Month: January 2011

Digitizing Player Piano Rolls

January 11, 2011 by 28 Comments

What do you do with 100 player piano rolls but no player piano? You come up with a way to digitize the information for MIDI playback. The rolls have 90 columns worth of holes, 88 for the keys and two more for pedals. Voids in the paper cause a note or pedal to be played, so an optical sensor can be used to transform the analog data into digital information. Simple enough, you’ll just need 90 sensors. But this brings up quite an alignment issue. The solution is to use fiber optic cable to position the IR light source in a hand-made 0.2″ spaced jig. At least the spacing meshes nicely with standard 0.1″ protoboard, which is what was used for mounting the sensors.

[Thanks Mike]

Button Cell Connectors For Breadboarding

January 11, 2011 by 34 Comments

We’re working on a project that has a battery backup, but we don’t have any more coin cell holders on hand. No problem, we remember seeing a double pin header used for this. But when we tried to shove the CR2032 battery in between the pins it was a no-go. We could swear we’d featured a project that does this but couldn’t find it here at Hackaday. After much searching we came up with the Guerrilla battery holder which is seen on the left. No wonder it wasn’t working, the CR1212 in that picture is a much smaller package. So we figured we’d have to come up with something else, until inspiration struck.

There must be some other way to configure the pin header to work with a fatter cell body. On the right you can see that a diagonal orientation works like a charm. Join us after the break for a couple of close-ups of that connector and our thoughts on using this with a variety of different cells.

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Speed Up Web Browsing In Linux

January 11, 2011 by 46 Comments

In modern computer systems, the biggest bottleneck of information tends to be in communicating with the hard disks. High seek times and relatively slow transmission rates when compared to RAM speeds can add up quickly. This was a necessary evil back when RAM space and costs were at a premium, but now it is not uncommon to see 4GB of RAM on laptops, and even 12GB on desktops. For  users whose primary computer use is browsing the internet (either for work, writing articles, or lolcats) and have some extra RAM, moving the browser cache to the RAM from the hard disk is a definite option for increasing speed.

In Linux systems (specifically Fedora and Ubuntu systems), this can be achieved for Chrome and Firefox by creating a larger ramdisk, mounting the ramdisk after boot, and then setting the browser of choice to use that ramdisk as a cache. The necessary commands to do this are readily available (internet archive) on the internet, which makes life easy. Using ramdisks for performance boosts are not exclusive to browsers, and can be used for other software such as Nagios for example.

We have previously covered a tool called Espérance DV for moving cache to RAM in Mac OSX, and for any Windows users feeling left out, there are ways of making Firefox bend to your will. Obviously you will see an increase in RAM use (duh), but this shouldn’t be a problem unless you are running out of free RAM on your system. Remember, free RAM is wasted RAM.

Halloween Hangover: Talking Heads

January 10, 2011 by 17 Comments

Here’s a Halloween prop leftover; [Chris] built his own version of singing heads from Disney’s Haunted Mansion on his porch for last year’s ghoulish decor. A projected image of actors singing a spooky song gives each of the four Styrofoam mannequin noggins its own digital life. There’s an optical sensor on the porch stairs that is tripped by unsuspecting candy-seekers. An Arduino monitors the sensor and uses AutoHotkey to start the video clip on a netbook. Check out the video after the break to see the finished display do its thing after dark.

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Outside-air Cooled PC

January 10, 2011 by 120 Comments

[Brian] came up with an interesting PC cooling setup. He lives up north where it’s chilly in the winter. Using a bit of dryer ductwork and he was able to harness the outside air to cool his box. The system uses a window insert along with a dryer hood to suck in the outside air with a PC fan. We hope the air is adequately warmed, as it is exhausted into the room. Join us after the break for more pictures of his setup.

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DIY Air Gap Flash Saves At Least Seven Grand

January 10, 2011 by 27 Comments

Did you know that a standard camera flash is much too slow to capture high quality images of bullets? A relatively long flash duration results in blurred images of the bullet. By building this air gap flash a bullet can be frozen in mid-air, producing some stunning results. There is an element of danger here, and not from the bullet. This flash uses a 35,000 volt capacitor to produce the mini-bolt of lightning which serves as the light source. The unit can be built for a few hundred dollars, which sounds like a heck of a deal if commercial models really do start at $8k and go up from there.

Now that the photographer has a super-fast flash, a camera axe takes care of the timing… which is everything.

555 Based AM Radio Transmitter

January 10, 2011 by 33 Comments

Bust out that 555 timer and use it to build your own AM radio transmitter. The circuit that [Rtty21] is using only needs the timer chip, an NPN transistor, three caps, three resistors, and a potentiometer. It generates an amplitude modulation signal around the 600 kHz range which you will be able to pick up with any normal AM radio. From the comments on the article it seems you’ll get around 30-40 feet of range out of the device. We don’t see this as a competitor for the FM spy microphone, but maybe you can use it as a diy baby monitor.