Hackaday Links: December 22, 2013

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[Korben] is using a picture frame as a Bluetooth speaker (translated). He hacked a Rock’R² for this project. It’s a device that has a vibrating element which can be used to make any hollow item into a speaker.

Entertain yourself over the holidays by mastering the Apollo Guidance Computer simulator. It’s a JavaScript version of the computer used in the modules of the Apollo moon missions.  [Thanks Gregory and Paul]

Here’s a little mirror attachment that lets you use your laptop as an overhead projector. [Ian] calls it the ClipDraw. Affix it to the webcam and use the keyboard as the drawing surface. Since it’s simply using the camera this works for both live presentations and video conferencing. What we can’t figure out is why the image doesn’t end up backward?

This guide will let you turn a Carambola board into an AirPlay speaker.

Those who suck at remembering the rules for a game of pool will enjoy this offering. It’s some add-on hardware that uses a color sensor to detect when a ball is pocketed. The Raspberry Pi based system automatically scores each game.

We spend waaaay too much time sitting at the computer. If we had a treadmill perhaps we’d try building [Kirk's] treadmill desk attachment. It’s made out of PVC and uses some altered reduction fittings to make the height adjustable. It looks like you lose a little bit of space at the front of the belt, but if you’re just using it at a walking pace that shouldn’t matter too much.

You can have your own pair of smart tweezers for just a few clams. [Tyler] added copper tape to some anti-static tweezers. The copper pads have wires soldered to them which terminate on the other end with some alligator clips. Clip them to your multimeter and you’ve got your own e-tweezers.

AquaTop: a gaming touch display that looks like demon possessed water

AquaTop_touch_displayAre you ready to make a utility sink sized pool of water the location of your next living room game console? This demonstration is appealing, but maybe not ready for widespread adoption. AquaTop is an interactive display that combines water, a projector, and a depth camera.

The water has bath salts added to it which turn it a milky white. This does double duty, making it a reasonably reflective surface for the projector, and hiding your hands when below the surface. The video below shows several different games being played. But the most compelling demonstration involves individual finger tracking when your digits break the surface of the water (show on the right above).

There is also a novel feedback system. The researchers hacked some speakers so they could be submerged in the tank, adding a large speaker with LEDs on it in the same manner. When fed a 50 Hz signal they make the surface of the pool dance.

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Build a waterproof music controller on the cheap

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[Aaron] wrote in to show off the waterproof music controller (translated) he just finished building. He uses it in the shower — which makes us wonder how long he’s spending in there. We could also see it being useful by the pool, on the beach, or anywhere else that you need a cheap and easy control system.

His computer plays tunes while he’s getting ready for the day. This means he was able to use an inexpensive wireless keyboard for control. The donor keyboard has dedicated music control keys which he carefully traced to the PCB before removing the flexible sheets that detect key presses. Next he found a water tight food container and sized his protoboard to fit. You can see his button layout above. Holes were cut in the lid of the container, with a plastic membrane glued on the underside. This will keep the water out while still allowing him to actuate the momentary push switches.

Most mobile devices will work with wireless keyboards. If your car is nearby just hook your phone to the stereo and control it with this rather than building a dedicated beach stereo system.

Computer tracking of billiard balls

The folks at the London-based startup GoCardless have a pool table at their office. Being the techies they are, they decided to build a system that automatically scores games. The results, while not fully complete, are still pretty impressive for something whipped up during a 48 hour hackathon.

The automated score keeper uses a webcam duct taped to the ceiling right above the center of the pool table, The balls – red and yellow balls replace the rainbow of solids and stripes to make things easier – are found using OpenCV.

This build isn’t quite finished yet. The people at GoCardless are looking to improve the accuracy of their setup by using a camera with a higher frame rate and possibly moving on to physics simulation to predict where the balls should be. If these guys get the time, they could add something like augmented reality pool table to improve shot accuracy.

Vidia after the break.

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Skateboard tagging

We abhor vandalism, but we love art. Here’s a skateboard hack that lets skate punks young and old tag their turf while they ride. [D*Face], a multimedia street artist who grew up in London, added a mounting system to the bottom of his skateboard which includes a can of spray paint. We’re a bit surprised that there’s room enough for that, but the system fits nicely. They’re not locked into a constant stream because the system lets the rider (or a bystander) actuate the spray can via remote control.

But the brush is only one part of the painter’s tool chain. To get the most interesting effect, a pool was painted white to serve as canvas and a troupe of skaters was unleashed on it to try out the modified boards. Check out the video after the break to see the colorful and pleasing curves that result. We just hope nobody bailed and smeared the canvas at the same time.

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The PR2 calls the shots

Can you beat this robot at pool? This sparks something of a “let the wookie win” attitude for us, but we still love to watch the video. This is the PR2 playing pool thanks to the folks over at the Willow Garage. It uses a laser sensor to detect the legs of the pool table, and cameras to find the diamonds and balls at the playing surface rather than using an overhead camera. They cut down on the coding work needed by using FastFiz, an open source Billiards physics library. The final step was building an interface so the robot could use a cue. Check it out after the break (no pun intended).

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Virtual pool, real-world interface

Sunday we saw robots playing pool and an augmented reality pool game. Today we’ll complete the pool trifecta: virtual pool using a real cue stick and ball in another vintage video from Hack a Day’s secret underground vault. The video is noteworthy for a couple of reasons:

First is the year it was made: 1990. There’s been much buzz lately over real-world gaming interfaces like the Nintendo Wii motion controller or Microsoft’s Project Natal. Here we’re seeing a much simpler but very effective physical interface nearly twenty years prior.

Second: the middle section of the video reveals the trick behind it all, and it turns out to be surprisingly simple. No complex sensors or computer vision algorithms; the ball’s speed and direction are calculated by an 8-bit processor and a clever arrangement of four infrared emitter/detector pairs.

The visuals may be dated, but the interface itself is ingenious and impressive even today, and the approach is easily within reach of the casual garage tinkerer. What could you make of this? Is it just a matter of time before we see a reader’s Mini-Golf Hero III game here?