DVD thermometer

dvd thermometer

Reader [alberto ricci bitti]’s DVD thermometer is a temperature sensing infrared remote that controls a DVD showing the temperature. Since the box doesn’t get any feedback from the DVD player, it stops and starts the disc to make sure it is at a known state. The brain of the device is a Motorola MC68HC908QT4, an 8-pin microcontroller. Communication with the Maxim DS1621 temperature sensor I2C bus is done in software. Even if you don’t want to build a gaudy thermometer the article features a lot of interesting information. It covers reverse engineering the remote, emulating an I2C bus, and creating a programmable pulse generator instead of bitbanging.

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Hack Media: Security podcasts

Do you want to listen to four and a half hours of security podcasts? Well, you don’t have to because I did. Here are the highlights from podcasts released this last week:

Security Now! #27 How Local Area Networks Work, Part 1 37:09 If you don’t know the difference between DHCP and static IP, then this is the podcast for you! Next week promises to be a little more interesting when they get into the problems with ARP.

CyberSpeak Feb 18 76:36 has some pretty good news coverage, but the real highlight is the interview with Bruce Potter from The Shmoo Group that starts after 20:00. If you don’t know about the group and the work they’ve done, this is a good intro.

LiveAmmo: Digital Forensics and Hacking Investigations, Part 2 46:54 Woof. If you are persuing digital forensics as a career then this would be a great start. Otherwise, avoid, unless you want to know what particular subsection of a law you are violating.

SploitCast #006 36:26 probably has the best atmosphere of these podcasts (and it’s the shortest). The team covers the recent news of a phishing site using a valid SSL cert. You could probably wait till next week when they talk to Lance James to get all of the details. I will say that the Web 2.0 discussion is about as inane as arguing which year the millennium starts. They do earn some extra points since my mom doesn’t read Schneier.

Blue Box #16 69:00 is all about VoIP and naturally the best produced. I don’t follow VoIP very closely, so the news roundup for the first 20 minutes was really interesting. If you aren’t doing enterprise VoIP then this podcast isn’t for you.

Each of these had some high points (even LiveAmmo). They could all do better if they were shorter. I would say that CyberSpeak was my favorite this week, but I don’t want to encourage another 76 minute podcast. What podcasts do you recommend?

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Low-cost sensing and communication with an LED


LEDs are extremely common in electronic devices. They are used as light emitters, but can also be used as light detectors since they are photodiodes. By quickly switching between light emitting and detecting, you can use the LEDs to determine the ambient lighting and even do bidirectional communication. MERL has a good paper covering the basics of how this system works and how they used it as a “last-centimeter” communication device. The system can be implemented using one LED, a resistor, and two I/O pins. So, it could be used cheaply in almost any device. The microprocessor quickly switches the LED between emitting light, detecting light (LED acts as a charging capacitor), and measuring the discharge rate of the LED to determine light level. Jeff Han has a neat video demo of how this system can be used as a proximity sensor.

UPDATE: [hawkeyeaz1] pointed to a blog covering one person’s investigations into LED sensors.

[thanks branen]

Hacking the Commodore 64 DTV version 2


The original C64 DTV was a joystick containing 30 games sold in 2004. It attracted hackers because it could be modified into a fully functioning console. The latest version of the chip is being sold inside a Radio Shack Hummer game. This version fixes bugs in the original and adds several features to improve memory access and CPU speed. Before you get started there are several modifications that need to be done to improve the video and audio quality of the system. Once these mods are complete you can start playing with the machine just like an original C64. Oh, the Hummer game will look a lot better too.

[thanks av1d]

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Ball and plate doohickey

ball table

So, if you were wondering what [Kenn Sebesta] was working on that needed yesterday’s hack, this is it. The plate can maintain the cue ball in its current position or make it travel an arbitrary path like a circle or figure-eight. It can also avoid obstacles placed on the plate. Kenn has documented his project thoroughly and covers many of the problems he faced along the way, like how to find the ball in the webcam image. Like most quality thesis projects, it’s constructed out of LEGO.

UPDATE: Now with video!

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Digitally reading analog gauges

analog gauge

While working on his masters degree in controls and robotics, Hack-A-Day reader [Kenn Sebesta] developed a cheap method for digitally reading analog gauges. This method was necessitated by needing to take over 3000 measurements using a dial indicator during his thesis work. The system is implemented in Matlab and uses a webcam to take a picture of the gauge. Once picture is taken it goes through several steps: First, it is reduced to a single color. Then, edge extraction is used to find the lines. Next, the lines are thickened. Finally, the Hough transform is applied to find the longest line: the needle. All that is left to do is measure the arc back to the zero point and match it to your scale. Using this method Kenn’s laptop can take 4 measurements per second.

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