The Notebook

Sunday Roundup

2010-01-10T08:13:00.000-08:00

First: I did get the button controls added to the random number generator. The left-hand button selects the number of faces desired on the die (4,6,8,10,12,20,99) and the right hand button rolls the die. The min and max values for each face (0-99 for 99, 1 to n for all the others) are stored in arrays. It rolls and increments reliably, but the randomness of the number is sketchy and highly dependent on noise on the board. I'm not posting video yet because of the embarassing number of repeated rolls.

Second: in spite of the problem with the randomness, I am building a permanent version of the board on a prototype board. This is my first time building out a prototype board, especially one of my own design. I had a moment this week where I realized it was a lot like writing a program... You can't just expect to *know* how to get everything to work the first time you try. You have to layer your steps so that you can see and fix problems before they become permanent. I'm currently having a problem with the insulation melting on the jumpers I'm using, so the build is on pause until I can pick up some teflon tubing to use as insulation.

Third: One of the things my Dad tried to teach me -- which we had much conflict over -- is the principle of beginning where you are. I had hoped to get a couple of xBee's in SparkFun's giveaway this week, but I was one of the 69,000 some odd folks who clicked and didn't win. So instead I'm working on interfacing a keyboard with my Arduino. The principle of starting where you are comes into play because while there is an ideal keyboard out there for something like this, I don't want to spend $40 in an auction or $80 new for it. So then I was going to go to a thrift store and pick up a used keyboard. And then I realized I have used keyboards already -- in particular a cheap Microsoft one which I gummed up with a Coke and then replaced with an ergonomic keyboard. So my new project is going to be learning about serial communication over a USB interface and building a lookup table so I can do keyboard and/or keypad input for Arduino projects. I'm using this Instructable for guidance.

How to control a 7-segment LED using an Arduino

2010-01-01T11:34:00.000-08:00

A couple of weeks ago Make: Online posted a link to a project on connecting a 7-Segment LED to the Arduino. It uses the technique of using one pin for each LED segment, which does get the job done, but it also gobbles a lot of pins in the process. I wanted to try to use binary data to reduce the number of pins used.

Method:

Binary data can code values 0 to 7 in 3 bits and values 0 to 15 in four, so a 7-segment LED could use as few as 3 lines for each display but taking advantage of that would require a logic circuit on the board to decode the data. I was short on transistors to make my own decoder, but I still have an assortment of 74LS logic devices I got from Jameco around 2003.

Unfortunately, all three of the three chips I had (74LS47, 74LS138, 74LS139) that would get me close to what I wanted assumed a common anode on my 7 segment display, and I had a common cathode display (RadioShack's stocked-in-store display). So I waited out the weekend and then went by Sparkfun and got a few of these common anode displays.

Back at home, I wired up two of the displays to two 74LS47 chips. The easy part of this was that matching up the diagrams of the two devices was a matter of drawing a line from little a to little a. The tougher part was putting a 100 ohm resistor in that line and routing it across my breadboard. I did get everything hooked up and running well on the 3 volts.

Next I had to get signal lines from the Arduino to the breadboard which quickly became a rat's nest of wires. I knew from my time in the shop that every wire was increasing the confusing and the potential for creating a fault I would never find, so I stopped and made a cable.

I had on hand a cat-5 cable my dog chewed up during one of her first couple of months with us. Slicing it open, I found 8 stranded wires twisted into four color-coded pairs. I used crimp connectors and two 1x4 housings to make an 8 to 8 cable to carry the data to each chip.

With the cable, it was time to write some code.

The 74LS47 takes 4 lines of binary coded data (BCD) and turns them into a map of the associated decimal number.

For my first pass, I used a switch case to set four separate variables for each display, each containing one of the four bits. This worked as long as I was sending the same data to each display. But the same thing could be accomplished with an extra set of jumpers on the breadboard, so clearly I needed different data to each.

This step ended up simplifying the code because using the switch case to set all 8 bits would require 99 cases. What I found trying to avoid that was bitRead(x,n). This allowed me to use the bits of my value as the code to send the chip.

The heart of my new sketch is this:

    for (d=0; d<4; d++){
     digitalWrite(Rled[d],bitRead(j,d));
     digitalWrite(Lled[d],bitRead(i,d));
   }

This loops through two arrays which contain the pins (i.e. 7,8,9,10) and sets the pin high or low depending on the value of that bit (d) in the current number (i or j).

Result:

The results are quite satisfactory. I'm using a 0 to 9 loop for the 10s digit and another 0 to 9 loop for the ones. The 10s increments once for each loop of the ones. The size of the full sketch is 2378 bytes and I'm using only 8 of 14 digital pins to get the output. This compares to 3212 bytes for my switch case code and 8 pins for the original example.

Next:

My next steps with this project are to use button input to affect the numbers displayed. My plan is to make a universal gaming die where the user selects 4, 6, 8, 10, 12, 20, or 100 faces, presses the go button, and gets a random output. Results to follow!

Project: Dice

2009-12-27T09:16:00.000-08:00

I ran across this project for a single 6-sided die at the Electronics Club website and I was intrigued by their use of a grouped logic for presenting the results. I wanted to use my Duemilanova for both the randomizer and the LED driver though. Here are my results.

The first step was to set up the breadboard circuit. I'm using a solderless breadboard so I ended up with the seven pips on a diagonal.

The logic of the circuit is this: every time an odd number is rolled on a die, the center pip is included. Every number other than one has pairs of pips showing, with or without the center.

So the center has a pin to itself (13), and the other pips are paired by the white jumpers. Each pair gets a pin, which allows me to represent 6 (actually 7) numbers using 4 pins -- and no decoder.

My first sketch computes a random number (using pin 0 as a seed as suggested in the randomize() documentation) from 1 to 6, turns on the appropriate pips, waits a second, then does it again.

Here's video:

And here's the sketch:


/*
 Die

computes a random number from 1 to 6 and displays it using 7 LEDs as a die face

The circuit:
* LED connected from digital pin 13 to ground.
* 2 LEDs in serial connected from digital pin 12 to ground. (2s place)
* 2 LEDs in serial connected from digital pin 11 to ground. (4s place)
* 2 LEDs in serial connected from digital pin 10 to ground. (6s place)


Created 26 Dec 2009
By Anne Speck

*/

int die1; // container for current value of die1 (possible future expansion)
int basket; // variable for processing die values

int ledPin13 =  13;    // LED connected to digital pin 13
int ledPin12 =  12;    // 2 LEDs connected to digital pin 12
int ledPin11 =  11;    // 2 LEDs connected to digital pin 11
int ledPin10 =  10;    // 2 LEDs connected to digital pin 10

int one = LOW;
int two = LOW;
int four = LOW;
int six =LOW;

// The setup() method runs once, when the sketch starts

void setup()   {              
 // initialize the digital pin as an output:
 pinMode(ledPin13, OUTPUT);   
 pinMode(ledPin12, OUTPUT);   
 pinMode(ledPin11, OUTPUT);   
 pinMode(ledPin10, OUTPUT);

 //use serial output for debugging
  Serial.begin(9600);
}

// the loop() method runs over and over again,
// as long as the Arduino has power

void loop()                   
{
 // generate random number
   // if analog input pin 0 is unconnected, random analog
 // noise will cause the call to randomSeed() to generate
 // different seed numbers each time the sketch runs.
 // randomSeed() will then shuffle the random function.
  randomSeed(analogRead(0));
  die1 = random(1, 7);


 // translate number into pins for display
 basket = die1;
 if (basket%2) {
   //If there's a modulo, this is an odd number.
   basket--;
   one=HIGH;
 }
 if (basket == 6) {
   //If six, turn on sixes place and subtract two
   basket--;
   basket--;
   six=HIGH;
 }
 if (basket == 4) {
   //If four, turn on fours place and subtract two
   basket--;
   basket--;
   four=HIGH;
 }
 if (basket == 2) {
   //If this has a value it's two.
   basket=0;
   two=HIGH;
 }


 digitalWrite(ledPin13, one);   // set the LED on
 digitalWrite(ledPin12, two);   // set the LED on
 digitalWrite(ledPin11, four);   // set the LED on
 digitalWrite(ledPin10, six);   // set the LED on

 //serial output for debugging
  Serial.print("The number is: ");
  Serial.println(die1);
  Serial.print(one);
  Serial.print(two);
  Serial.print(four);
  Serial.println(six);


 delay(1000);                  // wait for a second

 //Reset all pins
 one = LOW;
 two = LOW;
 four = LOW;
 six =LOW;

}

Aha!

2009-12-12T13:00:00.000-08:00

I'm having aha moments left and right this weekend...

Thing I wish I'd been told in High School:
"Engineering is the useful application of science." (Will have to get the citation later. It's at the beginning of this lecture.)

Book I wish I'd read in college:
Mathematics for Liberal Arts by Morris Kline (Reprinted as Mathematics for the Nonmathematician)

Science Education

2009-12-08T06:36:00.000-08:00

On the 7th, NPR ran a story on TV shows that teach science. In that story they played clips from the President giving a speech (and welcoming Mythbusters to the White House) on the need for more science education in the United States. "More" is my word, and it's not quite right. He's trying to get Americans to care enough about scientific acheivements -- "meeting these challenges -- to improving our health and well-being, to harnessing clean energy, to protecting our security, and succeeding in the global economy" (from the linked speech) -- that we educate ourselves and our kids about science.

As Bill Nye says in the NPR article "Everybody loves science when he or she is young. You cannot find a kid that doesn't want to taste the kitchen floor, or that doesn't want to know how houseflies make a living."

The first question I had on hearing the quote from the president was, "But where are the jobs?" When I look at Craigslist, it isn't the science jobs section that is crammed full of good jobs. My sister, who majored in Biology, was qualified for a lab tech position on leaving school. It was her Master's degree in information systems that landed her a good job. I think enrollment in science is driven at least partly by the perception that there are an abundance of good jobs to go for at every level.

The second question I had was, "What do you mean by "science"?". We call psychology a science, but most people who major in it go into some form of counseling, not applying the scientific method in some form of research. The president welcomed the Mythbusters folks as examples of people who make science cool. But the Mythbusters lead-in calls Jamie and Adam special effects guys. They do apply the scientific method and use equations and record effects of their action. They propose and then prove or disprove hypotheses. So do you have to get a science degree to get their job?

The third question I had was, "You're talking about science education as a method, but innovation as the goal. Does innovation follow from education?" I think innovation happens when you have the skills to recognize and try a new idea and that may or may not come from education. The person I know who holds the most patents has something like a hundred thousand hours of hacking together electronics, reading spec sheets, trying code, talking to people, and running experiments under his belt. That's different from more classroom time.

The fourth question I had was, "but what if companies don't value science?" This is different from the jobs thing. Statistics and Calculus are the languages of the complex sciences, but at my company, managers weren't expected to be conversant in either. It wasn't a requirement to get promoted and it wasn't offered among the Seven Habits, creativity, work-life balance classes. Which is ironic, because the hit book in our industry at the time was about six-sigma investing.

Now, this is not to say I disagree with the president at all. And I don't think he'd disagree with me. There is a cultural inertia to overcome if we're really going to become conversant in science, and we each have to do our piece. His piece right now is to stem the tide of school districts deciding that science is optional. My piece is to get my but back to studying for my physics final.

Hello World!

2009-12-01T06:44:00.000-08:00

I picked up my Arduino Duemilanove board yesterday from Sparkfun and started working through Lady Ada's tutorial. This is from lesson 3. I wanted the lights to chase.

Phssst!

2009-11-28T10:38:00.000-08:00

That is the sound of me dusting off this blog.

While it's been a couple of years since I've posted anything here, I've kept tinkering. And I'm hoping to do a whole lot more.

My current buzz is the Arduino culture. I love the open source nature of it. The community of people encouraging each other in Make:, in Instructables, and on Facebook.

I also love that I see women involved in these products: Ladyada from adafruit, Leah Buechler who helped design the Lilypad Arduino sold by Sparkfun, and Cheryl Hrynkiw making videos of Solarbotics products for their website.

It is also nice for me to see Arduino introductions in Craft: magazine, and women shown helping build projects in Make: magazine... which gives me hope that one of these days I will see women writing regularly in Make: or some other geeky hardware magazine.

Still, progress is progress. Mythbusters may not have a lot of women experts to choose from but they do their best to make sure there are women doing interesting technical things on every show... and they're not just writing the documentation.

The freaky/cool think about the Arduino community is that in the early 80's my dad launched a product line from his company that went in exactly this direction. We called them hobby robots and tried to pitch them to teachers for classroom use. Which made me the youngest exhibitor at the First International Personal Robotics Convention. I cut my technical writing teeth writing code for and documenting our Elementary Automation kit, Mobile Mouse, a vision bot, and our 3 axis arm (all available for interfacing with the Commodore 64 and Apple IIe), but by 1990 the line had failed to take off and dad shut it down. I guess now I get to be the hobbyist.

MacGyver Challenge Index

2007-12-13T14:47:00.000-08:00

I'm assembling an index of all of ReadyMade's MacGyver Challenge articles here. The reason I'm doing an index is they don't actually list MacGyver Challenge as a section in the browse bars. So one has to go through manually and look at the projects in the magazine to find the MacGyvers.

I have a list of the winners by issue number, a list of materials used linked to the winners, and the current challenges.

Come check it out!

Nice Box!

2006-05-26T07:31:00.000-07:00

I didn't make this box, but I've decorated it. I'm exploring decoupage techniques. This box has some physical elements that have been applied using paint, a stencil element (I used painter's tape), a pallete of three acrylic paints, stamps using permanent ink and some hand written elements in permanent ink.
The photo below shows the different faces of the box. It looks like the auto focus was thrown off by the glossy surface in these shots, so I appologize for the blur.
I have not shown the bottom or the inside of the box because they are not done yet. I plan to sign and date the bottom and then apply wood stain to all bare areas. I haven't decided if I'm going to wax or varnish over the stain.

Adirondack Chair II

2005-09-17T14:01:00.000-07:00

This week I took Wednesday off work to work on the chair. My deadline is September 17th so it can go in the art auction. (I figure, "If a painting of an adirondack chair is art, why not a painted adirondack chair?")

At the start of the day, I had the back in one piece, the core of the chair together, and the legs tacked on. By the end of the day I'd:

Attached each leg with 5 counter-sunk screws
Shaped the arms with a sander to take the corners off
Sanded the arm supports down so each side was smooth
Attached the back at a 105 degree angle to the seat with three counter-sunk screws on each side
Determined the inside angle of the back to the arms was 55 degrees.
Trimmed the middle brace on the back and cut the arm supports to the correct angle.
Glued the arms supports to the front legs using the dowels.
Attached the arms to the front legs and the brace.
Attached the remaining seat slats.
Tested the chair for comfort... Pass!
Primed the chair using an indoor/outdoor water-based primer.

Friday afternoon I painted all the surfaces visible with the chair in it's upright position.

Saturday morning I turned the chair over and got the rest. I discovered an answer to a problem I was having:
Q. How do you paint the cracks between the slats?
A. You notice the problem is you can't get the brush in there and use a smaller brush.
In this case, I used a brush for painting on canvas out of a cheapie set I got a while back. It's nice to finally have paint on one of those handles!

And finally, I dragged the chair into the sun and applied a final coat on all the wear surfaces: seat, arms, and back.

Adirondack Chair

2005-09-07T15:07:00.000-07:00

The current project is an adirondack chair. The original goal was to make one for home and then a second one for the church art auction... but time has gotten away from me and now I'm headed straight for the art auction.

The Adirondack chair seems to be the original Tinkerer's Delight: 1.) Take scrap wood 2.) assemble.

I downloaded plans that had a lovely cutting diagram and lots of photos. My first problem was the lumberyard didn't have dimensional lumber in the dimensions called for by the plans, so I improvised, substituting a 2x6 for the original 1x8 stringers. They also didn't have the Southern Yellow Pine, recommended for its bug resistance. So I looked at the next two bug resistant options - redwood and pressure-treated lumber.

I went with the pressure-treated lumber. These boards are stashed in two different locations in the lumber yard. Most of the dimensions are with the deck materials, but the 1x4s are sold as fascia material and are with the fencing supplies.

Lumber scored, I headed home to start cutting. Turns out the safety goggles got packed at some point and couldn't be located with either the tools or the stained glass supplies. So back to the lumber yard for another pair of glasses.

Then I started cutting. And cutting went fine. Lots of memories of woodshop and metal shop classes as I made sure to measure twice and fit pieces together as I went along and using already cut pieces as the standard for additional cuts instead of just trusting my ruler.

Then it came time to start assembly. Problem 1: My plans have no measurments or angles for assembling pieces. In fact, none of the chairs in the photos were actually made from the pieces shown in the cutting diagram. Problem 2: There is no explaination for how the bottom of the back slats are anchored. I improvise and attach them to the back piece of what I am calling "the box." Problem 3: The screws I bought were for attaching 1" pieces to other 1" pieces, but I am now attaching 2" pieces to 2" pieces. I need more screws. Problem 4: If you put the arm uprights too far away from the front of the chair, the seat is uncomfortably steep. Problem 5: Using 2x6's for "the box" makes the chair darn heavy.

I am in the middle of trying to solve problem 5. I think I'm going to go to 1x6's. I don't have photos yet, but I'm looking forward to seeing the blue I picked out on the chair.

Report from Rendezvous

2005-08-09T14:21:00.000-07:00

So the goal of the tipi was to have a visible sign of "Camp Butchland", our entry in the "Butchest Campsite" contest at Rendezvous. The motivating vision was to have a Boy scout-like encampment.

Here's our sign, made from a discarded roadsign picked up at a recycling center (Thanks Alex!) and decorated in electrical tape and black marker (Thanks Trish!)

We're not sure who we lost out to as we missed the camp awards part of Saturday's presentation, but we're pretty sure we didn't win. We were up against some stiff competition. At the very least, we need a catchier name to compete with "Beaver Creek" and "Bush Gardens".

Here's the tipi staked out at our campsite in Wyoming. The wind had an interesting effect on the tent... it moved the poles in. This photo was taken nearly 20 hours since I'd put it up, and the cover went from being taut to being this slack.

I elected to not sleep in the tipi, mostly because I was worried about bugs. So I did a test and left the door open on my dome tent to see what the bug and critter level was like. The result: not too bad. Of course, that's following the principle that food should be kept away from the sleeping area. We stored dry food in my car trunk and all other food in coolers in the kitchen area. While I spotted a few ground squirrels, we didn't have any in camp.

My parents had a set of tarp connectors in the early 70's that were made of a ball and a keyhole-shaped loop of wire. The tarp went over the ball, the tarp and the ball went through the round part of the loop, then the tarp and the ball were pulled into the smaller end. A guy rope was then tied to the round part and the other end of that staked out. Apparently, the traditional way to stake out a tipi was to use the same kind of setup around the cover. The cover then provides the opposition that keeps the tipi poles from collapsing.

I did something similar. This uses a practice golf ball (looks like a wiffle ball). The hank of rope has a slipknot around the ball and fabric and a non-slip knot in the other end. The other end is around the stakes. The sites I'm using as references call this a "pebble tie" and I'm going to go with that until I find or remember the other name.

My tipi blew over within 30 minutes of being put up without the pebble ties, but stood for over 24 hours in blustery Wyoming wind with them.

I also used the pebble ties to stake out the trailing ends of our shade canopy. Since these are two unused sides of an easy-up tent, the leading edge is the velcro ties of the tarp connected to a cable strung between the trees.

Tipi

2005-08-02T08:26:00.000-07:00

The goal is to make a tipi for our campsite at Rendezvous. The UGLW folks hold a variety of competitions every year, and Kathi has decided that this is the year to go for "butchest camp."

The original idea was to make a tipi out of flannel, but when I confessed my lifelong dream of building and sleeping in a tipi, construction got a bit more serious. My grandfather's copy of "Woodcraft" by Earnest Thompson Seton came off the shelf and I got to work.

The poles of the tipi are 3/4" PVC tubing. Instead of doing a tripod, I'm doing a "quadpod"... bungee-ing four poles together. The bungee cord is looped around three times and tied, not hooked. These four poles are then spread out and four additional poles are nested into the structure at the top. This provides 8 poles.

These are 10 foot poles, the length right off the shelves. There is a slight bow in the poles at this height. The poles meet at about 8.5 ft. This results in the tipi being about 6 ft tall... I can stand up in it and reach the knot.

Originally, we were going to try to make the tipi 15 feet tall, hoping that by jointing the PVC in 5 ft intervals, the poles would be rigid enough. They weren't. It was like standing partially-cooked spaghetti on end. ;-)

Changing the design for the smaller poles created a tipi that was uncomfortably claustrophobic when we covered it with the coated tarp we'd bought. So I went back to my original canvas plan.

This is 9 yards of 62" wide canvas printed with a pixelated camoflauge design. It also has a nice clean khaki on the back (no bleed through from the design), so the cover will be reversable.

I cut the fabric into 3 yard sections and re-assembled them to get a final piece that is 9 ft tall and 180" wide. This is a quick fix (and we don't have a sewing machine right now) so the seams are done first with quilting safety pins and then taped over with Duck "200mph" duct tape.

After that, I used a 20 lb dumbbell, a hank of clothes line, and a piece of chalk to make a compass that would measure a 9 ft radius semi-circle. I traced the semi-circle on the cloth and cut it out. I used some of the scrap from the corners to finish out the front corners.

Here's the finished product!

The floor space is about the same as a two-man dome tent. The cost is about the same as a high-end two-man dome tent, and it lacks a lot of those features. I will be using a tarp for the ground cover and dealing with bugs all weekend as there no netting in sight. I will probably also rig another tarp as a rain fly. I'm imagining that going over the top of the poles and being staked out to provide an entry area over the door.

I'll take photos over the weekend and report back.

Slide together forms

2005-06-30T08:23:00.000-07:00

These are "slide together forms".

This one is made from 20 equilateral triangles. The result is a truncated icosahedron with "flourishes" -- each hexagonal face has three points that meet across it. The pentagonal faces are "ports" in this version. Looking into the ball, you can see it's resemblance to a soccer ball.

Straw and pipecleaner truncated icosahedron

2005-06-29T09:15:00.000-07:00

A truncated icosahedron is an Archemedian Solid. I don't know what that means.

I do know that an icosahedron is the shape a 20-sided die is made in, and that each face is an equilateral triangle and 5 triangles meet at each point. When you cut those points off, you get a mess of pentagons and hexagons that equals a "truncated icosahedron." But if you want a familiar name for it, it's a soccer ball. Have you ever noticed that each hexagon on a soccer ball has three pentagons and three hexagons bordering it? And that each pentagon has five hexagons bordering it?

I will post on "why" I'm doing this later... there will be cool pictures! But for now I am exploring another property of the structure. Every edge on the structure is exactly the same length. So I have cut 60 2" sections of straw and I am weaving them together with pipe cleaners. (Originally, I made 60 three pointed joints as well, but they didn't fit the straws with enough tension to actually "hang on" and the thing collapsed.

Here's the weaving in progress. (Yes, everything in the house is a kitty toy. Especially new things.)

Here's the finished product: