Ben Krasnow

Monday, February 22, 2021

Measuring human digestive efficiency vs. a flame

"200 Calories" on a nutrition label doesn't describe the total flammable caloric content. I explore the differences between digestible and flammable calories using a homemade calorimeter with glass windows.

Pressure sensor: https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/M5842-000005-10KPG/7592854 Schedule 160 pipe on McMaster: https://www.mcmaster.com/7733K259/ 32 ga nichrome wire: https://www.amazon.com/gp/product/B07DL4DSWD/ Power supply (used for ignition wire): https://www.amazon.com/gp/product/B07SS77N7K/ Keithley 6.5 digit multimeter: https://www.tek.com/tektronix-and-keithley-digital-multimeter/dmm6500 Tek MSO 4 series oscilloscope: https://www.tek.com/oscilloscope/4-series-mso-mixed-signal-oscilloscope Soylent: https://soylent.com/ Support Applied Science on Patreon: https://www.patreon.com/AppliedScience

Sunday, January 17, 2021

Prototyping with Applied Science: Design and build a bite sensor

Join me in brainstorming and building a bite force sensor that allows paraplegic musicians to smoothly control an expression pedal. This video will include construction tips and tricks, methods, material selection, and a little design philosophy.

Tiny linear potentiometer used in final design: https://www.digikey.com/en/products/detail/bourns-inc/3046L-1-103/3781580 Spring-loaded linear potentiometer: https://www.digikey.com/en/products/detail/tt-electronics-bi/404R10KL1-0/2408603 Sil-Poxy for bonding silicone rubber to itself and other materials: https://www.smooth-on.com/product-line/sil-poxy/ Sorta Clear 40 - Platinum-cure silicone molding: https://www.smooth-on.com/products/sorta-clear-40/ Light-cure 3311 adhesive: https://www.mcmaster.com/1700A253/ (expensive, but this tube will last a long time) Blue lasers on eBay "5mW" *wink* https://www.ebay.com/itm/3-Packs-900Mile-Strong-Laser-Pointer-Pen-Green-Blue-Red-Light-Visible-Beam-Lazer/174479770737 Braided shield, highly flexible, 4-conductor cable: https://www.digikey.com/en/products/detail/tensility-international-corp/30-00218/5270175 Fabric reinforced silicone sheet: https://www.mcmaster.com/8612K51/ Mechanical CAD on github: https://github.com/benkrasnow/BiteSensor Support Applied Science on Patreon: https://www.patreon.com/AppliedScience

Sunday, November 15, 2020

Etching silicon wafers to make colorful Rugate optical filters (porous silicon)

Passing an electrical current through a silicon wafer in a special acid etchant will create a porous layer with a variable index of refraction. I describe how this process works, and how the Fourier transform relates filter design to electrical etch waveform and resulting spectral response.

Notes: 1. The Rugate filters look especially good in polarized light because the reflection from the silicon wafer is reduced, but the reflection from the filter remains strong. I noticed this while holding the wafer in front of my computer monitor. Later, when showing it to friends, the color intensity was poor. Their monitor must have been horizontally polarized, so holding the wafer low, and tilting it upward didn't work! Some monitors are horizontally polarized, and some are vertical. 2. The magnet used to hold down the PTFE cup to the wafer may have a very slight impact on the etch process. The dramatic shift in filter performance at the periphery is due to O-ring restricting the conductive etchant to a sharp edge, creating an electrical field concentration. Outstanding visual Fourier series tutorial:http://www.jezzamon.com/fourier/index.html LR-1 spectrometer: http://www.aseq-instruments.com/LR1.html p-type wafers on eBay. (You have to hunt around and check the photos for info on the label attached to the box of wafers. Be sure to get wafers less than 0.01 ohm-cm) eg https://www.ebay.com/itm/25-silicon-wafer-P-type-150mm-100-sumco/263441166009 n-type wafers are photosensitive during the etch process. Online graphing calculator page from this video: https://www.desmos.com/calculator/hiju8zdqfz Original Desmos page that I used: https://www.desmos.com/calculator/qpnz9celzf Code for Keithley 2450 control and processing.org waveform generation: https://github.com/benkrasnow/Porous_Silicon_Optics Fourier transform to understand optical coatings: http://www.willeyoptical.com/pdfs/92_180.pdf Porous silicon refs: https://www.rp-photonics.com/rugate_filters.html https://www.intechopen.com/books/porosity-process-technologies-and-applications/porous-silicon https://sci-hub.se/https://doi.org/10.1016/j.mee.2011.03.143 https://sci-hub.se/https://doi.org/10.1080/10408436.2010.495446 https://sci-hub.se/https://doi.org/10.1007/978-3-319-71381-6_2 https://sci-hub.se/https://doi.org/10.1364/AO.44.005415 https://sci-hub.se/10.1364/OE.16.015531 https://sci-hub.se/https://doi.org/10.1002/adma.19940061214 https://sci-hub.se/https://doi.org/10.1063/1.2906337

Silicon wafer identification flats: https://www.tf.uni-kiel.de/matwis/amat/elmat_en/kap_5/illustr/i5_2_4.html Applied Science on Patreon: https://www.patreon.com/AppliedScience

Sunday, September 20, 2020

Shooting an electron beam through air

A special 100nm thick window allows 25 KeV electrons to pass from a vacuum tube to the atmosphere where they hit a fluorescent screen -- a CRT in air!