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




Thursday, August 25, 2011

Getting started with the Altera DE1 FPGA board: Create and download a simple counter

This is my first experience with FPGA programming, and so I made this video to show how easy it is to get started. Many of the tutorials on the web and the DE1 manual make the process seem more difficult than it actually is (as usual).

Monday, August 22, 2011

CNC milling glass plates and mirrors

I've been cutting glass plates and mirrors with my CNC milling machine machine for years. In this video, I describe a few tips and the general technique that I use.

Clamping the glass plate to the table is the critical part of the process, and so I built a jig that allows the glass to be held laterally with shims, but does not require a high clamping force, which would crack the glass.

Cutting parameters:
.085" dia diamond burr
3000 RPM
1-3 inches per minute feed
Cut depth .130" (full material thickness)
Flood coolant with soluble oil cutting fluid

Older post: http://benkrasnow.blogspot.com/2008/08/cnc-milling-glass-plates-and-mirrors.html

Saturday, August 20, 2011

Effect of acetone vapor on thermal printer paper

I am not sure of the chemistry involved, but I have found that acetone and isopropanol vapor will darken the ink in thermal printer paper. There is also a strange reversible blanking effect, where continued vapor application will cause the dye to temporarily become colorless. Do you know the chemistry involved?

Saturday, August 13, 2011

Water vortex display from SJ City Hall exhibition -- repair and upgrade

I built this project a few years ago with a friend to help get him interested in mechanical design. Later, the project was adapted for display at a "tech and art" exhibition at San Jose City Hall. After 8 months, the painted steel impeller began to rust and discolor the water in the tube. I took the device back to my shop and replaced the original aluminum shaft with a stainless steel shaft, replaced the shaft seal, and changed the impeller to an all-plastic design. If I were designing the device again, I would opt for a spring-loaded PTFE (Teflon) shaft seal, which I have used with great success in other applications.

Drill motor control:

Original video showing the WiFi-controlled watering can and vortex tube:

Thursday, August 11, 2011

Repairing the 5V output from a Mastech HY3005D-3 (cheap import) power supply

The 5V fixed output on my Shenzhen Mastech HY3005D-3 power supply died the other day, and so I took the device apart to investigate. The 5V regulator board had a bad solder joint where the bridge rectifier attaches to the PCB. I used a soldering gun to reflow the joints, and all seems good.

Sunday, August 7, 2011

Transcranial Magnetic Stimulation project - part 2

I achieved neuronal stimulation of my primary motor cortex by using a single 15-turn coil and 1700 volt charge on the capacitor bank of about 190uF. The exact position of the coil on my scalp makes a very big difference in how much stimulation is achieved in the motor cortex. I would have suspected the single coil would produce much more diffuse stimulation and positioning would not be so critical. I never got any decent neuronal stimulation with the butterfly coil.

Wednesday, August 3, 2011

Cooking with thermite

I ignited four pounds of thermite made with aluminum / iron (III) oxide in a flower pot. The thermite reaction quickly formed liquid iron which dripped down out of the pot, and into a ceramic pan. I put a beef kebab directly onto the liquid iron, which cooked the food in under a minute. It was delicious!