Simple robot knows its bounds


The [Dallas Personal Robotics Group] recently put together a set of tutorials for their members, including the build process of a table-top robot, they call the Tiny Wanderer. The bot can be constructed pretty easily, and is meant as an introduction to robot building.

The small servo-driven bot uses simple edge sensors to ensure that it doesn’t fall off a raised surface. The sensors were built using a small IR LED and photo transistor, which is partially isolated from the LED by a piece of shrink tubing. An ATiny micro-controller takes two measurements of the amount of IR light entering the photo transistor – one with the LED on, the other with the LED off. The difference of these measurements is compared to determine if the edge sensors are hanging off the side of the table. The logic used here is pretty simple – the difference will be high if the sensors are hovering over a surface, due to reflected light, and low if the sensors are hanging over open space.

The writeup contains templates for building the bot’s structure, as well as source code and schematics for all of the electronic bits.

Be sure to stick around to see a video of the robot in action.

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People-tracking orb demo makes us want to build our own


Earlier this week, we came across a video of an orb-based eyeball that would follow you throughout the room, based on data gathered from a Kinect sensor. Try as we might, we couldn’t find much more than the video, but it seems that the guys behind the project have spoken up in a recent blog post.

[Jon George] of The Design Studio UK explained that the person-tracking eyeball visualization was built using a PC, a Kinect, and a product called the Puffersphere, which projects a 360 degree image on the inside of a glass orb. A panoramic image is converted for use by the special lens inside the sphere by applying a filter which warps the image into a circular shape.

After the image has been created, a simple Windows app is used in conjunction with the OpenNI framework that allows the image to follow you around the room.

The only problem with this fun little project is the price of the sphere – we’re not sure what it is exactly, but rest assured it is more than we are willing to pay for such a toy. We’re thinking there has to be a way to simulate the orb’s effect to some degree using cheaper hardware. It’s possible that it could be done using a small-scale DIY version of this spherical mirror projection build, though it consists of concave half-spheres rather than full orbs.

In the meantime, take a look at these two videos of the orb in action. Don’t worry – we know you were totally thinking about the Eye of Sauron, so the second video should not disappoint.

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Converting a scanner into a touchscreen

[Sprite_TM] was cleaning up his hacking workbench when he came across an all-in-one device that had seen better days. After a bit of consideration he decided to tear down the scanner portion of the device and ended up turning it into a multi-touch display.

The scanner relies on a long PCB with a line CCD sensor. This sensor is read in a similar way that information is passed along a shift register. Tell it to take a reading, and then start a clock signal to pulse out each analog value from the pixels of the sensor. In order to scan color images it uses multicolored LEDs to take different readings under different illumination.

[Sprite_TM] takes advantage of this functionality to turn it into a multitouch sensor. The sensor board itself is mounted below an LCD display along with a shield with a slit in it to help filter out ambient light. Above the screen a series of LEDs shine down on the sensor. When you break the beams with your finger it casts a series of shadows which are picked up by the sensor and processed in software. Watch the clip after the break to see it for yourself. It has no problem detecting and tracking multiple contact points.

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Don’t buy an amp, build one to suit

In need of an amplifier for his home entertainment system [Afroman] decided to build an amp rather than buying one. If nothing else, doing it himself allowed for a form factor that can’t just go out and buy.

He designed the project on two separate boards, one for the power supply and the other for the amplifier circuit. Both are of his own design, and although he doesn’t share the schematic, we know he’s based his work on a National Semiconductor reference design for the LM4780 audio amplifier chip. There’s a few other clues, like his mention of the toroidal transformer seen at the left in the image above and hi-res photos of the unpopulated board that has component values printed in the silk screen.

The final design allows him to get great performance out of his speakers with a very clean look. You’ll need to be logged to the forum linked above to view all of the images, but we’ve embedded three more of them after the break to whet your appetite.

Oh, and cost? This gets up there, just sneaking past the $500 mark.

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Tricycle robot using omni-wheels

[Markus Gritsch] built this six-wheeled robot using omni-wheels. Two wheels are used on each axis in order to ensure perpendicular rotation is possible no matter where the axis rotation stops. The wheels have also been improved by dipping the elliptical components to give them a rubbery coating.

The robot gets its commands wirelessly from a separate controller unit. That controller, as well as the bot seen above, uses a Teensy microcontroller board. Two analog sticks take input from the operator and transmit commands using an inexpensive RF pair. The wheel movement is facilitated by three servo motors which may seem like an odd choice. But we think that it simplifies the electronic side of the build because you do not need an H-bridge to control a servo motors. It’s a bit loud, as you can hear in the video after the break, but it certainly works quite well.

One of the commenters on the thread above asks why [Markus] didn’t use mechanum wheels. These would have allowed him to use just one wheel on each axis but the omni-wheels were so inexpensive that he went this route instead.

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Kinect, mouse, and nerf gun combine for House of the Dead

[Tony Blanch] built his own motion controller for playing House of the Dead. It should work with any shooter that follows the ‘rail’ type of game play (your character is not free walking, but moves along a set path beyond your control).

Two parts come together to make this happen. The first is the Nerf dart gun that you see above. The circuit board fitted into the top portion of the plastic housing is from a five-button wireless mouse. The buttons are used to sense trigger pulls from the player. The second portion of the controller is a Kinect. It has been set up to work with a Windows 7 machine. [Tony] used the Flexible Action and Articulated Skeleton Toolkit (FAAST) to bind and track the gun controller, moving the mouse cursor on the screen to match the movements of the weapon. Check out the video after the break to see how responsive this system is.

This is a very interesting departure from the gun controllers we’ve seen before.

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