Archive for category Misc projects

Toxic Gas Sensors are up and running

The air pollution sensors are now up and running. You can follow them on Twitter.

Sensors quickly installed

Sensors quickly installed

Levels are read straight from the LTC2496 ADC, with 65536 being the maximum level, corresponding to a voltage of 1.65V at the output of the sensor. The sensors (TGS2600 and TGS2602 from Figaro) are powered at 3.3V through a 1k resistor. The sensor heaters are also (under-)powered at 3.3V, this seems to work even though it is out of the specs.

A new Twitter post is made every time a value varies by more by 30%, compared to the last posted value.

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DOpE port to Milkymist

DOpE, a high-quality embedded GUI software stack developed by Genode Labs, a start-up company from Dresden, is now beginning to work on the Milkymist SoC platform.

DOpE running on Milkymist

DOpE running on Milkymist

What is currently missing is support for input devices (a PS/2 core is missing). Also, this port crashes when the CPU data cache is enabled, which suggests a hardware problem as people working on the ucLinux port experience a similar issue.

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Pollution sensors experiments

First experimental setup

First experimental setup


The Figaro gas sensors mounted on a piece of Veroboard. There is still plenty of space left for maybe AOPs and ADCs...

The Figaro gas sensors mounted on a piece of Veroboard. There is still plenty of space left for maybe AOPs and ADCs...


View of the Ardui... sorry, the digital oscilloscope used to plot the first graphs. 1min/div. Looks like it's working as both smell (from the chemical factory) and measured voltage go up during the third minute...

View of the Ardui... sorry, the digital oscilloscope used to plot the first graphs. 1min/div. Looks like it's working as both smell (from the chemical factory) and measured voltage go up during the third minute...


See here for a description of the project.

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Toxic Gas Sensors at /tmp/lab

Those of you who have been to the /tmp/lab may have experienced the delicate smells of the nearby chemical factory.

We want to learn more about this pollution, so we will implement an automated measurement system.

Block diagram

Block diagram

To monitor the air concentration of pollutants, we use cheap sensors made by a company called Figaro. The models used are TGS2600 and TGS2602; the same are used by the FridaV project. The TGS2600 measures contaminants such as hydrogen and carbon monoxide, while the TGS2602 detects ammonia and hydrogen sulfide (that we think is responsible for the occasional foul smells at the lab).

The outputs of these sensors is digitized and sent to an advanced Arduino called Fonera. It even has 802.11! And it can run Linux! Those features of this Arduino for experts (we hope we will be still able to use it despite our little DIY skills) make it perfect to post automatically the results on the web, by using the popular Twitter for example.

We are thinking about using a SPI analog to digital converter, as the Arduino hardware seems to be able to handle it.

More to come soon, check out the wiki page.

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Tube Amp at HSF2009

A very nice shot of my home-made tube amp (click to see inside the device – see the bottom of the post) connected to an iPhone at the Hacker Space Festival.

Low and High Tech

Low and High Tech

(From photosixun)

More photos of the HSF are here: http://www.hackerspace.net/photos-videos.

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Milkymist Presenter

Here is a small tool whose purpose is to make simple slide-shows with a Milkymist board.

It will be used on June 28th at Hacker Space Fest 2009 to give a presentation about Milkymist using itself :)

As it is extremely simple, it is also a good example of how to write a custom firmware for Milkymist. This tool is pure software, which is booted by the Milkymist BIOS using any supported method (read from the CF card or downloaded via the RS232 link) and executed by the softcore CPU. It does not require any modification of the FPGA bitstream.

You can download a tarball here or browse the latest revision from the SVN repository.

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Hacker Space Fest presentations

I will make the following presentations at the Hacker Space Fest :

Milkymist, an open hardware VJ platform
The Milkymist™ project develops a stand-alone device in a small form factor that is capable of rendering MilkDrop-esque visuals effects in real time, with a high level of interaction with many sensors and using live audio or video streams as a base.
Open source components and design tools have been developed or used as much as possible. A system-on-chip implemented in a FPGA has been chosen for meeting this goal at the IP core level.
The flexibility of the FPGA enables advanced users to modify the design, and also permits compact integration of many interfaces (MIDI, DMX512, analog sensors, video inputs), making Milkymist™ a platform of choice for the mobile VJ.
The design is also highly modular and documented, making the code easy to re-use in other open source system-on-chips.
Project homepage: http://www.milkymist.org
The conference focuses on the technical aspects of the project. Live demonstration included !

FPGA and Verilog introductory workshop
(This is an English re-edition of the FPGA workshops at /tmp/lab)
Agenda :

  1. Using Xilinx tools in command-line
  2. Logic design and Verilog introduction
  3. Hands-on: basic functions + implementation of a small audio generator
  4. Simulation techniques

Pages from the previous workshops (in French) :

FPGA boards needed, please bring your development kits for those who have (even if you don’t come to the workshop).

Vacuum tubes, your grandpa’s electronics
Since the invention of the transistor, vacuum tubes have been progressively phased out and are now quite rare. Yet, for the hacker, they can still be of interest :

  • Fun factor. Who doesn’t like the warm glow of the filaments, the green/blue light of the magic eye tubes, and that mess of low-tech capacitors, coils and wires inside the devices ?
  • DIY potential. Yes, with a little recklessness it is possible to make your own tubes, and use them in practical applications. And even if you don’t make your tubes, they are much easier to use in simple -yet good- analog circuits than transistors, that you truly understand. A modern circuit of the same quality typically requires black-box integrated circuits that require much more knowledge to completely understand.
  • Demonstration of the laws of physics. Tubes can be used to show fundamental laws of electromagnetism, which are the basis for making high-end radioactivity detectors or particle accelerators.

This conference will explain in detail the functioning of different tubes and will show how to build circuits like audio amplifiers or radio receivers/transmitters.

Live demonstration of tube equipment included !

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