[Onefivefour] was surprised that his E-flite Blade MCX radio controlled helicopter came with a charger that used AA batteries to recharge the lithium batteries in the flying unit. Yeah, that’s a bit crazy. He set out to modify the base unit to work with AC power. There are four batteries inside this base unit, one of them powers the charge detector circuit and the others are used to juice-up the chopper’s rechargeable cells. He took a 5V regulated charger from a Motorola cellphone and modified it to interface with the contacts for the three AA cells. Like the Magic Trackpad hack, he did this without altering the holder by cutting a couple of pencils to length and attaching the positive and negative contacts from the AC charger to them. Check out the video after the break for a walk though, noting how he still has the option to go back to battery power if he so chooses.

Who wouldn’t want to install this little bot as your newest pencil holder? Place a pencil tip-down and it will keep it from falling using two motors. There is a Dynamic Vision Sensor for each axis that provides feedback, but it’s not the same as using a camera. These sensors pick up changes in pixel contrast, outputting a positive or negative number based on the direction the pencil is beginning to fall. An NXP2103 running at 64 MHz reads in the values and drives the pair of servo motors accordingly.

If you’re interested in the nitty-gritty the full paper is available from the page linked above. It goes into great detail about the algorithm used, and includes plots and histograms showing the data capture during a balancing session. Or you can skip the eggheaded exercises and watch the video after the break.

[via ycombinator]

If you don’t mind getting your fingers a little dirty you can replace your mouse with a piece of paper. [Dr. West] made this touchpad himself, which measures signals at the corners of the paper using four voltage dividers. The paper has been completely covered with graphite from a pencil (which we see in hacks from time to time), making it conductive. The user wears an anti-static strap that grounds their hand, allowing an Arduino to calculate contact points on two axes when a finger completes the circuit. See this controlling a cursor in the video after the break.

So you’re stuck in a boring class and you can’t fight off the urge to hack something, even your pencil, to pass the time. Maybe you are performing a live electronics show and you drop your synth down a flight of stairs and all that you are left with is a handful of components, a screw terminal block and a pencil. There are thousands, perhaps millions of these kinds of situations and for each one the answer is the solderless drawdio clone by [Martin].

You may have seen the original Drawdio here before, a fun piece of technology that is simple enough to recreate. This latest approach would make an excellent introductory project for a hacking workshop seeing as the guide is straightforward and the lack of soldering would make logistics so much easier. The results are very similar to the original–check the video after the break.

[Robb Godshaw] put together a pencil production line for home use. The whimsical assembly line starts with a graphite rod and extrudes clay polymer around it. From there it’s down a conveyor belt to get stamped and then into the oven made from a hacked toaster. The final step is to cut out a plug of eraser and attach it to the back-end of the pencil. This low-speed assembly line reminds us of a Rube Goldberg machine with all the wasteful steps cut out.

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]

a Ruler, rubber band, and a pen make a bow and arrow? How about tape, a ping pong ball, and a lighter coming together to make a ‘Zooka. We didn’t think such destructive weapons could possibly be made from office supplies, but the famous [John Austin] is here to prove us wrong. He’s been miniaturizing toys and their munitions including Transformers, Star Wars, Jurassic Park for years. With the resent release of his new book, he’s left us the grace of a few teasers.

[Thanks Chris]

Drawdio, designed by [Jay Silver], is a fun, simple toy that uses the conductive nature of pencil graphite to generate different sounds. When you use the Drawdio pencil to draw or write, you also simultaneously create music. The entire kit is available for sale at Adafruit Industries, or for the more adventurous, separate components and parts are listed. The circuit is fairly simple and we wonder what other devices people can come up with based on this theme.