Hot resistors used for color-changing clock face

[Sprite_TM] built a full clock display using thermochromic paint. This picks up where he left off with his paint-based 7-segment display prototype. He never really saw that design through to a finished project, but he recently came across the leftover paint and decided to do something with it. Instead of making thin traces on a PCB he’s heating up resistors mounted on protoboard. Each resistor has been coated with the black/light grey paint after getting a rough sanding on the tops of the packages. Run around 500mW through a segment and they heat up enough to change the paint to light grey. Once shut off, the segments gradually fade over the next 60 seconds.

Patching into Android music control

Here’s a look at the TRRS cable that Android phones use. [Rich Kappmeier] want to control the music player on his Nexus One while driving. It’s not necessarily a safe endeavor if you’re staring at the screen and poking away with one hand while trying to stay in your lane. A little bit of research helped him figure out how the hardware in a headphone controller worked and he decided to incorporate that into a connector cable for the car.

The control signals rely on a specific resistance between the TRRS function ring and ground. Once he worked out the chart above and targeted the correct resistance values he built a rocker switch for Fast Forward and Reverse, as well as a Play/Pause button into the connector cable. You should be able to use this for more than just music control. Take a look at our Android Development tutorial and see what else you can come up with.

[Thanks Alastair]

Typewriter as I/O; lets you play Zork

Okay, for many the fact that this typewriter plays Zork on paper instead of a CRT is the fascinating part of this hack. But we love the implementation that makes the keys of the device an input and output.

The electric typewriter has been fitted with a solenoid for each key (wow, that’s a lot of work). In the image above you can see they are housed on plywood platforms behind the typewriter and connect using a piece of mono-filament fishing line. This flexible connection means the solenoids have no adverse effect when you want to do the typing instead of the Arduino which drives the solenoids. [Johnathan M. Guberman] took advantage of this, adding a resistor for each key. When depressed the key completes a circuit with the resistor, acting as the input. In this way, you can play Zork with a piece of paper as the monitor, typing for the input, and watching the typewriter magically pound out responses. See it happen after the break.

[Read more...]

Building a discrete digital-analog-converter

Want to take back control of how your digital audio files become sound? One thing you can do is to build your own digital to analog converter. This one is made from discrete components, centered around a resistive ladder. Yes, there are a couple of integrated circuits in there which are used for demultiplexing the incoming signal but the magic happens in that R-2R network. The project is an interesting read and makes a point of looking at the issues raised when trying to precision match resistors. Apparently it can be done with 0.1% components if you have a lot of them and a multimeter that can measure down to seven decimal places.

[Thanks Bigbob]

Hackaday links: June 13, 2010

Painting with light

[Jo0ngle] wanted a fun toy and an easy conversation piece. He painted a square on the back of his door with some glow-in-the-dark paint. Now he can draw on it using a blu-ray laser or a UV flashlight. Either way, the effect is quite pleasing. [Thanks Justin]

Resistor decoder rings

This resistor reference card allows you to spin a wheel and dial in the resistor color code for easy reading. We know, you have the simple act of reading resistor code down cold by now. This is still a fun idea that you might use if you’re ever helping someone get into electronics. [Thanks Osgeld]

Resistor bending template

Speaking of resistors, [Jerome] helped us out by designing a resistor bending template. He’s actually marketing himself at the same time. His bending template is folded from one of his business cards, which he came up with after being inspired by some of the unique business cards we’ve covered in the past.

Fake stained glass using old PCBs

[Agg] floated some old PCBs to his friend [Dan] the mason. [Dan] proceeded to turn out an amazing looking stained glass window unit using the colorful leftovers. The picture above doesn’t do it justice, you have to click through to see the real art.

Monovelo monowheel

[Ernst] asked if we’d heard of the Monovelo monowheel. Well we hadn’t. It’s a human-powered vehicle where you sit inside of one large wheel. We don’t see ourselves building one or riding one, but we enjoyed watching someone else do so. We’d like to catch somebody commuting to work with one of these. Seeing this in the bike lane will brighten up anyone’s day.

Are you human? Resistor edition

[PT] tipped us off about a new way to screen bots from automatically leaving comments. Resisty is like CAPTCHA but it requires you to decipher color bands on a resistor instead of mangled text. This won’t do much for the cause of digitizing books, but if you can never remember your color codes this is a good way to practice. Resisty comes as a plug-in for WordPress, add it to your blog and for a geek cred +1.

194 Transistor Clock will blow your mind

It’s nice to have tip put on our desks that we think everyone, yes everyone can enjoy. The Transistor Clock is just as its name implies, A clock that doesn’t rely on ICs. 194 Transistors, 400 resistors, 566 diodes, and 87 capacitors are all that makes this clock tick – no programing, and most importantly no Arduino. The clock is offered as a kit, but there is a complete parts list and manual (including debugging help) so anyone can build (and fix) their own. The Transistor Clock might even beat out the VFD Clock and the Word Clock on the ‘pure awesome’ scale, tell us your favorite in the comments.

[Thanks Hoopstar]

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