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

Friday, June 24, 2011

Extech IR250 infrared thermometer disassembly and plans for thermal imaging

One of my ongoing projects is to develop a low-cost thermal imaging camera. In this video, I take apart an Extech IR250 infrared thermometer with the intention of grabbing an analog or digital signal so that I can record temperature measurements while using a scanning or image processing device to select portions of the scene being examined. Unfortunately, it looks like the analog circuitry is completely sealed inside a custom IC that is hidden under a blob of potting material. I'll remove the IR sensor from the board and build my own analog amplification and digitization hardware.






Common digital output IR thermometer sensor:
http://www.melexis.com/Infrared-Thermometer-Sensors/Infrared-Thermometer-Sensors/MLX90614-615.aspx

TPS334 sensor datasheet:
http://www.datasheetcatalog.org/datasheet/perkinelmer/TPS334.pdf

Analog Devices app note regarding thermopile sensors:
http://www.analog.com/en/all-operational-amplifiers-op-amps/operational-amplifiers-op-amps/products/technical-articles/using_thermopile_sensor_in_ir_digital_thermometers/resources/fca.html


Servo pan/tilt IR imaging scanner project:
http://www.cheap-thermocam.tk/

Redshift thermal imaging:
http://redshiftsystems.com/site

Sunday, June 19, 2011

What should I build with six ultracapacitors?

I bought six 2600F 2.5V ultracapacitors from Electronic Goldmine. They were on sale a couple weeks ago, and this was one of my rare impulse purchases. I am thinking of building a portable capacitive discharge welder, or perhaps conventional spot welder. What are your ideas?

Lavalier microphone comparison: Audio-Technica ATR-3350 vs Sony ECM-55B

My first youtube videos were made with my camera's on-board stereo microphone. The camera is a Lumix GH1, and the mics are fairly good as far as prosumer video DSLR cameras go. One problem is that the camera's automatic gain control cannot be turned off, and having unexpected gain changes during an audio recording is not preferable. Another problem is that the audio preamplifiers in the camera are somewhat noisy, and lead to a lot of hiss (high noise floor) in the recording. Finally, it's impossible to get good sound when the microphone is positioned far away from the sound source when room tone and echoes are present. The solution to all of these problems is to make use of a lavalier or lapel microphone and use a low-noise dedicated recording device. I use a Zoom Handy H4 recorder. The H4's on-board mics are really nice, but it is still preferable to have a microphone very close to the subject's mouth to capture detailed, high-quality sound.

I started using an Audio Technica ATR-3350, which is only $20 or $30 new, and the mic is OK, but has very little high-frequency response. This can be corrected with equalizer settings in post-production fairly well. I recently upgraded to a Sony ECM-55B, which sounds better, but I am not sure it was worth the expense. I was really expecting the mic to have a much higher output level than the ATR-3350, thus allowing me to turn down the gain on my recorder and have a much lower noise floor. As it happens, the mic requires even more gain than the ATR-3350. Overall, I am pretty satisfied with my sound recording setup -- the only addition I might make is a low-noise preamp to try boosting the lavalier mic signal while adding less noise than the H4 adds during the high pre-amp gain stage.


Tutorial: Electrical impedance made easy - Part 2

This is the second video of a short series in which I discuss the basics of electrical impedance from a practical standpoint. In this video, I explain the importance of knowing the magnitude and angle of impedance, as well as how this affects the power factor of a given electrical circuit.



Wednesday, June 8, 2011

Tutorial: Electrical impedance made easy - Part 1

This is the first video of a short series in which I discuss the basics of electrical impedance from a practical standpoint.

In this video, I show how a simple LED power supply circuit can be made more efficient by replacing a resistor with a capacitor. I describe the difference between resistance, reactance, and impedance.

Saturday, June 4, 2011

DIY Scanning Electron Microscope - Operation procedure

After getting back from Maker Faire (which is always a hugely enjoyable and inspiring event), I thought that my microscope might need some repairs. As it turned out, I only had to change the filament and tighten some screws that came loose during the trip back from the Faire. The microscope works just as well as it ever has -- I didn't even need to move my alignment magnets. I made this video to show everyone what using it is really like.

Also, if you haven't been able to attend Maker Faire yet, it really is as amazing and epic as you have heard. The intelligent and inspiring people who make it happen are a large part of the motivation that I had to build and display this microscope. In turn, I hope my project inspires others to create things and share their ideas with everyone. There's no better way to have fun and celebrate accomplishment at the same time!