Polar Pen Plotter Draws Huge Images Very Slowly

November 17, 2011 by Brian Benchoff 7 Comments

[Euphy] just posted an Instructable of his Polargraph drawing machine that’s able to draw huge images slower than molasses in November. The plotter only uses two stepper motors to control the position of the pen and can be made nearly entirely from salvaged parts – [Euphy] built his for just about £150.

The Polargraph uses two stepper motor on the top corners of a large, flat surface. A weighted pen carriage is attached to both motors with beaded cord that’s often seen in window blinds. By controlling the distance from the carriage to each motor, the position of the pen can be precisely controlled. It’s not a very fast way of drawing an image (check out the real-time video), but it sure is interesting to watch.

There have been a few other rope-and-chain plotters, like Der Kritzler and Hektor. [Euphy]’s work is the is one of the best documented builds we’ve seen, and he’s also put up the code and a website.

We really could have used [Euphy]’s plotter when we wanted to draw some whiteboard art. While we’re out dumpster diving for some small stepper motors, check out the time-lapse video of the Polargraph after the break.

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Taking GPS Where No Man Has Gone Before

November 14, 2011 by Brian Benchoff 24 Comments

[Willem] has a friend that wanted to take a GPS datalogger up an unclimbed mountain the wilds of Kyrgyzstan. The GPS logger built for the expedition made it to the summit of Eggmendueluek, but it didn’t work the whole way up. Since the logger came back to London, [Willem] was able to do a complete teardown and failure analysis.

The data logger was built around a Jeenode with a GPS unit and MicroSD card reader added on. A few breakout boards were made and two of these bad boys were ensconced in water and dust proof enclosures. Powered by four AA batteries, the data loggers were able to handle the rigorous testing of being thrown down a staircase and also the harsh temperatures of London. Things changed in the wilds of Kyrgyzstan, though.

The data retrieved from the mountaineering expedition wasn’t the greatest – a few wires came loose after being thrown into the back of a Russian truck and jostled around. The AA batteries only powered the data loggers for three days, compared to the 12 day battery life in London. There are a few improvements needed for the next trip – some thermal insulation and not using solid core wire – but not that [Willem] has figured out the bugs he’s ready for his friend’s next expedition.

Controlling Shift Registers Via SPI

November 5, 2011 by Brian Benchoff 12 Comments

Hack a Day’s very own (and very prolific contributor) [Mike Szczys] put up a great tutorial on how to drive shift registers with an SPI interface.

[Mike]’s earlier tutorial of the 595 shift register goes through the functions of a shift register pin by pin. In a 595, bits for each position in the register are sent over one at a time. Most microprocessors have an Serial Peripheral Interface, and using an SPI bus means a lot less mucking about.

An ATmega168 was used for this build, although most Atmel chips can be made to work as an SPI master device. There are just three wires connecting the microcontroller to the shift register – SER, SRCLK, and RCLK. Like any other shift register setup, the build can be expanded by connecting the QH’ pin of the first 595 to the SER pin of the second.

[Mike] graciously made all the code for his build available. The video after the break is a 16-bit binary counter, a good stopping point before [Mike] rebuilds his Larson scanner/Cylon/Kitt, moving away from a PWM-based build to a register-based one.

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Cheap OLED Display For Your TI Launchpad

November 2, 2011 by Brian Benchoff 30 Comments

The guys over at the 43oh forums have been working on an OLED display booster pack for the TI Launchpad. The booster pack is now available in the 43oh store and is pretty cheap to boot.

The TI Launchpad is an awesome little dev board with a ravenous fan base. We’ve seen a lot of projects on Hack a Day use a Launchpad – everything from intervalometers to chicken coops. Unfortunately, the MSP430 doesn’t have the market penetration of the ‘board that shall remained unnamed,’ so it’s not very common to see a new Launchpad “shield.”

[bluehash] on the 43oh forums has been hard at work for the past month to put together his OLED booster pack. The display is 128×64 pixels with an incredible amount of brightness that we would expect from an OLED display. The software for the display is based on the SSD1306 driver with two font packs – Courier New large and small. Not a bad little piece of kit for an under appreciated dev board.

Insanely Kludgy Pen Plotter Actually Works

October 31, 2011 by Brian Benchoff 10 Comments

This pen plotter, held together with structural epoxy, is an amazing piece of engineering, and almost as impressive as a bridge made entirely out of Bondo.

[Brian] at the Rochester, NY hackerspace Interlock needed to build something for the BarCamp geek “unconference.” To lure BarCamp attendees over to the Interlock table, they needed a small tabletop device with whirring motors that was able to make some decent swag. Hacking together a pen plotter sounded like the perfect project.

The mechanics of the build were scavenged from old printers and scanners. [Brian] decided to use pin-feed card stock, so the take-up wheels from an old dot matrix printer was sacrificed as well. This paper feed mechanism serves as the Y axis, and the X axis rides above the paper on precision rods. The pen holder is supported by a tiny solenoid.

Things start getting crazy at the software level. grbl was loaded onto an Arduino with a stepper driver shield, and vector text drawings were printed. After a bit of live-action hackery, [Brian] figured out how to plot captured webcam images. OpenCV captures and does a trace outline. This is converted to vectors with autotrace, and from EPS to HPGL by pstoedit. A Python script then cleans up the HPGL and converts it to G code and sends it to the printer. Confused? So are we, so just check out the video of the plotter in action after the break.

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Pololu Compatible Relay Driver

October 28, 2011 by Brian Benchoff 3 Comments

[Bart] built a couple dozen Pololu compatible relay drivers.

If you have a Reprap, you’re probably familiar with the Pololu stepper motor driver. These tiny pieces of kit provide stepper motor control for Gen 6, RAMPS, or Sanguinololu Reprap electronics. There’s a small problem with all these boards, though; there’s no way to control any high-power devices from these boards except for stepper motors. Controlling a spindle for a home-built CNC router would be great, but apart from attaching a Dremel to your x-axis, you’re just about out of luck.

[Bart]’s relay driver takes the step and direction inputs from the stock Pololu stepper driver and connects each of those to a MOSFET. From there, a relay can be hooked up to the driver to control the spindle for a router, or a whole bunch of fans for a homebrew laser cutter.

The schematic and Gerber files are up on [Bart]’s webzone. The part count is very low, and the entire board could easily be built on a piece of perfboard. Check out the demo on the other side of the jump.

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3D Printed Electromechanical Computer

October 27, 2011 by Brian Benchoff 23 Comments

A few nights ago, [Chris Fenton] was hanging out at NYC Resistor putting in some time on his electromechanical computer project. You might remember [Chris] from his tiny Cray that he’s putting an OS on. It seems [Chris] is going back in time about 150 years and has set his sights on a 3D printed version of [Babbage]’s Analytical Engine.

The Analytical Engine ~~was~~ is a remarkable feat of engineering and machining. It was the first programmable computer. Shame, then, that it was never built in the 1800s. [Chris] isn’t building a glorified calculator like [Babbage]’s polynomial-computing Difference Engine – he’s going all out and building something with conditional looping.

[Chris] calls his device an electromechanical computer, so we’re assuming it won’t be crank driven like the version in the British Science Museum. Right now, he’s constructed the decade-counting gears that are vitally important for the ALU of his design. All the parts were printed on a Thingomatic, so we’re betting [Chris] is going to be relying heavily on the MakerBot automated build platform for the thousands of parts he’ll have to fabricate.

Check out the video from NYC Resistor after the break.
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