Retrotectacular: Time Sharing

It’s easy to forget the layer upon layer of technological advances that led to the computers we use today. But this look at the state of the art half a century ago does a good job of reminding us. Here [Fernando J. Corbató] explains the concept of Time-Sharing. He is one of the pioneers of the topic which is now used in every computer system in the world.

Since processors (read: a single core) can only work on one operation at a time, it inherently creates a bottle-neck. This is a huge issue when you consider the cost of the computers used at the time. In the video he mentions $300-$600 an hour. That was in the 1960′s and would roughly equate to about $2300-$4600 in 2012. In other words, there’s big money in using the machine as efficiently as possible.

Early on in the discussion he mentions how programs were loaded and solutions were returned by computers of the day. It started with punch cards, then moved to magnetic tape. At the time this was filmed they had just started using teletype and were hoping to add a graphical interface in the near future. We’ve come a long way but the core principles he’s explaining are still quite important. See both parts of the film after the break.

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Some technical improvements on [Alton Brown's] hacked smoker

Bringing that smoky goodness to your cooking is neither hard, nor is it expensive. [Alton Brown], who we consider to be the MacGyver of cooking, always seems to be able to build cooking contraptions from common items. The smoker he built from a flower pot was the inspiration for [Tom's] own project. But [Tom] added in PID hardware to smoke at just the right temperature.

The enclosure hides a single electric burner at the bottom. A metal tray full of wood chips sits on top of it, smoldering as the burner gets hot. You could just set it and forget it, but it will take a lot of trial and error to figure out which setting achieves the best results. [Tom's] additional hardware, housed in the grey electrical box, switches the burner with a solid state relay. The PID controller takes measurements from a temperature sensor inserted in the lid of the smoker, ensuring perfectly prepared food every time.

If you’re interested in making your own you could try building a heating element from toaster oven parts.

QR code opens doors to you

[Jeremy Blum] wrote in to share his LibeTech QR Code Door Lock project. He developed it during his Senior year at Cornell University along with three of his classmates. It seeks to move away from magnetic card locks in favor of optical locks that authenticate based on a QR code.

The hardware he’s using here is definitely cost prohibitive, but we’re sure the concept could be greatly simplified. In this case a BeagleBone running embedded Linux monitors a feed from a webcam. When it detects a QR code it compares it with a database of approved keys and will unlock the door for you.

There are problems with this technique, one being that an attacker might be able to get a usable photograph of your key without you knowing. But the majority of hotel locks in use right now are even less secure than that. On the upside, the key to your room can be emailed to you for use on just about any device with a screen, or printed out on a piece of paper.

You can find [Jeremy's] presentation video embedded after the break.

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Vending machine prototyping

[Vending Mexico] plans to design, build, and sell their of vending machines. You’ve got to start somewhere so they’ve built this prototype. It offers a range of vending features but was built with parts we’re used to seeing in hobby projects.

The one challenge they didn’t take on is the ability to identify coins and make change. You can see they’ve chosen to use a Coinco Guardian 6000 changer. But the custom circuit taps into the device, identifying how much money has been dropped in the slot, and controlling the coin dispenser to make change. Right now there is only one item to choose from; some packs of gum  stored in a cardboard partition with the typical metal corkscrew — driven by a servo motor — to dispense the product. Just below that partition there is a row of IR LEDs which have a complimentary set of IR phototransistors. The machine uses these to detect when product has dropped through. This way if your candy gets stuck you get your money back.

The user interface is shown off in the video after the break. It uses a set of seven segment displays for feedback. An arcade button is used to select the desired product. The video dialog is in Spanish but we had no trouble telling what is being shown off even though we don’t speak the language.

We can’t remember seeing other scratch built vending machine. It seems all of them have been hacks on older commercial vending hardware.

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Incredible fabrication process makes this Word Clock stand out

From the look of it his is just another Word Clock, right? From the outside maybe. But if you take a look at the build photos this a good example of extreme fabrication.The design uses a five-layer lamination of glass bezel, vinyl lettering, diffuser, mounting plate, and back panel. The mounting and lettering layers were labor intensive, but are also the reason for the gorgeous finished look.

The bezel consists of black adhesive foil applied to the back of the glass faceplate. The letters were cut out using a vinyl cutter, and the lamination process happened in a pool of water. This technique helps to ensure that no fine particles end up between the glass and the foil.

The wooden mounting bracket was ordered from a local kitchen cabinet fabricator. It’s MDF that is 17.7″ and has been edge wrapped in glossy white PVC. Once it arrived, [Muris] started drilling the 248 holes and their counter sinks. This is on the front side of the layer and when sprayed with silver paint the countsinks act as reflectors. On the back side he milled groves to accept PCB strips to host the LEDs as well as the breakout boards that hold the MAX7219 drivers.

Don’t miss the video clip after the break that shows off the final product.

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Integrating a power bus into a quadcopter frame

When working on flying vehicles weight is always a consideration. [Brendin] found a way to get rid of a wiring harness on his quadcopter, simplifying the assembly while lightening the load. He did it by incorporating the power bus into the frame of the vehicle.

He started with some copper clad board. Because the substrate is a structural component he didn’t want to use a CNC mill to do the etching as it also removes a bit more than just copper. After using the mill to cut out the shape and drill holes he coated the board with flat black paint. This acts as the etch resist, which he sent through a 50W laser engraver to remove the paint and expose the areas he wants to etch. After etching he removed the rest of the resist, and masked off his solder pads with small rectangles of electrical tape. This protects the solder pads from the truck bed liner paint he uses to insulate the copper. He says it works great and plans to use the technique on all future builds.

Scrolling tweets with a WiFi LED matrix

For his most ambitious build to date, [Param] thought it would be a cool idea to have a LED matrix display spitting tweets out via a WiFi connection. The build is now done, and we’ve got to hand it to him for a very nice build.

The build is based on an Arduino with a Sparkfun WiFi shield providing the network connection. The Arduino pings a Javascript app that pulls down tweets from The Verge and displays them on an 8×8 LED matrix display.

What makes [Param]‘s build so cool is its portable nature; the entire device is completely wireless, getting its power from a Sparkfun LiPower shield  and an apparently extremely capacious LiPoly battery.

With a rat’s nest of wires hanging out the back of the LED display, [Param]‘s build is crying out for a proper enclosure, but even given that it remains a quality project. You can see a video of the WiFi’d Twitter display after the break.

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