September 17th, 2009 by Lizabeth Arum
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In order to wire the circuits and cover all the topics, I put the following information on the board before class started:
- VF= Forward Voltage/ Voltage Drop.
The minimum amount of voltage needed to light an LED
- lV= Luminous Intensity
The amount of light emitted from an LED in a particular direction.
The greater the numbers the brighter the light.
- IF= 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.
September 16th, 2009 by Lizabeth Arum
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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 |
IF |
VF Typ |
VF 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.
September 15th, 2009 by Lizabeth Arum
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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!
