About Me

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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail

http://www.youtube.com/user/bkraz333

http://www.linkedin.com/pub/ben-krasnow/4/6a9/679

http://www.twitter.com/BenKrasnow

Sunday, July 24, 2011

Frequency response test for thermal imaging sensor

I am testing the frequency response of the TPS334 IR sensor. My very crude tests agree with the datasheet, which means that the image scan time will be very long for high contrast images. Many low-cost microbolometer-based thermal imaging cameras have 80x80 sensors (6400 pixels). At a 10Hz pixel clock (-3dB sensitivity from datasheet), the frame scan time would be 640 seconds, or nearly 11 minutes. Yikes! At 100Hz, the sensor would only produce an output level of %10 of its DC capability, and still require just over a minute to scan the whole frame. Obviously, this will not be a "live video" system, but might still produce some interesting still image thermographs.

I am working on other methods of sensing long-wave IR too. More later.

Tuesday, July 19, 2011

Cat feeder improvements (video)

This is just a repost for people who are not subscribed to my youtube channel.

http://benkrasnow.blogspot.com/2009/08/improved-automatic-cat-feeder.html

Product Review: CP06 low-cost AC/DC clamp-on current probe

I bought this bargain basement clamp-on current probe on eBay. It doesn't even seem to have a manufacturer (shamed out of existence?), but the model number is CP06. It's $70 shipped, and is probably worth it, especially if you plan to measure DC and 50/60Hz AC waveforms. It will not do high-frequency measurements. The DC accuracy seems good enough for many different applications where cutting into the test wire is not preferable.

Note: Hold down the "zero" button for a couple seconds, then release.

Saturday, July 16, 2011

Transcranial Magnetic Stimulation project - part 1

Transcranial Magnetic Stimulation (TMS) is a technique to stimulate brain tissue directly through the skull. It works by sending a very high current pulse through a coil that is located on the subject's scalp. The fast-rising edge of the pulse induces a current in the brain tissue, causing neuron stimulation.





This device uses a capacitor bank, high current SCR, trigger circuit, figure-8 (or butterfly) coil, and high voltage charging circuit.

Link to the SCR datasheet: http://www.5scomponents.com/pdf/5STH_30J4501.pdf

Some good technical information: http://www.abovesobelow.com/TMS/cTMS.pdf

Wikipedia: http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation