Movie Night At The Lake Cabin

September 4, 2012 by Mike Szczys 19 Comments

[Andrew’s] family has a rustic lake cabin. There is a lot to do during the day, but since there’s no electricity your options are limited when the sun goes down. Sure there’s the traditional campfire, but lately they’ve been spicing things up with an outdoor movie viewing.

To get this up and running they needed to build a projection screen. He’s going for a 2.35:1 aspect ration, but the technique will work for any aspect if you do your own math. They had a couple of extruded aluminum channels from an old chalk board which work perfectly as the top and bottom rails of the frame. With the width set at fourteen feet he just needed to mount the cross pieces on uprights at 5.95 feet apart. This provides a 183″ viewing surface.

White bed sheets serve as the screen material. After it’s stretched into place they line the rails with binder clips to hold it in place. The projector is powered from two 12V batteries via an 800W inverter. During the day the batteries get topped off by a solar panel system.

128-inch Silver Screen For Your Viewing Room

August 21, 2012 by Mike Szczys 16 Comments

This huge projection screen fills an odd alcove in [Dodge Boy’s] screening room. He built it himself for under $200. The materials, tools, and techniques make this a possibility for anyone who wants their own projection setup.

The frame is made of pine 1×3 dimensional lumber. To keep the fabric from touching the supports in the center of the frame he added quarter-round trim to around the perimeter. From there he painted it black and went for a test-fit. The bad news is that the drywall is neither perfectly flat, nor parallel/square. He ended up taking the trim off and ripping down one side of the frame. That did the trick and he went on to stretch spandex over the whole thing. The frame hangs from a french cleat on either side of the opening. From what we can tell, the surface is just fabric and not painted as we usually see with these setups.

[Dodge Boy’s] utility room shares the back wall of the screening room. That’s where he stores the HTPC which feeds he project, with an RF remote to control it through the wall.

[via Reddit]

Automatic Speaker Control Via TV

August 15, 2012 by Mike Szczys 5 Comments

[Jon] wanted his speakers to come on and off along with his TV. The speaker heats up if left on so he didn’t want to do that. But killing the power also resets the volume level (this is an old set of PC speakers and the remote is wired, not IR) so using one of those switched power strips was out as well. He thought a bit about trying to use the power LED on the TV to build his own circuit when it dawned on him. It’s possible to monitor the USB port on the TV and use it to switch on the speakers.

The circuit above uses a couple of opto-isolators to protect both the television and the speakers. The 5V line from the USB port on the back of the TV is monitored by an XNOR gate (which helps to filter out some of the toggling at power-on). When that gate latches it activates a 555 timer which in turn fires up the speakers. Presumable this happens when power is cut as well, but we’ll let you work through the circuit logic yourself.

How Not To Dim EL Panels, TRIACs!

August 10, 2012 by Jesse Congdon 15 Comments

We’ve all been there: an exciting brilliant idea, scratched onto a napkin, hastily plugged into a breadboard, all for naught. Even the best ideas sometimes suffer from a heavy dose of reality. [Ch00f] over at ch00ftech recently had a similar experience dimming an EL panel of his using a TRIAC and some clever waveform manipulation. Instead of tossing the parts ~~across the room in a fit~~ aside and moving on he goes into a detailed analysis of what went wrong.

This method differs from the way most EL drivers dim output loads, instead of chopping the output like a PWM controlled LED the TRIAC snips the ends of the waveform and makes an ugly but less powerful output. The issue with this method is that when you cut the waveform during non-zero crossings it causes massive current spikes. These can wreak havoc on a cheap EL inverter and generally cause headaches all around. [Ch00f ] speculates that his woes may be due to the fact that EL wire is a capacitive load, causing voltage to fall out of phase with the current. This is one of those engineering problems with a thousand and one answers, we can’t wait to see what he comes up with.

Check out the writeup for all the “deets” (as [ch00f] would say) as it is a pretty good primer on TRIAC operation. If there isn’t enough glowy wire in this post you can also check out this sound reactive panel or an informative guide on EL or even more from [ch00f] in general.

MythTV Library On Apple TV Without A Jailbreak

August 2, 2012 by Mike Szczys 16 Comments

[Dan] wrote in to share a link to his MythTv to Apple TV setup. He found a way to make the recordings he made on his Linux box available on the 2nd Generation Apple TV. Our first thought is that he would use XBMC on a jailbroken device but that is not the case. The secret is to roll iTunes into the mix.

Take a look at the diagram above. The system starts with an Arch Linux box that runs MythTV, an open source program which allows you to record from tuner or encoder hardware. But actually watching those recordings on an iOS device is difficult for a couple of reasons. First, Apple likes to keep their devices locked up tight in hopes that you buy your entertainment rather than watching over-the-air records. Second, if you’re recording ATSC channels the files may be 1080i or 1080p, neither of which can be handled by the Apple TV 2. [Dan] gets around this by first using the command line version of Handbrake to transcode the recordings to an h264 format. He then uses iTunes running on an Windows 7 virtual machine (on the Linux box) to host the transcoded files in a library the Apple TV can access.

Digital TV Converter Reverse Engineering

August 1, 2012 by Mike Szczys 16 Comments

Back when broadcast television was first switching over from analog to digital most people needed to get a converter box to watch DTV broadcasts. Remember that abomination that was “HD-Ready”? Those TVs could display an HD signal, but didn’t actually have a digital tuner in them. Nowadays all TVs come with one, so [Craig] found his old converter box was just gathering dust. So he cracked it open and reverse engineered how the DTV hardware works.

The hardware includes a Thompson TV tuner, IR receiver for the remote control, and the supporting components for an LGDT1111 SoC. This is an LG chip and after a little searching [Craig] got his hands on a block diagram that gave him a starting place for his exploration. The maker of the converter box was also nice enough to include a pin header for the UART. It’s populated and even has the pins labeled on the silk screen. We wish all hardware producers could be so kind. He proceeds to pull all the information he can through the terminal. This includes a dump of the bootloader, readout of the IR codes, and much more.

Diablo 3 Is An Arcade Game, Apparently

July 26, 2012 by Brian Benchoff 7 Comments

MAME cabinets are simply awesome. They’re a great way to relive the stained and sticky fluorescent carpets, loud noises, and Neon signs and blacklights of old arcades. If there’s one problem with MAME cabinets, it’s that gaming has moved on from the quarter-eating cabinets of yesteryear. It simply doesn’t make sense to put Starcraft, TF2, or other popular games in an arcade cabinet.

[Dave] grew up playing Gauntlet in the arcade, but the various console ports never lived up to the experience of playing it with a joystick and buttons. When Diablo 3 came out, [Dave] knew what he had to do. He built a Diablo 3 arcade cabinet, fully playable and faithful to the dungeon crawlers of yore.

Thankfully, an old cabinet wasn’t gutted for this build; a month before the game came out, [Dave] picked up a few pieces of plywood and built himself an arcade cabinet. After applying some very nice graphics and installing buttons and a joystick, [Dave] had a fully functional Diablo arcade game that doesn’t even require quarters.

Recently, we’ve seen our share of builds that turn traditional game controls on their head, a trend we hope continues. You can check out [Dave]’s demo video after the break.

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