We’ve Adopted a Scanning Electron Microscope (SEM)!

SEM newly installedIt’s our pleasure to announce that HacDC is now the proud owner of a scanning electron microscope (SEM)! An SEM is a scientific instrument capable of producing extremely high-magnification images: magnifications of 5,000x to 500,000x are routinely achieved by these machines. Additionally, SEMs can be interfaced with additional detectors to examine the atomic composition and other characteristics of both organic and inorganic samples. These makes them extremely useful machines for imaging, scientific analysis, and even processes such as e-beam lithography.

If you’re unfamiliar with the incredible images that SEMs can produce, check out this gallery.

Our machine is an older, second-hand model, and was graciously donated to us by 757 Labs. It’s a Cambridge Stereoscan 200 from 1983. Despite its age, it was widely renowned for being a very versatile machine, and all the electronics are well within the realm of being understandable and repairable by the hobbyists and professionals at the hackerspace. It’s currently undergoing member-driven inspection and repair.

Its current status, as well as information about planned projects, can be found on our wiki.

For the inquiring mind: the theory of operation of a standard SEM is relatively straightforward: a metal specimen chamber and hollow column are pumped down to near-vacuum (between 10e-8 to 10e-11 atmospheres!) via the operation of a roughing pump and a turbomolecular or oil diffusion pump. A power supply then runs current through a tungsten filament to cause thermionic emission of electrons—very similar to the operation of a light bulb. Another power supply creates a voltage relative to a nearby anode, which accelerates the electrons to a high energy, adjustable from 1 to 40 keV (kiloelectronvolts). The electrons spray out from the filament towards the anode, but are gradually reduced down to a very small spot size via a series of electromagnetic lenses and one or more metal apertures. This small spot of electrons finally hits the sample. Additional circuitry deflects the small spot of electrons over the sample’s surface, effectively scanning it across the area to be examined, much like a beam inside of a cathode ray television. At this point secondary and backscattered electrons are kicked out of the sample and detected by a sensor inside the chamber, which passes the signal along to processing circuitry, ultimately resulting in an image being displayed on a TV.

If you’re as excited as we are by these images and would like to make your own, or if you’d like to learn more about the nitty-gritty details above, you’re probably the sort of person we’re looking for! We’d love to find members who would like to assist with the repair and operation of the machine, as well as planning future improvements.

(Written by: Dan K and Phil S)

Make: AVR Programming released this week

Make: AVR Programming

Way back in February/March of 2011, The Late Elliot Williams (TLEW)Δ taught a 6-session AVR Microcontroller Class that introduced hardware programming beyond Arduino to an eager roomful of wannabe bare-metal programmers.

Elliot‘s hard work on that course and it’s 2009 iteration formed the germ for the shiny new 472-page Make: AVR Programming Learning to Write Software for Hardware, released this week by Maker Media, Inc.:

Atmel’s AVR microcontrollers are the chips that power Arduino, and are the go-to chip for many hobbyist and hardware hacking projects. In this book you’ll set aside the layers of abstraction provided by the Arduino environment and learn how to program AVR microcontrollers directly. In doing so, you’ll get closer to the chip and you’ll be able to squeeze more power and features out of it.

We’re big fans of the Arduino but sometimes our projects demand smaller size, less power consumption, more control, faster processing, and/or MOAR CHIPS! (You can buy almost 10 of Atmel’s ATmega328 AVR chips for the average price of one Arduino.)

Photo of HacDC's 2011 AVR Class Project PCB Kit (assembled) ©2011 Elliot Williams

For the 2011 class, TLEW designed a(n awesome) custom PCB to illustrate major topics. [2011 AVR Kit wiki page.]

Δ Elliot is alive and well. However, he’s dead to us, mostly because after he left DC it was decreed that we would forevermore immaturely express our separation anxiety by referring to him only as “The Late Elliot Williams”.

Photolithography PCB Fabrication

PCB Fabrication IllustratedDIY printed circuit boards (PCB) are an intermediate step toward mass producing an industrial-grade integrated circuit.

After prototyping a project using tools like a solderless breadboard, small-run or one-off PCBs are a good choice when you want a more structurally stable version of your circuit that is destined for mass production. Perhaps you would like to be able to install it into a larger project prototype. Once all the what-ifs and tests are successful with these hand-made PCBs, higher resolution industrial processes can be used to fabricate more robust PCBs.

Thanks to members, mirage335 and Dan Barlow, we now have a standardized method to fabricate DIY PCBs with traces (conducting areas) and spacing (non-conductive areas) of 6 mil (0.15mm).

For projects where the 10 mil tolerances made possible by our CNC mill are not enough, photolithography is a good alternative. The process uses light-sensitive coatings to mask conductive surfaces before etching. The result is a a lovely printed circuit where before you had a jumble of wires. The process, workflow, and references are described by mirage335 on our wiki.

Interested in this topic? Check our events calendar and visit us! Want to see lots more like it? Support us!

Biosignal Amplifier Ready for Plug-and-Play

Mirage335 Biosignal Amp Host Schematic (detail)HacDC’s biohacking group has developed a new, ultra-low-noise biosignal amplifier and released it under the GPLv3.

The Mirage335 Biosignal Amp makes brainwave (EEG), heart (ECG), and muscle (EMG) detection all possible without reconfiguration.

Mirage335 Biosignal Amplifier Setup

Lead designer, mirage335, writes:

This system is geared for maximum performance close to theoretical limits. Ideally, the lower noise floor allows us to confirm the presence or absence of weak biosignals, especially electroencephalography signals, when they become difficult to detect with other systems.

Analog (direct-to-scope) and USB (direct-to-computer) outputs are provided. USB functionality is provided by an Arduino compatible ATMega32U4 and LTC2440 24-bit Analog-to-Digital converter.

EEG and ECG (Wikimedia Commons)

    Other features:

  • USA companies provide all parts, including circuit boards
  • Safety oriented architecture. Multiple isolation barrier and surge suppressor layers.
  • Active electrodes, wet and dry designs.
  • Extreme common-mode rejection measures.
  • Lowest noise amplifiers, based on new thermal noise research.
  • Future proof. Modular SATA data cable architecture provides smooth upgrade paths.
  • Isolation amplifier. Safe, high-resolution analog output for lab equipment (eg. oscilloscopes), sound cards, microcontrollers, and ADCs.
  • USB support, based on ArduinoDAQ (ATMega32U4 + LTC2440).
  • Efficient, high-order IIR biquad filters notch out 60Hz, 30Hz and high-frequency noise, right at the embedded microcontroller.
  • Wide supply voltage support. +/-6V to +/-15V
  • Resistor programmable gain. 13000x default.

Mirage335′s effort was supported by these members of our biohacker group, contributing to the design, testing, and funding of this versatile device:

  • Shawn Nock
  • Sharad Satsangi
  • Stuart Washington
  • The Real Plato
  • Logan Scheel

Usage instructions are available on the wiki.

Complete schematics, PCBs, BOMs, 3D printable enclosures, firmware, USB driver software, and documentation hosted on Github:

Additional documentation is available on the project’s webpage.

Join the HacDC biohacking community’s mailing list: https://groups.google.com/a/hacdc.org/forum/#!forum/meat