Home tanning lamps become organ donors for a PCB exposure bed

Some projects benefit greatly from the parts a builder is able to find. Take this UV exposure bed for photo-resist copper clad boards (translated). It looks like a commercial product, but was actually built by [TabascoEye] and his fellow hackers.

The main sources for parts were a flatbed scanner (which acts as the case) and two self-tanning lamps that use UVA flourescent bulbs. By sheer luck the bulbs and their reflectors are exactly the right size to fit into the top and bottom cavities of the scanner. The control hardware centers around an ATtiny2313 micorocontroller, which takes input from a clickable rotary encoder, and displays exposure information on a character LCD. The finished product deserves a place right next to other professional-looking exposure boxes that we’ve looked at.

Automated scanning for a pile of documents

The Gado project is part of the Johns Hopkins University Center for African Studies. It has been tasked with archiving documents having to do with the East Baltimore Oral Histories Project. In short, they’ve got a pile of old pictures and documents that they want digitized but are not easily run through a page-fed scanner because they are fragile and not standard sizes. The rig seen above is an automated scanner which picks up a document from the black bin on the left, places it on the flat-bed scanner seen in the middle, and moves it to the black bin on the right once it has been scanned. It’s not fast, but it’s a cheap build (great if you’ve got a tight budgt) and it seems to work.

The machine is basically a three-axis CNC assembly. Above you can see one motor which lifts the lid of the scanner. You can’t see the document gripper in this image, but check the video after the break which shows the machine in action. A vacuum powered suction cup moves on a gantry (y-axis) but is also able to adjust its height (z-axis) and distance perpendicular to the gantry (x-axis) in order to grab one page at a time.

The pictures on the build log have captions to give you an idea of how this was built. We didn’t see any info about post-processing but let’s hope they have an auto-crop and auto-deskew filter in place to really make this automatic.

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Cheap and reliable portable face recognition system


For their senior ECE 4760 project, engineering students [Brian Harding and Cat Jubinski] put together a pretty impressive portable face recognition system called FaceAccess. The system relies on the eigenface method to help distinguish one user from another, a process that the pair carried out using MatLab.

They say that the system only needs to be hooked up to a computer once, during the training period. It is during this period that faces are scanned and processed in MatLab to create the eigenface set, which is then uploaded to the scanner.

Once programmed, the scanner operates independently of the computer, powered by its own ATmega644 micro controller. Users enroll their face by pressing one button on the system, storing their identity as a combination of eigenfaces in the onboard flash chip. Once an individual has been enrolled, a second button can be pressed to gain access to whatever resources the face recognition system is protecting.

The students say that their system is accurate 88% of the time, with zero false positives – that’s pretty impressive considering the system’s portability and cost.

Stick around to see a quick demo video of their FaceAccess system in action.

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CNC mill built from junk and hardware store parts

[Csshop] is setting a new bar for building an inexpensive CNC mill. Not only did he complete his build at a very low cost, but it seems to work quite well too. Check out the video after the break to see the device cut out thin wood parts for a toy plane.

The majority of the build uses scrap wood for the body of the mill. The business end of the device is a flexible rotary attachment for a Dremel tool which takes a lot of the weight and bulk out of the gantry assembly. Old flat bed scanners were gutted for the precision ground rod and bearings, as well as the three stepper motors used to drive the axes. An Arduino board controls the device, commanding the stepper motors via EasyDriver boards.

Once the hardware is assembled there’s still a fair amount of work to do. [Csshop] builds his designs in Google Sketchup, but some conversion is necessary to arrive at code that the Arduino will understand. He’s got a second project write-up that covers the software side of things.

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Converting a scanner into a touchscreen

[Sprite_TM] was cleaning up his hacking workbench when he came across an all-in-one device that had seen better days. After a bit of consideration he decided to tear down the scanner portion of the device and ended up turning it into a multi-touch display.

The scanner relies on a long PCB with a line CCD sensor. This sensor is read in a similar way that information is passed along a shift register. Tell it to take a reading, and then start a clock signal to pulse out each analog value from the pixels of the sensor. In order to scan color images it uses multicolored LEDs to take different readings under different illumination.

[Sprite_TM] takes advantage of this functionality to turn it into a multitouch sensor. The sensor board itself is mounted below an LCD display along with a shield with a slit in it to help filter out ambient light. Above the screen a series of LEDs shine down on the sensor. When you break the beams with your finger it casts a series of shadows which are picked up by the sensor and processed in software. Watch the clip after the break to see it for yourself. It has no problem detecting and tracking multiple contact points.

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Phosphorescent Laser Painting

Here’s a simple and interesting idea that increases the visual persistence of a laser scanner image. Using glow-in-the-dark paint, [Daito Manabe] prepares a surface so that the intense light of a laser leaves a trace that fades slowly over time. He’s using the idea to print monochromatic images onto the treated surface, starting with the darkest areas and ending with the lightest. The effect is quite interesting, as the image starts out seeming quite abstract but reveals its self with more detail over time.

As evidenced in the test videos, the bursts of laser scanning are matched to the fade rate of the paint. Therefore it would seem that the time taken to “write” an image is directly proportional to the desired visual persistence of the final image. We wonder, by combining clever timing and variable laser intensity could you write images much more quickly? How hard would it be to use this for moving pictures? With the ability to create your own tiny laser projector, and even an RGB scanner, there must be a lot of potential in this idea for mind-blowing visual effects. Add portability by using a phosphor-treated projection screen!

Share your ideas and check out the test videos after the break.

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LEGO barcode scanner

Playing store just got really, really fun because you can now build your own LEGO barcode scanner. As you can see after the break, it works well and it’s fast like a real barcode scanner. Unfortunately it doesn’t scan real barcodes. Or at least not traditional ones. As we learned in the Barcode Challenge, standard barcodes are a set of white and black bars that make up the ones and zeros of the code. This system uses the same white and gray bar system but it seems that it’s only the number of bars that identify an item, not a code created by a particular combination of light and dark. The items above are all scannable because the scanner counts the 2, 3, 4, 5 or 6 white beams on the bottom of each package. Still, it’s incredibly clever and a great toy for the young hackers to build if they have a little help.

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