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9
Jan

Antique Radio Podcast Player

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One of my favorite things in the world is The Thrilling Adventure Hour (TAH), a stage production in the style of old-time radio, performed live on stage, and recorded as a podcast. I fly to LA once a month to see the live show, wherein actors stand on stage at microphones, scripts in hand, performing episodes of different story lines. The evening usually begins with an episode of “Sparks Nevada, Marshal on Mars,” and ends with an episode of “Beyond Belief.” There is a rotating story’s episode in the middle, and a couple of fake sponsor ads thrown in. They have surprise guest actors (often well-known from TV or movies), and then the entire cast and crew spend time after the show to chat with audience members. It’s funny and fun, and I wouldn’t miss it.

One of my friends (who often sees the show with me) has a father who collects old radios. This got me thinking about what it was like before television, how people gathered around their radios to listen to radio plays. What if you could listen to The Thrilling Adventure Hour on an old radio?

As it turns out, it’s very common to modify old radios to accept an auxiliary input for an MP3 player. With these modifications, whatever the MP3 player outputs is amplified through the vacuum tubes of the old radio and played on the old speaker.

But I wanted something different. I wanted to turn the tuning knob to “tune” in different podcasts. In the case of TAH, there would be “stations” for Sparks Nevada, Beyond Belief, Jefferson Reid, and so on. They have a lot of music in the show, too, so there’d be a station of TAH music. So, I built this:

Podtique: Antique Podcast Player

Video of it in action:

I call it “Podtique”, an amalgam of “podcast player” and “antique radio.” I took a 1936 Goldentone radio purchased on eBay, removed the old tube radio and speaker, and replaced them with a laser-cut wooden structure that contains a BeagleBone Black and audio components. Potentiometers attached to the knobs on the front are connected to the BBB’s analog-to-digital converters, and code on the BBB uses that to simulate tuning to different radio stations.

Adding backlight and amplifier mute control.

More photos are available.

As long as it’s powered, the BBB runs the radio simulator. The left knob contains an on-off switch and volume control. The third knob is the tuning control. The other two knobs are currently unused.

Each “station” is a playlist of MP3 files stored on the BBB. The tuning knob is attached to a five-turn potentiometer, giving fairly fine-grained tuning control to the user. As you approach the designated frequency for a station, the appropriate MP3 file is opened and begins decoding.

Whenever you’re not tuned to a station, pink noise plays. This is mixed with station content, gradually fading away as the tuning improves. The volume potentiometer is used to attenuate the resulting mixed samples. If the knob is turned all the way off, the BBB mutes the audio amplifier and turns off the dial backlight.

I used a SparkFun Proto Cape to wire in the potentiometers and add the electronics for interfacing with the audio amplifier and AdaFruit NeoPixel Ring 24. The NeoPixels introduced horrible, horrible noise into the audio, so I experimented with LC filtering until I was able to attenuate it fairly well, and added that to the Proto Cape, as well. The audio codec is an Audio Technica ATR2USB purchased at Fry’s. A SparkFun Audio Amplifier and 4″ speaker from Fry’s round out the audio components. There’s a giant R/C lithium-polymer battery pack hacked into it so I can demo this without being plugged in. A cheap DC-DC converter provides 5V from a wide input range (the amplifier needs 9-24 V). A 12 V switching wall wart adapter provides power (and its own share of noise, but nothing compared to the LEDs).

I’m working on a fully-custom BeagleBone Black Cape that will integrate audio DAC and amplifier, LED interface, power regulation, and battery charging. Hopefully this won’t have the noise issues, will be much more compact, and easier to use. If there’s any interest, I’ll manufacture and sell them. The software is available on GitHub.

The software runs on Debian and OS X. It uses libao for audio output, libmpg123 to decode MP3s, and C++11 features for threading. All that works well on Debian and inside a Cocoa app on OS X. On the BBB it uses LEDscape to control the NeoPixels (special thanks to Yona for making some changes to support a single NeoPixel string). LEDscape relies on prussdrv to handle the strict timing requirements of the NeoPixels.

Mechanically, it was necessary to duplicate the linkage between the tuning knob and the frequency indicator dial. In the original radio, this was accomplished by a pulley system. A thread wrapped once around the knob’s shaft went to a fairly large metal pulley on the indicator dial’s shaft. This was also connected to the variable tuning capacitor. The original system had a turn ratio of about 14:1.

In order to get good sensitivity with the knob, it was easier to put a five-turn potentiometer on the knob, and cut an appropriately-sized pulley for the indicator shaft. In the end, the ratio is a bit wrong, and the indicator goes past the dial at the extremes of the pot’s motion.

I learned a lot more about the Linux kernel than I ever wanted to know during this project. I’m still barely scraping by. I really do prefer OS X.

10
Mar

California Requirements for Wiring an Oven

Just in case you wanted to know, the Section 422.16 (B) (3) of the California Electric Code for 2013 contains the following:

(3) Wall-Mounted Ovens and Counter-Mounted Cooking Units. Wall-mounted ovens and counter- mounted cooking units complete with provisions for mounting and for making electrical connections shall be permitted to be permanently connected or, only for ease in servicing or for installation, cord-and-plug-connected.

A separable connector or a plug and receptacle combination in the supply line to an oven or cooking unit shall be approved for the temperature of the space in which it is located.

So, if you wanted to replace your oven’s direct wiring with a plug (in case you were experimenting with something that required 240 V power), you’re good to go (assuming you do it right).

11
Jan

Leadworth

A few days ago I got back from London. It was a great trip; I really love that city (and I’m from San Francisco, so that’s saying something).

One of my geekier sub-trips was a day trip out to Cardiff, Wales, where a lot of Doctor Who is filmed. Wales is beautiful, and I can’t wait to go back. I saw the area where Torchwood Headquarters is, and the Doctor Who Experience (which is surprisingly awesome). I also got it into my head that I wanted to see Amy’s duck pond.

For those of you who don’t know, the first episode of the fifth season of the new Doctor Who introduced a new companion Amy Pond, played by Karen Gillan. In the first episode, there was a short exchange between The Doctor and Amy about a small pond in her home town of Leadworth. The pond had no ducks, but Amy insisted it was a duck pond.

A little googling turned up the filming location, a place known as Cathedral Green in Cardiff. So, I took a bus out there to check it out. It’s much smaller in person than it appears to be on TV. The duck pond doesn’t actually exist. Its location is a parking lot, and the pond itself was created for the episode in a corner of the lot. A number of other elements aren’t there, either (the phone booth, the mailbox at the post office, etc.). Here are a few screen caps from the episode, and some of the photos I took while there (you can click on my images for a larger version).

On my way to Cardiff (via train; I love trains!), I met a woman from Texas who was also going because she was a big Doctor Who fan. Like me, she thought visiting Amy’s pond was cooler than expected.

Stone Wall

Walking from Amy’s house.

http://farm6.staticflickr.com/5480/11897727763_c47f0b6d99.jpg

My photo of the path from Amy’s house.

Stone Argh 2

Walking from Mrs. Angelo’s house.

http://farm3.staticflickr.com/2813/11897867604_dd50028e5a.jpghttp://farm8.staticflickr.com/7370/11897729773_54f986a2e6.jpg

My photos of the road and the stone arch behind them.

Duck Pond

Amy’s duck pond!

http://farm8.staticflickr.com/7449/11897734373_9b53956a77.jpg

A long shot in the direction the actors are walking.

http://farm6.staticflickr.com/5498/11897737253_4f3a0d7367.jpg

The corner of the lot where they built the pond.

http://farm8.staticflickr.com/7340/11898071063_089e7aba85.jpg

Me standing where the pond was.

Green 1

Green 2

Green 3

Memorial

More shots from the episode.

http://farm8.staticflickr.com/7419/11897887114_de818f0e50.jpghttp://farm3.staticflickr.com/2843/11897748023_e1a73b9775.jpghttp://farm6.staticflickr.com/5540/11897881874_708cd39840.jpghttp://farm6.staticflickr.com/5489/11897739413_23e8a46b51.jpg

http://farm4.staticflickr.com/3767/11897889064_f25b83cd41.jpg

http://farm3.staticflickr.com/2809/11897473535_1fcec7e57f.jpg

More photos from my visit.

For completeness, here are a few more photos from my visit to Cardiff:

Daleks This Way

Daleks this way.

http://farm6.staticflickr.com/5535/11898477425_b17839c4fe.jpg

Eleventh Doctor’s TARDIS.

http://farm3.staticflickr.com/2829/11898879834_880ccb582f.jpg

Season five costumes.

http://farm4.staticflickr.com/3772/11898884864_ff80b94480.jpg

Eleventh Doctor’s costume.

http://farm3.staticflickr.com/2840/11899327576_0c410e1271.jpg

Amelia Pond’s costume.

Kissogram Amy Costume

Kissogram Amy’s costume.

Amy Pond’s Costume

Amy Pond’s costume (one of many).

The Doctor’s and Melody Pond’s Cradle

The Doctor’s and Melody Pond’s cradle.

River Song’s Costume

River Song’s costume.

The Face of Boe

The Face of Boe.

Daleks

Daleks.

Weeping Angel

Weeping Angel.

Silence

Silence (sorry you’ll forget about this one).

http://farm3.staticflickr.com/2867/11899347566_72c0e79987.jpg

Oswin Oswald’s costume.

http://farm8.staticflickr.com/7398/11898904344_61fc97650c.jpg

Oswin as Dalek.

http://farm4.staticflickr.com/3735/11900694896_66db4ee2f2.jpg

Clara’s Book, 101 Places to See.

Torchwood HQ

Torchwood HQ.