Back from Hiatus

I have returned from the dead and am back from hiatus. This brief intermission was due to moving and real-life delays. Please enjoy this entertaining image of my cat carrying his favorite toy as a gesture, re-welcoming you to this blog now that I am back from hiatus.

He loves Da Bird

Book Binding – Part 2

The post last week showed you how to bind your class notes into a book.  This week, I will show how to finish compiling your documents with a hardcover bookbinding.  I chose to use a different example for my pictures here, as the bookbinding in these photos is more simplistic and instructive.

Materials

My hardcover bookbindings use matboard as the base material.  Matboard can be purchased from a hobby store which provides picture framing materials.  The board is cut to size, slightly larger than the paper which it is binding, with a razor and straightedge.

Next I use fabric scraps to prepare corners and spine coverings for the book.  For a more ornate book, I like to cover the entire matboard with one fabric, then use a second fabric for the corners and spine.  However, I want this post to show the bare minimum.  It is important to at least cover the corners of the matboard with material when binding a book in this manner, as the material is little more than thickened cardboard and can damage over time.

The corners are made by folding a trapezoidal shaped cutout of fabric at the corners.  The spine is made by using a strip of fabric to strap the matboard pices together.  Sometimes, I use a thicker material inside the spine fabric to improve the spine quality.

Cover to Book

The cover is secured to the book with at the edge of the spine.  A minimum, you can use a piece of gaffers tape to affix this point, but I chose to use colored paper.  The paper is glued to the the first page with a thin layer of PVA glue, and folded over.  The next half is glued to the hardened binding.

Note that the pictured example is NOT my best work.  This illustrates and experiment I made while coming up with this method.  The glue causes waves in the colored paper as it dries.  Furthermore, the cover which is thickened by the fabric causes waves as the paper settles into the matboard preferentially.  In later work, I have used another layer of material to thicken the matboard to match the fabric thickness.

Not the prettiest thing I've made, so learn from this mistake.

The end result is quite nice though.  The cover is substantial enough to protect the materials within, and the cloth hardcover bookbinding adds a bit of elegance to your shelf.  In my future experiments, I plan on adding embroidered titles to the spine before binding.

Hardcover bookbinding with cloth and matboard is a nice way to keep your documents on the shelf.

 

Bookbinding Class Notes – Part 1

Isn’t it a hassle when you go try to keep your class notes organized and bound, but your professor loves handouts?  Just take to bookbinding class notes into a copy worth keeping, like I have.  This and the post next week will show the steps I took to bind the notes from one of my classes into a hardbound copy.

Bookbinding Class Notes - I used LaTeX to make the table of contents

Printing and Sizing the Paper

When preparing my notes for bookbinding, I had to deal with a combination of page sizes.  I took my notes on lined paper which was slightly smaller than the handouts, which were printed on standard US Letter sized paper.  This was fixed by cutting down the letter paper with a straightedge and razor.  I chose to cut from the bottom edge of the letter paper rather than the top to resize.  Either works, and it is a matter of preference.  Be sure not to cut off something important!

Bookbinding Class Notes

Binding with String and Glue

Once you have all of your notes ready to go, place the copies in a stack and secure with clamps.  For this book, I used a piece of wood on either side of the stacked papers to prevent the C-clamps I was using from damaging the notes.  The wood was positioned to leave a margin on the binding side of the documents.

Next, line was traced on the top page 1 cm from the edge.  This line was marked at regular intervals (I think I used 1 cm for my intervals on this copy).  At each of these intervals, I drilled a small hole all the way through the papers.  I used a 3/32″ diameter drill bit.  It is important to note that while drilling these holes, the papers will tend to splay out.  I mitigated this issue by securing the area adjacent to the drill hole with channel lock pliers.

When all of the holes are drilled, use a needle and thread to bind the book.  There are several different binding techniques you can use, but I have found that a simple looping forward and backward along the spine of the book was sufficient.  With the string tied off, I used a liberal amount of PVA glue along the spine to further hold the pages together.

String is really all you need for the spine, but glue is extra security

Next week I will describe how I make my covers.

 

LaTeX: Drawing MOSFET in TikZ – Labels and Animation

Continuing from last week’s post, this week we will be adding labels to our MOSFET in TikZ and adding slide animations with Beamer.

As a reminder, last week we drew our image of a MOSFET in Tikz before adding colors. The colors we added were based on the materials used in each part of the n-type MOSFET. Now let’s add some labels to make sure that anyone we present this image to can understand what is going in.

Centered Labels

Now we take the code from last week and add “nodes” to certain of our shapes. We tell these nodes to have certain text and compile.

\documentclass{beamer}

\usepackage{tikz}
	\usetikzlibrary{patterns}

\title{\LaTeX~Surface Science and Electronics}
\author{Wesley T. Honeycutt}
\date{\today}

\newcommand{\metalone}{[pattern= horizontal lines, pattern color=blue]}
\newcommand{\metaltwo}{[pattern= vertical lines, pattern color=purple]}
\newcommand{\poly}{[pattern= grid, pattern color=red]}
\newcommand{\pdiff}{[pattern= north east lines, pattern color=orange]}
\newcommand{\ndiff}{[pattern= north west lines, pattern color=green]}
\newcommand{\pwell}{[pattern= crosshatch dots, pattern color=orange]}
\newcommand{\nwell}{[pattern= crosshatch dots, pattern color=green]}
\newcommand{\oxide}{[pattern = bricks, pattern color = olive]}
\newcommand{\silicon}{[fill = white]}
\newcommand{\metalthree}{[fill = teal]}

\begin{document}

	\frame{\titlepage}
	
	\frame{\frametitle{MOSFET}
		% General n-type mosfet
		\begin{tikzpicture}
		\draw \pdiff (0,.25) -- (0,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) -- (11,3) -- (11,.25) -- (0,.25) node {p-type};
		\draw \metalthree (0,0) rectangle (11,.25) node {Si Substrate};
		\draw \oxide (4,3) rectangle (7,4) node {oxide};
		\draw \metalone (4,4) rectangle (7,4.5);
		\draw \ndiff (4.25,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) node {n-type};
		\draw \ndiff (10,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) node {n-type};
		\draw \metalone (1.25,3) rectangle (3,3.5);
		\draw \metalone (8,3) rectangle (9.75,3.5);
		\end{tikzpicture}
	}

\end{document}

This gives us the following image with ill-placed text:

Ill-placed text on our MOSFET

The text looks odd because the node location in TikZ defaults to the last point in the drawing. We can tell it to place the node in a certain location with respect to this anchor point. Additionally, I might want to change some other properties such as text color for my labels. This can all be done in brackets after declaring the node. Now my code becomes:

\documentclass{beamer}

\usepackage{tikz}
	\usetikzlibrary{patterns}

\title{\LaTeX~Surface Science and Electronics}
\author{Wesley T. Honeycutt}
\date{\today}

\newcommand{\metalone}{[pattern= horizontal lines, pattern color=blue]}
\newcommand{\metaltwo}{[pattern= vertical lines, pattern color=purple]}
\newcommand{\poly}{[pattern= grid, pattern color=red]}
\newcommand{\pdiff}{[pattern= north east lines, pattern color=orange]}
\newcommand{\ndiff}{[pattern= north west lines, pattern color=green]}
\newcommand{\pwell}{[pattern= crosshatch dots, pattern color=orange]}
\newcommand{\nwell}{[pattern= crosshatch dots, pattern color=green]}
\newcommand{\oxide}{[pattern = bricks, pattern color = olive]}
\newcommand{\silicon}{[fill = white]}
\newcommand{\metalthree}{[fill = teal]}

\begin{document}

	\frame{\titlepage}
	
	\frame{\frametitle{MOSFET}
		% General n-type mosfet
		\begin{tikzpicture}
		\draw \pdiff (0,.25) -- (0,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) -- (11,3) -- (11,.25) -- (0,.25) node [midway,above] {p doped Si};
		\draw \metalthree (0,0) rectangle (11,.25) node [midway, color=white]
		 {Si Substrate};
		\draw \oxide (4,3) rectangle (7,4) node [pos=.5,font=\bf\Large] {oxide};
		\draw \metalone (4,4) rectangle (7,4.5);
		\draw \ndiff (4.25,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) node at (2.625,2.5) [align=center] {n-type};
		\draw \ndiff (10,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) node at (8.375,2.5) [align=center] {n-type};
		\draw \metalone (1.25,3) rectangle (3,3.5);
		\draw \metalone (8,3) rectangle (9.75,3.5);
		\end{tikzpicture}
	}
	
\end{document}

In this case, I have added some alignment options for different locations.

  • For the silicon substrate, I have told the node [midway, color=white] so the text appears in the middle of the rectangle and white to show up against the color of metalthree
  • For the p doped region, I have told the node [midway,above] so that the text is in the middle of the picture and at the bottom. Notice how midway does not place the text at the true center of custom shapes. It only knows to place it relative to the previous line.
  • For the n doped regions, I did not want the text to sit relative to the line, I wanted it to be in the center of the shape. Thus, I told the node to be at a certain set of coordinates which I calculated to be the center of that shape, and set [align=center].
  • For the oxide layer, I wanted the text to show up against the oddly colored bricks. Therefore, I used [pos=.5,font=\bf\Large]. The “pos=.5” argument is functionally the same as “midway”, but offers greater freedom to customize. The font arguments tell the node to use text in boldface with a Large size.

The image ends up looking like this:

Placement and Style

Labels on Arrows

I’ve decided that I want to label the metal connections on our MOSFET, but I don’t want to place the text directly over the shape. Instead, I want to tell TikZ to draw little arrows pointing to what is labeled. This is easy. We just draw a line, which we tell to have an arrowhead, from a point to another point. At the first point, we tell it to have a label. I have used:

\draw [->] (1,5) node [above] {Source} -- (2.125,3.5);
		\draw [->] (10,5) node [above] {Drain} -- (8.975,3.5);
		\draw [->] (5.5,5) node [above] {Gate} -- (5.5,4.5);

Which when implemented, looks like this:

Animation with Beamer

Did you know that the same person that wrote TikZ wrote Beamer, the LaTeX slideshow creator? It’s true. This makes things quite convenient, as the author has designed it such that it is easy to integrate slide animations into your TikZ code.

For the final part of our MOSFET in TikZ, I’m going to add some animation. I want to make it obvious to the viewer how my MOSFET works going from the off state to saturation mode. I will do this by adding nodes to present the voltage relationship of each state on the screen, then pop up an image of the electron rich areas of the MOSFET. This is very easy to do with \only. Check out the final code below:

\documentclass{beamer}

\usepackage{tikz}
	\usetikzlibrary{patterns}

\title{\LaTeX~Surface Science and Electronics}
\author{Wesley T. Honeycutt}
\date{\today}

\newcommand{\metalone}{[pattern= horizontal lines, pattern color=blue]}
\newcommand{\metaltwo}{[pattern= vertical lines, pattern color=purple]}
\newcommand{\poly}{[pattern= grid, pattern color=red]}
\newcommand{\pdiff}{[pattern= north east lines, pattern color=orange]}
\newcommand{\ndiff}{[pattern= north west lines, pattern color=green]}
\newcommand{\pwell}{[pattern= crosshatch dots, pattern color=orange]}
\newcommand{\nwell}{[pattern= crosshatch dots, pattern color=green]}
\newcommand{\oxide}{[pattern = bricks, pattern color = olive]}
\newcommand{\silicon}{[fill = white]}
\newcommand{\metalthree}{[fill = teal]}

\begin{document}

	\frame{\titlepage}
	
	\frame{\frametitle{MOSFET}
		% General n-type mosfet
		\begin{tikzpicture}
		\draw \pdiff (0,.25) -- (0,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) -- (11,3) -- (11,.25) -- (0,.25) node [midway,above] {p doped Si};
		\draw \metalthree (0,0) rectangle (11,.25) node [midway, color=white]
		 {Si Substrate};
		\draw \oxide (4,3) rectangle (7,4) node [pos=.5,font=\bf\Large] {oxide};
		\draw \metalone (4,4) rectangle (7,4.5);
		\draw \ndiff (4.25,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) node at (2.625,2.5) [align=center] {n-type};
		\draw \ndiff (10,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) node at (8.375,2.5) [align=center] {n-type};
		\draw \metalone (1.25,3) rectangle (3,3.5);
		\draw \metalone (8,3) rectangle (9.75,3.5);
		\draw [->] (1,5) node [above] {Source} -- (2.125,3.5);
		\draw [->] (10,5) node [above] {Drain} -- (8.975,3.5);
		\draw [->] (5.5,5) node [above] {Gate} -- (5.5,4.5);
		\only<1> {\node at (5.5,-.5) [align=center] {$V_{GS} < V_{threshold}$};}
		\only<2-3> {\node at (5.5,-.5) [align=center] {$V_{GS} \geq V_{threshold}$};
			\node at (5.5,-1) [align=center] {$V_{DS} < V_{GS} - V_{threshold}$};
			}
		\only<3> {\draw [fill=white] (4.25,3) rectangle (6.75,2.5);
			\draw \ndiff (4.25,3) rectangle (6.75,2.5);
			}
		\only<4-5> {\node at (5.5,-.5) [align=center] {$V_{GS} \geq V_{threshold}$};
			\node at (5.5,-1) [align=center] {$V_{DS} = V_{GS} - V_{threshold}$};
			}
		\only<5> {\draw [fill=orange,orange] (4.25,3) rectangle (6.75,2.5);
			\draw [fill=white] (4.25,3) -- (4.25,2.65) -- (6.75,3) -- (4.75,3);
			\draw \ndiff (4.25,3) -- (4.25,2.65) -- (6.75,3) -- (4.75,3);
			}
		\only<6-7> {\node at (5.5,-.5) [align=center] {$V_{GS} \geq V_{threshold}$};
			\node at (5.5,-1) [align=center] {$V_{DS} > V_{GS} - V_{threshold}$};
			}
		\only<7> {\draw [fill=orange,orange] (4.25,3) rectangle (6.75,2.5);
			\draw [fill=white] (4.25,3) -- (4.25,2.85) -- (6.75,3) -- (4.75,3);
			\draw \ndiff (4.25,3) -- (4.25,2.85) -- (6.75,3) -- (4.75,3);
			}
		\end{tikzpicture}
	}
	
\end{document}

Each time I add an \only, I put slide numbers in pointed braces. The code between the curly braces will “only” show up on the slides listed in the pointed braces. The result of this code is shown in the following gif:

Animated

Wrap Up

I know that creating a MOSFET in TikZ is a bit specific. Still, I hope that this little tutorial gives everyone a feel for how to take make nice scale-able images in LaTeX using TikZ.

LaTeX: Drawing MOSFET in TikZ

I’m a big fan of using LaTeX for my scientific writing.  (What is LaTeX? It is a typesetting programming language that gives you much more flexibility than other writing environments.  wikipedia)  Since I have some time on my hands, I wanted to prepare for future presentations by writing up some notes and slides using in LaTeX for future use.  This includes drawing diagrams using TikZ.  This post describes how to draw a simple, generalized MOSFET in TikZ while standardizing some of the layer notation.

Setting up the Beamer environment

Before we get started with our drawing, let’s first set up a simple LaTeX environment.  Let’s say we want to make some slides for a lecture.  We can use the Beamer class in LaTeX to make these slides.  We tell LaTeX what we what to do.

\documentclass{beamer}

\begin{document}

\end{document}

Now, we add some title information into the preamble of the code, and we tell the document to produce a title slide.

\documentclass{beamer}

\title{Dr. Honeycutt's \LaTeX Surface Science and Electronics}
\author{Wesley T. Honeycutt}
\date{\today}

\begin{document}

	\frame{\titlepage}

\end{document}

The “\frame” command tells the LaTeX compiler to produce a single slide with the content in the curly braces. For our title slide, we want the content to be the information title information we included in the preamble. After compiling, it should look like this:

Title Slide

If you want to make your slides look fancy, there are plenty of things you can do. For this demonstration, we are only need a simple framework for the TikZ drawing, so we will just leave it at the default.

Drawing the MOSFET in TikZ

Now we are going to make a new slide with our drawing. We tell LaTeX that we will be using TikZ in the preamble. Then, we start a new slide (“\frame”) and begin our drawing. If you don’t know what a MOSFET is, or you just need a bit of a refresher, check out this for reference. Here is what my code looks like:

\documentclass{beamer}

\usepackage{tikz}

\title{\LaTeX~Surface Science and Electronics}
\author{Wesley T. Honeycutt}
\date{\today}

\begin{document}

	\frame{\titlepage}
	
	\frame{\frametitle{MOSFET}
		% General n-type mosfet
		\begin{tikzpicture}
		\draw (0,.25) -- (0,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) -- (11,3) -- (11,.25) -- (0,.25);
		\draw (0,0) rectangle (11,.25);
		\draw (4,3) rectangle (7,4);
		\draw (4,4) rectangle (7,4.5);
		\draw (4.25,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3);
		\draw (10,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3);
		\draw (1.25,3) rectangle (3,3.5);
		\draw (8,3) rectangle (9.75,3.5);
		\end{tikzpicture}
	}

\end{document}

In the preamble, I have told LaTeX I will be using the TikZ package. After the title slide, I added a new “\frame” and gave it a “\frametitle”. Note how the curly brace of the “\frame” does not close until line 25. In this “\frame” I have started a tikzpicture environment. This tells LaTeX that it should start using the TikZ code in this section. I have two types of drawings here. The first are simple rectangles. These rectangles are bounded by the opposing corners in (x,y) coordinates. The default units here are cm. The second type of drawing is a complex line shape. The code tells TikZ that I want a line “–” drawn from one (x,y) coordinate to a second coordinate. Multiples of these lines can be drawn in a single line. I have drawn curved lines with a different notation. I tell TikZ to draw from the first (x,y) coordinate “to [out=a,in=b]” where “a” and “b” are angles. This creates a curved line which connects to the previous and next segment at the defined angles. There are many ways to draw curves in TikZ, but for simple figures such as depicted here, this approach is sufficient. Finally, note how each line of the “tikzpicture” code is ended by a semicolon. This line ending is not something that you normally see in LaTeX, so be sure you don’t forget it.

When I compile my code, the slide with the drawing of the MOSFET in TikZ looks like this:

Drawing of MOSFET in TikZ

Adding some color

Now let’s add some color to our image. Using TikZ, adding a color is as easy as mentioning a fill color. But this is a special case. When drawing electronic components at the surface level, there are standard colors used for certain things. The standardized colors make it easy for Engineers to understand how a circuit works at a glance. These colors, from the classic VLSI design program “Magic”, are show in the picture (from Prof. Stine’s guide to Magic) below:

Standard VLSI colors

I want to use these colors for all of the drawings in my slides and notes. Therefore, I am going to make a new command for the colors in LaTeX. Additionally, since I expect my drawings to overlap at times, I want to give the colors patterns as well. I add the following code to my preamble:

\newcommand{\metalone}{[pattern= horizontal lines, pattern color=blue]}
\newcommand{\metaltwo}{[pattern= vertical lines, pattern color=purple]}
\newcommand{\poly}{[pattern= grid, pattern color=red]}
\newcommand{\pdiff}{[pattern= north east lines, pattern color=orange]}
\newcommand{\ndiff}{[pattern= north west lines, pattern color=green]}
\newcommand{\pwell}{[pattern= crosshatch dots, pattern color=orange]}
\newcommand{\nwell}{[pattern= crosshatch dots, pattern color=green]}
\newcommand{\oxide}{[pattern = bricks, pattern color = olive]}
\newcommand{\silicon}{[fill = white]}
\newcommand{\metalthree}{[fill = teal]}

In this section, I am defining a new custom command for LaTeX with the command name in the first set of curly braces, and the action to be performed in the second set of curly braces. The actions include a pattern and a pattern color in a format acceptable to TikZ notation. All I have to do is include the command in my drawing for the color and pattern to apply. If I decide to change a color later on (maybe metalthree needs to be pink instead of teal), all I have to do is change the command in one location and every instance of the command in the code is changed.

Additionally, since we decided to use patterns with the color fill commands, we need to add a line in the preamble declaring that we are going to use patterns. This is the case for all optional TikZ libraries we use in the future.

When we take a look at the complete code for the MOSFET in TikZ slide, it should look like this:

\documentclass{beamer}

\usepackage{tikz}
	\usetikzlibrary{patterns}

\title{\LaTeX~Surface Science and Electronics}
\author{Wesley T. Honeycutt}
\date{\today}

\newcommand{\metalone}{[pattern= horizontal lines, pattern color=blue]}
\newcommand{\metaltwo}{[pattern= vertical lines, pattern color=purple]}
\newcommand{\poly}{[pattern= grid, pattern color=red]}
\newcommand{\pdiff}{[pattern= north east lines, pattern color=orange]}
\newcommand{\ndiff}{[pattern= north west lines, pattern color=green]}
\newcommand{\pwell}{[pattern= crosshatch dots, pattern color=orange]}
\newcommand{\nwell}{[pattern= crosshatch dots, pattern color=green]}
\newcommand{\oxide}{[pattern = bricks, pattern color = olive]}
\newcommand{\silicon}{[fill = white]}
\newcommand{\metalthree}{[fill = teal]}

\begin{document}

	\frame{\titlepage}
	
	\frame{\frametitle{MOSFET}
		% General n-type mosfet
		\begin{tikzpicture}
		\draw \pdiff (0,.25) -- (0,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3) -- (11,3) -- (11,.25) -- (0,.25);
		\draw \metalthree (0,0) rectangle (11,.25);
		\draw \oxide (4,3) rectangle (7,4);
		\draw \metalone (4,4) rectangle (7,4.5);
		\draw \ndiff (4.25,3) -- (1,3) -- (1,2.5) to [out=270,in=180] (1.5,2) -- (3.75,2) to [out=0,in=270] (4.25,2.5) -- (4.25,3);
		\draw \ndiff (10,3) -- (6.75,3) -- (6.75,2.5) to [out=270,in=180] (7.25,2) -- (9.5,2) to [out=0,in=270] (10,2.5) -- (10,3);
		\draw \metalone (1.25,3) rectangle (3,3.5);
		\draw \metalone (8,3) rectangle (9.75,3.5);
		\end{tikzpicture}
	}

\end{document}

Compiling this code will give us this as our second slide:

Color Pattern Filled MOSFET in TikZ

Witch3

Continued from the last two weeks, here is the final installment of The Witch Mask.

Internals

With the witch mask exterior painted and sealed, the internals were applied.  The interior was painted black with acrylic paint and sealed with Mod Podge.  I wanted to avoid using a strap around the back, as I have found that is unreliable for keeping things on without slipping.  Instead, I opted to use a hat.  Cutting the bill off of a baseball cap, the fabric was glued in place with hot glue.  Sheer black fabric was placed over the mouth and eye holes, as pictured below.  When pulled taut, this allows the wearer to see through the fabric while not allowing others to see the eyes.  The fabric was glued in place with PVA.  To keep the fabric taut, masking tape was used while the glue was drying, and it was removed upon completion.

Mask internals showing hat, blackout fabric, and paint

A hood was sewn to fit around the mask.  Made from black cotton quilting fabric, the forward opening of the hood fit directly to the mask edge.  This was secured with hot glue.  Remaining black cotton fabric was sewn into an impromptu robe.

Hair

A nest of hair was made for the witch mask.  The material I chose to use was raffia.  This fiber is produced from the frond of the raffia palm.  While you might have seen this material used in twine or hats, it is also used in traditional African tribal masks.  The raffia fibers were combed parallel to each other and folded in half.  Along the fold, a double stitched seam was sewn to hold the fibers together.  The stitch distance was short enough to penetrate most of the individual fibers so they would be retained during use.  The hairpiece was secured with staples to the paper mache portion of the mask and sewn onto the black hood with some quick stitches.

Witch mask hair made from raffia fibers

The Completed Witch Mask with Costume

Pictures of the completed mask can be seen below.  The lighting isn’t great, and the photos don’t capture dark, unnerving quality this has.  I blame my old phone for the poor picture quality.

The witch mask, completed

I wish the gloves matched the robe.

Tales of Terror

As you can tell from the previous photo, I made the mask into a complete Halloween costume.  Since I’m an adult, I naturally decided that I would wear the costume around town.  On my walk to work, I received plenty of stares.  The best part was when I took the elevator to my office.  I got on the elevator, let the doors close, and squatted in the corner near the buttons.  I did not speak.  The next few times someone would come on the elevator, I would slowly arise from my squatting position to my full standing height.  Eventually, someone went to my floor, and I got off to get some work done, but not before I scared one of my colleagues so badly, he refused to take the elevator.

On my way home from work, took the same path back.  Possibly my favorite reaction occurred when I passed by the library and two guys started shouting at me about how scary/awesome I was.  I ignored them for a beat, stopped, and turned my mask toward them while keeping my body rigid.  They screamed like little girls and ran off, the perfect reaction.

I noticed two people running towards me at one point.  One held a camera, the other a microphone.  They were interviewing people on campus for a Halloween special.  I was very excited to be interviewed.  Yet, my commitment to staying in character is very strong.  I remained silent.  All the microphone would pick up from the witch mask’d man was a deep rasping of breath.  The only motion I made to the camera was a slight tilt of my head, staring directly forward.  The interviewers loved this, but I could tell they wanted more.  After about 5 minutes of footage, I just walked away.

Since Halloween fell on a Friday that year, there were loads of parties around town.  I decided that the witch mask needed to go make some friends.  I stopped at my usual bar at one point, and I just stared at the bouncer.  Later, talking to him, I found out that this actually freaked him out pretty bad.  At the time, he remained stalwart, laughing off the fear and asking for my ID.  Since I forgot my wallet at home, I decided I didn’t need a drink that night.  No, the fear sweat would sustain me.

My last stop was a fraternity/sorority party at a house near my apartment.  I stood outside on their lawn while I could see them staring at me through the blinds.  As the watching individual turned to tell her other scantily clad friends about the creepy thing in the yard, I would dash forward and freeze, mimicking schoolyard red-light-green-light games.  Eventually, I made it up to their door, and they were truly terrified.  I stood there, and I was about to leave when some guys came out and confronted me.  One pulled my mask off, which I found rude, but I suppose I can’t complain since I was being creepy.  Leaving with a “I’ve been kicked out of better parties than this”, I decided to end my night.

To this day, the Witch Mask hangs on my wall.  A solemn visage to give visitors pause when they enter my home – a real conversation starter.

Witch2

Continuing from last week’s post, here is part 2 of The Witch Mask.

Designing the Face

After several more layers of my special paper mache/plaster mix, the mask has been built up to a the final texture.  For this mask, I believe I have 5 more layers since the first two I showed last week.  The top layer is sanded slightly to remove most of the major surface defects.  I wanted to keep the surface slightly unfinished for this project, as I was hoping to evoke a sense that this witch mask was produced in a rough, imperfect manner.

The face design is similar to the inspiration.  The eyes and mouth are cut with a Dremel tool.  The cuts are very shallow on the mask.  Cutting into this material is not as simple as it seems.  Deep cuts can cause the cut wheel to snag due to the flexibility of the material.  Yet the high strength requires mechanical cutting to pierce the repeated PVA and gypsum layers.  The cuts end up turning brown due to burning from the friction.

Witch Mask, first cuts.

After using a dremel for the shallow cuts, the final cuts are made with a thin chisel.  A razor blade is used to cut out any remaining ridges inside.  Finally, the interior of the open areas are sanded down with the Dremel, giving an even texture for working.

The shallow cuts are finished with other tools

Paint

The first layer for this project was a tan acrylic paint.  Darker browns and black are used to texture the first layer of paint.  Certain areas receive more attention than others for the shadowing colors.  Contours of the mask are shaded and highlighted to give depth to the relatively round surface.  Although the witch mask is not meant to look like a real human skull would, shading is applied to certain areas such as the cheekbone.  The lips are painted red, and the teeth are white.  This was done in a sloppy manner to fit with the theme of the piece.  Edges of the eyes and mouth are painted black where the cuts took place.  I wanted the final product to be a very obvious facade.

Paint is applied.  Looks like a rough makeup day.

After the mask was painted, the paint surface was roughened with mid-grain sandpaper.  This roughening helps remove the obvious brush strokes from the mask and age it.

Fire

Additional shading was added using carbon soot.  A candle was lit, and the mask was held close above the flame.  The point was not to burn the mask, but make it look burnt.  Soot from the candle would collect on the mask when done properly.  By angling the mask over the flame, the soot collected on the surface in different sorts of strokes.  A little practice is recommended first before trying this at home so you don’t burn your artwork and so you can get a feel for how to “brush” the soot.

For this mask, I sooted the eyes near the bridge of the nose, the underside of the eyes increasing near the edge, the actual edge of the mask, under the nose, and between the teeth.  The carbon was blended in certain places with my finger.

To seal in the paint and soot, several layers of Mod Podge were applied.  Since soot may run in water based environments, I elected not to brush on the Mod Podge.  Instead, I dabbed it on for the first layer.  This produced an uneven surface at first, but this effect was minimized by adding more layers.

Soot is added for shading

To be continued…

Witch1

In early 2014, I was inspired to make some mask art.  The final piece has no proper name, but I refer to it when speaking to others as “The Witch Mask”.  Work on the mask was undertaken over several months, finally completed in October 2014.  This post and the related follow up posts will detail the creation of this mask from concept to reality.

Inspiration 1 – Israeli Stone Mask

The original inspiration for the creation of the witch mask came from two sources.  First, was an article on the world’s oldest masks going on display in Jerusalem.  An article in National Geographic goes over the exhibit.  One of the masks in particular caught my eye as something creepy and unnatural.   Among the finds recovered from Nahal Hamar is this Neolithic stone mask:

Israeli Neolithic stone mask ca. 7,000 BCE

It is reported to be ~9,000 years old.

This unnamed piece was discovered in the vicinity of Horvat Duma by a farmer.  The journey from field to find is slightly unpleasant as well.  According to the story, the mask was purchased from the farmer who discovered it by Israeli general Moshe Dayan.  However, Gen. Dayan was not the nicest guy.  While he fancied himself an archaeologist, he acquired much of his collection through shady means.  An article by Raz Kletter (see § 4.3) pulls quotes from the various memoirs of Gen. Dayan relating how he did not actually purchase the mask, he just paid the driver to take him there.

The emptiness of the mask’s expression and the sordid tale to accompany it makes for some interesting inspiration.  But it took a second source to produce my idea.

Inspiration 2 – Witch

The image below is a digital painting I found while browsing around Reddit.  The work as I saw it had no source to accompany it at the time, but it struck a chord with me.  The empty expression, the facial features, and the darkness produced a connection to the Israeli mask.  Even if they weren’t related by, there was a certain kinship to them.  At that point I was inspired to create.

"Witch" by Maaria Laurinen

With post facto research, I have discovered that the illustration is entitled “Witch”, appropriately enough.  It was published to DeviantArt around 2008 or 2009 by Maaria Laurinen.  You can view more of her work here and here.

The First Layers

The witch mask was started with an oval ring cut from matboard.  The oval hole in the center had an opening with an approximate size to fit my face.  Using matboard gave me a flat surface to start building up the contour.

The face was produced in a layered process using a paper mache variant I enjoy using.  I create this using shreds of old printouts from the lab.  The first step is to grind the paper with water in a blender to produce a slurry.  Then I press out the water using cheesecloth.  The still wet paper mash is mixed with white glue (polyvinyl acetate) and plaster of paris (anhydrous calcium sulfate).  The glue gives helps bind the paper shreds together, and the plaster provides weight and strength.  The final texture of the material is like an old fashioned plaster cast.  It makes for a nice stone-like feel.

First Layers of the witch mask

A side view of the first two layers.

For the start of the witch mask, I did domed shape with a nose on the first layer.  Each layer, after drying for several days, is coated with matte surface Mod Podge or sealant to keep the things together.  In this case, drying the first layer was accelerated by placing it in an oven.  Use of the oven degrades the PVA white glue, causing the slight browning of the first layer shown above.  The matte surface is important, as it lends greater surface area for future layers or paints to bond to.  Pictures above depict the front and side view of the mask after the inital domed/nose layer, Mod Podge, and the start of the second layer.

After everything was dried and coated, I tested the fit of the mask for the first time.

A blank slate.

To be continued…

3D Printed Sheath for 8-in Chef Knife

I was recently gifted a new Shun knife without a sheath.  Obviously, I did what any normal person would do – I designed my own custom 3D printed sheath.

The perfect cover, a 3D printed sheath for my chef's knife.

The Design

The original design is based on the Shun DM0706 Classic 8-Inch Chef’s Knife. The curvature of the blade is similar between knives, and the hollow portion for the blade was given ample room to accommodate other variations. The opening of the sheath is directional, there is a simple clasping architecture to hold the sharp bits in place. For my print and my knife, this is very tight, which is what I wanted. It takes some muscle to unsheath the blade, making it a bit more child/idiot-safe.

The blade fits tight the custom opening.

An external comparison.

This wireframe image lets you see how the interior of the sheath is shaped.

The Pizzazz

I wanted to add a little something extra to the design of my 3D printed sheath, so I decided to add some lettering.  As I have more than one Shun knife with very similar handles, I added some lettering to denote that this was a 3D printed sheath for a chef’s knife.  So, I created some raised letters on the edge of the sheath which read CHEF in a narrow Impact typeface.

CHEF

I’m quite happy with the design.  The curvature has a nice exotic feel to it, and the lettering adds that extra “something”.  I am very happy with how tight the fit is for the blade, as I like to feel secure that the knife won’t be slipping free any time soon.  My other Shun knife is responsible for a non-trivial flesh wound, so I am especially concerned for safety with these amazing extra-sharp kitchen razors.

The Part

The little widget below is clickable, and it will let you move the 3D object around to see for yourself how it is designed.

Just want to try the parts out for yourself?  The  .stl file you will want to download is below.

chef_knife_holder.stl

DIY Bone Conduction Headphones

EDIT 07/18/17: This post has been getting a lot of hits lately. Since I don’t have comments enabled for my site, if you have questions or would like to comment on anything, please feel free to email me directly. My email can be found on my CV (I won’t post it here so the spam bots don’t eat me!)

I discovered something fascinating while browsing around the other day: headphones that transmit sound directly to your skull.  This method of sound transfer has been dubbed bone conduction.  All you do is press the little transducers up to your temple, jaw, or skull, and the vibrations in the little electrical device transfer to the waves through the solid bone medium to your inner ear.  This way you can listen to things without blocking your ears with big cans or buds.  Rather than go out and purchase one of the little premade units, I decided to make my own DIY bone conduction headphones.

I have my own issues with headphones.  I am the type who strongly prefers earbuds.  Sure, you can get better sound out of headphones, but I find that the large strap and bulky padding smashes my ears and glasses together in an uncomfortable way.  Furthermore, the shape of my skull with causes the applied pressure of the headphones to pull my glasses out of alignment.  That puts pressure on one side of my nose or the other, and it makes my vision all out of alignment.  To make things just that much worse, my very fine hair is easily molded, a quality that makes it easy to get ready in the morning but causes instant hat hair.  Headphone bands give me this weird wave in my perfect, voluminous follicle coif.  If you look at the bone conductivity headphones available on the market, they all use a strap to keep them in place like a normal pair of headphones.  With the extra pressure required to push the transducers up to my jaw, I can only imagine that they would have even more issues.

So I thought to myself: how can I make a set of DIY bone conduction headphones with properties closer to earbuds?

Answer: use the straps that you wear every day, your glasses.

The Build

For this build, I purchased equipment from Adafruit which was very similar to the stuff recommended in the Ruiz Brothers build.  I used

I followed the build similar to the Ruiz Brothers instructions linked above with substitutions made for the parts I sourced elsewhere, such as the battery pack.

I glued the completed breadboard to the battery pack and called it a success.  My first tests (using the transducers on my apartment’s door to introduce my partying neighbors to Norwegian black metal) proved the build to be a success.

For future modifications to this, I plan on soldering a jumper on the gain pins instead of using the removable jumper.  I also would wire the headphones directly to the board rather than using the European headers included with the breakout board.

The amp circuitry and transducers for the DIY bone conduction headphones.

The Buds

As you can see in the picture of the build, there are these strange brown boxes wired to the device.  These are the containers for the bone conduction transducers.  These were designed in Fusion360 to fit the transducers quite snugly.  The Adafruit page offers a technical drawing of the transducer, but I found that my units were slightly off of this specification.  I wanted the transducers to fit in the housings without much room to rattle and lose volume and quality, so I went with my measurements.

These are the housings for the bone conductor transducers.

The hooks on the end of each housing are designed to fit onto the earpieces of my glasses.  The plastic glasses I wear have a slightly tapered profile.  This means with a little push of the parts onto the earpieces, they stay in place without sliding off.  The inside of each of the hooks on the housing are slanted, e.g. one end is more open than the other.  This means that the housings are not interchangeable, and fit on either the left or the right side of the glasses.  The cover of the housing fits into the remaining room around the transducer and these can be glued into place.  The slit at the bottom provides enough room for my cheap wires to go through or a bit bigger gauge if you are concerned about sound quality.

The parts fit onto the earpieces of my glasses.

The housings were printed on a Makerbot 5th Gen in dark brown PLA filament.  The print was scaled at 102.4% from the actual design size.  This scaling was based on a previous calibration curve of the printer PLA shrinkage and print accuracy.  Like I said, I wanted the tightest tolerance the little 3D printed parts could manage.

The little widget below is clickable, and it will let you move the 3D object around to see for yourself how it is designed.

This is the “left” container.

This is the cover which fits over both the “left” and “right” versions of the above model.

Just want to try the parts out for yourself?  The three .stl files you will want to download are below.

bonecond1.stl

bonecond2.stl

bonecond3.stl

 

 

The Fit

With my little DIY bone conduction headphones complete, it is time to try them out.

 

 

A handsome man with his DIY bone conduction headphones

Look at that handsome fellow in the picture.  The transducer housings fit as expected on my glasses.  The sound transferred well to my skull.  If you have ever used bone conducting transducers before, think of it like a medium press sound transfer rather than a super hard press.  The brown color is still stands out a bit from the color of my glasses and my hair.  Finishing paint would be necessary to make it look nicer.

The sound quality was pretty good as far as these little transducers can go.  They won’t be replacing my in-ear monitors any time soon, but they are sufficient to listen to spoken word audio.

Bonus trial: my mother is partially deaf due to Meniere’s disease.  She tried my DIY bone conduction headphones and was able to hear things on better on her deaf side.  Further development of this technology may prove to be useful for sufferers of mild hearing loss who do not desire the full hearing aid.