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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




Monday, June 25, 2012

Frying a potato chip in Fluorinert FC-40

I recently bought some Fluorinert FC-40 on eBay since it is such an intriguing chemical. This fluid is 1.8 times as dense as water, but has almost the same viscosity. It is also very inert, has a boiling point of 160*C, is immiscible with water, and has exceptionally low electrical conductivity. The fluid can dissolve large amounts of gas and was shown in the movie The Abyss where it allowed a rat (and later a human!) to breath the oxygenated fluid, by submerging the rat in  a container of Fluorinert and having the rat take the fluid into its lungs.

Measuring the voltage and current of a microwave oven magnetron

I took apart my microwave oven and measured the voltage and current supplied to the magnetron. The device appears to start conducting current at 4KV, and will allow lots of current to flow once this threshold voltage is reached.

My current probe is pretty cheapo, so I wouldn't trust its measurement too much, but the final determination of 1300 W average seems pretty spot-on.

Monday, June 11, 2012

Liquid level sensor and controller (auto top-off for aquarium)

I built a liquid level controller that senses the level of water in my aquarium and powers a water pump when necessary to compensate for evaporated water. This is known as an "automatic top-off" system. The controller is based around a Keyence FS-V11, which sends light out a plastic fiberoptic, and measures the amount received via another fiberoptic. The optical probe makes use of total internal reflection to control how much light is returned to the Keyence based on how far the probe is immersed in the water. It is also completely passive, non-metallic, and has no moving parts for high reliability. The Keyence triggers a solid state relay that supplies power to a standard AC outlet. The pump is then plugged into the outlet, and moves water from a reservoir into the aquarium on command.

Avocado vs high pressure nitrous oxide

Chris Agerton (http://www.youtube.com/user/cagerton) suggested that I try adding nitrous oxide bubbles to an avocado -- a wonderful idea since avocados are fatty, and the gas should readily dissolve in the fat. I placed some avocado slices in my pressure chamber and dispensed two nitrous cartridges into the chamber. I let it sit for about 7 hours. I then took the slices out, and reduced the pressure with a vacuum pump. Unfortunately, the avocado was resistant to the nitrous infusion process. I will try again with guacamole and shaking/stirring to encourage gas absorption.