Liz Arum's Blog » Physical Computing

A cute soft circuit project

Lizabeth Arum — Tue, 06 Oct 2009 18:55:59 +0000

Here’s a soft circuit with 2 LEDs and a button. It is basically an electronic sock puppet.

I used a sock covered in a knitted bag. The button is a sewing snap. When the mouth closes, the button returns a 1 and the LEDs flicker.

height="850" codebase='http://www.apple.com/qtactivex/qtplugin.cab'> controller="true" loop="false" pluginspage='http://www.apple.com/quicktime/download/'>

Here’s the code

#define btn 4 #define led1 3 #define led2 9 int btnState;


void setup(){

  pinMode(led1,OUTPUT);

   pinMode(led2,OUTPUT);

  pinMode(btn,INPUT);
}

void loop(){ btnState=digitalRead(btn); if(btnState){ for(int i=50;i<255;i+=5){ analogWrite(led1,i); analogWrite(led2,i); delay(10); } for(int i=255;i>100;i-=5){ analogWrite(led1,i); analogWrite(led2,i); delay(10); } }else{ digitalWrite(led1,LOW); digitalWrite(led2,LOW); } Serial.println(digitalRead(btn)); }

Freeduinos!

Lizabeth Arum — Thu, 01 Oct 2009 04:08:36 +0000

Both my middle school and high school classes worked on putting together the Freeduino kits.

In order to avoid any soldering mistakes, I asked students to place all there resistors in the board first, and once I checked them, they could solder away. Capacitors were next, then LEDs then everything else. The middle school class had more success with putting the kits together quickly. Maybe soldering was more of a novelty for them? They completed their boards within two classes, but the high school students had the potential to drag the process into a third class. Rather than do that, I finished all but one of the boards. There was one high school student who completed his Freeduino over the weekend and worked on the Proto Shield from Adafruit in class.

My intention was to also have both groups make Proto Shields, but now I’m thinking that that project should be optional.

A Tone Generator and a Cool Purchase

Lizabeth Arum — Fri, 25 Sep 2009 02:19:12 +0000

A few years back, I took a summer physical computing class at Parsons with Dan Mikesell. For our first circuit he gave us the following schematic and image to work with:

I like this assignment because it introduces an IC chip, the NE555 Timer, and it makes an awful noise when it works. I also like it because initially it seems hard, but when students take a moment to think about the connections, it turns out to be quite simple. I always tell students to start with the GND and Vcc pins and go from there. It’s like solving a puzzle.

After displaying the schematic, I hand out a bag with the components. For each student, or group of students, I remove the components from the bag, name them, and describe their function. Then I leave students alone to figure out the wiring.

Today was Middle School Physical Computing and it was the last class of the day. Everyone was exhausted, but we still managed to play with the LED Resistor Calculator and two students out of eight were able to generate annoying tones.

Success!

I also purchased the Makerbot CupCake CNC for school today. Makerbot describes the “CupCake CNC as a rock solid open source 3D printer that is easy to build, easy to run, and easy to use. Its 100% open source, built to be hacked, and beginner friendly.” The plan is to have the High School students research digital fabrication and then build the printer in November. Very cool!

Piranha Leds and LED Resistance Calculators

Lizabeth Arum — Wed, 23 Sep 2009 01:08:37 +0000

It was the first Middle School Physical Computing class of the week today. Class was split between two activities. The first was lighting a 5mm Flux RGB LED piranha. While not told whether they had a common cathode or common anode LED, students were given the following information:

DC forward current 20mA
Red: 2V typ, 2.4V max
Green: 3V typ, 3.6V max
Blue: 3V typ, 3.6V max

After determining their resistor values, each student wired up their circuits to discover if their led was common cathode or common anode. Only one student managed to burn out the led by wiring both sides to power.

After creating some blended colors, students put the lights aside and went on to construct Evil Mad Scientists‘s LED Resistance Calculators.

Next class we’ll put the calculators to use and solve a few problems!

The Second Time Around

Lizabeth Arum — Fri, 18 Sep 2009 02:13:07 +0000

In order to wire the circuits and cover all the topics, I put the following information on the board before class started:

V_F= Forward Voltage/ Voltage Drop.
The minimum amount of voltage needed to light an LED
l_V= Luminous Intensity
The amount of light emitted from an LED in a particular direction.
The greater the numbers the brighter the light.
I_F= Forward Current
The amount of current the LED uses.
Viewing Angle
The distribution or spread of light.

And the following diagram:

Again, all materials were either distributed or placed on the floor in the middle of the group. Students worked together and everyone wired the first circuit using alligator clips, the second circuit using the 12VDC power supply and the third and fourth which wired the LEDs in series and then in parallel. In order to demonstrate the different voltage drops, the class experimented with different colored LEDs.

Flashing LEDs were thrown into the mix because they’re cool.

Today’s class was the last of the day and when it was over, some students stayed late to chat and help clean up.

First Circuits with High School

Lizabeth Arum — Thu, 17 Sep 2009 02:48:10 +0000

So today we wired up our first circuits. Before class started I put together boxes for each student with a breadboard, LEDs and a voltage regulator. When students came into class, I handed them their boxes and placed wires, batteries, alligator clips, wire cutters and strippers in the center of the room. Sitting on the floor, we started with nine volt batteries and LEDs with a forward voltage of 3V and a forward current of 0.03A. After using Ohm’s Law to figure out the resistance, we selected resistors and used alligator clips to make connections and light the LEDs.

The second circuit included a breadboard, a 12V DC power supply, an LM7805 voltage regulator, an LED and a resistor. As students were less confident about wiring up the voltage regulator and figuring out the new resistance, this circuit took a bit longer to complete.

voltage regulator detail

After a final wiring check, power supplies were plugged in, and LEDs lit up.

The next circuits involved wiring LEDs in parallel and in series. The challenge here was to see how many could be lit in series and how many in parallel.

Forty-five minutes goes fast. Even though all the materials were prepared ahead of time, I didn’t get a chance to cover LED properties or the resistor values involved with illuminating an RGB LED in the way that I planned. No one had time to wire up the Piranhas, or High-Flux LEDs, and no one had a chance to clean up before running to their next class.

Type	Color	I_F	V_F Typ	V_F Max	Luminous Intensity	Viewing Angle	Wavelength
Standard	Red	30mA	1.7V	2.1V	5mcd@10mA	60°	660nm
Standard	Yellow	30mA	2.1V	2.5V	32mcd@20mA	60°	565nm
Super bright	Red	30mA	1.85V	2.5V	500mcd@20mA	60°	660nm

Well, tomorrow I’ll get another shot at it when the Middle School Physical Computing class works on their first circuits.

This assignment was inspired by Syuzi Pakhchan’s book Fashioning Technology and from the first circuit I made at ITP in 1998.

Hello World!

Lizabeth Arum — Wed, 16 Sep 2009 02:54:58 +0000

After spending the past summer gathering materials for my different classes, I thought it might be nice to share what I found inspiring, what I learned and how it all panned out.

Over the year, I will write about my experiences teaching Physical Computing, IPhone programming, and 2D and 3D animation to kids. I’ll try to explore what worked and what didn’t, what I would do again, and what I wouldn’t.

I’ve learned so much from various people, books and websites, and I hope that by sharing my thoughts, successes and failures, I can give back to a community that I have gotten so much from.

This is my first blog. wish me luck!