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]

RepRap acrylic extrusion using hotbed

[Nophead] started the year off by successfully extruding acrylic using a RepRap machine. The problem when working with this material is that when the hot ooze hits the cold air the printed material tends to warp, badly. [Nophead] raised the ambient air temperature around the part being extruded by replacing the bed of the RepRap machine with a heated aluminum plate.

We took at look at his build details for the hotbed. The plate itself is aluminum that he had milled by a machinist friend of his. It looks like the heat is produced by a network of power resistors bolted and soldered to the bottom of the plate. The original idea was to produce a controllable SMT soldering platform. Unfortunately this heating method doesn’t have the power needed to raise the temp quickly but that failure turned out to be a RepRap success.

Better resistors from a pencil

Many of us here in the office (myself included) can’t tell the difference, but the audiophiles out there who want the best sound from their resistors should check out [Troel’s] write-up for making your own non-inductive graphite resistors. Graphite resistors have the traits for being non-inductive, have a negative temperature coefficient, and supposedly sound better. We liked the detail of his tutorial and how he gives many examples for making your own graphite resistor.

[Thanks Maxime]

Top 10 iPhone apps for electronics hackers

HAD

There are so many apps available for the iPhone, one might even say there are a plethora. We would like to take a moment to help you find a few that might help with your hacking projects. Ever have problems remember a formula when you need it? Need to track the acceleration of your brand new rover? How about beginners needing help remember resistor codes. Well, there’s an app for that. Check out our suggestions after the break.

Continue reading “Top 10 iPhone apps for electronics hackers”

Resistive ladder volume control

preamp

[jefffolly] published some straight forward plans for a passive volume control. It uses a resistive ladder built across the contacts of 12W rotary switches. Each resistor provides a 5dB difference, and he recommends using 0.1% tolerance resistors to maintain accuracy. The use of discrete resistors instead of volume pots means that the output is much more predictable. All of the RCA sockets were connected using oxygen-free copper wire.