingly endless data without the slightest clue to what it means or even how to go about figuring out what it means? To literally feel the brain damage seeping in as you start to see ‘ones’ and ‘zeros’ reach out to you from every day electronic devices…like some ghost in the wires. But do not fear, wise hacker! For we have good news to report! [Rory O’hare] has dived into this very abyss, and has emerged successful.

While others were out and about playing games and doing whatever non-hackers do to entertain themselves, [Rory O’hare] decided to reach out and grab some random wireless signals for a little fun and excitement. And what he found was not just a strong, repeating signal at 433Mhz. Not just a signal that oozed with evidence of ASK. What he found was a challenge…a mystery that was begging to be solved. A way to test his skill set. Could he reverse engineer a signal by just looking at the signal alone? Read on, and find out.




tachtastic diy tachometer

Fantastic Tach Is Strangely Called Tachtastic

We all have projects from yesteryear that we wish had been documented better. [EjaadTech] is fighting back by creating a project page about a tachometer he built 3 years ago while in college. He’s done a great write-up documenting all the steps from bread-boarding to testing to finished project. All of the code necessary for this tachometer is available too, just in case you’d like to make one yourself.

At the heart of the project is an AVR ATMega8 chip that performs the calculations and controls the LCD output screen that displays both the immediate RPM as well as the average. To hold everything together, [EjaadTech] etched his own custom PCB board that we must say looks pretty good. In addition to holding all the necessary components, there is also an ISP connector for programming and re-programming.

There are two attachment options for sensing the RPM. One is a beam-break style where the IR emitter is on one side of the object and the receiver is on the other. This type of sensor would work well with something like a fan, where the blades would break the IR beam as they passed by. Then other attachment has the IR emitter and receiver on one board mounted next to each other. The emitter continually sends out a signal and the receiver counts how often it sees a reflection. This works for rotating objects such as shafts where there would not be a regular break in the IR beam. For this reflective-based setup to work there would have to be a small piece of reflective tape on the shaft providing a once-per-revolution reflection point. Notice the use of female headers to block any stray IR beams from causing an inaccurate reading… simple and effective.

Basement-cooled AC

Zero-Dollar AC System Looks Funny But Works Well

Summer is here and with summer comes hot days. You probably know that us humans get uncomfortable if the temperature rises too much. Sure, we could turn on the loud and inefficient window AC unit and try to stay mildly comfortable while the electric company pick-pockets pennies from our change purse, but what is the fun in that? [Fran] had a better idea.

He noticed that his basement was always in the upper 50°F range regardless of how hot it was outside. He wanted the cool basement air to reside upstairs in the living area. After thinking long and hard about it he decided that a box fan and two long, skinny cardboard boxes assembled together would be enough to move the required amount of air. Both the fan and boxes were kicking around the house so was no cost and no risk to try this out. Continue reading “Zero-Dollar AC System Looks Funny But Works Well”