I need someone to explain this to me.

Understanding op-amps from simple to hard

[Tim] wanted to help out a ECE student struggling with some Op-Amp problems. He put together a video which does a good job of explaining what an Op-Amp does, then tackles each of the questions one at a time.

His analogy is illustrated in this image. There’s an operator using a crane to lift a crate. He is watching a ‘radio man’ in a window of the building to know how high it should be lifted. These roles are translated to the function of an Op-Amp in a way that makes understanding the common parts quite easy. The crane is the Op-Amp and the floor to which it is trying to lift the crate is the input pin. The current height of the crate is the output signal. The radio man is the feedback resistor which is trying to get the desired height and current height to equal each other. Watch the video after the break and all becomes clear.

After this analogy is explained [Tim] tackles the actual homework problems. He’s going through everything pretty quickly, and doesn’t actually give the answers. What he does is show how this — like most circuit solving problems — depends on how you group the components in order to simplify the questions. Grab a pen and paper and put on your electron theory hats to see if you can solve the questions for yourselves.

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Recovering from a Seagate HDD firmware bug

Hard drive firmware is about the last place you want to find a bug. But that turned out to be the problem with [BBfoto's] Seagate HDD which he was using in a RAID array. It stopped working completely, and he later found out the firmware has a bug that makes the drive think it’s permanently in a busy state. There’s a firmware upgrade available, but you have to apply it before the problem shows its face, otherwise you’re out of luck. Some searching led him to a hardware fix for the problem.

[Brad Garcia] put together the tutorial which illustrates the steps needed to unbrick the 7200.11 hard drive with the busy state bug. The image in the lower right shows the drive with a piece of paper between the PCB and the connectors which control the head. This is necessary to boot the drive without it hanging due to the bug. From there he issues serial commands to put it into Access Level 2, then removes the cardboard for the rest of the fix.

In the tutorial [Brad] uses a serial-TTL converter. [BBfoto] grabbed an Arduino instead, using it as a USB-ttl bridge.

[Dino] builds a Fetch-O-Matic for this month’s Make

Perennial Hackaday favorite [Dino] has an article in this months Make magazine. It’s an automated ball launcher that allows you to play fetch with your dog without wearing your arm out.

The powerhouse inside [Dino]‘s ball launcher is a windshield wiper motor powered by an 18 Volt cordless drill battery pack. When a ball in dropped into the hopper, it turns on a switch sending some power to the motor.

The swing arm that actually launches the ball is anchored to the frame of the ball launcher with a spring. This stores energy for one half of a rotation of the motor until the arm rotates half way around inside the box. Then, the arm quickly accelerates and launches the ball across the yard.

[Dino] says he’s working on training his dog to drop the ball into the chute after retrieving it, creating a perpetual game of fetch. At least until the battery runs down, that is. Video after the break.

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Reading punch cards with an Arduino and digital camera

[digitaltrails] wanted the data on a few old IBM 80-column punch cards he had lying around, but didn’t have decades old computer hardware in his garage. He decided to build his own out of LEGO, an Arduino, a digital camera, and a bit of Python.

The hardware portion of [digitaltrails] build includes a crank-operated feed mechanism made entirely out of LEGO. For each turn of the crank, the feed mechanism sends one card down a chute where a photodetector wired into an Arduino tells a camera to take a picture. After that, a servo is activated, sending the card into the ‘already scanned’ bin.

On the software side of the build, [digitatrails] used the Python Imaging Library to scan one row of pixels where each column is expected to be. The software outputs the code and data contained on the 80-column card as well as a very cool ASCII art version of each card.

Considering you just can’t go down to Fry’s and buy an IBM 80-column punch card reader, we’re loving [digitatrails]‘ clever way of getting data off an otherwise unreadable storage medium. Check out the video of the card reader in action after the break.

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Gumball machine delivers ebooks and games to your phone

Instead of rock-hard bubble gum that loses its flavor after 2 minutes, this gumball machine delivers apps and games directly to your smartphone.

The communications protocol used by this app-delivering gumball machine isn’t bluetooth or WiFi but near field communication. This protocol allows for a point-to-point network between the app dispenser and a phone to deliver games, music, videos, and ebooks to any compatible portable device.

The hardware for the gumball machine is a Galaxy Tab, an Adafruit NFC shield, two Arduinos, and a few switches and other components stuffed into an old gumball machine. To get purchase an app, just put a quarter or two in the machine, turn the crank, and put your phone up against the dispenser. Through the magic of near field communications, you phone or tablet receives whatever media you purchased.

Near field communication has been a standard for a while, but hasn’t been available in most phones. With oracles of Apple speculating the upcoming iPhone will have NFC capability other phone manufacturers are sure to pick up the tech. Very cool project, and we can’t wait to see some truly home-brew versions of this build.

Vidia after the break.

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Refurbing an old piano with carbon fiber

[Chris] picked up a baby grand. Of course for a complex mechanical device made out of wood, it wasn’t in the best shape. He’s doing his best to refurbish this $350 piano and turn it into something that plays and sounds like a $200,000 concert grand

The 1941 Kimball baby grand piano [Chris] picked up for $350 was a complete mess when it arrived in his house. After cleaning up the wood and replacing some felt the piano looked much better, but [Chris] wanted to make it play better.

After picking up a set of hammers from a 1909 Steinway, [Chris] tore apart the action on his Kimball. The Steinway hammers were removed from their shanks, carbon fiber shanks glued into place, and the entire assembly put back into the piano.

With new felt, new hammers, and light weight shanks on every key, [Chris] has a remarkable piano that is most likely better than new. Not a bad result for a $350 piano.

You can check out [Chris]‘ build video after the break along with a little [Mozart] (we think) after the break.

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Building the most offensive video game ever

[Autuin] created the most offensive video game ever. Inside a small cocktail arcade cabinet, he installed his own video game that recreates the experiences of the Space Shuttle Challenger and her crew on their last flight.

The build started off by picking up an old cocktail version of Space Zap from The Hackery, a neat little recycling place that turns old computers, monitors, and even old arcade machines into something useful again. After [Autuin] lugged his arcade machine back to his home base at Free Geek Vancouver.

After drooling over the 30-year-old circuitry, [Autuin] disassembled the old machine and installed a mint condition 19″ VGA monitor where an ancient black and white CRT once resided. The control panels replete with their comically large buttons were refurbished and connected to an Arduino and the whole shebang hooked up to a slightly outdated computer.

The real magic happened when [Autuin] coded his game. He created a few sprites from NASA archival footage and made a game where a shuttle takes off and is controllable by each player. As the most offensive video game ever, the space shuttle blows up shortly after launch, declaring ‘game over’ for both players.

[Autuin] will be showing off his new arcade game with a new bezel and cabinet graphics during Vancouver’s Eastside Culture Crawl this November. The game will probably be updated by then; we suggested editing the ‘time to explosion’ to T+73 seconds, but [Autuin] said he’s thinking of ways to make it even more awful.