Homemade Omnidirectional Speakers in a Unique Enclosure

While studying acoustics in college (university for non-Americans), [Nick] had a great idea for an omnidirectional speaker. Some models available for purchase have a single speaker with a channel to route the sound in all directions, but [Nick] decided that a dodecahedron enclosure with 12 speakers would be a much more impressive route.

To accommodate the array of speakers, the enclosure needs twelve pentagons with a 58.3 degree bevel so that they fit together in a ball shape. After thinking about all of the complicated ways he could get this angle cut into the wood pentagons, he ended up using a simple circular saw!

Once the enclosure was painted [Nick] started wiring up the speakers. The equivalent impedance of the array of 8-ohm speakers works out to just around 10 ohms, which is easily driven by most amplifiers. The whole thing was hung from a custom-made galvanized pipe (all the weight adds up to about 15 kilograms, or 33 pounds for Americans, so the rig needed to be sturdy). We’ve featured other unique speaker builds, but this is the first 12-speaker omnidirectional speaker we’ve seen. [Nick] is happy to report that the speakers sound great, too!

Tribot robotics platform

For a number of children born of geek parents, the WowWee Tribot is sure to make an appearance underneath a Christmas tree this year. By New Year’s, though, this toy will surely make its way to the back of a closet to sit unused until spring cleaning. It’s a shame to let such an interesting robotics platform go to waste, so [haltux] sent in a nice guide to unlocking the motor controller of this talking robot.

The ‘legs’ of the WowWee Tribot have three omnidirectional wheels mounted 120 degrees apart. We’ve seen this drive system before, so getting a pre-built platform out of the toy box is pretty interesting.

[haltux] found three H-bridges inside the Tribot and connected the direction and enable pins for each motor directly to an Arduino. The build was a success, and the new robot platform scurried along the floor. There are also rotary encoders on the Tribot, but these run at 12 Volts. [haltux] said he’ll cover these in a future post, and we’re waiting to see it.

Student built robot chassis has something you can learn from

This is a four-wheeled robot chassis built by high school students over the summer. They were participating in workshops put on by xbot robotics in Seattle, Washington. The goal is to get them participating in events like FIRST Robotics and LEGO league, and eventually into science related careers.

At first glance we thought: oh, that’s a nice chassis build… on to the next tip. But then the difference in front and rear wheel types caught our eye. The problem with four-wheeled designs is that you need differential steering to overcome the skidding issue when turning. This usually means two independently powered rear wheels and one unpowered front wheel that can swivel. One way to overcome this is to use three omniwheels, each with their own motor. And more recently we have seen four-wheelers that use mechanum wheels to get around the issue… but that takes four motors.

The design seen above uses just two motors, each with a chain to drive both wheels on one side. The rear wheels have rubber grippers which give them great traction. The front wheels are omni-wheels which allow them to move side to side easily during turns while aiding in forward progress when not turning. This gives the robot enough grip to push object around, like you can see in the video after the break.

Continue reading “Student built robot chassis has something you can learn from”

Omniwheel robot

Like all of us, [Jonathan Guberman] has a list of projects and builds that ‘will get done when I have time.’ His Kiwi drive robot is no exception. It’s intended to be one piece of a much larger project, but he decided to document it anyway (we think in the hope of getting is rear in gear).

The robot uses a holonomic drive to get around. A holonomic drive uses three fixed wheels placed 120 degrees apart. The wheels can be independently controlled and with some vector addition the robot can move in any direction and rotate 360º inside its own wheelbase. Of course the wheels will have to be able to roll in two dimensions, so an omniwheel is used. Everything is controlled with a Wiimote nunchuck, and the movement is very smooth.

[Jonathan] has had a few projects featured on Hack A Day before, like his Mechanical Pac-Man and his adorable Portal turret plushie. [Jonathan] really demonstrates his artistry and skill in his project, so we’re really wondering what his ‘larger project’ actually is. Take a guess in the comments section, that might get [Jonathan]’s rear in gear.

Check out the video of the omnidirectional robot after the break.

Continue reading “Omniwheel robot”

Robocup bot places wheels perpendicularly

[Eric] built this robot for the 2009 Robocup Jr. competition. The game ball has IR LEDs inside of it and this little bot uses eight IR detectors for tracking. Four motors mounted perpendicular to each other provide locomotion. Since this would normally have you traveling in circles, he used some omnidirectional wheels walled Transwheels. As you can see, they have small rollers built-in and allow movement in any direction if the motors work together. A couple of L298 controller chips handle the motors. [Eric] wrote a program to calculate the PWM necessary to drive the controllers and to coordinate movement of the wheels.

Don’t miss the demo videos after the break and, if you’re not a fan of wheels, stop by and see the bi-pedal soccer robots. Continue reading “Robocup bot places wheels perpendicularly”

Omni-car

We stumbled onto one of [Nik Melton]’s projects, an Omni-car. It is omnidirectional, meaning it can go any direction at any time without having to turn. The body was designed by him, then printed with a 3D printer. The control scheme is what interests us though. He has found a simple way to wire it to get the job done. Sure you can see that it suffers from some pretty bad “drift” when trying to go in a straight line, but overall, we think he pulled it off well.

You might want to take a few moments to look around his project page. This guy has done a bunch of fun stuff  like delta robots, strange hybrid wheel/leg robots, tesla coils, and arm mounted flamethrowers. Judging by the videos, he’s pretty young too. We think his guy has a bright future ahead of him.