Ben Krasnow

Cookie Machine Project Update 3

2013-04-29T23:34:00.003-07:00

Cookie Machine Project Update 2

2013-04-29T23:34:00.000-07:00

Cookie Machine project update

2013-04-29T23:33:00.000-07:00

Bubble tube lamps - explanation and construction

2013-04-10T22:07:00.004-07:00

I've always liked these bubble tube lamps that used to be built into Christmas tree ornaments, and were also featured in classic jukeboxes. I decided to make one in my own shop and here I explain how they work and how I built one.

Blow molding plastic water bottles

2013-04-10T22:07:00.000-07:00

This video is a response to Grant Thompson's water bottle challenge. Check out Grant Thompson "The King of Random"
http://www.thekingofrandom.com

You don't need much special equipment to blow mold plastic bottles in a home shop. If I had more time, I would have made a custom wooden form on the lathe, then made a two-part plastic mold around it, and blow molded the bottle into the plaster mold.

Cookie perfection machine - butter dispenser

2013-03-05T00:11:00.001-08:00

I am building a machine that will dispense and mix ingredients to make a single cookie. The benefit is that each cookie on the sheet can have its own recipe, and the baker can sample all of the cookies to better understand how ingredient variations will affect taste and texture. In this video, I talk about the butter dispenser.

The folks at Meta Mate gave me the idea for customer-rating via QR code.
http://www.metamate.cc/

Hacking a milligram balance (scale) with a Parallax Propeller microcontroller

2013-03-05T00:09:00.004-08:00

For an upcoming project, I'd like to develop a dispensing system that can measure out a desired mass of material. The idea would be to use a microcontroller, dispensing valve, and electronic balance to provide feedback. I already have an American Weigh Scales miniPro-100, and decided to hack it so that my microcontroller can discover how much mass is on the balance. It can then regulate the dispensing valve appropriately.

The balance contains a Cirrus CS5530 24-bit ADC. I tapped the clock and data lines and found bursts of data that occurred at 7.5Hz. The clock is about 150KHz. I used a Parallax Propeller running assembly in one of its cores to capture the data stream and load it into my main program.

Cleaning a high-vacuum Penning gauge (cold cathode vacuum gauge)

2013-02-11T23:01:00.000-08:00

My high-vacuum Penning gauge has been having some problems lately. The last time that I "fixed" it, I used lead solder to create a crushable metal seal between the parts of the gauge body. Eventually the rosin leaked out and probably caused contamination within the gauge.

I bought some Indium wire on eBay to replace the metal seals after cleaning the gauge with a bead blaster, sandpaper on glass, and lots of alcohol swabs.

Proper explanation of Penning Gauges:
http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/IG1hotapp.pdf

Rheoscopic coffee table

2013-01-21T20:25:00.000-08:00

I've received a few questions about my coffee table, which I built in 2006. I used fairly standard woodworking techniques (floating tenons, breadboard ends) with maple, walnut, and bloodwood for contrasting colors. I didn't use any stains or colored finishes -- all of the color is from the wood's natural appearance.

The table has a 30" diameter disc that contains about 2 gallons of water mixed with Pearl Swirl fluid. This fluid is essentially very fine glitter that becomes suspended in the water, and will show flow currents as the water moves within the disk. I positioned the disc on a 24" diameter lazy susan bearing for low-friction rotation. When the disc suddenly changes rotational speed, there will be turbulence in the water, which causes the rheoscopic fluid to show fluid vortices and eddies that are part of the turbulence.

The outer metal ring was custom-built by a shop that specializes in metal rings (see sources below). All of the other parts were bought from McMaster, eBay, and Steve Spangler Science for the Pearl Swirl fluid.

I got the idea for this table after see a tornado visualization exhibit at the Carnegie Science Center in Pittsburgh. The Exloratorium has an orb filled with a similar fluid to show flow patterns similar to those on a rotating planet with an atmosphere.

The main pieces are: 3/8" thick glass top, aluminum ring with L cross-section, a 3/4" thick O-ring with square cross-section and a 1/2" thick PVC plastic bottom. There are a bunch of screws that pull the aluminum ring down onto the glass, which pushes onto the O-ring, which pushes on the PVC bottom. There is no glue used anywhere in the disk. The overall diameter is about 32".

The disk holds about 2 gallons of liquid, and weighs a total of 80 lbs (just a good estimate -- I never measured it). There are two threaded fill-holes with plugs on the bottom, and the whole thing sits on a 24" lazy susan bearing.

These are my sources:
Glass top
http://www.glasstopsdirect.com/glass-round-30.php
3/8" thick tempered $85 shipped

Outer metal ring
http://www.nmfrings.com/rings/
Custom 2" x 2" x 3/16" thick, angle-in, "L" cross section, 32" outer dia
about $150 shipped

O-ring
http://www.mcmaster.com/
3/4", square cross-section, O-ring cord stock -- I made a scarf joint
to make this into a ring, about $40

Bottom plate
http://www.mcmaster.com/
1/2" thick gray PVC plastic $100

Fluid
http://www.stevespanglerscience.com/product/1218
$20
Get some food coloring too

Screws, cushioning rubber, stuff to wire-brush the aluminum ring:
http://www.mcmaster.com
$30

lazy susan bearing
eBay -- search for "aluminum lazy susan"
12" will not work, you need to find a 24" dia bearing on eBay
$50

Random X-ray photos

2013-01-20T01:07:00.000-08:00

Timelapse video of crystal growth in novelty toy

2013-01-14T17:11:00.000-08:00

I used my programmable turntable and camera control to create a timelapse video of crystal growth on a small novelty toy. I took one photo (1920x1080) every two minutes, and advanced the turntable by about 3/4 of a degree between photos. I encoded the photos into a 29.97fps timeline in Adobe Premiere, but used two video frames for each photo, so 1 second of playback = 15 photos = 30 minutes. I covered the windows in my shop with black plastic to prevent sunlight from changing the scene as morning arrived. Each exposure was 1/10 at ISO100 f/8, with standard fluorescent lighting in my shop.

DIY X-ray CT scanner controlled by an Arduino

2013-01-08T01:22:00.000-08:00

I built a CT scanner from an x-ray tube that I bought on eBay, a stepper motor, a large ring bearing, and an Arduino. I used a phosphor screen and my camera to capture x-ray shadow images of a frozen chicken, while the Arduino and stepper motor rotated the chicken by 8 degrees between shots. The resulting 45 images were combined via filtered back projection to create a 3D volume reconstruction of the chicken.

Software used:

Panasonic SilkyPix (for .RW2 development)

Adobe Bridge/Photoshop for image perspective correction

Cygwin/Octave for filtered backprojection

Cone Beam Computed Tomography algorithm
http://www.mathworks.com/matlabcentral/fileexchange/35548-3d-cone-beam-ct-cbct-projection-backprojection-fdk-mlem-reconstruction-codes-for-matlab-students

3D Slicer for visualization and volume rendering
http://www.slicer.org/

Raw CT images animation

2012-12-16T22:39:00.000-08:00

Here's an animation of the raw images from my CT scanner. Full video to follow soon.

Jukebox color wheel synchronizer

2012-12-10T22:26:00.001-08:00

I built a system to synchronize the two color wheel motors in a Wurlitzer Model 1015 jukebox. Originally, the jukebox used two synchronous clock motors, and the designers assumed that the motors would stay synchronous and keep the colors wheels at the same orientation after manually setting it. As it turns out, the torque required to spin the color wheels is enough to cause the motors to slip. Eventually, the color wheels get out of sync, and the left and right side of the jukebox do not match in color.

My upgraded system uses two small DC gearmotors that interface with the original drive mechanics via a nylon gear from McMaster. I drive the two motors via a PN2222A transistor and sense the position of the color wheels with the optical sensors from an old computer mouse. An arduino controls the motors via PWM (20 or 30 KHz), and runs a phase-locked-loop routine with P-I control. This system could use a little tuning, but it's pretty close.

DIY X-ray backscatter imaging system (airport body scanner)

2012-11-26T22:08:00.000-08:00

I built an X-ray backscatter imaging system from parts found on eBay. This system works by scanning a very thin beam of X-rays across the target, and measures the amount of backscatter for a given beam position. The beam is scanned mechanically by a rotating chopper (collimator) wheel, and by tilting the rotating wheel on an orthogonal axis. The output image is generated on an oscilloscope by matching the horizontal scan speed to the rotating wheel, and using a potentiometer to measure the vertical axis position. The scope's brightness (z axis) is controlled by the amount of backscatter signal received by a large-area detector. Thus, the image is constructed bit by bit. I used a long-exposure shutter on my camera to see the image formed by the moving oscilloscope trace.

http://www.google.com/patents/US5181234

Carbon fiber bridge from 2005 SAMPE competition

2012-11-23T16:38:00.001-08:00

While at UCSB, I built a bridge from carbon fiber and aluminum with the help of three other students. We took first place in the SAMPE lightweight bridge-building competition held at Long Beach in 2005. The bridge spanned 24", weighed 2.62 lbs, and supported 8905 lbs at mid-span before failure. It was built from pre-made carbon fiber tubes for compression loads, which we joined together with aluminum end brackets. We added unidirectional carbon fiber ribbons to handle tension loads. The fibers were pre-impregnated with epoxy resin, and kept in a freezer until they were laid in place and cured at high temperature and pressure.

Intro to Fourier Optics and the 4F correlator

2012-11-23T16:12:00.001-08:00

It seems strange that a single piece of glass can compute the Fourier transform of an image, but it is true (sort of). I explore an optical arrangement known as a 4F correlator, and note the practical considerations that are rarely discussed in existing sources.

http://www.imagemagick.org/Usage/fourier/

Large area detector for X-rays

2012-11-04T22:28:00.000-08:00

I built a large area detector that is sensitive to X-rays and will be used in an upcoming project. The detector is constructed from a "Lanex Regular" X-ray intensifying screen, and a Hamamatsu R6094 photomultiplier tube (PMT). The PMT amplifies the light from the intensifying screen which is emitted when an X-ray strikes the screen. The area of the screen allows it to catch many X-ray photons created by backscatter. The PMT is setup with a simple 100K resistor between the anode and ground. A 1V output corresponds to a 1 microamp anode current. I'll probably add a very simple opamp circuit to this, and then pipe it into an A/D converted for digitization.

Reverse-engineering and testing an x-ray filament supply

2012-10-29T18:31:00.004-07:00

I bought a set of x-ray equipment on eBay, which included an x-ray head unit, 50KV supply, and filament power supply. The filament supply has a 25-pin connector, and no data or markings on the case or board. I spent some time reverse-engineering the circuit, and determined how it should be connected to make an emission-controlled x-ray system. I tested the whole thing, and it appears to be working as intended at 50KV / 1 mA. The head unit produces a beam of about 25 degrees total angle.

Turning a laminated wooden vase on the lathe

2012-10-15T22:27:00.003-07:00

I've made a series of wooden vases and similar items by laminating contrasting boards, then turning them on the lathe. I like to use walnut, maple and either bloodwood or padauk to create a white/black/red theme. I almost never use stains, instead I just finish the wood with clear wipe-on polyurethane, using two coats for a fairly matte finish.

Measuring the voltage, current, and light output of a strobe flash lamp (Speedotron 4803)

2012-10-14T14:29:00.000-07:00

I wired up a high-power photography strobe light to my oscilloscope and made some measurements of the input voltage, current and light output.

Hybrid rocket engine with acrylic and gaseous oxygen

2012-09-24T01:35:00.003-07:00

I built a small rocket engine for demonstration purposes. The engine is built from a 2" diameter acrylic rod through which I drilled a 0.5" hole. The oxygen at 80 psi or less is passed through the hole and then is forced through a convergent-divergent nozzle at the tail end. The nozzle's throat is about 0.25" and expands to 0.625". I lit the engine by inserting a burning cotton swab (with wooden stick) while a small amount of oxygen was flowing. The acrylic catches fire very easily in a pure oxygen environment. The engine can be throttled and shut off completely, which is a major benefit to hybrid engine designs. Solid-fuel rockets cannot be throttled or shut off, which makes them difficult to control.

Viewing an active electronic circuit with a scanning electron microscope

2012-09-06T11:31:00.000-07:00

I used my DIY scanning electron microscope to view a 555 timer circuit while it was powered. The circuit is a simple oscillator with a very long time constant to make the changes easy to see. My plan was to view the silicon die itself, and hopefully discern changes in its internal circuitry as the oscillations occurred. As it turns out, I was only able to "see" the charge of the electrical wires going to the chip socket. There is likely a clear oxide layer that covers the silicon die, and needs to be removed with hydrofluoric acid in order to use the SEM to inspect the die itself while powered.

First test with eBay x-ray tube

2012-09-02T22:58:00.003-07:00

I found an X-ray tube on eBay and fired it up with my Spellman high voltage supply. I ran the tube at about 35-40KV at 180uA. This required a filament current of about 1.5A at 2.5V DC. With the room very dark, I could clearly see the phosphorescent screen glowing green. It wasn't bright enough for my eye to discern details in the X-ray images, but the camera with a 4 second exposure at f/5.6 and ISO400 was perfect. I took some pictures of various electronic components. I also X-rayed a dead, dried-up bumble bee, and it produced no image at all! The X-rays completely penetrated the insect without any visible absorption. I should have turned down the anode voltage, but I didn't think of this until after I threw away the bee.
The tube is a Nago GFH2-0.3-85-60

First test with 4.8KJ xenon flash lamp (Speedotron 4803 strobe light)

2012-08-20T23:33:00.002-07:00

This video shows my entry into the world of high-intensity flash tubes. I was inspired by the work done by the famous Doc Edgerton who built a strobe system for nighttime aerial photography. I've heard the biggest system he built was somewhere between 50 and 75 KJ per flash -- the power needed to illuminate the ground from 1000 feet in the air!

The system in this video is a Speedotron 4803, which delivers up to 4800J per flash. Photographers use the units watt-seconds (Ws) to describe the energy in each flash, which are the same as Joules. I plan to add capacitance to the bank in order to increase the total discharge power, but the voltage may also need to be adjusted since the higher power flashes also tend to require higher voltages. I'm also planning to try different xenon flash tubes, which are capable of more intense flashes.