Robotic Player Guitar Rocks Out On Its Own

Back in 1988 [Ben Reardon] walked through the Japanese pavilion at the World Expo held in Brisbane, Australia. He saw a robot playing a classical guitar, and was in awe. Later in his life, he decided to learn guitar, and always thought back to that robot. After going to SIGGRAPH 2014 and being inspired by all the creative makers out there, he realized the technology was here — to build his own Robot Guitar.

He started small though — with a prototype robotic Tambourine. It helped flush out some of the ideas for coding that he would eventually employ on the Robot Guitar. The guitar features both an Arduino and a Raspberry Pi, along with six RC servos — one for each string. The biggest challenge with the project was getting the servos mounted just right — stiff, but with adjustment so each pick could be tuned for identical timing. He ended up using aluminum extrusion to mount the servos, three per side in order to leave space for the picks.

Once the mechanical portion was done — onto the coding…

In the end, it ended up being only 460 lines of code. Python and a bit of Bash for the Raspberry Pi — and of course a few sketches for the Arduino. But enough talking about it — let’s hear it!

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Cultivating The Fungus Amongus

A while ago, [Kyle] built an automated mushroom cultivator. This build featured a sealed room to keep contaminants out and enough air filtering and environmental controls to produce a larger yield of legal, edible mushrooms than would otherwise normally be possible.

Now, he’s at it again. He’s expanded the hardware of his build with a proper, grounded electrical box for his rig, added more relays, implemented PID for his temperature and humidity controller, and greatly expanded the web interface for his fungiculture setup.

Like the previous versions of his setup, this grow chamber is controlled by a Raspberry Pi with a camera and WiFi module. Instead of the old plastic enclosure, [Kyle] is stepping things up with a proper electrical enclosure, more relays, more humidity and temperature sensors, and a vastly improved software stack. Inside the enclosure are eight relays for heaters and humidifiers. The DHT22 sensors around the enclosure are read by the Pi, and with a proper PID control scheme, controlling both the temperature and humidity is simply a matter of setting a number and letting the machine do all the work.

The fungi of [Kyle]’s labor include some beautiful pink and white oyster mushrooms, although with a setup like this there’s not much fungiculture he can’t do.

Homemade 3D Carving Duplicator

[Frank] is a guitar builder and has to make a quantity of acoustic guitar bridges that wouldn’t make sense to do manually by hand each time. He wanted a way of duplicating bridges quickly and precisely but he didn’t want to go to a CNC machine. Instead, he build a 3D duplicating machine.

The machine has 3 perpendicular axes, just like a milling machine. Mounted to the Z Axis is an air powered spindle that can reach 40,000 RPM. All 3 axes are moved by the operators hands. Normally, free-hand cutting something like this would be very difficult. [Frank’s] solved this in his machine by using a stylus that is offset from the cutting bit. The stylus is the same effective length and diameter of the cutting bit and is guided over a finished bridge pattern. While the stylus is tracing the pattern, the spindle and bit are removing material from a bridge blank. The stylus is continually moved over the entire pattern bridge until the spindle is finished carving out a new bridge out of the blank.

To aid in lifting the heavy Z Axis and spindle, [Frank] added a counter balance to make tracing the pattern extremely easy. Once the new bridge is carved, it only requires minor sanding to remove the tool marks before being installed on a guitar! [Frank] admits his linear bearings and rails are very rigid but also very expensive. If you’re interested in a less-expensive 3D duplicator, check out this project.

A VU-meter Indicator For A Commodore 1530 Datasette

For present-day owners of vintage Commodore computers, keeping data and programs safe and backed up is top priority. Disk drive storage was more common in the US, whereas in Europe, the audio cassette was the preferred medium of storage.

The Datasette device was what allowed interfacing the cassettes to the computer. Tape head alignment was critical to successfully writing and reading data to the cassette. Some models of the Datasette came with a small hole above the keys, to allow access to the adjustment screw of the tape head azimuth position. Tweaking this while looking at a signal meter could help you improve the signal from a bad cassette and prevent load errors. [Jani] tried a commercial solution called “Load-IT” which had a LED bargraph, but it couldn’t help much dealing with tapes with very bad signals. So he built a signal strength meter for his Datasette. He calls it the VU-sette since it uses an analog style meter quite similar to the VU-meters found in many audio equipment.

The hardware is simple and uses commonly available parts. The analog meter is extracted from a Battery Checker sourced from eBay. An op-amp drives the analog meter, and another transistor drives a separate speaker. This can be used to listen in on the cassette, if the speaker is enabled via a push button. [Jani] first breadboarded and tested the circuit before ordering out prototype boards.

To test performance, [Jani] used FinalTAP, a tool for examining, cleaning and restoring digitized data cassette tapes (TAP files) for the Commodore 64 computer. The “LOAD-IT” version worked well with tapes that were in fairly good condition. But his VU-sette version allowed him to adjust the head more precisely and get out a much better read from bad tapes. While on the subject, check out this nice 7-segment bubble LED digital counter for the 1530.

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Overengineering Beer Pong

If there’s one game that deserves to be overengineered with hundreds of LEDs, sensors, and electronic modules, it’s beer pong. [Jeff] has created the most ostentatious beer pong table we’ve ever seen. It’s just shy of playing beer pong on a single gigantic LED display, and boy, does it look good.

The table includes a 32×12 grid of LEDs in the center of the table, with 10 pods for Solo cups at each end of the table. These pods have 20 RGB LEDs each and infrared sensors that react to a cup being placed on them. The outer edge of the table has 12 LED rings for spectators, giving this beer pong table 1122 total LEDs on 608 individual channels.

With that many LEDs, how to drive all of them becomes very important. There’s a very large custom board in this table with a PIC24 microcontroller, TLC5955 PWM drivers, and enough IDC headers to seriously reconsider using IDC headers.

Put enough LEDs on something and it’s bound to be cool, but [Jeff] is taking this several steps further with some interesting features. There’s a Bluetooth module for controlling the table with a phone, a VU meter to give the table some audio-based visualizations, and air baths for cleaning the balls; drop a ball down the ‘in’ hole, and it pops out the ‘out’ hole, good as new. If you’ve ever wondered how much effort can go into building a beer pong table, there you go. Video below.

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Reverse Engineering Galaga To Fix The No-Fire Cheat

We didn’t know there was a cheat to Galaga, but [Chris Cantrell] did. And so he did what any curious hacker would do — reverse-engineer the game to diagnose and eventually fix the bug.

Spoilers ahoy! Go read the website first if you’d like to follow [Chris]’s reversing efforts in the order that they actually happened.

The glitch is triggered by first killing most of the bees. When only six are left, they go into a second pattern where they swoop across the screen and wrap around the edges. While swooping, sometimes the bees will fire a shot when they’re at coordinates with X=0. Now two facts: there’s a maximum of eight missiles on the screen at any given time, and the position X=0 was reserved by the software to hide sprites that don’t need updating.

The end result is that eight missiles get stuck in a place where they never drop and don’t get drawn. No further shots are fired in the entire game. You win.

So that’s the punchline, but everyone knows that a good joke is in the telling. If you’re at all interested in learning reverse engineering, go read [Chris]’s explanations and work through them on your own.

And here’s our generic plug for Computer Archaeology:

Ancient video games run on MAME or similar emulators are the perfect playground for learning to reverse engineer; you can pause the machine, flip a bit in memory, and watch what happens next. Memory was expensive back then too, so the games themselves are small. (It’s not like trying to reverse engineer all however many jiggabytes of Microsoft Office.) The assembly languages for the old chips are small and well-documented, and most of the time you’ve also got a good dissasembler. What more could you ask for?

A walkthrough tutorial?  We’ve just given you one.

Oh and PS: If you get past level 255, the game freaks out.

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Building A Pinball Emulator

Building a MAME machine – an arcade cabinet that will play everything from Galaga to Street Fighter II – is surely on the ‘to build’ list of thousands of Hackaday readers around the world. It’s a relatively simple build, provided you can put a sheet of MDF in your car; it’s just an emulator, and if you can find a CRT and have an old computer sitting around, you’re already halfway there.

There is another class of arcade games that can be emulated. This is, of course, pinball machines. [Jan] built a virtual pinball cabinet over the last few months and his build log is incredible. If you’ve ever wanted to build a pinball emulator, this is the guide to reference.

The most important part of a pinball emulator is the displays. For this, [Jan] is using a 40-inch TV for the playfield, a 28-inch monitor to display the backglass art, and a traditional 128×32 DMD. Instead of manufacturing his own cabinet, he repurposed an old electromechanical machine, Bally’s Little Joe.

The software is the real star of the show with PinballX serving as the front end, with Future Pinball and Visual Pinball serving as the emulators. These emulators drive the displays, changing out back glasses, and simulating the physics of the ball. The computer running all of this has a few neat electromechanical bits including a shaker motor, an original Williams replay knocker, and some relays or solenoids give the digital table a tremendous amount of force feedback. This is the way to do it, and if you don’t have these electromechanical bits and bobs securely fastened to the machine, you really lose immersion.

You can check out a video of the table in action below.

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