[islandlabs] Meeting / Workshop recap + stuff

Jonathan Dahan jedahan
Tue Sep 15 11:49:26 EDT 2009


Thanks for the follow up Bill. Here's a proposal I think will work well:
General body meetings every Wednesday @ 7:00pm. Open to everyone but chances
are only the core people will show up. Everyone is in charge of something
different and reports. President handles campus relations / room
reservations / USG funding. Technical chair (Bill) reports on educational
material / preparation for projects. Anyone can chair their own project, and
reports on the status of that. Webmaster / PR reports on postering and
website updates. This makes it short and sweet, and focuses on getting
events / projects underway.

Suggestions welcome,
Jonathan


On Tue, Sep 15, 2009 at 1:00 AM, Burns, William <burns at cshl.edu> wrote:

>
> Meeting recap:
> On Wednesday, September 9th, island labs met (at 7:00pm?) in a "crafts"
> room in the basement of the student union building. I arrived late, at about
> 7:30, and the meeting lasted quite a while. (past 10:00pm?)
> The campus postering must have been effective because it was our largest
> meeting, w/ about 15? in attendance.
>
> Despite difficulties in answering some basic electronics questions, the
> last IslandLabs was a great success.
> The meeting space was awesome.
> Johnathan arrived w/ basic/small papercraft and electronics projects in
> mind.
> It was possibly our first real "workshop" format meeting, where some people
> followed a certain main project through to the end, and others followed
> their own interests, finding their own projects.
> This was very cool.
>
> One approach to maintaining this success would be to keep the regular
> islandlabs meetings limited to a core group that would do
> planning+preparation for each new workshop.
>
> During the workshop, we had problems w/ burning LEDs, and draining
> batteries.
>
> SOLUTIONS:
>
> Burning LEDs:
> I found myself unprepared to answer basic questions that we've come up with
> before, like what resistor to combine with an LED to keep it from burning.
> (I assume everyone is in the same boat here)
>
> The general solution to this problem is the:
> LED Current Controller:
> http://caladan.nanosoft.ca/c4/ccorner/4.php
> This is a small circuit, but it's a bit awkward for first-timers to
> assemble.
>
> The short answer is 100 ohms.
> The long answer can be found in the rest of my ramblings.
>
> Finding parts:
> The drawers of labeled components were impressive.
> I noticed that there was a resistor-code reference-card there, to help
> people read resistor values.
>
>
> So, I was thinking that it would be good to come up w/ a bunch of 3X5
> index-cards, illustrating the answers to
> the basic questions:
>
> Basic Electricity:
> One card example would be the basic electricity stuff from high-school:
> E=I*R, I=E/R, R=E/I
>
> The last equation shows what resistor value is needed to limit current flow
> to a certain amount, given a certain voltage. (a.k.a. potential_difference)
> A current_limiting_resistor is what we needed for our LEDs.
>
> LED Resistors:
> Knowledge of how those basic equations combined w/ the "magic" behavior of
> semiconductors is what would go onto the LED_Resistor 3x5 card.
> http://en.wikipedia.org/wiki/LED_circuit
>
> Basically, you need to know (or know how to measure) the voltage drop
> (potential_difference) across an LED.
> Once that is known, you subtract that value from the voltage of the power
> supply.
> Two button_batteries in series add up to 2.8V
> A basic red LED should have a potential difference of 1.8 volts.
> most LEDs desire a current of 10, 20 or 30 milliAmps.
>
> The 2.8V supply is too large for the 1.8V drop across a red LED, the
> internal resistance of the battery is too small to protect the LED from
> burnout, or the battery from draining. Let's assume the battery has no
> resistance, and calculate the limiting resistor value required to dissipate
> the remaining 1 Volt.
>
> 2.8V volt_supply - 1.8V LED_voltage_drop = 1 Volt
>
> R=E/I
> Resistance = 1 Volt / 10 milliAmps
> Resistance = 1 / 0.01
> Resistance = 100 Ohms.
>
> So, we needed a 100-ohm resistor to be paired w/ 2 button batteries, and a
> 10mA red LED.
>
> I assume that the different types of LEDs available for the workshop had
> different voltage drops.
> white, green or blue LEDs apparently maintain a potential difference of
> over 3-volts each. Some RGB, and UV LEDs want 30 milliAmps.
>
> A 36 Ohm resistor would need to be combined w/ a set of 3 button batteries,
> and an RGB LED that has a 3.1V drop, and wants a 30mA current.
>
> (a 100 ohm resistor should be safe for both applications)
>
> end of meeting recap.
>
> -----------------
>
> Here are lots of LED (and other) projects:
> http://www.educypedia.be/electronics/circuitsled.htm
> Here's an h-bridge design that seems to match my non-functional h-bridge
> http://caladan.nanosoft.ca/c4/ccorner/2.php
> Here's an NPN + PNP design that's better.
> http://www.armory.com/~rstevew/Public/Motors/H-Bridges/HBridge_NPN-PNP.gif<http://www.armory.com/%7Erstevew/Public/Motors/H-Bridges/HBridge_NPN-PNP.gif>
> Lots more circuits:
> http://freecircuitdiagram.com/
> A wiki including some basic circuits:
> http://opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks
>
> http://opencircuits.com/index.php?title=Special%3AAllPages&from=1&to=modules&namespace=0
>
> http://opencircuits.com/index.php?title=Special%3AAllPages&from=modules&to=Xilinx+XC3S500E+pins&namespace=0
> A decent + free book on PIC microcontrollers
> http://www.mikroe.com/en/books/picbook/0_Uvod.htm
> Another PIC book
> http://www.mikroe.com/en/books/picmcubook/
>
> _______________________________________________
> List mailing list
> List at islandlabs.org
> http://freeculture.org/cgi-bin/mailman/listinfo/list
>
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