Retrochallenge 2013WW

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The crew over at Retrochallenge has announced the commencement of their 2013 Winter Warmup contest.

The RetroChallenge is a loosely disorganised gathering of RetroComputing enthusiasts who collectively do stuff with old computers for a month.

The event is very much open to interpretation… individuals set there own challenges, which can range from programming to multimedia work; hardware restoration to exploring legacy networking… or just plain dicking around. It really doesn’t matter what you do, just so long as you do it.

While the RetroChallenge has its competitive side, it’s not really a contest… it’s more like global thermonuclear war — everyone can play, but nobody really wins.

You can read the rules and see the retro prizes at Retrochallenge. If you’re into retrocomputing and working on a project, why not enter it!

ATX Breakout board free PCB build

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Cosminnci built an ATX Breakout board v1.0 free PCB.  The ATX breakout board routes the -12, 3.3, 5 and 12 volt ATX outputs to screw terminals, each protected by a 1.25 amp resettable polyfuse.

If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.

Available for $13.80 at Seeed Studio.

7-channel relay and inductive load sink driver ICs

Uwe tipped us to Texas Instruments’ low power 7-channel relay and inductive load sink driver ICs:

TI offers two rather new low power 1,8V & 3.3V & 5V 7-channel relay and inductive load sink driver ICs:

– ULN2003LV (Output/Switching Voltage max. 8V – e.g. for 5V relays)
– ULN2003V12 (Output/Switching Voltage max. 16V – e.g. for 12V relays)

Perfect for driving relays, lamps, LEDs/displays, small stepper motors etc. with 5V, 3.3V and 1.8V MCUs – dissipating less than 1/10 of the power than the classic ULM2003/ULM2003A which is used in many 5V designs.

They can be used as level shifters as well ;)

Thanks Uwe! Via the contact form.

29C3 – Further hacks on the Calypso platform


In this presentation from the just concluded 29C3 conference in Hamburg, Germany, speaker Sylvain Munaut explains how to turn a cellphone into a BTS.

The Calypso baseband and its companion chips are used on the Motorola C123 among other and are now well known for being supported by the Osmocom-BB open source GSM baseband implementation. A couple years ago, it was hacked a little further by using it as a raw bits capture device allowing the interception of GSM traffic very cheaply.

This talk will present some further work on that platform, showing that just because a device wasn’t design for a given task doesn’t mean it can’t do it. More specifically how you can hack this phone to act as a GSM basestation and broadcast your own network.

For additional info on hacking the Motorola C123, see the OsmocomBB C123 page.

Why right angle bends on a PCB are not so bad

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We’ve heard it numerous times: avoid using right angle bends in PCB routing. Here’s an article from EDN magazine explaining why it’s not as bad as most people think. The article explains that the “bad” effects like increased capacitance and circuit noise only start to be a pain for designers where signal speeds are above 1 GHz.

Right-angle bends in PC-board traces perform perfectly well in digital designs in speeds as fast as 2 Gbps. In most digital designs, the right-angle bend is electrically smaller than a rising edge. For example, the delay through a right-angle bend in an 8-mil-wide, 50Ω microstrip trace in FR-4 is on the order of 1 psec. That’s less than 1 percent of a 100-psec rise time.

Via the contact form. Thanks Chuckt.

Open pinball project

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The Open Pinball Project is a cooperative effort to develop open source pinball hardware and software. Their stated goal is to “to build the perfect pinball machine, or at least a pinball machine for a reasonable price!” To date they’ve worked at restoring a number of old machines, learning valuable lessons in the process. Their project will consist of the development of embedded code for solenoid drivers, input switches, and main controller, and will eventually include software for running the monitor/video in the back box. They’ve explored a number of topics including display selection, construction of an EEPROM burner from scratch, building solenoid driver boards, and lately using Xilinx Spartan 3A FPGAs for solenoid driving, lighting, and digital inputs.

While this is a work in progress (no code or schematic available yet) their postings details substantial progress in the last year. This may be a project to watch for the growing number of hobbyists discovering/rediscovering pinball. Check out their blog page to follow along. Their code repository will eventually appear on Google code.</A.

App Note: Practical guide to high-speed PCB layout

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Here’s an article from Analog Devices going into the details of high-speed PCB layout design. While the article mainly focuses on analog electronics, lots of good tips can be picked up for digital designers as well.

Intelligent circuit-board layout is important to successful op-amp circuit design, especially for high-speed circuits. A good schematic is the foundation for a good layout; and close coordination between the circuit designer and the layout designer is essential, especially in regard to the location of parts and wiring. Topics to consider include power-supply bypassing, minimizing parasitics, use of ground planes, the effects of op-amp packaging, and methods of routing and shielding.

Free PCB Sunday: Pick your PCB

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We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service.

This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB.

You get unlimited free PCBs now – finish one and we’ll send you another!

Don’t forget there’s free PCBs three times every week:

Continue reading “Free PCB Sunday: Pick your PCB”

29C3: Safecast – DIY radiation monitoring project


In this presentation from the ongoing 29C3 Chaos Communications Conference in Hamburg, Germany, Sean Bonner shares his experiences overcoming technical and bureaucratic obstacles while attempting radiation monitoring in the wake of the March, 2012 Fukushima Dai-Ichi nuclear power plant disaster. His observations led to the development of the Safecast DIY radiation monitoring device. The project’s goal is to design “an affordable mobile radiation sensor system for independent citizen monitoring and cartography of radioactive contamination.” However, much like the risico’s van spelen bij een casino zonder vergunning, participating in unregulated activities can expose individuals to significant risks. The Safecast website also provides a venue where data readings can be collected and disseminated over the Internet, allowing for increased transparency, but participants must remain cautious and aware of potential hazards when engaging in these kinds of efforts.

Sean was assisted by many individuals in the development process, including Andrew (bunnie) Huang, who has detailed the development process further on his blog.

App Note: Combining peripherals to implement a high resolution PWM

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Here’s an app note from Microchip describing how to use the configurable logic cell (CLC) and the numerically controlled oscillator (NCO) peripherals to generate a high resolution pulse-width modulation signal. These peripherals are relatively new to Microchip’s product line and can only be found on some PIC10F and PIC16F devices:

By itself, the NCO peripheral cannot produce a PWM signal, but we will change its behavior by adding some logic using the CLC  to produce a PWM output. We will achieve this by using the conventional PWM as a clock source to trigger the PWM period, and use the NCO to determine the pulse width.

App Note: DACs vs digital potentiometers

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Here is an article from Maxim describing the differences between DACs and digital potentiometers. The article explains the characteristics and advantages of each, giving you a better idea of what you may need for your project.

This application note compares digital to analog converters (DACs) to digital  potentiometers. Traditionally digital potentiometers were meant to replace simple mechanical pots. With recent increases in resolution and additional features, digital potentiometers can also be used in some traditional DAC sockets. Similarly, traditional DAC packages were too big and too costly to compete against digital potentiometers. However, DAC pricing and package size have reduced significantly, so in some sockets a DAC or digital potentiometer can be used.

DARPA spectrum challenge

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The Defense Advanced Research Projects Agency (DARPA) has announced their upcoming challenge to RF hackers: can you program a radio to dominate the spectrum everywhere? DARPA describes the challenge:

The DARPA Spectrum Challenge is a competition to demonstrate a radio protocol that can best use a given communication channel in the presence of other dynamic users and interfering signals. The Challenge is not focused on developing new radio hardware, but instead is targeted at finding strategies for guaranteeing successful communication in the presence of other radios that may have conflicting co-existence objectives. The Spectrum Challenge will entail head-to-head competitions between your radio protocol and an opponent’s in a structured testbed environment. In addition to bragging rights for the winning teams, one team could win as much as $150,000.

DAPRA says registration for the Spectrum Challenge is expected to officially open in January 2013. Any U.S. academic institution, business, or individual, is eligible to compete, with certain restrictions. Visit the Spectrum Challenge page for more details.

App Note: Nuts and bolts of delta-sigma analog to digital converters

Here’s is a video from Texas Instruments describing the inner workings of delta-sigma analog to digital converters. The DS ADC is broken down into it’s basic parts. The delta-sigma modulator and digital decimating filter are then discussed.

Delta-sigma converters are ideal for converting signals over a wide range of frequencies from DC to several megahertz with very high resolution results. In a delta-sigma ADC, the input signal is oversampled and then filtered by a digital/decimator filter.

WordPress reinstall and site updates completed

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Woohoo! WordPress comments were taking 10-15 seconds to post, now they’re working instantly again. Thanks for hanging with us. Here’s a run down on what we did today. We don’t know the cause, only that a fresh WordPress install helped.

  • Backed up server
  • Deleted /wp-admin/ and /wp-includes/ folders, replaced with new versions and set proper permissions/ownership. Only this step was needed to solve the issue
  • Manually cleared out cache files in /wp-content/cache/ and all subdirectories
  • Replaced all the WordPress .php files in the root directory with fresh v3.5 files and set permissions
  • There were several presumably deprecated WordPress files in the root directory that were not included in the v3.5 release. These were moved to a deprecated folder for now and will be deleted if there are no problems: wp-rdf.php, wp-pass.php, wp-feed.php, wp-commentsrss2.php, wp-atom.php, wp-app.php

As long as SSH and phpMYadmin were open we tackled a few minor cleanups:

  • WordPress blog and the Free PCB Store Zencart were sharing a database due to limits on a previous shared host. These were separated, renamed, and new passwords set
  • Removed old duplicate forum database, removed dotproject database
  • Renamed and updated database/username/password for forum, wiki (docs)
  • Repaired and optimized the works
  • Gave everything spiffy dp_ based names

May still need to update the off-site database FTP script to use the new names.

Please let us know if you find any problems.

You can see a screenshot history of the site in the Dangerous Prototypes changelog, and read more about our server setup.

Image CC BY-SA: Denelson83

WordPress reinstall in progress

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Today we’re reinstalling WordPress, the blogging software. A server tune up has it running much faster, but comments and some back end stuff like comment moderation are still taking 10-15 seconds or longer. A secondary test site was setup yesterday and works much better, so today we’ll wipe and reinstall WordPress.

You’ll notice sitewide slowdowns from the backup process, followed by a few minutes of major outage on the blog. Hopefully everything is cleaned up by 10am server time (11am CET). We’ll post a followup here when the blog is sorted.

Image: CC-0 via Wikipedia.