Salvaged Robot Arm Makes A Big 3d Printer

June 19, 2012 by Mike Szczys 34 Comments

Wow, building a precision 3d printer is amazingly easy if you can get your hands on an industrial-quality robot arm. [Dane] wrote in to tell us about this huge extruder printer made from an ’80s-era SCARA robot arm. It is capable of printing objects as large as 25″x12″x6.5″.

This 190 pound beast was acquired during a lab clean out. It was mechanically intact, but missing all of the control hardware. Building controllers was a bit of a challenge since the it’s designed with servo motors and precision feedback sensors. This is different from modern 3d printers which use stepper motors and no feedback sensors. A working controller was built up one component at a time, with a heated bed added to the mix to help prevent warping with large builds. We love the Frankenstein look of the controller hardware, which was mounted hodge-podge as each new module was brought online.

You can see some printing action in the clip after the break. A Linux box takes a design and spits out control instructions to the hardware.

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STM32 Demo Code Carries Extra (hidden?) Copyrights

June 19, 2012 by Mike Szczys 31 Comments

Recently I started a repository that houses a template which may be used to compile STM32F0 projects with a GCC toolchain. There are two code packages from STM that I used when putting this together, the firmware for the Discovery board itself, and the Standard Peripheral Library for the chip family. I read the license agreements in the root of both packages and I think they’re quite fair. Basically the agreement is you can use them for any purposes as long as the code is only being used on STM hardware. Fair enough.

You can image I was quite upset so see a comment from a reader stating that I have a copyright violation with one of the files in the repo. It seems the linker script that is given as an example for Atollic’s TrueSTUDIO has it’s own extremely strict copyright:

** (c)Copyright Atollic AB.
** You may use this file as-is or modify it according to the needs of your
** project. Distribution of this file (unmodified or modified) is not
** permitted. Atollic AB permit registered Atollic TrueSTUDIO(R) users the
** rights to distribute the assembled, compiled & linked contents of this
** file as part of an application binary file, provided that it is built
** using the Atollic TrueSTUDIO(R) toolchain.

First off, I’m in violation just for posting the file in a repository. But read a bit deeper. Any code that is compiled with this using a GCC toolchain also breaks the copyright unless it’s Atollic’s toolchain.

My beef here is that STM is distributing this. Why? Why put something so restrictive into a software library with such an otherwise reasonable license? Surely there are many engineers at STM capable of writing a linker script that they could release under their own license which would work with TrueSTUDIO. And, it would have the added benefit of allowing other GCC-based toolchains a convenient (and legal) method of linking code.

So I’ve completely removed the file from the repository. If you were one of the ten people watching it on github, this had the unintended consequence of dumping your watch request. In the mean time I’m trying to learn how to write my own linker. This guide regarding Cortex-M3 linkers has been a great help. If you have the skills to contribute a working linker script, please issue a pull request or raise an issue over at github.

Multi-channel Analog Input Module Is A Good Jumping-off Point For Many Projects

June 19, 2012 by Mike Szczys 12 Comments

[Scott Harden] has already produced some projects which measure analog inputs. But he’s got plans for more and wanted a base system for graphing analog signals. You can see the small board next to his laptop which offers the ability to sample up to six signals and push them to a PC via USB.

The ATmega48 and a few supporting components are all you’ll find on that board. The USB connection is taken care of by an FTDI cable. He went that route because the cables are relatively cheap, easy to come by, and already have driver support on all the major operating systems. If you look at the screen you can see a window graphing one analog input in real-time. He wrote this in Python (which is once again a cross-platform tool) and it has no problem graphing all six inputs at once.

This is immediately useful as an upgrade to [Scott’s] ECG machine. His future plans include a Pulse Oximeter, EEG, and EEG.

Using Solar Cells To Track The Sun For Your Solar Cells (dawg)

June 19, 2012 by Mike Szczys 13 Comments

This solar panel tracks the sun using solar cells. It’s a pretty interesting technique, and can be done on the cheap.

The rectangular panels are doing the actual energy harvesting. The circular modules seen below are solar cells from some landscaping lights. They’re being used as sensors to help judge if the device is aimed directly at the sun. We’ve already seen this type of thing done with a quartet of light dependent resistors. In this case, if the negative leads for both landscaping lights are connected, a voltage may be read from the positive lead of each panel. If you measure that voltage, and use a rotating stand to adjust the position until the readings balance, you can be assured that your array is getting the optimal amount of sunlight.

[Gtoal] had been trying to drive motors directly from the output lines of these panels without success. We’re sure there’s a simple analog comparator circuit which would facilitate this. Grabbing a small microcontroller is another option (and some chips have an analog comparator built in).

Driving A PSP Screen With An FPGA

June 18, 2012 by Mike Szczys 12 Comments

Here’s [FlorianH’s] setup for driving a PlayStation Portable screen with an FPGA. He’s using the DE0-Nano board to do this, and the first order of business was to establish a way to connect the two. He did a great job of etching his own breakout board, which has some traces that are less than 10 mils thick. Soldering the connectors for the screen was a bit of a challenge, and he shared several pictures of the process for your enjoyment.

With everything hooked up he fired it up with just a couple of lines of code to draw a test pattern. From there it was on to building a more intensive driver. [FlorianH] mentioned to us that he’s just starting to learn about FPGAs after having worked extensively with 8-bit microcontrollers. He’s been documenting his work on his site, and finds himself frequently referencing his own material so remember how he did things. Our vicarious enjoyment is an unintended (but welcomed) consequence of that habit.

Shake Phone To Start Scooter

June 18, 2012 by Mike Szczys 14 Comments

This scooter starts right up with a shake of your Android device. This shake must be done from front-to-back, because a side-to-side shake is reserved for unlocking the saddle ([Brad] stores his helmet within).

Connectivity is facilitated over Bluetooth, with a rocker switch near the left handle bar to disable the receiver so that you don’t run down the battery. You can see the locking panel hanging open on the front portion of the scooter. Inside he installed the driver board which patches into the ignition system and drives a solenoid for the seat latch. It sounds like the latching mechanism used a bowden cable whose handle was inside that locking panel. By adding a solenoid and generously lubricating the cable he managed to get it functioning from the driver board.

Check out the video after the break for a proper demonstration. The phone is running a Python script via SL4A, which takes care of the user interface.

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Motion Sprinkler Chases Away Defecating Dogs

June 18, 2012 by Mike Szczys 36 Comments

Don’t want dogs pooping on the front lawn? You could put up a sign, your could chase them away like a crotchety old miser, or you could build a motion detecting sprinkler system. It’s pretty hard to line up for a doody when you’re getting sprayed in the face (or worse) with cold water.

The setup is pretty simple. The bump-in image above shows the view from a webcam. The server monitoring the video is running software that detects motion between one frame and the next. When it sees something in the right position it signals an Arduino to trigger the solenoid which has been holding back the water. Check out the movie after the break which shows [Phil Tucker] tramping across the grass to trigger the trap.

Sprinkler hacks are always a lot of fun. This variable-range sprinkler is still one of our favorites.

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