- 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
Saturday, December 31, 2011
I finally succeeded in extracting caffeine from green coffee beans by using supercritical CO2. I built a high pressure chamber from 2" steel pipe fittings, and poured in 200mL of water. There is an aluminum screen above the water line, which held 0.75 lbs of moisturized green coffee beans in the upper part of the chamber. I added liquid CO2 to the chamber, then closed all valves and raised the temperature, making the CO2 pass into the supercritical phase. I left the system overnight at about 60*C, 3000 psi, then drained the water. It was very black due to impurities and some bean burning that occurred where my electric strip heater caused localized overheated zones in the chamber. The water was highly caffeinated, and tasted somewhat like coffee. I used a typical hydrocarbon extraction process to isolate the caffeine from the water (will show this in a later video).
Monday, December 26, 2011
Sunday, December 25, 2011
Monday, December 19, 2011
Every so often, internet news aggregator sites run a story about a research group that put an LED into a contact lens, then inserted it into a rabbit's eye. I figured that I would try the same thing, but put the lens into my own eye. I accomplished this by laminating a coil of wire and an 0402 surface-mount LED between two ordinary soft contact lenses. I was hoping the lenses would stick to each other, but they did not, so I ended up fixing the edges together by pinching the plastic together with hot tweezers. This held well enough to capture a minute of video with the LED illuminated in my eye. For video purposes, I mounted the LED facing outward. An actual VR/AR display would have the LED facing inward.
I powered the LED by using a very primitive spark-gap transmitter built from a mechanical relay to send RF energy into a larger coil held near my eye. The large coil coupled the energy into the contact lens coil and pulsed the LED.
Wednesday, December 7, 2011
In an earlier video, I tried to visualize alpha particles in supercritical CO2, similar to an isopropanol vapor cloud chamber. Someone commented that the alpha particles will not travel very far (maybe 10 microns) in liquid or supercritical CO2, and recommended that I try beta particles, which should have a path length of almost 10mm. Unfortunately, I still don't see any bubble or droplet trails using strontium-90 and thallium-204 sources. It's possible that the ionizing effect of the radiation particles does not interact with the CO2 phase change as it does by condensing droplets in a cloud chamber. Also, cloud chambers are very finicky, and if this CO2 visualization method is as finicky or worse, it may take some more time to figure out the right combination of environmental variables.