# The Mechanical Diode

A diode allows current to travel in only one direction. With that in mind, [Alex] built a mechanical diode that will only allow gear rotation in one direction to be transmitted through the system. But wait, by connecting two of these devices together he’s built something of a mechanical rectifier. An electrical rectifier converts alternating current to direct current and this mechanical version outputs clockwise rotation no matter what direction of rotation is coming into the device.

There’s video which we’ve embedded after the break as well as many pictures on his site but not much explanation. Here’s what we’ve deduced. The two large gears are inputs. Mounted on top of them is a smaller ratcheting gear that will only turn in one direction. This ratcheting gear selects whether the smallest gear on the left or right will rotate, which then feeds the output gear at the top of this image. Continue reading “The Mechanical Diode”

# Leapfrog Didj: Followup

Yesterday we mentioned the Woot! sale of the Didj, and we had some comments and emails from readers who had purchased one. We couldn’t resist either, and ordered a couple to take apart and modify. We will probably be following the work laid out by [Claude Schwarz], who seems to be one of the leading hackers on the scene. [Claude] has done some work in porting the GP2x libraries to the Didj, which gives a tremendous head start to anyone looking to have a working game system any time soon. There will also be a build log for everyone to follow along at home, and contribute what you want and have, as well as a follow up How-To when a working system is attained. Happy Hacking, everyone.

If you think there’s never enough computerized numerical control in your life perhaps the pizza plotter should be your next project. This is a large 2-axis machine that shoots pressurized sauce onto a pizza crust. It’s a food-grade RepStrap and appears to use a garden sprayer as a reservoir. They learned their lesson when a loose hose clamp sprayed sauce around the room. We’re thinking this is a bit of reinventing the wheel as pizza-making factories but it’s fun nonetheless.

# Lego Spider-bot

[MkMan’s] LEGO spider robot combines pieces from a Mindstorm kit with a few milled plastic parts. The legs are a locomotive concept called a Klann Linkage. They operate in pairs and convert the rotational force from one motor into movement for two legs. Here, a total of four rotating gears moves eight legs, besting the hexapods we saw a couple of weeks ago in both leg count and motor economy.

Each limb is made up of five pieces plus one base for each pair. That makes eleven pieces per pair and a total of 44 for the entire robot. [MkMan] milled these parts out of 3/8″ HDPE stock. He’s made videos of forward motion and turning which we’ve embedded after the break. Even on a polished surface the bot looks fairly efficient at getting around.

# Amplifier Built Inside A 9v Battery

It’s pretty creative to use a 9v battery as an enclosure. That’s what [Osgeld] did when building this amplifier. There are several advantages; they’re easy to find, it keeps a bit of the dead battery out of the landfill, and this method provides a built-in connector for a 9v power source. In this case the circuit is built around a LM386 audio amplifier. It’s glued to the back of a potentiometer and wired up with the other components for a package smaller than a quarter. A stereo jack reside in the side of the battery case with a cable and alligator clips for connection with a speaker. Now the amp can be quickly connect to any 4-8 ohm speaker.