Screen Tracking Projector

February 26, 2011 by Mike Szczys 7 Comments

[Jon Howell] came up with what he calls a gratuitous project which projects his name on his office door. The thing is, his office door slides on tracks so he made a projector that can follow the movement of that screen. He used a laser printer to make a black and white pattern that indexes the movement of the door using a quadrature encoder. When it senses door movement a servo motor rotates the projector to match the change in the door’s location. As you can see in the video after the break it works even if the door is moved quickly.

We do agree with [Jon], this is a bit much. But it might be something to build into smart white boards that are mounted on sliding tracks. We guess that if you don’t plan to change the message being projected, which is the case with [Jon’s] office door nameplate, this would be a great way to use the image projector build we looked at yesterday.

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Entrust You Kid’s Life To A Homemade Roller Coaster?

February 26, 2011 by Mike Szczys 49 Comments

So you fancy yourself as an amateur engineer? Been working on those welding skills for a while? The real test is to trust your children’s lives on a roller coaster you’ve designed and built (translated).

Now we’re not talking some tired old carnival ride like the teacups. This is a full-blown roller coaster, complete with an upside-down loop. The ride starts off with a chain-lift to the top of the garage/barn roof. From there it’s off and away on the single-rider train. We’d recommend keeping your hands and feet inside the car… if there was a car. The ride utilizes an automobile seat, but you’ll have to settle for a lap-belt as there’s no shoulder restraint here. We’re a bit wary of the track footings – we’d bet they’re not well anchored in the ground – but the fact that the entire length of track has been painted makes us think that [John Ivers] might have known at least a little bit about what he was doing. Don’t forget to catch the video below the fold.

Update: Much better video now embedded after the break thanks to [Tom 101’s] link in the comments.

Update: Source link changes to the original thanks to [Mike’s] comment.

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Image Projector Can Be Built In Minutes

February 25, 2011 by Mike Szczys 14 Comments

There’s a pretty good chance that you already have everything needed to make this image projector. We thought that yesterday’s video projector was simple, but this one makes it look like a super-computer in comparison. [Esrun] grabbed a flood light, some transparency film, and a common magnifying glass for use in his still-image project. This is more-or-less an overhead projector without the mirror, but we though it was worth sharing in hopes that it would spark your imagination and produce some other projector-oriented hacks.

The real tricks in this build are alignment and focal length. A single piece of lumber was used to help keep everything in a straight line, leaving just the vertical alignment to account for. In order to get the image in focus, [Esrun] had to do some testing for positioning the transparency film and the lens. In the end he added strips of velcro to the base to make the components easy to move. He plans to add an enclosure and change from an incandescent bulb over to a set of LEDs. We’d like to see the addition of a carousel that can house multiple transparency sheets. That or a side-scrolling roll to give it more of a film-strip feel.

555 Inductance Meter

February 25, 2011 by Mike Szczys 7 Comments

[Apexys] is performing some experiments with switched-mode power supplies and needed to compare the inductance of the coils he was using. His multimeter doesn’t have an inductance testing function, but he does have a 555 timer on hand. He put the 555 and some other parts together to create his own L meter. The writeup includes the theory behind this meter, with an incoming AC source converted to a voltage by an RC network.

Once he’d worked out the design it was time to build the circuit. Instead of printing a circuit board he created what he calls a DCB; Drawn Circuit Board. We’ve got to admit that this was way faster than using toner transfer or soldering point-to-point. We also like his use of an Erlenmeyer flask and a torch to heat the etchant. We don’t make PCBs in the winter because our Cupric Chloride is too cold to use outside but that may change now. The final piece in the puzzle is an analog meter which he pulled from an extra microamp meter he had on hand. Check out the demo after the break.

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Video Projector From An Old Single-slide Unit

February 24, 2011 by Mike Szczys 21 Comments

Here’s a video projector that [Matt] hacked together. He needed a small and inexpensive solution to use with his R2D2 build. As you can see in the video after the break, it has no problem playing back the Princess’ distress call. But even if R2D2 is not one of the droids you’re looking for, we think this can be useful in other ways. One use that pops into mind is for projector-based Halloween displays.

As with past projector hacks, all you really need to pull this off is a light source, an LCD screen on which you can playback video, and a lens to focus the light onto a screen. Usually the LCD is the most expensive part of the project and building an enclosure to the correct dimensions can be a bit difficult. [Matt’s] solution was to use an MP4 knockoff media player. The rest of the setup is a ’50s era slide projector. The screen from the media player is about the same size as a single film slide, so he removed the screen from the case and put it where the slides go.

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Debugging MSP430 Using Eclipse

February 24, 2011 by Mike Szczys 8 Comments

[Springuin] just posted a tutorial about debugging MSP430 projects using Eclipse. He read our feature about debugging under IAR, a proprietary IDE which TI offers as a code-limited freebie with the TI Launchpad. In that writeup we wondered if anyone would put together a tutorial using open source tools like DDD and GDB to make debugging easier for those that choose to use operating systems other than Windows. Even though he didn’t directly use those particular packages, this should work just as well.

Eclipse is a popular IDE for many different languages like C, C++, Java, and others. We’ve already seen it used to develop for the TI Evalbot on Linux systems. [Springuin] is using the Java-based IDE on a Windows system, and this is the first time we recall seeing directions on using an open-source alternative for programming with the TI Launchpad under Windows. That being said, the only real Windows specific parts are the steps necessary for communicating with the programmer. Since this method uses MSP-GCC and msp430-gdbproxy, it should be easy to do this under Linux as well. Use our tutorial to set up those tools if you haven’t already, then follow this one for a setting up and debugging in the Eclipse environment.

Vanishing Point Robot Guidance

February 24, 2011 by Mike Szczys 15 Comments

Students at the National University of Computer and Emerging Sciences in Pakistan have been working on a robot to assist the visually impaired. It looks pretty simple, just a mobile base that carries a laptop and a webcam. The bot doesn’t have a map of its environment, but instead uses vanishing point guidance. As you can see in the image above, each captured frame is analyzed for indicators of perspective, which can be extrapolated all the way to the vanishing point where the green lines above intersect. Here it’s using stripes on the floor, as well as the corners where the walls meet the ceiling to establish these lines. From the video after the break you can see that this method works, and perhaps with a little bit of averaging they could get the bot to drive straight with less zig-zagging.

Similar work on vanishing point navigation is being done at the University of Minnesota. [Pratap R. Tokekar’s] robot can also be seen after the break, zipping along the corridor and even making turns when it runs out of hallway.

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