Recently, as part of an iPhone development project I’ve been working on with the Institute of Zoology and Birkbeck, I had a need for an audio line in adapter so that we’d be able to record stereo audio from an audio sensor. The application tags audio data with GPS information as part of a citizen-scientist data collection project.

Strangely (or perhaps I didn’t dig around the interweb long enough) I didn’t find many resources for a home-brew line-in adapter and the ones I found were pretty vague and hard to follow. So Peter and I put our heads together and rolled our own. It’s a fairly straightforward circuit, but has a little twist, because the iPhone OS is smart enough to detect what’s plugged into the stereo jack. (The diagram above is a lot more clear than anything I found.) This particular project only required a left channel audio input to the monaural iPhone mic, but if you wanted to route both left and right channels to the mic, that’s represented by the dashed line.

The resistor+capacitor network provides a pull-up that the iPhone is looking for to detect whether you’ve got a standard stereo headset plugged in or whether you’ve got a microphone (i.e., iPhone) headset and can take a phone call with it. This particular circuit is tuned for the audio sensor we’ve been using, but is about the right spec for most audio recording purposes and works fine with the audio recording app that ships with the iPhone. The parts cost about £3 and I whipped one up in about 10 minutes!

I’m still marvelling at what you can do with SmartSockets, a 14 segment display driver for multi-segment display tubes like ZM1350s and in particular, B7971 grand-daddies. Enthusiasts such as John Taylor have created some really nice transition animations to demonstrate what you can do to add visual interest to clocks and other alphanumeric displays, like the four-letter word display. There’s also a SmartSockets group on Yahoo, which is an offshoot of the more popular NeoNixie group of which I’ve been a member  (lurker) for years. Traffic on SmartSockets is relatively low…for now.

Spacehopper Demo

I’ve been working with my colleagues on a project for SonyEricsson around the release of their latest mobile phones series (Satio and Aino). The project involves using twitter to inflate a warehouse full of spacehoppers on a live webcam. The hoppers will be “released in the wild” as part of the product launch, and tweeters can suggest what their fate should be. The whole system uses an Arduino-controlled solenoid array which takes its input from a Ruby script which is listening to the twitter streaming API. Tweets sent via the API are used to randomly inflate one of the 49 hoppers on the array. The hoppers, username and the tweet message are displayed via a live feed. Sony Ericsson have posted the “making-of” video on YouTube, and I found myself simplifying the technical details, yet again…

Sometimes, the ideal little package comes along and you don’t have to do all the hard work fabricating a physical user interace. While working on the Spot-On project at LKL, I found a very nify little “finger torch” that solves the problem of powering up an LED in a small form factor. This little guy’s is perfect for retrofitting with an LD271 infrared emitter, for Wiimote hacking, IR Motion tracking, and generally mucking about moving around infrared sources, for you Johnny Lee fans. This package combines 3 button cells, a switch and an LED into a tight little case with a hook-and-loop strap. Not sure if it’s emitting continuously or in pulses (PWM) but there’s a microcontroller under that resin blob (pic 2), so it seems likely. A little de/re-soldering and, you’ve got yourself a perfect finger-mounted IR pointer!

Wow. It had to happen, of course. Shapeways have developed 3D printing in a material other than resin or polymer, the traditional materials for rapid prototyping physical objects. They can do it in stainless steel! The magic isn’t toooo surprising though, as they use the same techniques. Stainless steel dust is fused into a solid form layer by layer. The finished model is then bronze filled and baked. The piece comes out with a matte finish but can then be tumbled for a polished finish. They appear to be targeting the maker/craft community and I can think of a lot of fiddly parts that I’d need to make. But it’s still not as good as the 3D printer that the clever guys at EvilMadScientist Labs (rock on, guys!!) homebrewed, which makes 3D models in cane sugar!